Data Display

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Application.Stop function is called or when Ctrl-C is pressed. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, styles are specified using the tcell.Style type. Styles specify colors with the tcell.Color type. Functions such as tcell.GetColor, tcell.NewHexColor, and tcell.NewRGBColor can be used to create colors from W3C color names or RGB values. The tcell.Style type also allows you to specify text attributes such as "bold" or "underline" or a URL which some terminals use to display hyperlinks. Almost all strings which are displayed may contain style tags. A style tag's content is always wrapped in square brackets. In its simplest form, a style tag specifies the foreground color of the text. Colors in these tags are W3C color names or six hexadecimal digits following a hash tag. Examples: A style tag changes the style of the characters following that style tag. There is no style stack and no nesting of style tags. Style tags are used in almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. A style tag's full format looks like this: Each of the four fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered style tags.) Fields that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags to turn on certain attributes (some flags may not be supported by your terminal): Use uppercase letters to turn off the corresponding attribute, for example, "B" to turn off bold. Uppercase letters have no effect if the attribute was not previously set. Setting a URL allows you to turn a piece of text into a hyperlink in some terminals. Specify a dash ("-") to specify the end of the hyperlink. Hyperlinks must only contain single-byte characters (e.g. ASCII) and they may not contain bracket characters ("[" or "]"). Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. Note that most terminals will not report information about their color theme. This package therefore does not support using the terminal's color theme. The default style is a dark theme and you must change the Styles variable to switch to a light (or other) theme. This package supports all unicode characters supported by your terminal. If your terminal supports mouse events, you can enable mouse support for your application by calling Application.EnableMouse. Note that this may interfere with your terminal's default mouse behavior. Mouse support is disabled by default. Many functions in this package are not thread-safe. For many applications, this is not an issue: If your code makes changes in response to key events, the corresponding callback function will execute in the main goroutine and thus will not cause any race conditions. (Exceptions to this are documented.) If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate or Application.QueueUpdateDraw (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw from any goroutine without having to wrap it in Application.QueueUpdate. And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use Application.QueueUpdate as that may lead to deadlocks. It is also not necessary to call Application.Draw from such callbacks as it will be called automatically. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. Please note that if you are using the functions of Box on a subclass, they will return a *Box, not the subclass. This is a Golang limitation. So while tview supports method chaining in many places, these chains must be broken when using Box's functions. Example: You will need to call Box.SetBorder separately: All widgets also implement the Primitive interface. The tview package's rendering is based on version 2 of https://github.com/gdamore/tcell. It uses types and constants from that package (e.g. colors, styles, and keyboard values).

Package sessions provides cookie and filesystem sessions and infrastructure for custom session backends. The key features are: Let's start with an example that shows the sessions API in a nutshell: First we initialize a session store calling NewCookieStore() and passing a secret key used to authenticate the session. Inside the handler, we call store.Get() to retrieve an existing session or a new one. Then we set some session values in session.Values, which is a map[interface{}]interface{}. And finally we call session.Save() to save the session in the response. Note that in production code, we should check for errors when calling session.Save(r, w), and either display an error message or otherwise handle it. Save must be called before writing to the response, otherwise the session cookie will not be sent to the client. That's all you need to know for the basic usage. Let's take a look at other options, starting with flash messages. Flash messages are session values that last until read. The term appeared with Ruby On Rails a few years back. When we request a flash message, it is removed from the session. To add a flash, call session.AddFlash(), and to get all flashes, call session.Flashes(). Here is an example: Flash messages are useful to set information to be read after a redirection, like after form submissions. There may also be cases where you want to store a complex datatype within a session, such as a struct. Sessions are serialised using the encoding/gob package, so it is easy to register new datatypes for storage in sessions: As it's not possible to pass a raw type as a parameter to a function, gob.Register() relies on us passing it a value of the desired type. In the example above we've passed it a pointer to a struct and a pointer to a custom type representing a map[string]interface. (We could have passed non-pointer values if we wished.) This will then allow us to serialise/deserialise values of those types to and from our sessions. Note that because session values are stored in a map[string]interface{}, there's a need to type-assert data when retrieving it. We'll use the Person struct we registered above: By default, session cookies last for a month. This is probably too long for some cases, but it is easy to change this and other attributes during runtime. Sessions can be configured individually or the store can be configured and then all sessions saved using it will use that configuration. We access session.Options or store.Options to set a new configuration. The fields are basically a subset of http.Cookie fields. Let's change the maximum age of a session to one week: Sometimes we may want to change authentication and/or encryption keys without breaking existing sessions. The CookieStore supports key rotation, and to use it you just need to set multiple authentication and encryption keys, in pairs, to be tested in order: New sessions will be saved using the first pair. Old sessions can still be read because the first pair will fail, and the second will be tested. This makes it easy to "rotate" secret keys and still be able to validate existing sessions. Note: for all pairs the encryption key is optional; set it to nil or omit it and and encryption won't be used. Multiple sessions can be used in the same request, even with different session backends. When this happens, calling Save() on each session individually would be cumbersome, so we have a way to save all sessions at once: it's sessions.Save(). Here's an example: This is possible because when we call Get() from a session store, it adds the session to a common registry. Save() uses it to save all registered sessions.

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialized. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/google/jsonapi

Package codepipeline provides the API client, operations, and parameter types for AWS CodePipeline. This is the CodePipeline API Reference. This guide provides descriptions of the actions and data types for CodePipeline. Some functionality for your pipeline can only be configured through the API. For more information, see the CodePipeline User Guide. You can use the CodePipeline API to work with pipelines, stages, actions, and transitions. Pipelines are models of automated release processes. Each pipeline is uniquely named, and consists of stages, actions, and transitions. You can work with pipelines by calling: CreatePipeline DeletePipeline GetPipeline GetPipelineExecution GetPipelineState ListActionExecutions ListPipelines ListPipelineExecutions StartPipelineExecution StopPipelineExecution UpdatePipeline Pipelines include stages. Each stage contains one or more actions that must complete before the next stage begins. A stage results in success or failure. If a stage fails, the pipeline stops at that stage and remains stopped until either a new version of an artifact appears in the source location, or a user takes action to rerun the most recent artifact through the pipeline. You can call GetPipelineState, which displays the status of a pipeline, including the status of stages in the pipeline, or GetPipeline, which returns the entire structure of the pipeline, including the stages of that pipeline. For more information about the structure of stages and actions, see CodePipeline Pipeline Structure Reference. Pipeline stages include actions that are categorized into categories such as source or build actions performed in a stage of a pipeline. For example, you can use a source action to import artifacts into a pipeline from a source such as Amazon S3. Like stages, you do not work with actions directly in most cases, but you do define and interact with actions when working with pipeline operations such as CreatePipelineand GetPipelineState. Valid action categories are: Source Build Test Deploy Approval Invoke Compute Pipelines also include transitions, which allow the transition of artifacts from one stage to the next in a pipeline after the actions in one stage complete. You can work with transitions by calling: DisableStageTransition EnableStageTransition For third-party integrators or developers who want to create their own integrations with CodePipeline, the expected sequence varies from the standard API user. To integrate with CodePipeline, developers need to work with the following items: Jobs, which are instances of an action. For example, a job for a source action might import a revision of an artifact from a source. You can work with jobs by calling: AcknowledgeJob GetJobDetails PollForJobs PutJobFailureResult PutJobSuccessResult Third party jobs, which are instances of an action created by a partner action and integrated into CodePipeline. Partner actions are created by members of the Amazon Web Services Partner Network. You can work with third party jobs by calling: AcknowledgeThirdPartyJob GetThirdPartyJobDetails PollForThirdPartyJobs PutThirdPartyJobFailureResult PutThirdPartyJobSuccessResult

Package ql implements a pure Go embedded SQL database engine. QL is a member of the SQL family of languages. It is less complex and less powerful than SQL (whichever specification SQL is considered to be). 2018-08-02: Release v1.2.0 adds initial support for Go modules. 2017-01-10: Release v1.1.0 fixes some bugs and adds a configurable WAL headroom. 2016-07-29: Release v1.0.6 enables alternatively using = instead of == for equality operation. 2016-07-11: Release v1.0.5 undoes vendoring of lldb. QL now uses stable lldb (github.com/cznic/lldb). 2016-07-06: Release v1.0.4 fixes a panic when closing the WAL file. 2016-04-03: Release v1.0.3 fixes a data race. 2016-03-23: Release v1.0.2 vendors github.com/cznic/exp/lldb and github.com/camlistore/go4/lock. 2016-03-17: Release v1.0.1 adjusts for latest goyacc. Parser error messages are improved and changed, but their exact form is not considered a API change. 2016-03-05: The current version has been tagged v1.0.0. 2015-06-15: To improve compatibility with other SQL implementations, the count built-in aggregate function now accepts * as its argument. 2015-05-29: The execution planner was rewritten from scratch. It should use indices in all places where they were used before plus in some additional situations. It is possible to investigate the plan using the newly added EXPLAIN statement. The QL tool is handy for such analysis. If the planner would have used an index, but no such exists, the plan includes hints in form of copy/paste ready CREATE INDEX statements. The planner is still quite simple and a lot of work on it is yet ahead. You can help this process by filling an issue with a schema and query which fails to use an index or indices when it should, in your opinion. Bonus points for including output of `ql 'explain <query>'`. 2015-05-09: The grammar of the CREATE INDEX statement now accepts an expression list instead of a single expression, which was further limited to just a column name or the built-in id(). As a side effect, composite indices are now functional. However, the values in the expression-list style index are not yet used by other statements or the statement/query planner. The composite index is useful while having UNIQUE clause to check for semantically duplicate rows before they get added to the table or when such a row is mutated using the UPDATE statement and the expression-list style index tuple of the row is thus recomputed. 2015-05-02: The Schema field of table __Table now correctly reflects any column constraints and/or defaults. Also, the (*DB).Info method now has that information provided in new ColumInfo fields NotNull, Constraint and Default. 2015-04-20: Added support for {LEFT,RIGHT,FULL} [OUTER] JOIN. 2015-04-18: Column definitions can now have constraints and defaults. Details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. 2015-03-06: New built-in functions formatFloat and formatInt. Thanks urandom! (https://github.com/urandom) 2015-02-16: IN predicate now accepts a SELECT statement. See the updated "Predicates" section. 2015-01-17: Logical operators || and && have now alternative spellings: OR and AND (case insensitive). AND was a keyword before, but OR is a new one. This can possibly break existing queries. For the record, it's a good idea to not use any name appearing in, for example, [7] in your queries as the list of QL's keywords may expand for gaining better compatibility with existing SQL "standards". 2015-01-12: ACID guarantees were tightened at the cost of performance in some cases. The write collecting window mechanism, a formerly used implementation detail, was removed. Inserting rows one by one in a transaction is now slow. I mean very slow. Try to avoid inserting single rows in a transaction. Instead, whenever possible, perform batch updates of tens to, say thousands of rows in a single transaction. See also: http://www.sqlite.org/faq.html#q19, the discussed synchronization principles involved are the same as for QL, modulo minor details. Note: A side effect is that closing a DB before exiting an application, both for the Go API and through database/sql driver, is no more required, strictly speaking. Beware that exiting an application while there is an open (uncommitted) transaction in progress means losing the transaction data. However, the DB will not become corrupted because of not closing it. Nor that was the case before, but formerly failing to close a DB could have resulted in losing the data of the last transaction. 2014-09-21: id() now optionally accepts a single argument - a table name. 2014-09-01: Added the DB.Flush() method and the LIKE pattern matching predicate. 2014-08-08: The built in functions max and min now accept also time values. Thanks opennota! (https://github.com/opennota) 2014-06-05: RecordSet interface extended by new methods FirstRow and Rows. 2014-06-02: Indices on id() are now used by SELECT statements. 2014-05-07: Introduction of Marshal, Schema, Unmarshal. 2014-04-15: Added optional IF NOT EXISTS clause to CREATE INDEX and optional IF EXISTS clause to DROP INDEX. 2014-04-12: The column Unique in the virtual table __Index was renamed to IsUnique because the old name is a keyword. Unfortunately, this is a breaking change, sorry. 2014-04-11: Introduction of LIMIT, OFFSET. 2014-04-10: Introduction of query rewriting. 2014-04-07: Introduction of indices. QL imports zappy[8], a block-based compressor, which speeds up its performance by using a C version of the compression/decompression algorithms. If a CGO-free (pure Go) version of QL, or an app using QL, is required, please include 'purego' in the -tags option of go {build,get,install}. For example: If zappy was installed before installing QL, it might be necessary to rebuild zappy first (or rebuild QL with all its dependencies using the -a option): The syntax is specified using Extended Backus-Naur Form (EBNF) Lower-case production names are used to identify lexical tokens. Non-terminals are in CamelCase. Lexical tokens are enclosed in double quotes "" or back quotes “. The form a … b represents the set of characters from a through b as alternatives. The horizontal ellipsis … is also used elsewhere in the spec to informally denote various enumerations or code snippets that are not further specified. QL source code is Unicode text encoded in UTF-8. The text is not canonicalized, so a single accented code point is distinct from the same character constructed from combining an accent and a letter; those are treated as two code points. For simplicity, this document will use the unqualified term character to refer to a Unicode code point in the source text. Each code point is distinct; for instance, upper and lower case letters are different characters. Implementation restriction: For compatibility with other tools, the parser may disallow the NUL character (U+0000) in the statement. Implementation restriction: A byte order mark is disallowed anywhere in QL statements. The following terms are used to denote specific character classes The underscore character _ (U+005F) is considered a letter. Lexical elements are comments, tokens, identifiers, keywords, operators and delimiters, integer, floating-point, imaginary, rune and string literals and QL parameters. Line comments start with the character sequence // or -- and stop at the end of the line. A line comment acts like a space. General comments start with the character sequence /* and continue through the character sequence */. A general comment acts like a space. Comments do not nest. Tokens form the vocabulary of QL. There are four classes: identifiers, keywords, operators and delimiters, and literals. White space, formed from spaces (U+0020), horizontal tabs (U+0009), carriage returns (U+000D), and newlines (U+000A), is ignored except as it separates tokens that would otherwise combine into a single token. The formal grammar uses semicolons ";" as separators of QL statements. A single QL statement or the last QL statement in a list of statements can have an optional semicolon terminator. (Actually a separator from the following empty statement.) Identifiers name entities such as tables or record set columns. An identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter. For example No identifiers are predeclared, however note that no keyword can be used as an identifier. Identifiers starting with two underscores are used for meta data virtual tables names. For forward compatibility, users should generally avoid using any identifiers starting with two underscores. For example The following keywords are reserved and may not be used as identifiers. Keywords are not case sensitive. The following character sequences represent operators, delimiters, and other special tokens Operators consisting of more than one character are referred to by names in the rest of the documentation An integer literal is a sequence of digits representing an integer constant. An optional prefix sets a non-decimal base: 0 for octal, 0x or 0X for hexadecimal. In hexadecimal literals, letters a-f and A-F represent values 10 through 15. For example A floating-point literal is a decimal representation of a floating-point constant. It has an integer part, a decimal point, a fractional part, and an exponent part. The integer and fractional part comprise decimal digits; the exponent part is an e or E followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided. For example An imaginary literal is a decimal representation of the imaginary part of a complex constant. It consists of a floating-point literal or decimal integer followed by the lower-case letter i. For example A rune literal represents a rune constant, an integer value identifying a Unicode code point. A rune literal is expressed as one or more characters enclosed in single quotes. Within the quotes, any character may appear except single quote and newline. A single quoted character represents the Unicode value of the character itself, while multi-character sequences beginning with a backslash encode values in various formats. The simplest form represents the single character within the quotes; since QL statements are Unicode characters encoded in UTF-8, multiple UTF-8-encoded bytes may represent a single integer value. For instance, the literal 'a' holds a single byte representing a literal a, Unicode U+0061, value 0x61, while 'ä' holds two bytes (0xc3 0xa4) representing a literal a-dieresis, U+00E4, value 0xe4. Several backslash escapes allow arbitrary values to be encoded as ASCII text. There are four ways to represent the integer value as a numeric constant: \x followed by exactly two hexadecimal digits; \u followed by exactly four hexadecimal digits; \U followed by exactly eight hexadecimal digits, and a plain backslash \ followed by exactly three octal digits. In each case the value of the literal is the value represented by the digits in the corresponding base. Although these representations all result in an integer, they have different valid ranges. Octal escapes must represent a value between 0 and 255 inclusive. Hexadecimal escapes satisfy this condition by construction. The escapes \u and \U represent Unicode code points so within them some values are illegal, in particular those above 0x10FFFF and surrogate halves. After a backslash, certain single-character escapes represent special values All other sequences starting with a backslash are illegal inside rune literals. For example A string literal represents a string constant obtained from concatenating a sequence of characters. There are two forms: raw string literals and interpreted string literals. Raw string literals are character sequences between back quotes “. Within the quotes, any character is legal except back quote. The value of a raw string literal is the string composed of the uninterpreted (implicitly UTF-8-encoded) characters between the quotes; in particular, backslashes have no special meaning and the string may contain newlines. Carriage returns inside raw string literals are discarded from the raw string value. Interpreted string literals are character sequences between double quotes "". The text between the quotes, which may not contain newlines, forms the value of the literal, with backslash escapes interpreted as they are in rune literals (except that \' is illegal and \" is legal), with the same restrictions. The three-digit octal (\nnn) and two-digit hexadecimal (\xnn) escapes represent individual bytes of the resulting string; all other escapes represent the (possibly multi-byte) UTF-8 encoding of individual characters. Thus inside a string literal \377 and \xFF represent a single byte of value 0xFF=255, while ÿ, \u00FF, \U000000FF and \xc3\xbf represent the two bytes 0xc3 0xbf of the UTF-8 encoding of character U+00FF. For example These examples all represent the same string If the statement source represents a character as two code points, such as a combining form involving an accent and a letter, the result will be an error if placed in a rune literal (it is not a single code point), and will appear as two code points if placed in a string literal. Literals are assigned their values from the respective text representation at "compile" (parse) time. QL parameters provide the same functionality as literals, but their value is assigned at execution time from an expression list passed to DB.Run or DB.Execute. Using '?' or '$' is completely equivalent. For example Keywords 'false' and 'true' (not case sensitive) represent the two possible constant values of type bool (also not case sensitive). Keyword 'NULL' (not case sensitive) represents an untyped constant which is assignable to any type. NULL is distinct from any other value of any type. A type determines the set of values and operations specific to values of that type. A type is specified by a type name. Named instances of the boolean, numeric, and string types are keywords. The names are not case sensitive. Note: The blob type is exchanged between the back end and the API as []byte. On 32 bit platforms this limits the size which the implementation can handle to 2G. A boolean type represents the set of Boolean truth values denoted by the predeclared constants true and false. The predeclared boolean type is bool. A duration type represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years. A numeric type represents sets of integer or floating-point values. The predeclared architecture-independent numeric types are The value of an n-bit integer is n bits wide and represented using two's complement arithmetic. Conversions are required when different numeric types are mixed in an expression or assignment. A string type represents the set of string values. A string value is a (possibly empty) sequence of bytes. The case insensitive keyword for the string type is 'string'. The length of a string (its size in bytes) can be discovered using the built-in function len. A time type represents an instant in time with nanosecond precision. Each time has associated with it a location, consulted when computing the presentation form of the time. The following functions are implicitly declared An expression specifies the computation of a value by applying operators and functions to operands. Operands denote the elementary values in an expression. An operand may be a literal, a (possibly qualified) identifier denoting a constant or a function or a table/record set column, or a parenthesized expression. A qualified identifier is an identifier qualified with a table/record set name prefix. For example Primary expression are the operands for unary and binary expressions. For example A primary expression of the form denotes the element of a string indexed by x. Its type is byte. The value x is called the index. The following rules apply - The index x must be of integer type except bigint or duration; it is in range if 0 <= x < len(s), otherwise it is out of range. - A constant index must be non-negative and representable by a value of type int. - A constant index must be in range if the string a is a literal. - If x is out of range at run time, a run-time error occurs. - s[x] is the byte at index x and the type of s[x] is byte. If s is NULL or x is NULL then the result is NULL. Otherwise s[x] is illegal. For a string, the primary expression constructs a substring. The indices low and high select which elements appear in the result. The result has indices starting at 0 and length equal to high - low. For convenience, any of the indices may be omitted. A missing low index defaults to zero; a missing high index defaults to the length of the sliced operand The indices low and high are in range if 0 <= low <= high <= len(a), otherwise they are out of range. A constant index must be non-negative and representable by a value of type int. If both indices are constant, they must satisfy low <= high. If the indices are out of range at run time, a run-time error occurs. Integer values of type bigint or duration cannot be used as indices. If s is NULL the result is NULL. If low or high is not omitted and is NULL then the result is NULL. Given an identifier f denoting a predeclared function, calls f with arguments a1, a2, … an. Arguments are evaluated before the function is called. The type of the expression is the result type of f. In a function call, the function value and arguments are evaluated in the usual order. After they are evaluated, the parameters of the call are passed by value to the function and the called function begins execution. The return value of the function is passed by value when the function returns. Calling an undefined function causes a compile-time error. Operators combine operands into expressions. Comparisons are discussed elsewhere. For other binary operators, the operand types must be identical unless the operation involves shifts or untyped constants. For operations involving constants only, see the section on constant expressions. Except for shift operations, if one operand is an untyped constant and the other operand is not, the constant is converted to the type of the other operand. The right operand in a shift expression must have unsigned integer type or be an untyped constant that can be converted to unsigned integer type. If the left operand of a non-constant shift expression is an untyped constant, the type of the constant is what it would be if the shift expression were replaced by its left operand alone. Expressions of the form yield a boolean value true if expr2, a regular expression, matches expr1 (see also [6]). Both expression must be of type string. If any one of the expressions is NULL the result is NULL. Predicates are special form expressions having a boolean result type. Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be comparable as defined in "Comparison operators". Another form of the IN predicate creates the expression list from a result of a SelectStmt. The SelectStmt must select only one column. The produced expression list is resource limited by the memory available to the process. NULL values produced by the SelectStmt are ignored, but if all records of the SelectStmt are NULL the predicate yields NULL. The select statement is evaluated only once. If the type of expr is not the same as the type of the field returned by the SelectStmt then the set operation yields false. The type of the column returned by the SelectStmt must be one of the simple (non blob-like) types: Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be ordered as defined in "Comparison operators". Expressions of the form yield a boolean value true if expr does not have a specific type (case A) or if expr has a specific type (case B). In other cases the result is a boolean value false. Unary operators have the highest precedence. There are five precedence levels for binary operators. Multiplication operators bind strongest, followed by addition operators, comparison operators, && (logical AND), and finally || (logical OR) Binary operators of the same precedence associate from left to right. For instance, x / y * z is the same as (x / y) * z. Note that the operator precedence is reflected explicitly by the grammar. Arithmetic operators apply to numeric values and yield a result of the same type as the first operand. The four standard arithmetic operators (+, -, *, /) apply to integer, rational, floating-point, and complex types; + also applies to strings; +,- also applies to times. All other arithmetic operators apply to integers only. sum integers, rationals, floats, complex values, strings difference integers, rationals, floats, complex values, times product integers, rationals, floats, complex values / quotient integers, rationals, floats, complex values % remainder integers & bitwise AND integers | bitwise OR integers ^ bitwise XOR integers &^ bit clear (AND NOT) integers << left shift integer << unsigned integer >> right shift integer >> unsigned integer Strings can be concatenated using the + operator String addition creates a new string by concatenating the operands. A value of type duration can be added to or subtracted from a value of type time. Times can subtracted from each other producing a value of type duration. For two integer values x and y, the integer quotient q = x / y and remainder r = x % y satisfy the following relationships with x / y truncated towards zero ("truncated division"). As an exception to this rule, if the dividend x is the most negative value for the int type of x, the quotient q = x / -1 is equal to x (and r = 0). If the divisor is a constant expression, it must not be zero. If the divisor is zero at run time, a run-time error occurs. If the dividend is non-negative and the divisor is a constant power of 2, the division may be replaced by a right shift, and computing the remainder may be replaced by a bitwise AND operation The shift operators shift the left operand by the shift count specified by the right operand. They implement arithmetic shifts if the left operand is a signed integer and logical shifts if it is an unsigned integer. There is no upper limit on the shift count. Shifts behave as if the left operand is shifted n times by 1 for a shift count of n. As a result, x << 1 is the same as x*2 and x >> 1 is the same as x/2 but truncated towards negative infinity. For integer operands, the unary operators +, -, and ^ are defined as follows For floating-point and complex numbers, +x is the same as x, while -x is the negation of x. The result of a floating-point or complex division by zero is not specified beyond the IEEE-754 standard; whether a run-time error occurs is implementation-specific. Whenever any operand of any arithmetic operation, unary or binary, is NULL, as well as in the case of the string concatenating operation, the result is NULL. For unsigned integer values, the operations +, -, *, and << are computed modulo 2n, where n is the bit width of the unsigned integer's type. Loosely speaking, these unsigned integer operations discard high bits upon overflow, and expressions may rely on “wrap around”. For signed integers with a finite bit width, the operations +, -, *, and << may legally overflow and the resulting value exists and is deterministically defined by the signed integer representation, the operation, and its operands. No exception is raised as a result of overflow. An evaluator may not optimize an expression under the assumption that overflow does not occur. For instance, it may not assume that x < x + 1 is always true. Integers of type bigint and rationals do not overflow but their handling is limited by the memory resources available to the program. Comparison operators compare two operands and yield a boolean value. In any comparison, the first operand must be of same type as is the second operand, or vice versa. The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows - Boolean values are comparable. Two boolean values are equal if they are either both true or both false. - Complex values are comparable. Two complex values u and v are equal if both real(u) == real(v) and imag(u) == imag(v). - Integer values are comparable and ordered, in the usual way. Note that durations are integers. - Floating point values are comparable and ordered, as defined by the IEEE-754 standard. - Rational values are comparable and ordered, in the usual way. - String and Blob values are comparable and ordered, lexically byte-wise. - Time values are comparable and ordered. Whenever any operand of any comparison operation is NULL, the result is NULL. Note that slices are always of type string. Logical operators apply to boolean values and yield a boolean result. The right operand is evaluated conditionally. The truth tables for logical operations with NULL values Conversions are expressions of the form T(x) where T is a type and x is an expression that can be converted to type T. A constant value x can be converted to type T in any of these cases: - x is representable by a value of type T. - x is a floating-point constant, T is a floating-point type, and x is representable by a value of type T after rounding using IEEE 754 round-to-even rules. The constant T(x) is the rounded value. - x is an integer constant and T is a string type. The same rule as for non-constant x applies in this case. Converting a constant yields a typed constant as result. A non-constant value x can be converted to type T in any of these cases: - x has type T. - x's type and T are both integer or floating point types. - x's type and T are both complex types. - x is an integer, except bigint or duration, and T is a string type. Specific rules apply to (non-constant) conversions between numeric types or to and from a string type. These conversions may change the representation of x and incur a run-time cost. All other conversions only change the type but not the representation of x. A conversion of NULL to any type yields NULL. For the conversion of non-constant numeric values, the following rules apply 1. When converting between integer types, if the value is a signed integer, it is sign extended to implicit infinite precision; otherwise it is zero extended. It is then truncated to fit in the result type's size. For example, if v == uint16(0x10F0), then uint32(int8(v)) == 0xFFFFFFF0. The conversion always yields a valid value; there is no indication of overflow. 2. When converting a floating-point number to an integer, the fraction is discarded (truncation towards zero). 3. When converting an integer or floating-point number to a floating-point type, or a complex number to another complex type, the result value is rounded to the precision specified by the destination type. For instance, the value of a variable x of type float32 may be stored using additional precision beyond that of an IEEE-754 32-bit number, but float32(x) represents the result of rounding x's value to 32-bit precision. Similarly, x + 0.1 may use more than 32 bits of precision, but float32(x + 0.1) does not. In all non-constant conversions involving floating-point or complex values, if the result type cannot represent the value the conversion succeeds but the result value is implementation-dependent. 1. Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer. Values outside the range of valid Unicode code points are converted to "\uFFFD". 2. Converting a blob to a string type yields a string whose successive bytes are the elements of the blob. 3. Converting a value of a string type to a blob yields a blob whose successive elements are the bytes of the string. 4. Converting a value of a bigint type to a string yields a string containing the decimal decimal representation of the integer. 5. Converting a value of a string type to a bigint yields a bigint value containing the integer represented by the string value. A prefix of “0x” or “0X” selects base 16; the “0” prefix selects base 8, and a “0b” or “0B” prefix selects base 2. Otherwise the value is interpreted in base 10. An error occurs if the string value is not in any valid format. 6. Converting a value of a rational type to a string yields a string containing the decimal decimal representation of the rational in the form "a/b" (even if b == 1). 7. Converting a value of a string type to a bigrat yields a bigrat value containing the rational represented by the string value. The string can be given as a fraction "a/b" or as a floating-point number optionally followed by an exponent. An error occurs if the string value is not in any valid format. 8. Converting a value of a duration type to a string returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format using a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0, with no unit. 9. Converting a string value to a duration yields a duration represented by the string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h". 10. Converting a time value to a string returns the time formatted using the format string When evaluating the operands of an expression or of function calls, operations are evaluated in lexical left-to-right order. For example, in the evaluation of the function calls and evaluation of c happen in the order h(), i(), j(), c. Floating-point operations within a single expression are evaluated according to the associativity of the operators. Explicit parentheses affect the evaluation by overriding the default associativity. In the expression x + (y + z) the addition y + z is performed before adding x. Statements control execution. The empty statement does nothing. Alter table statements modify existing tables. With the ADD clause it adds a new column to the table. The column must not exist. With the DROP clause it removes an existing column from a table. The column must exist and it must be not the only (last) column of the table. IOW, there cannot be a table with no columns. For example When adding a column to a table with existing data, the constraint clause of the ColumnDef cannot be used. Adding a constrained column to an empty table is fine. Begin transactions statements introduce a new transaction level. Every transaction level must be eventually balanced by exactly one of COMMIT or ROLLBACK statements. Note that when a transaction is roll-backed because of a statement failure then no explicit balancing of the respective BEGIN TRANSACTION is statement is required nor permitted. Failure to properly balance any opened transaction level may cause dead locks and/or lose of data updated in the uppermost opened but never properly closed transaction level. For example A database cannot be updated (mutated) outside of a transaction. Statements requiring a transaction A database is effectively read only outside of a transaction. Statements not requiring a transaction The commit statement closes the innermost transaction nesting level. If that's the outermost level then the updates to the DB made by the transaction are atomically made persistent. For example Create index statements create new indices. Index is a named projection of ordered values of a table column to the respective records. As a special case the id() of the record can be indexed. Index name must not be the same as any of the existing tables and it also cannot be the same as of any column name of the table the index is on. For example Now certain SELECT statements may use the indices to speed up joins and/or to speed up record set filtering when the WHERE clause is used; or the indices might be used to improve the performance when the ORDER BY clause is present. The UNIQUE modifier requires the indexed values tuple to be index-wise unique or have all values NULL. The optional IF NOT EXISTS clause makes the statement a no operation if the index already exists. A simple index consists of only one expression which must be either a column name or the built-in id(). A more complex and more general index is one that consists of more than one expression or its single expression does not qualify as a simple index. In this case the type of all expressions in the list must be one of the non blob-like types. Note: Blob-like types are blob, bigint, bigrat, time and duration. Create table statements create new tables. A column definition declares the column name and type. Table names and column names are case sensitive. Neither a table or an index of the same name may exist in the DB. For example The optional IF NOT EXISTS clause makes the statement a no operation if the table already exists. The optional constraint clause has two forms. The first one is found in many SQL dialects. This form prevents the data in column DepartmentName to be NULL. The second form allows an arbitrary boolean expression to be used to validate the column. If the value of the expression is true then the validation succeeded. If the value of the expression is false or NULL then the validation fails. If the value of the expression is not of type bool an error occurs. The optional DEFAULT clause is an expression which, if present, is substituted instead of a NULL value when the colum is assigned a value. Note that the constraint and/or default expressions may refer to other columns by name: When a table row is inserted by the INSERT INTO statement or when a table row is updated by the UPDATE statement, the order of operations is as follows: 1. The new values of the affected columns are set and the values of all the row columns become the named values which can be referred to in default expressions evaluated in step 2. 2. If any row column value is NULL and the DEFAULT clause is present in the column's definition, the default expression is evaluated and its value is set as the respective column value. 3. The values, potentially updated, of row columns become the named values which can be referred to in constraint expressions evaluated during step 4. 4. All row columns which definition has the constraint clause present will have that constraint checked. If any constraint violation is detected, the overall operation fails and no changes to the table are made. Delete from statements remove rows from a table, which must exist. For example If the WHERE clause is not present then all rows are removed and the statement is equivalent to the TRUNCATE TABLE statement. Drop index statements remove indices from the DB. The index must exist. For example The optional IF EXISTS clause makes the statement a no operation if the index does not exist. Drop table statements remove tables from the DB. The table must exist. For example The optional IF EXISTS clause makes the statement a no operation if the table does not exist. Insert into statements insert new rows into tables. New rows come from literal data, if using the VALUES clause, or are a result of select statement. In the later case the select statement is fully evaluated before the insertion of any rows is performed, allowing to insert values calculated from the same table rows are to be inserted into. If the ColumnNameList part is omitted then the number of values inserted in the row must be the same as are columns in the table. If the ColumnNameList part is present then the number of values per row must be same as the same number of column names. All other columns of the record are set to NULL. The type of the value assigned to a column must be the same as is the column's type or the value must be NULL. For example If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. Explain statement produces a recordset consisting of lines of text which describe the execution plan of a statement, if any. For example, the QL tool treats the explain statement specially and outputs the joined lines: The explanation may aid in uderstanding how a statement/query would be executed and if indices are used as expected - or which indices may possibly improve the statement performance. The create index statements above were directly copy/pasted in the terminal from the suggestions provided by the filter recordset pipeline part returned by the explain statement. If the statement has nothing special in its plan, the result is the original statement. To get an explanation of the select statement of the IN predicate, use the EXPLAIN statement with that particular select statement. The rollback statement closes the innermost transaction nesting level discarding any updates to the DB made by it. If that's the outermost level then the effects on the DB are as if the transaction never happened. For example The (temporary) record set from the last statement is returned and can be processed by the client. In this case the rollback is the same as 'DROP TABLE tmp;' but it can be a more complex operation. Select from statements produce recordsets. The optional DISTINCT modifier ensures all rows in the result recordset are unique. Either all of the resulting fields are returned ('*') or only those named in FieldList. RecordSetList is a list of table names or parenthesized select statements, optionally (re)named using the AS clause. The result can be filtered using a WhereClause and orderd by the OrderBy clause. For example If Recordset is a nested, parenthesized SelectStmt then it must be given a name using the AS clause if its field are to be accessible in expressions. A field is an named expression. Identifiers, not used as a type in conversion or a function name in the Call clause, denote names of (other) fields, values of which should be used in the expression. The expression can be named using the AS clause. If the AS clause is not present and the expression consists solely of a field name, then that field name is used as the name of the resulting field. Otherwise the field is unnamed. For example The SELECT statement can optionally enumerate the desired/resulting fields in a list. No two identical field names can appear in the list. When more than one record set is used in the FROM clause record set list, the result record set field names are rewritten to be qualified using the record set names. If a particular record set doesn't have a name, its respective fields became unnamed. The optional JOIN clause, for example is mostly equal to except that the rows from a which, when they appear in the cross join, never made expr to evaluate to true, are combined with a virtual row from b, containing all nulls, and added to the result set. For the RIGHT JOIN variant the discussed rules are used for rows from b not satisfying expr == true and the virtual, all-null row "comes" from a. The FULL JOIN adds the respective rows which would be otherwise provided by the separate executions of the LEFT JOIN and RIGHT JOIN variants. For more thorough OUTER JOIN discussion please see the Wikipedia article at [10]. Resultins rows of a SELECT statement can be optionally ordered by the ORDER BY clause. Collating proceeds by considering the expressions in the expression list left to right until a collating order is determined. Any possibly remaining expressions are not evaluated. All of the expression values must yield an ordered type or NULL. Ordered types are defined in "Comparison operators". Collating of elements having a NULL value is different compared to what the comparison operators yield in expression evaluation (NULL result instead of a boolean value). Below, T denotes a non NULL value of any QL type. NULL collates before any non NULL value (is considered smaller than T). Two NULLs have no collating order (are considered equal). The WHERE clause restricts records considered by some statements, like SELECT FROM, DELETE FROM, or UPDATE. It is an error if the expression evaluates to a non null value of non bool type. Another form of the WHERE clause is an existence predicate of a parenthesized select statement. The EXISTS form evaluates to true if the parenthesized SELECT statement produces a non empty record set. The NOT EXISTS form evaluates to true if the parenthesized SELECT statement produces an empty record set. The parenthesized SELECT statement is evaluated only once (TODO issue #159). The GROUP BY clause is used to project rows having common values into a smaller set of rows. For example Using the GROUP BY without any aggregate functions in the selected fields is in certain cases equal to using the DISTINCT modifier. The last two examples above produce the same resultsets. The optional OFFSET clause allows to ignore first N records. For example The above will produce only rows 11, 12, ... of the record set, if they exist. The value of the expression must a non negative integer, but not bigint or duration. The optional LIMIT clause allows to ignore all but first N records. For example The above will return at most the first 10 records of the record set. The value of the expression must a non negative integer, but not bigint or duration. The LIMIT and OFFSET clauses can be combined. For example Considering table t has, say 10 records, the above will produce only records 4 - 8. After returning record #8, no more result rows/records are computed. 1. The FROM clause is evaluated, producing a Cartesian product of its source record sets (tables or nested SELECT statements). 2. If present, the JOIN cluase is evaluated on the result set of the previous evaluation and the recordset specified by the JOIN clause. (... JOIN Recordset ON ...) 3. If present, the WHERE clause is evaluated on the result set of the previous evaluation. 4. If present, the GROUP BY clause is evaluated on the result set of the previous evaluation(s). 5. The SELECT field expressions are evaluated on the result set of the previous evaluation(s). 6. If present, the DISTINCT modifier is evaluated on the result set of the previous evaluation(s). 7. If present, the ORDER BY clause is evaluated on the result set of the previous evaluation(s). 8. If present, the OFFSET clause is evaluated on the result set of the previous evaluation(s). The offset expression is evaluated once for the first record produced by the previous evaluations. 9. If present, the LIMIT clause is evaluated on the result set of the previous evaluation(s). The limit expression is evaluated once for the first record produced by the previous evaluations. Truncate table statements remove all records from a table. The table must exist. For example Update statements change values of fields in rows of a table. For example Note: The SET clause is optional. If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. To allow to query for DB meta data, there exist specially named tables, some of them being virtual. Note: Virtual system tables may have fake table-wise unique but meaningless and unstable record IDs. Do not apply the built-in id() to any system table. The table __Table lists all tables in the DB. The schema is The Schema column returns the statement to (re)create table Name. This table is virtual. The table __Colum lists all columns of all tables in the DB. The schema is The Ordinal column defines the 1-based index of the column in the record. This table is virtual. The table __Colum2 lists all columns of all tables in the DB which have the constraint NOT NULL or which have a constraint expression defined or which have a default expression defined. The schema is It's possible to obtain a consolidated recordset for all properties of all DB columns using The Name column is the column name in TableName. The table __Index lists all indices in the DB. The schema is The IsUnique columns reflects if the index was created using the optional UNIQUE clause. This table is virtual. Built-in functions are predeclared. The built-in aggregate function avg returns the average of values of an expression. Avg ignores NULL values, but returns NULL if all values of a column are NULL or if avg is applied to an empty record set. The column values must be of a numeric type. The built-in function contains returns true if substr is within s. If any argument to contains is NULL the result is NULL. The built-in aggregate function count returns how many times an expression has a non NULL values or the number of rows in a record set. Note: count() returns 0 for an empty record set. For example Date returns the time corresponding to in the appropriate zone for that time in the given location. The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1. A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which. A location maps time instants to the zone in use at that time. Typically, the location represents the collection of time offsets in use in a geographical area, such as "CEST" and "CET" for central Europe. "local" represents the system's local time zone. "UTC" represents Universal Coordinated Time (UTC). The month specifies a month of the year (January = 1, ...). If any argument to date is NULL the result is NULL. The built-in function day returns the day of the month specified by t. If the argument to day is NULL the result is NULL. The built-in function formatTime returns a textual representation of the time value formatted according to layout, which defines the format by showing how the reference time, would be displayed if it were the value; it serves as an example of the desired output. The same display rules will then be applied to the time value. If any argument to formatTime is NULL the result is NULL. NOTE: The string value of the time zone, like "CET" or "ACDT", is dependent on the time zone of the machine the function is run on. For example, if the t value is in "CET", but the machine is in "ACDT", instead of "CET" the result is "+0100". This is the same what Go (time.Time).String() returns and in fact formatTime directly calls t.String(). returns on a machine in the CET time zone, but may return on a machine in the ACDT zone. The time value is in both cases the same so its ordering and comparing is correct. Only the display value can differ. The built-in functions formatFloat and formatInt format numbers to strings using go's number format functions in the `strconv` package. For all three functions, only the first argument is mandatory. The default values of the rest are shown in the examples. If the first argument is NULL, the result is NULL. returns returns returns Unlike the `strconv` equivalent, the formatInt function handles all integer types, both signed and unsigned. The built-in function hasPrefix tests whether the string s begins with prefix. If any argument to hasPrefix is NULL the result is NULL. The built-in function hasSuffix tests whether the string s ends with suffix. If any argument to hasSuffix is NULL the result is NULL. The built-in function hour returns the hour within the day specified by t, in the range [0, 23]. If the argument to hour is NULL the result is NULL. The built-in function hours returns the duration as a floating point number of hours. If the argument to hours is NULL the result is NULL. The built-in function id takes zero or one arguments. If no argument is provided, id() returns a table-unique automatically assigned numeric identifier of type int. Ids of deleted records are not reused unless the DB becomes completely empty (has no tables). For example If id() without arguments is called for a row which is not a table record then the result value is NULL. For example If id() has one argument it must be a table name of a table in a cross join. For example The built-in function len takes a string argument and returns the lentgh of the string in bytes. The expression len(s) is constant if s is a string constant. If the argument to len is NULL the result is NULL. The built-in aggregate function max returns the largest value of an expression in a record set. Max ignores NULL values, but returns NULL if all values of a column are NULL or if max is applied to an empty record set. The expression values must be of an ordered type. For example The built-in aggregate function min returns the smallest value of an expression in a record set. Min ignores NULL values, but returns NULL if all values of a column are NULL or if min is applied to an empty record set. For example The column values must be of an ordered type. The built-in function minute returns the minute offset within the hour specified by t, in the range [0, 59]. If the argument to minute is NULL the result is NULL. The built-in function minutes returns the duration as a floating point number of minutes. If the argument to minutes is NULL the result is NULL. The built-in function month returns the month of the year specified by t (January = 1, ...). If the argument to month is NULL the result is NULL. The built-in function nanosecond returns the nanosecond offset within the second specified by t, in the range [0, 999999999]. If the argument to nanosecond is NULL the result is NULL. The built-in function nanoseconds returns the duration as an integer nanosecond count. If the argument to nanoseconds is NULL the result is NULL. The built-in function now returns the current local time. The built-in function parseTime parses a formatted string and returns the time value it represents. The layout defines the format by showing how the reference time, would be interpreted if it were the value; it serves as an example of the input format. The same interpretation will then be made to the input string. Elements omitted from the value are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored. In the absence of a time zone indicator, parseTime returns a time in UTC. When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location, then parseTime uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset. When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parses and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset. If any argument to parseTime is NULL the result is NULL. The built-in function second returns the second offset within the minute specified by t, in the range [0, 59]. If the argument to second is NULL the result is NULL. The built-in function seconds returns the duration as a floating point number of seconds. If the argument to seconds is NULL the result is NULL. The built-in function since returns the time elapsed since t. It is shorthand for now()-t. If the argument to since is NULL the result is NULL. The built-in aggregate function sum returns the sum of values of an expression for all rows of a record set. Sum ignores NULL values, but returns NULL if all values of a column are NULL or if sum is applied to an empty record set. The column values must be of a numeric type. The built-in function timeIn returns t with the location information set to loc. For discussion of the loc argument please see date(). If any argument to timeIn is NULL the result is NULL. The built-in function weekday returns the day of the week specified by t. Sunday == 0, Monday == 1, ... If the argument to weekday is NULL the result is NULL. The built-in function year returns the year in which t occurs. If the argument to year is NULL the result is NULL. The built-in function yearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, and [1,366] in leap years. If the argument to yearDay is NULL the result is NULL. Three functions assemble and disassemble complex numbers. The built-in function complex constructs a complex value from a floating-point real and imaginary part, while real and imag extract the real and imaginary parts of a complex value. The type of the arguments and return value correspond. For complex, the two arguments must be of the same floating-point type and the return type is the complex type with the corresponding floating-point constituents: complex64 for float32, complex128 for float64. The real and imag functions together form the inverse, so for a complex value z, z == complex(real(z), imag(z)). If the operands of these functions are all constants, the return value is a constant. If any argument to any of complex, real, imag functions is NULL the result is NULL. For the numeric types, the following sizes are guaranteed Portions of this specification page are modifications based on work[2] created and shared by Google[3] and used according to terms described in the Creative Commons 3.0 Attribution License[4]. This specification is licensed under the Creative Commons Attribution 3.0 License, and code is licensed under a BSD license[5]. Links from the above documentation This section is not part of the specification. WARNING: The implementation of indices is new and it surely needs more time to become mature. Indices are used currently used only by the WHERE clause. The following expression patterns of 'WHERE expression' are recognized and trigger index use. The relOp is one of the relation operators <, <=, ==, >=, >. For the equality operator both operands must be of comparable types. For all other operators both operands must be of ordered types. The constant expression is a compile time constant expression. Some constant folding is still a TODO. Parameter is a QL parameter ($1 etc.). Consider tables t and u, both with an indexed field f. The WHERE expression doesn't comply with the above simple detected cases. However, such query is now automatically rewritten to which will use both of the indices. The impact of using the indices can be substantial (cf. BenchmarkCrossJoin*) if the resulting rows have low "selectivity", ie. only few rows from both tables are selected by the respective WHERE filtering. Note: Existing QL DBs can be used and indices can be added to them. However, once any indices are present in the DB, the old QL versions cannot work with such DB anymore. Running a benchmark with -v (-test.v) outputs information about the scale used to report records/s and a brief description of the benchmark. For example Running the full suite of benchmarks takes a lot of time. Use the -timeout flag to avoid them being killed after the default time limit (10 minutes).

Package telnet provides TELNET and TELNETS client and server implementations in a style similar to the "net/http" library that is part of the Go standard library, including support for "middleware"; TELNETS is secure TELNET, with the TELNET protocol over a secured TLS (or SSL) connection. ListenAndServe starts a (un-secure) TELNET server with a given address and handler. ListenAndServeTLS starts a (secure) TELNETS server with a given address and handler, using the specified "cert.pem" and "key.pem" files. Example TELNET Client: DialToAndCall creates a (un-secure) TELNET client, which connects to a given address using the specified caller. Example TELNETS Client: DialToAndCallTLS creates a (secure) TELNETS client, which connects to a given address using the specified caller. If you are communicating over the open Internet, you should be using (the secure) TELNETS protocol and ListenAndServeTLS. If you are communicating just on localhost, then using just (the un-secure) TELNET protocol and telnet.ListenAndServe may be OK. If you are not sure which to use, use TELNETS and ListenAndServeTLS. The previous 2 exaple servers were very very simple. Specifically, they just echoed back whatever you submitted to it. If you typed: ... it would send back: (Exactly the same data you sent it.) A more useful TELNET server can be made using the "github.com/reiver/go-telnet/telsh" sub-package. The `telsh` sub-package provides "middleware" that enables you to create a "shell" interface (also called a "command line interface" or "CLI") which most people would expect when using TELNET OR TELNETS. For example: Note that in the example, so far, we have registered 2 commands: `date` and `animate`. For this to actually work, we need to have code for the `date` and `animate` commands. The actual implemenation for the `date` command could be done like the following: Note that your "real" work is in the `dateHandlerFunc` func. And the actual implementation for the `animate` command could be done as follows: Again, note that your "real" work is in the `animateHandlerFunc` func. If you are using the telnet.ListenAndServeTLS func or the telnet.Server.ListenAndServeTLS method, you will need to supply "cert.pem" and "key.pem" files. If you do not already have these files, the Go soure code contains a tool for generating these files for you. It can be found at: So, for example, if your `$GOROOT` is the "/usr/local/go" directory, then it would be at: If you run the command: ... then you get the help information for "generate_cert.go". Of course, you would replace or set `$GOROOT` with whatever your path actually is. Again, for example, if your `$GOROOT` is the "/usr/local/go" directory, then it would be: To demonstrate the usage of "generate_cert.go", you might run the following to generate certificates that were bound to the hosts `127.0.0.1` and `localhost`: If you are not sure where "generate_cert.go" is on your computer, on Linux and Unix based systems, you might be able to find the file with the command: (If it finds it, it should output the full path to this file.) You can make a simple (un-secure) TELNET client with code like the following: You can make a simple (secure) TELNETS client with code like the following: The TELNET protocol is best known for providing a means of connecting to a remote computer, using a (text-based) shell interface, and being able to interact with it, (more or less) as if you were sitting at that computer. (Shells are also known as command-line interfaces or CLIs.) Although this was the original usage of the TELNET protocol, it can be (and is) used for other purposes as well. The TELNET protocol came from an era in computing when text-based shell interface where the common way of interacting with computers. The common interface for computers during this era was a keyboard and a monochromatic (i.e., single color) text-based monitors called "video terminals". (The word "video" in that era of computing did not refer to things such as movies. But instead was meant to contrast it with paper. In particular, the teletype machines, which were typewriter like devices that had a keyboard, but instead of having a monitor had paper that was printed onto.) In that era, in the early days of office computers, it was rare that an individual would have a computer at their desk. (A single computer was much too expensive.) Instead, there would be a single central computer that everyone would share. The style of computer used (for the single central shared computer) was called a "mainframe". What individuals would have at their desks, instead of their own compuer, would be some type of video terminal. The different types of video terminals had named such as: • VT52 • VT100 • VT220 • VT240 ("VT" in those named was short for "video terminal".) To understand this era, we need to go back a bit in time to what came before it: teletypes. Terminal codes (also sometimes called 'terminal control codes') are used to issue various kinds of commands to the terminal. (Note that 'terminal control codes' are a completely separate concept for 'TELNET commands', and the two should NOT be conflated or confused.) The most common types of 'terminal codes' are the 'ANSI escape codes'. (Although there are other types too.) ANSI escape codes (also sometimes called 'ANSI escape sequences') are a common type of 'terminal code' used to do things such as: • moving the cursor, • erasing the display, • erasing the line, • setting the graphics mode, • setting the foregroup color, • setting the background color, • setting the screen resolution, and • setting keyboard strings. One of the abilities of ANSI escape codes is to set the foreground color. Here is a table showing codes for this: (Note that in the `[]byte` that the first `byte` is the number `27` (which is the "escape" character) where the third and fouth characters are the **not** number literals, but instead character literals `'3'` and whatever.) Another of the abilities of ANSI escape codes is to set the background color. (Note that in the `[]byte` that the first `byte` is the number `27` (which is the "escape" character) where the third and fouth characters are the **not** number literals, but instead character literals `'4'` and whatever.) In Go code, if I wanted to use an ANSI escape code to use a blue background, a white foreground, and bold, I could do that with the ANSI escape code: Note that that start with byte value 27, which we have encoded as hexadecimal as \x1b. Followed by the '[' character. Coming after that is the sub-string "44", which is the code that sets our background color to blue. We follow that with the ';' character (which separates codes). And the after that comes the sub-string "37", which is the code that set our foreground color to white. After that, we follow with another ";" character (which, again, separates codes). And then we follow it the sub-string "1", which is the code that makes things bold. And finally, the ANSI escape sequence is finished off with the 'm' character. To show this in a more complete example, our `dateHandlerFunc` from before could incorporate ANSI escape sequences as follows: Note that in that example, in addition to using the ANSI escape sequence "\x1b[44;37;1m" to set the background color to blue, set the foreground color to white, and make it bold, we also used the ANSI escape sequence "\x1b[0m" to reset the background and foreground colors and boldness back to "normal".

Package dataurl parses Data URL Schemes according to RFC 2397 (http://tools.ietf.org/html/rfc2397). Data URLs are small chunks of data commonly used in browsers to display inline data, typically like small images, or when you use the FileReader API of the browser. A dataurl looks like: Or, with base64 encoding: Common functions are Decode and DecodeString to obtain a DataURL, and DataURL.String() and DataURL.WriteTo to generate a Data URL string.

Package template implements data-driven templates for generating textual output. To generate HTML output, see package html/template, which has the same interface as this package but automatically secures HTML output against certain attacks. Templates are executed by applying them to a data structure. Annotations in the template refer to elements of the data structure (typically a field of a struct or a key in a map) to control execution and derive values to be displayed. Execution of the template walks the structure and sets the cursor, represented by a period '.' and called "dot", to the value at the current location in the structure as execution proceeds. The input text for a template is UTF-8-encoded text in any format. "Actions"--data evaluations or control structures--are delimited by "{{" and "}}"; all text outside actions is copied to the output unchanged. Actions may not span newlines, although comments can. Once parsed, a template may be executed safely in parallel. Here is a trivial example that prints "17 items are made of wool". More intricate examples appear below. Here is the list of actions. "Arguments" and "pipelines" are evaluations of data, defined in detail below. An argument is a simple value, denoted by one of the following. Arguments may evaluate to any type; if they are pointers the implementation automatically indirects to the base type when required. If an evaluation yields a function value, such as a function-valued field of a struct, the function is not invoked automatically, but it can be used as a truth value for an if action and the like. To invoke it, use the call function, defined below. A pipeline is a possibly chained sequence of "commands". A command is a simple value (argument) or a function or method call, possibly with multiple arguments: A pipeline may be "chained" by separating a sequence of commands with pipeline characters '|'. In a chained pipeline, the result of the each command is passed as the last argument of the following command. The output of the final command in the pipeline is the value of the pipeline. The output of a command will be either one value or two values, the second of which has type error. If that second value is present and evaluates to non-nil, execution terminates and the error is returned to the caller of Execute. A pipeline inside an action may initialize a variable to capture the result. The initialization has syntax where $variable is the name of the variable. An action that declares a variable produces no output. If a "range" action initializes a variable, the variable is set to the successive elements of the iteration. Also, a "range" may declare two variables, separated by a comma: in which case $index and $element are set to the successive values of the array/slice index or map key and element, respectively. Note that if there is only one variable, it is assigned the element; this is opposite to the convention in Go range clauses. A variable's scope extends to the "end" action of the control structure ("if", "with", or "range") in which it is declared, or to the end of the template if there is no such control structure. A template invocation does not inherit variables from the point of its invocation. When execution begins, $ is set to the data argument passed to Execute, that is, to the starting value of dot. Here are some example one-line templates demonstrating pipelines and variables. All produce the quoted word "output": During execution functions are found in two function maps: first in the template, then in the global function map. By default, no functions are defined in the template but the Funcs method can be used to add them. Predefined global functions are named as follows. The boolean functions take any zero value to be false and a non-zero value to be true. There is also a set of binary comparison operators defined as functions: For simpler multi-way equality tests, eq (only) accepts two or more arguments and compares the second and subsequent to the first, returning in effect (Unlike with || in Go, however, eq is a function call and all the arguments will be evaluated.) The comparison functions work on basic types only (or named basic types, such as "type Celsius float32"). They implement the Go rules for comparison of values, except that size and exact type are ignored, so any integer value, signed or unsigned, may be compared with any other integer value. (The arithmetic value is compared, not the bit pattern, so all negative integers are less than all unsigned integers.) However, as usual, one may not compare an int with a float32 and so on. Each template is named by a string specified when it is created. Also, each template is associated with zero or more other templates that it may invoke by name; such associations are transitive and form a name space of templates. A template may use a template invocation to instantiate another associated template; see the explanation of the "template" action above. The name must be that of a template associated with the template that contains the invocation. When parsing a template, another template may be defined and associated with the template being parsed. Template definitions must appear at the top level of the template, much like global variables in a Go program. The syntax of such definitions is to surround each template declaration with a "define" and "end" action. The define action names the template being created by providing a string constant. Here is a simple example: This defines two templates, T1 and T2, and a third T3 that invokes the other two when it is executed. Finally it invokes T3. If executed this template will produce the text By construction, a template may reside in only one association. If it's necessary to have a template addressable from multiple associations, the template definition must be parsed multiple times to create distinct *Template values, or must be copied with the Clone or AddParseTree method. Parse may be called multiple times to assemble the various associated templates; see the ParseFiles and ParseGlob functions and methods for simple ways to parse related templates stored in files. A template may be executed directly or through ExecuteTemplate, which executes an associated template identified by name. To invoke our example above, we might write, or to invoke a particular template explicitly by name,

Package goncurses is a new curses (ncurses) library for the Go programming language. It implements all the ncurses extension libraries: form, menu and panel. Minimal operation would consist of initializing the display: It is important to always call End() before your program exits. If you fail to do so, the terminal will not perform properly and will either need to be reset or restarted completely. CAUTION: Calls to ncurses functions are normally not atomic nor reentrant and therefore extreme care should be taken to ensure ncurses functions are not called concurrently. Specifically, never write data to the same window concurrently nor accept input and send output to the same window as both alter the underlying C data structures in a non safe manner. Ideally, you should structure your program to ensure all ncurses related calls happen in a single goroutine. This is probably most easily achieved via channels and Go's built-in select. Alternatively, or additionally, you can use a mutex to protect any calls in multiple goroutines from happening concurrently. Failure to do so will result in unpredictable and undefined behaviour in your program. The examples directory contains demonstrations of many of the capabilities goncurses can provide.

Package psgo is a ps (1) AIX-format compatible golang library extended with various descriptors useful for displaying container-related data. The idea behind the library is to provide an easy to use way of extracting process-related data, just as ps (1) does. The problem when using ps (1) is that the ps format strings split columns with whitespaces, making the output nearly impossible to parse. It also adds some jitter as we have to fork and execute ps either in the container or filter the output afterwards, further limiting applicability. Please visit https://github.com/containers/psgo for further details about supported format descriptors and to see some usage examples.

Package ql implements a pure Go embedded SQL database engine. Builder results available at QL is a member of the SQL family of languages. It is less complex and less powerful than SQL (whichever specification SQL is considered to be). 2020-12-10: sql/database driver now supports url parameter removeemptywal=N which has the same semantics as passing RemoveEmptyWAL = N != 0 to OpenFile options. 2020-11-09: Add IF NOT EXISTS support for the INSERT INTO statement. Add IsDuplicateUniqueIndexError function. 2018-11-04: Back end file format V2 is now released. To use the new format for newly created databases set the FileFormat field in *Options passed to OpenFile to value 2 or use the driver named "ql2" instead of "ql". - Both the old and new driver will properly open and use, read and write the old (V1) or new file (V2) format of an existing database. - V1 format has a record size limit of ~64 kB. V2 format record size limit is math.MaxInt32. - V1 format uncommitted transaction size is limited by memory resources. V2 format uncommitted transaction is limited by free disk space. - A direct consequence of the previous is that small transactions perform better using V1 format and big transactions perform better using V2 format. - V2 format uses substantially less memory. 2018-08-02: Release v1.2.0 adds initial support for Go modules. 2017-01-10: Release v1.1.0 fixes some bugs and adds a configurable WAL headroom. 2016-07-29: Release v1.0.6 enables alternatively using = instead of == for equality operation. 2016-07-11: Release v1.0.5 undoes vendoring of lldb. QL now uses stable lldb (modernc.org/lldb). 2016-07-06: Release v1.0.4 fixes a panic when closing the WAL file. 2016-04-03: Release v1.0.3 fixes a data race. 2016-03-23: Release v1.0.2 vendors gitlab.com/cznic/exp/lldb and github.com/camlistore/go4/lock. 2016-03-17: Release v1.0.1 adjusts for latest goyacc. Parser error messages are improved and changed, but their exact form is not considered a API change. 2016-03-05: The current version has been tagged v1.0.0. 2015-06-15: To improve compatibility with other SQL implementations, the count built-in aggregate function now accepts * as its argument. 2015-05-29: The execution planner was rewritten from scratch. It should use indices in all places where they were used before plus in some additional situations. It is possible to investigate the plan using the newly added EXPLAIN statement. The QL tool is handy for such analysis. If the planner would have used an index, but no such exists, the plan includes hints in form of copy/paste ready CREATE INDEX statements. The planner is still quite simple and a lot of work on it is yet ahead. You can help this process by filling an issue with a schema and query which fails to use an index or indices when it should, in your opinion. Bonus points for including output of `ql 'explain <query>'`. 2015-05-09: The grammar of the CREATE INDEX statement now accepts an expression list instead of a single expression, which was further limited to just a column name or the built-in id(). As a side effect, composite indices are now functional. However, the values in the expression-list style index are not yet used by other statements or the statement/query planner. The composite index is useful while having UNIQUE clause to check for semantically duplicate rows before they get added to the table or when such a row is mutated using the UPDATE statement and the expression-list style index tuple of the row is thus recomputed. 2015-05-02: The Schema field of table __Table now correctly reflects any column constraints and/or defaults. Also, the (*DB).Info method now has that information provided in new ColumInfo fields NotNull, Constraint and Default. 2015-04-20: Added support for {LEFT,RIGHT,FULL} [OUTER] JOIN. 2015-04-18: Column definitions can now have constraints and defaults. Details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. 2015-03-06: New built-in functions formatFloat and formatInt. Thanks urandom! (https://github.com/urandom) 2015-02-16: IN predicate now accepts a SELECT statement. See the updated "Predicates" section. 2015-01-17: Logical operators || and && have now alternative spellings: OR and AND (case insensitive). AND was a keyword before, but OR is a new one. This can possibly break existing queries. For the record, it's a good idea to not use any name appearing in, for example, [7] in your queries as the list of QL's keywords may expand for gaining better compatibility with existing SQL "standards". 2015-01-12: ACID guarantees were tightened at the cost of performance in some cases. The write collecting window mechanism, a formerly used implementation detail, was removed. Inserting rows one by one in a transaction is now slow. I mean very slow. Try to avoid inserting single rows in a transaction. Instead, whenever possible, perform batch updates of tens to, say thousands of rows in a single transaction. See also: http://www.sqlite.org/faq.html#q19, the discussed synchronization principles involved are the same as for QL, modulo minor details. Note: A side effect is that closing a DB before exiting an application, both for the Go API and through database/sql driver, is no more required, strictly speaking. Beware that exiting an application while there is an open (uncommitted) transaction in progress means losing the transaction data. However, the DB will not become corrupted because of not closing it. Nor that was the case before, but formerly failing to close a DB could have resulted in losing the data of the last transaction. 2014-09-21: id() now optionally accepts a single argument - a table name. 2014-09-01: Added the DB.Flush() method and the LIKE pattern matching predicate. 2014-08-08: The built in functions max and min now accept also time values. Thanks opennota! (https://github.com/opennota) 2014-06-05: RecordSet interface extended by new methods FirstRow and Rows. 2014-06-02: Indices on id() are now used by SELECT statements. 2014-05-07: Introduction of Marshal, Schema, Unmarshal. 2014-04-15: Added optional IF NOT EXISTS clause to CREATE INDEX and optional IF EXISTS clause to DROP INDEX. 2014-04-12: The column Unique in the virtual table __Index was renamed to IsUnique because the old name is a keyword. Unfortunately, this is a breaking change, sorry. 2014-04-11: Introduction of LIMIT, OFFSET. 2014-04-10: Introduction of query rewriting. 2014-04-07: Introduction of indices. QL imports zappy[8], a block-based compressor, which speeds up its performance by using a C version of the compression/decompression algorithms. If a CGO-free (pure Go) version of QL, or an app using QL, is required, please include 'purego' in the -tags option of go {build,get,install}. For example: If zappy was installed before installing QL, it might be necessary to rebuild zappy first (or rebuild QL with all its dependencies using the -a option): The syntax is specified using Extended Backus-Naur Form (EBNF) Lower-case production names are used to identify lexical tokens. Non-terminals are in CamelCase. Lexical tokens are enclosed in double quotes "" or back quotes “. The form a … b represents the set of characters from a through b as alternatives. The horizontal ellipsis … is also used elsewhere in the spec to informally denote various enumerations or code snippets that are not further specified. QL source code is Unicode text encoded in UTF-8. The text is not canonicalized, so a single accented code point is distinct from the same character constructed from combining an accent and a letter; those are treated as two code points. For simplicity, this document will use the unqualified term character to refer to a Unicode code point in the source text. Each code point is distinct; for instance, upper and lower case letters are different characters. Implementation restriction: For compatibility with other tools, the parser may disallow the NUL character (U+0000) in the statement. Implementation restriction: A byte order mark is disallowed anywhere in QL statements. The following terms are used to denote specific character classes The underscore character _ (U+005F) is considered a letter. Lexical elements are comments, tokens, identifiers, keywords, operators and delimiters, integer, floating-point, imaginary, rune and string literals and QL parameters. Line comments start with the character sequence // or -- and stop at the end of the line. A line comment acts like a space. General comments start with the character sequence /* and continue through the character sequence */. A general comment acts like a space. Comments do not nest. Tokens form the vocabulary of QL. There are four classes: identifiers, keywords, operators and delimiters, and literals. White space, formed from spaces (U+0020), horizontal tabs (U+0009), carriage returns (U+000D), and newlines (U+000A), is ignored except as it separates tokens that would otherwise combine into a single token. The formal grammar uses semicolons ";" as separators of QL statements. A single QL statement or the last QL statement in a list of statements can have an optional semicolon terminator. (Actually a separator from the following empty statement.) Identifiers name entities such as tables or record set columns. There are two kinds of identifiers, normal idententifiers and quoted identifiers. An normal identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter. For example A quoted identifier is a string of any charaters between guillmets «». Quoted identifiers allow QL key words or phrases with spaces to be used as identifiers. The guillemets were chosen because QL already uses double quotes, single quotes, and backticks for other quoting purposes. «TRANSACTION» «duration» «lovely stories» No identifiers are predeclared, however note that no keyword can be used as a normal identifier. Identifiers starting with two underscores are used for meta data virtual tables names. For forward compatibility, users should generally avoid using any identifiers starting with two underscores. For example The following keywords are reserved and may not be used as identifiers. Keywords are not case sensitive. The following character sequences represent operators, delimiters, and other special tokens Operators consisting of more than one character are referred to by names in the rest of the documentation An integer literal is a sequence of digits representing an integer constant. An optional prefix sets a non-decimal base: 0 for octal, 0x or 0X for hexadecimal. In hexadecimal literals, letters a-f and A-F represent values 10 through 15. For example A floating-point literal is a decimal representation of a floating-point constant. It has an integer part, a decimal point, a fractional part, and an exponent part. The integer and fractional part comprise decimal digits; the exponent part is an e or E followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided. For example An imaginary literal is a decimal representation of the imaginary part of a complex constant. It consists of a floating-point literal or decimal integer followed by the lower-case letter i. For example A rune literal represents a rune constant, an integer value identifying a Unicode code point. A rune literal is expressed as one or more characters enclosed in single quotes. Within the quotes, any character may appear except single quote and newline. A single quoted character represents the Unicode value of the character itself, while multi-character sequences beginning with a backslash encode values in various formats. The simplest form represents the single character within the quotes; since QL statements are Unicode characters encoded in UTF-8, multiple UTF-8-encoded bytes may represent a single integer value. For instance, the literal 'a' holds a single byte representing a literal a, Unicode U+0061, value 0x61, while 'ä' holds two bytes (0xc3 0xa4) representing a literal a-dieresis, U+00E4, value 0xe4. Several backslash escapes allow arbitrary values to be encoded as ASCII text. There are four ways to represent the integer value as a numeric constant: \x followed by exactly two hexadecimal digits; \u followed by exactly four hexadecimal digits; \U followed by exactly eight hexadecimal digits, and a plain backslash \ followed by exactly three octal digits. In each case the value of the literal is the value represented by the digits in the corresponding base. Although these representations all result in an integer, they have different valid ranges. Octal escapes must represent a value between 0 and 255 inclusive. Hexadecimal escapes satisfy this condition by construction. The escapes \u and \U represent Unicode code points so within them some values are illegal, in particular those above 0x10FFFF and surrogate halves. After a backslash, certain single-character escapes represent special values All other sequences starting with a backslash are illegal inside rune literals. For example A string literal represents a string constant obtained from concatenating a sequence of characters. There are two forms: raw string literals and interpreted string literals. Raw string literals are character sequences between back quotes “. Within the quotes, any character is legal except back quote. The value of a raw string literal is the string composed of the uninterpreted (implicitly UTF-8-encoded) characters between the quotes; in particular, backslashes have no special meaning and the string may contain newlines. Carriage returns inside raw string literals are discarded from the raw string value. Interpreted string literals are character sequences between double quotes "". The text between the quotes, which may not contain newlines, forms the value of the literal, with backslash escapes interpreted as they are in rune literals (except that \' is illegal and \" is legal), with the same restrictions. The three-digit octal (\nnn) and two-digit hexadecimal (\xnn) escapes represent individual bytes of the resulting string; all other escapes represent the (possibly multi-byte) UTF-8 encoding of individual characters. Thus inside a string literal \377 and \xFF represent a single byte of value 0xFF=255, while ÿ, \u00FF, \U000000FF and \xc3\xbf represent the two bytes 0xc3 0xbf of the UTF-8 encoding of character U+00FF. For example These examples all represent the same string If the statement source represents a character as two code points, such as a combining form involving an accent and a letter, the result will be an error if placed in a rune literal (it is not a single code point), and will appear as two code points if placed in a string literal. Literals are assigned their values from the respective text representation at "compile" (parse) time. QL parameters provide the same functionality as literals, but their value is assigned at execution time from an expression list passed to DB.Run or DB.Execute. Using '?' or '$' is completely equivalent. For example Keywords 'false' and 'true' (not case sensitive) represent the two possible constant values of type bool (also not case sensitive). Keyword 'NULL' (not case sensitive) represents an untyped constant which is assignable to any type. NULL is distinct from any other value of any type. A type determines the set of values and operations specific to values of that type. A type is specified by a type name. Named instances of the boolean, numeric, and string types are keywords. The names are not case sensitive. Note: The blob type is exchanged between the back end and the API as []byte. On 32 bit platforms this limits the size which the implementation can handle to 2G. A boolean type represents the set of Boolean truth values denoted by the predeclared constants true and false. The predeclared boolean type is bool. A duration type represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years. A numeric type represents sets of integer or floating-point values. The predeclared architecture-independent numeric types are The value of an n-bit integer is n bits wide and represented using two's complement arithmetic. Conversions are required when different numeric types are mixed in an expression or assignment. A string type represents the set of string values. A string value is a (possibly empty) sequence of bytes. The case insensitive keyword for the string type is 'string'. The length of a string (its size in bytes) can be discovered using the built-in function len. A time type represents an instant in time with nanosecond precision. Each time has associated with it a location, consulted when computing the presentation form of the time. The following functions are implicitly declared An expression specifies the computation of a value by applying operators and functions to operands. Operands denote the elementary values in an expression. An operand may be a literal, a (possibly qualified) identifier denoting a constant or a function or a table/record set column, or a parenthesized expression. A qualified identifier is an identifier qualified with a table/record set name prefix. For example Primary expression are the operands for unary and binary expressions. For example A primary expression of the form denotes the element of a string indexed by x. Its type is byte. The value x is called the index. The following rules apply - The index x must be of integer type except bigint or duration; it is in range if 0 <= x < len(s), otherwise it is out of range. - A constant index must be non-negative and representable by a value of type int. - A constant index must be in range if the string a is a literal. - If x is out of range at run time, a run-time error occurs. - s[x] is the byte at index x and the type of s[x] is byte. If s is NULL or x is NULL then the result is NULL. Otherwise s[x] is illegal. For a string, the primary expression constructs a substring. The indices low and high select which elements appear in the result. The result has indices starting at 0 and length equal to high - low. For convenience, any of the indices may be omitted. A missing low index defaults to zero; a missing high index defaults to the length of the sliced operand The indices low and high are in range if 0 <= low <= high <= len(a), otherwise they are out of range. A constant index must be non-negative and representable by a value of type int. If both indices are constant, they must satisfy low <= high. If the indices are out of range at run time, a run-time error occurs. Integer values of type bigint or duration cannot be used as indices. If s is NULL the result is NULL. If low or high is not omitted and is NULL then the result is NULL. Given an identifier f denoting a predeclared function, calls f with arguments a1, a2, … an. Arguments are evaluated before the function is called. The type of the expression is the result type of f. In a function call, the function value and arguments are evaluated in the usual order. After they are evaluated, the parameters of the call are passed by value to the function and the called function begins execution. The return value of the function is passed by value when the function returns. Calling an undefined function causes a compile-time error. Operators combine operands into expressions. Comparisons are discussed elsewhere. For other binary operators, the operand types must be identical unless the operation involves shifts or untyped constants. For operations involving constants only, see the section on constant expressions. Except for shift operations, if one operand is an untyped constant and the other operand is not, the constant is converted to the type of the other operand. The right operand in a shift expression must have unsigned integer type or be an untyped constant that can be converted to unsigned integer type. If the left operand of a non-constant shift expression is an untyped constant, the type of the constant is what it would be if the shift expression were replaced by its left operand alone. Expressions of the form yield a boolean value true if expr2, a regular expression, matches expr1 (see also [6]). Both expression must be of type string. If any one of the expressions is NULL the result is NULL. Predicates are special form expressions having a boolean result type. Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be comparable as defined in "Comparison operators". Another form of the IN predicate creates the expression list from a result of a SelectStmt. The SelectStmt must select only one column. The produced expression list is resource limited by the memory available to the process. NULL values produced by the SelectStmt are ignored, but if all records of the SelectStmt are NULL the predicate yields NULL. The select statement is evaluated only once. If the type of expr is not the same as the type of the field returned by the SelectStmt then the set operation yields false. The type of the column returned by the SelectStmt must be one of the simple (non blob-like) types: Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be ordered as defined in "Comparison operators". Expressions of the form yield a boolean value true if expr does not have a specific type (case A) or if expr has a specific type (case B). In other cases the result is a boolean value false. Unary operators have the highest precedence. There are five precedence levels for binary operators. Multiplication operators bind strongest, followed by addition operators, comparison operators, && (logical AND), and finally || (logical OR) Binary operators of the same precedence associate from left to right. For instance, x / y * z is the same as (x / y) * z. Note that the operator precedence is reflected explicitly by the grammar. Arithmetic operators apply to numeric values and yield a result of the same type as the first operand. The four standard arithmetic operators (+, -, *, /) apply to integer, rational, floating-point, and complex types; + also applies to strings; +,- also applies to times. All other arithmetic operators apply to integers only. sum integers, rationals, floats, complex values, strings difference integers, rationals, floats, complex values, times product integers, rationals, floats, complex values / quotient integers, rationals, floats, complex values % remainder integers & bitwise AND integers | bitwise OR integers ^ bitwise XOR integers &^ bit clear (AND NOT) integers << left shift integer << unsigned integer >> right shift integer >> unsigned integer Strings can be concatenated using the + operator String addition creates a new string by concatenating the operands. A value of type duration can be added to or subtracted from a value of type time. Times can subtracted from each other producing a value of type duration. For two integer values x and y, the integer quotient q = x / y and remainder r = x % y satisfy the following relationships with x / y truncated towards zero ("truncated division"). As an exception to this rule, if the dividend x is the most negative value for the int type of x, the quotient q = x / -1 is equal to x (and r = 0). If the divisor is a constant expression, it must not be zero. If the divisor is zero at run time, a run-time error occurs. If the dividend is non-negative and the divisor is a constant power of 2, the division may be replaced by a right shift, and computing the remainder may be replaced by a bitwise AND operation The shift operators shift the left operand by the shift count specified by the right operand. They implement arithmetic shifts if the left operand is a signed integer and logical shifts if it is an unsigned integer. There is no upper limit on the shift count. Shifts behave as if the left operand is shifted n times by 1 for a shift count of n. As a result, x << 1 is the same as x*2 and x >> 1 is the same as x/2 but truncated towards negative infinity. For integer operands, the unary operators +, -, and ^ are defined as follows For floating-point and complex numbers, +x is the same as x, while -x is the negation of x. The result of a floating-point or complex division by zero is not specified beyond the IEEE-754 standard; whether a run-time error occurs is implementation-specific. Whenever any operand of any arithmetic operation, unary or binary, is NULL, as well as in the case of the string concatenating operation, the result is NULL. For unsigned integer values, the operations +, -, *, and << are computed modulo 2n, where n is the bit width of the unsigned integer's type. Loosely speaking, these unsigned integer operations discard high bits upon overflow, and expressions may rely on “wrap around”. For signed integers with a finite bit width, the operations +, -, *, and << may legally overflow and the resulting value exists and is deterministically defined by the signed integer representation, the operation, and its operands. No exception is raised as a result of overflow. An evaluator may not optimize an expression under the assumption that overflow does not occur. For instance, it may not assume that x < x + 1 is always true. Integers of type bigint and rationals do not overflow but their handling is limited by the memory resources available to the program. Comparison operators compare two operands and yield a boolean value. In any comparison, the first operand must be of same type as is the second operand, or vice versa. The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows - Boolean values are comparable. Two boolean values are equal if they are either both true or both false. - Complex values are comparable. Two complex values u and v are equal if both real(u) == real(v) and imag(u) == imag(v). - Integer values are comparable and ordered, in the usual way. Note that durations are integers. - Floating point values are comparable and ordered, as defined by the IEEE-754 standard. - Rational values are comparable and ordered, in the usual way. - String and Blob values are comparable and ordered, lexically byte-wise. - Time values are comparable and ordered. Whenever any operand of any comparison operation is NULL, the result is NULL. Note that slices are always of type string. Logical operators apply to boolean values and yield a boolean result. The right operand is evaluated conditionally. The truth tables for logical operations with NULL values Conversions are expressions of the form T(x) where T is a type and x is an expression that can be converted to type T. A constant value x can be converted to type T in any of these cases: - x is representable by a value of type T. - x is a floating-point constant, T is a floating-point type, and x is representable by a value of type T after rounding using IEEE 754 round-to-even rules. The constant T(x) is the rounded value. - x is an integer constant and T is a string type. The same rule as for non-constant x applies in this case. Converting a constant yields a typed constant as result. A non-constant value x can be converted to type T in any of these cases: - x has type T. - x's type and T are both integer or floating point types. - x's type and T are both complex types. - x is an integer, except bigint or duration, and T is a string type. Specific rules apply to (non-constant) conversions between numeric types or to and from a string type. These conversions may change the representation of x and incur a run-time cost. All other conversions only change the type but not the representation of x. A conversion of NULL to any type yields NULL. For the conversion of non-constant numeric values, the following rules apply 1. When converting between integer types, if the value is a signed integer, it is sign extended to implicit infinite precision; otherwise it is zero extended. It is then truncated to fit in the result type's size. For example, if v == uint16(0x10F0), then uint32(int8(v)) == 0xFFFFFFF0. The conversion always yields a valid value; there is no indication of overflow. 2. When converting a floating-point number to an integer, the fraction is discarded (truncation towards zero). 3. When converting an integer or floating-point number to a floating-point type, or a complex number to another complex type, the result value is rounded to the precision specified by the destination type. For instance, the value of a variable x of type float32 may be stored using additional precision beyond that of an IEEE-754 32-bit number, but float32(x) represents the result of rounding x's value to 32-bit precision. Similarly, x + 0.1 may use more than 32 bits of precision, but float32(x + 0.1) does not. In all non-constant conversions involving floating-point or complex values, if the result type cannot represent the value the conversion succeeds but the result value is implementation-dependent. 1. Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer. Values outside the range of valid Unicode code points are converted to "\uFFFD". 2. Converting a blob to a string type yields a string whose successive bytes are the elements of the blob. 3. Converting a value of a string type to a blob yields a blob whose successive elements are the bytes of the string. 4. Converting a value of a bigint type to a string yields a string containing the decimal decimal representation of the integer. 5. Converting a value of a string type to a bigint yields a bigint value containing the integer represented by the string value. A prefix of “0x” or “0X” selects base 16; the “0” prefix selects base 8, and a “0b” or “0B” prefix selects base 2. Otherwise the value is interpreted in base 10. An error occurs if the string value is not in any valid format. 6. Converting a value of a rational type to a string yields a string containing the decimal decimal representation of the rational in the form "a/b" (even if b == 1). 7. Converting a value of a string type to a bigrat yields a bigrat value containing the rational represented by the string value. The string can be given as a fraction "a/b" or as a floating-point number optionally followed by an exponent. An error occurs if the string value is not in any valid format. 8. Converting a value of a duration type to a string returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format using a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0, with no unit. 9. Converting a string value to a duration yields a duration represented by the string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h". 10. Converting a time value to a string returns the time formatted using the format string When evaluating the operands of an expression or of function calls, operations are evaluated in lexical left-to-right order. For example, in the evaluation of the function calls and evaluation of c happen in the order h(), i(), j(), c. Floating-point operations within a single expression are evaluated according to the associativity of the operators. Explicit parentheses affect the evaluation by overriding the default associativity. In the expression x + (y + z) the addition y + z is performed before adding x. Statements control execution. The empty statement does nothing. Alter table statements modify existing tables. With the ADD clause it adds a new column to the table. The column must not exist. With the DROP clause it removes an existing column from a table. The column must exist and it must be not the only (last) column of the table. IOW, there cannot be a table with no columns. For example When adding a column to a table with existing data, the constraint clause of the ColumnDef cannot be used. Adding a constrained column to an empty table is fine. Begin transactions statements introduce a new transaction level. Every transaction level must be eventually balanced by exactly one of COMMIT or ROLLBACK statements. Note that when a transaction is roll-backed because of a statement failure then no explicit balancing of the respective BEGIN TRANSACTION is statement is required nor permitted. Failure to properly balance any opened transaction level may cause dead locks and/or lose of data updated in the uppermost opened but never properly closed transaction level. For example A database cannot be updated (mutated) outside of a transaction. Statements requiring a transaction A database is effectively read only outside of a transaction. Statements not requiring a transaction The commit statement closes the innermost transaction nesting level. If that's the outermost level then the updates to the DB made by the transaction are atomically made persistent. For example Create index statements create new indices. Index is a named projection of ordered values of a table column to the respective records. As a special case the id() of the record can be indexed. Index name must not be the same as any of the existing tables and it also cannot be the same as of any column name of the table the index is on. For example Now certain SELECT statements may use the indices to speed up joins and/or to speed up record set filtering when the WHERE clause is used; or the indices might be used to improve the performance when the ORDER BY clause is present. The UNIQUE modifier requires the indexed values tuple to be index-wise unique or have all values NULL. The optional IF NOT EXISTS clause makes the statement a no operation if the index already exists. A simple index consists of only one expression which must be either a column name or the built-in id(). A more complex and more general index is one that consists of more than one expression or its single expression does not qualify as a simple index. In this case the type of all expressions in the list must be one of the non blob-like types. Note: Blob-like types are blob, bigint, bigrat, time and duration. Create table statements create new tables. A column definition declares the column name and type. Table names and column names are case sensitive. Neither a table or an index of the same name may exist in the DB. For example The optional IF NOT EXISTS clause makes the statement a no operation if the table already exists. The optional constraint clause has two forms. The first one is found in many SQL dialects. This form prevents the data in column DepartmentName to be NULL. The second form allows an arbitrary boolean expression to be used to validate the column. If the value of the expression is true then the validation succeeded. If the value of the expression is false or NULL then the validation fails. If the value of the expression is not of type bool an error occurs. The optional DEFAULT clause is an expression which, if present, is substituted instead of a NULL value when the colum is assigned a value. Note that the constraint and/or default expressions may refer to other columns by name: When a table row is inserted by the INSERT INTO statement or when a table row is updated by the UPDATE statement, the order of operations is as follows: 1. The new values of the affected columns are set and the values of all the row columns become the named values which can be referred to in default expressions evaluated in step 2. 2. If any row column value is NULL and the DEFAULT clause is present in the column's definition, the default expression is evaluated and its value is set as the respective column value. 3. The values, potentially updated, of row columns become the named values which can be referred to in constraint expressions evaluated during step 4. 4. All row columns which definition has the constraint clause present will have that constraint checked. If any constraint violation is detected, the overall operation fails and no changes to the table are made. Delete from statements remove rows from a table, which must exist. For example If the WHERE clause is not present then all rows are removed and the statement is equivalent to the TRUNCATE TABLE statement. Drop index statements remove indices from the DB. The index must exist. For example The optional IF EXISTS clause makes the statement a no operation if the index does not exist. Drop table statements remove tables from the DB. The table must exist. For example The optional IF EXISTS clause makes the statement a no operation if the table does not exist. Insert into statements insert new rows into tables. New rows come from literal data, if using the VALUES clause, or are a result of select statement. In the later case the select statement is fully evaluated before the insertion of any rows is performed, allowing to insert values calculated from the same table rows are to be inserted into. If the ColumnNameList part is omitted then the number of values inserted in the row must be the same as are columns in the table. If the ColumnNameList part is present then the number of values per row must be same as the same number of column names. All other columns of the record are set to NULL. The type of the value assigned to a column must be the same as is the column's type or the value must be NULL. If there exists an unique index that would make the insert statement fail, the optional IF NOT EXISTS turns the insert statement in such case into a no-op. For example If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. Explain statement produces a recordset consisting of lines of text which describe the execution plan of a statement, if any. For example, the QL tool treats the explain statement specially and outputs the joined lines: The explanation may aid in uderstanding how a statement/query would be executed and if indices are used as expected - or which indices may possibly improve the statement performance. The create index statements above were directly copy/pasted in the terminal from the suggestions provided by the filter recordset pipeline part returned by the explain statement. If the statement has nothing special in its plan, the result is the original statement. To get an explanation of the select statement of the IN predicate, use the EXPLAIN statement with that particular select statement. The rollback statement closes the innermost transaction nesting level discarding any updates to the DB made by it. If that's the outermost level then the effects on the DB are as if the transaction never happened. For example The (temporary) record set from the last statement is returned and can be processed by the client. In this case the rollback is the same as 'DROP TABLE tmp;' but it can be a more complex operation. Select from statements produce recordsets. The optional DISTINCT modifier ensures all rows in the result recordset are unique. Either all of the resulting fields are returned ('*') or only those named in FieldList. RecordSetList is a list of table names or parenthesized select statements, optionally (re)named using the AS clause. The result can be filtered using a WhereClause and orderd by the OrderBy clause. For example If Recordset is a nested, parenthesized SelectStmt then it must be given a name using the AS clause if its field are to be accessible in expressions. A field is an named expression. Identifiers, not used as a type in conversion or a function name in the Call clause, denote names of (other) fields, values of which should be used in the expression. The expression can be named using the AS clause. If the AS clause is not present and the expression consists solely of a field name, then that field name is used as the name of the resulting field. Otherwise the field is unnamed. For example The SELECT statement can optionally enumerate the desired/resulting fields in a list. No two identical field names can appear in the list. When more than one record set is used in the FROM clause record set list, the result record set field names are rewritten to be qualified using the record set names. If a particular record set doesn't have a name, its respective fields became unnamed. The optional JOIN clause, for example is mostly equal to except that the rows from a which, when they appear in the cross join, never made expr to evaluate to true, are combined with a virtual row from b, containing all nulls, and added to the result set. For the RIGHT JOIN variant the discussed rules are used for rows from b not satisfying expr == true and the virtual, all-null row "comes" from a. The FULL JOIN adds the respective rows which would be otherwise provided by the separate executions of the LEFT JOIN and RIGHT JOIN variants. For more thorough OUTER JOIN discussion please see the Wikipedia article at [10]. Resultins rows of a SELECT statement can be optionally ordered by the ORDER BY clause. Collating proceeds by considering the expressions in the expression list left to right until a collating order is determined. Any possibly remaining expressions are not evaluated. All of the expression values must yield an ordered type or NULL. Ordered types are defined in "Comparison operators". Collating of elements having a NULL value is different compared to what the comparison operators yield in expression evaluation (NULL result instead of a boolean value). Below, T denotes a non NULL value of any QL type. NULL collates before any non NULL value (is considered smaller than T). Two NULLs have no collating order (are considered equal). The WHERE clause restricts records considered by some statements, like SELECT FROM, DELETE FROM, or UPDATE. It is an error if the expression evaluates to a non null value of non bool type. Another form of the WHERE clause is an existence predicate of a parenthesized select statement. The EXISTS form evaluates to true if the parenthesized SELECT statement produces a non empty record set. The NOT EXISTS form evaluates to true if the parenthesized SELECT statement produces an empty record set. The parenthesized SELECT statement is evaluated only once (TODO issue #159). The GROUP BY clause is used to project rows having common values into a smaller set of rows. For example Using the GROUP BY without any aggregate functions in the selected fields is in certain cases equal to using the DISTINCT modifier. The last two examples above produce the same resultsets. The optional OFFSET clause allows to ignore first N records. For example The above will produce only rows 11, 12, ... of the record set, if they exist. The value of the expression must a non negative integer, but not bigint or duration. The optional LIMIT clause allows to ignore all but first N records. For example The above will return at most the first 10 records of the record set. The value of the expression must a non negative integer, but not bigint or duration. The LIMIT and OFFSET clauses can be combined. For example Considering table t has, say 10 records, the above will produce only records 4 - 8. After returning record #8, no more result rows/records are computed. 1. The FROM clause is evaluated, producing a Cartesian product of its source record sets (tables or nested SELECT statements). 2. If present, the JOIN cluase is evaluated on the result set of the previous evaluation and the recordset specified by the JOIN clause. (... JOIN Recordset ON ...) 3. If present, the WHERE clause is evaluated on the result set of the previous evaluation. 4. If present, the GROUP BY clause is evaluated on the result set of the previous evaluation(s). 5. The SELECT field expressions are evaluated on the result set of the previous evaluation(s). 6. If present, the DISTINCT modifier is evaluated on the result set of the previous evaluation(s). 7. If present, the ORDER BY clause is evaluated on the result set of the previous evaluation(s). 8. If present, the OFFSET clause is evaluated on the result set of the previous evaluation(s). The offset expression is evaluated once for the first record produced by the previous evaluations. 9. If present, the LIMIT clause is evaluated on the result set of the previous evaluation(s). The limit expression is evaluated once for the first record produced by the previous evaluations. Truncate table statements remove all records from a table. The table must exist. For example Update statements change values of fields in rows of a table. For example Note: The SET clause is optional. If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. To allow to query for DB meta data, there exist specially named tables, some of them being virtual. Note: Virtual system tables may have fake table-wise unique but meaningless and unstable record IDs. Do not apply the built-in id() to any system table. The table __Table lists all tables in the DB. The schema is The Schema column returns the statement to (re)create table Name. This table is virtual. The table __Colum lists all columns of all tables in the DB. The schema is The Ordinal column defines the 1-based index of the column in the record. This table is virtual. The table __Colum2 lists all columns of all tables in the DB which have the constraint NOT NULL or which have a constraint expression defined or which have a default expression defined. The schema is It's possible to obtain a consolidated recordset for all properties of all DB columns using The Name column is the column name in TableName. The table __Index lists all indices in the DB. The schema is The IsUnique columns reflects if the index was created using the optional UNIQUE clause. This table is virtual. Built-in functions are predeclared. The built-in aggregate function avg returns the average of values of an expression. Avg ignores NULL values, but returns NULL if all values of a column are NULL or if avg is applied to an empty record set. The column values must be of a numeric type. The built-in function coalesce takes at least one argument and returns the first of its arguments which is not NULL. If all arguments are NULL, this function returns NULL. This is useful for providing defaults for NULL values in a select query. The built-in function contains returns true if substr is within s. If any argument to contains is NULL the result is NULL. The built-in aggregate function count returns how many times an expression has a non NULL values or the number of rows in a record set. Note: count() returns 0 for an empty record set. For example Date returns the time corresponding to in the appropriate zone for that time in the given location. The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1. A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which. A location maps time instants to the zone in use at that time. Typically, the location represents the collection of time offsets in use in a geographical area, such as "CEST" and "CET" for central Europe. "local" represents the system's local time zone. "UTC" represents Universal Coordinated Time (UTC). The month specifies a month of the year (January = 1, ...). If any argument to date is NULL the result is NULL. The built-in function day returns the day of the month specified by t. If the argument to day is NULL the result is NULL. The built-in function formatTime returns a textual representation of the time value formatted according to layout, which defines the format by showing how the reference time, would be displayed if it were the value; it serves as an example of the desired output. The same display rules will then be applied to the time value. If any argument to formatTime is NULL the result is NULL. NOTE: The string value of the time zone, like "CET" or "ACDT", is dependent on the time zone of the machine the function is run on. For example, if the t value is in "CET", but the machine is in "ACDT", instead of "CET" the result is "+0100". This is the same what Go (time.Time).String() returns and in fact formatTime directly calls t.String(). returns on a machine in the CET time zone, but may return on a machine in the ACDT zone. The time value is in both cases the same so its ordering and comparing is correct. Only the display value can differ. The built-in functions formatFloat and formatInt format numbers to strings using go's number format functions in the `strconv` package. For all three functions, only the first argument is mandatory. The default values of the rest are shown in the examples. If the first argument is NULL, the result is NULL. returns returns returns Unlike the `strconv` equivalent, the formatInt function handles all integer types, both signed and unsigned. The built-in function hasPrefix tests whether the string s begins with prefix. If any argument to hasPrefix is NULL the result is NULL. The built-in function hasSuffix tests whether the string s ends with suffix. If any argument to hasSuffix is NULL the result is NULL. The built-in function hour returns the hour within the day specified by t, in the range [0, 23]. If the argument to hour is NULL the result is NULL. The built-in function hours returns the duration as a floating point number of hours. If the argument to hours is NULL the result is NULL. The built-in function id takes zero or one arguments. If no argument is provided, id() returns a table-unique automatically assigned numeric identifier of type int. Ids of deleted records are not reused unless the DB becomes completely empty (has no tables). For example If id() without arguments is called for a row which is not a table record then the result value is NULL. For example If id() has one argument it must be a table name of a table in a cross join. For example The built-in function len takes a string argument and returns the lentgh of the string in bytes. The expression len(s) is constant if s is a string constant. If the argument to len is NULL the result is NULL. The built-in aggregate function max returns the largest value of an expression in a record set. Max ignores NULL values, but returns NULL if all values of a column are NULL or if max is applied to an empty record set. The expression values must be of an ordered type. For example The built-in aggregate function min returns the smallest value of an expression in a record set. Min ignores NULL values, but returns NULL if all values of a column are NULL or if min is applied to an empty record set. For example The column values must be of an ordered type. The built-in function minute returns the minute offset within the hour specified by t, in the range [0, 59]. If the argument to minute is NULL the result is NULL. The built-in function minutes returns the duration as a floating point number of minutes. If the argument to minutes is NULL the result is NULL. The built-in function month returns the month of the year specified by t (January = 1, ...). If the argument to month is NULL the result is NULL. The built-in function nanosecond returns the nanosecond offset within the second specified by t, in the range [0, 999999999]. If the argument to nanosecond is NULL the result is NULL. The built-in function nanoseconds returns the duration as an integer nanosecond count. If the argument to nanoseconds is NULL the result is NULL. The built-in function now returns the current local time. The built-in function parseTime parses a formatted string and returns the time value it represents. The layout defines the format by showing how the reference time, would be interpreted if it were the value; it serves as an example of the input format. The same interpretation will then be made to the input string. Elements omitted from the value are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored. In the absence of a time zone indicator, parseTime returns a time in UTC. When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location, then parseTime uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset. When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parses and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset. If any argument to parseTime is NULL the result is NULL. The built-in function second returns the second offset within the minute specified by t, in the range [0, 59]. If the argument to second is NULL the result is NULL. The built-in function seconds returns the duration as a floating point number of seconds. If the argument to seconds is NULL the result is NULL. The built-in function since returns the time elapsed since t. It is shorthand for now()-t. If the argument to since is NULL the result is NULL. The built-in aggregate function sum returns the sum of values of an expression for all rows of a record set. Sum ignores NULL values, but returns NULL if all values of a column are NULL or if sum is applied to an empty record set. The column values must be of a numeric type. The built-in function timeIn returns t with the location information set to loc. For discussion of the loc argument please see date(). If any argument to timeIn is NULL the result is NULL. The built-in function weekday returns the day of the week specified by t. Sunday == 0, Monday == 1, ... If the argument to weekday is NULL the result is NULL. The built-in function year returns the year in which t occurs. If the argument to year is NULL the result is NULL. The built-in function yearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, and [1,366] in leap years. If the argument to yearDay is NULL the result is NULL. Three functions assemble and disassemble complex numbers. The built-in function complex constructs a complex value from a floating-point real and imaginary part, while real and imag extract the real and imaginary parts of a complex value. The type of the arguments and return value correspond. For complex, the two arguments must be of the same floating-point type and the return type is the complex type with the corresponding floating-point constituents: complex64 for float32, complex128 for float64. The real and imag functions together form the inverse, so for a complex value z, z == complex(real(z), imag(z)). If the operands of these functions are all constants, the return value is a constant. If any argument to any of complex, real, imag functions is NULL the result is NULL. For the numeric types, the following sizes are guaranteed Portions of this specification page are modifications based on work[2] created and shared by Google[3] and used according to terms described in the Creative Commons 3.0 Attribution License[4]. This specification is licensed under the Creative Commons Attribution 3.0 License, and code is licensed under a BSD license[5]. Links from the above documentation This section is not part of the specification. WARNING: The implementation of indices is new and it surely needs more time to become mature. Indices are used currently used only by the WHERE clause. The following expression patterns of 'WHERE expression' are recognized and trigger index use. The relOp is one of the relation operators <, <=, ==, >=, >. For the equality operator both operands must be of comparable types. For all other operators both operands must be of ordered types. The constant expression is a compile time constant expression. Some constant folding is still a TODO. Parameter is a QL parameter ($1 etc.). Consider tables t and u, both with an indexed field f. The WHERE expression doesn't comply with the above simple detected cases. However, such query is now automatically rewritten to which will use both of the indices. The impact of using the indices can be substantial (cf. BenchmarkCrossJoin*) if the resulting rows have low "selectivity", ie. only few rows from both tables are selected by the respective WHERE filtering. Note: Existing QL DBs can be used and indices can be added to them. However, once any indices are present in the DB, the old QL versions cannot work with such DB anymore. Running a benchmark with -v (-test.v) outputs information about the scale used to report records/s and a brief description of the benchmark. For example Running the full suite of benchmarks takes a lot of time. Use the -timeout flag to avoid them being killed after the default time limit (10 minutes).

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Stop() function is called or when Ctrl-C is pressed. If we have a primitive which consumes key presses, we call the application's SetFocus() function to redirect all key presses to that primitive. Most primitives then offer ways to install handlers that allow you to react to any actions performed on them. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, colors are specified using the tcell.Color type. Functions such as tcell.GetColor(), tcell.NewHexColor(), and tcell.NewRGBColor() can be used to create colors from W3C color names or RGB values. Almost all strings which are displayed can contain color tags. Color tags are W3C color names or six hexadecimal digits following a hash tag, wrapped in square brackets. Examples: A color tag changes the color of the characters following that color tag. This applies to almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. Color tags may contain not just the foreground (text) color but also the background color and additional flags. In fact, the full definition of a color tag is as follows: Each of the three fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered color tags.) Colors that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags (some flags may not be supported by your terminal): Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. This package supports unicode characters including wide characters. Many functions in this package are not thread-safe. For many applications, this may not be an issue: If your code makes changes in response to key events, it will execute in the main goroutine and thus will not cause any race conditions. If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate() or Application.QueueUpdateDraw() (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw() from any goroutine without having to wrap it in QueueUpdate(). And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use QueueUpdate() as that may lead to deadlocks. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. All widgets also implement the Primitive interface. The tview package is based on https://github.com/derailed/tcell. It uses types and constants from that package (e.g. colors and keyboard values). This package does not process mouse input (yet).

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Stop() function is called or when Ctrl-C is pressed. If we have a primitive which consumes key presses, we call the application's SetFocus() function to redirect all key presses to that primitive. Most primitives then offer ways to install handlers that allow you to react to any actions performed on them. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, colors are specified using the tcell.Color type. Functions such as tcell.GetColor(), tcell.NewHexColor(), and tcell.NewRGBColor() can be used to create colors from W3C color names or RGB values. Almost all strings which are displayed can contain color tags. Color tags are W3C color names or six hexadecimal digits following a hash tag, wrapped in square brackets. Examples: A color tag changes the color of the characters following that color tag. This applies to almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. Color tags may contain not just the foreground (text) color but also the background color and additional flags. In fact, the full definition of a color tag is as follows: Each of the three fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered color tags.) Colors that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags (some flags may not be supported by your terminal): Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. This package supports unicode characters including wide characters. Many functions in this package are not thread-safe. For many applications, this may not be an issue: If your code makes changes in response to key events, it will execute in the main goroutine and thus will not cause any race conditions. If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate() or Application.QueueUpdateDraw() (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw() from any goroutine without having to wrap it in QueueUpdate(). And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use QueueUpdate() as that may lead to deadlocks. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. All widgets also implement the Primitive interface. There is also the Focusable interface which is used to override functions in subclassing types. The tview package is based on https://github.com/diamondburned/tcell. It uses types and constants from that package (e.g. colors and keyboard values). This package does not process mouse input (yet).

Package testscript provides support for defining filesystem-based tests by creating scripts in a directory. To invoke the tests, call testscript.Run. For example: A testscript directory holds test scripts with extension txtar or txt run during 'go test'. Each script defines a subtest; the exact set of allowable commands in a script are defined by the parameters passed to the Run function. To run a specific script foo.txtar or foo.txt, run where TestName is the name of the test that Run is called from. To define an executable command (or several) that can be run as part of the script, call RunMain with the functions that implement the command's functionality. The command functions will be called in a separate process, so are free to mutate global variables without polluting the top level test binary. In general script files should have short names: a few words, not whole sentences. The first word should be the general category of behavior being tested, often the name of a subcommand to be tested or a concept (vendor, pattern). Each script is a text archive (go doc golang.org/x/tools/txtar). The script begins with an actual command script to run followed by the content of zero or more supporting files to create in the script's temporary file system before it starts executing. As an example: Each script runs in a fresh temporary work directory tree, available to scripts as $WORK. Scripts also have access to these other environment variables: The environment variable $exe (lowercase) is an empty string on most systems, ".exe" on Windows. The script's supporting files are unpacked relative to $WORK and then the script begins execution in that directory as well. Thus the example above runs in $WORK with $WORK/hello.txtar containing the listed contents. The lines at the top of the script are a sequence of commands to be executed by a small script engine in the testscript package (not the system shell). The script stops and the overall test fails if any particular command fails. Each line is parsed into a sequence of space-separated command words, with environment variable expansion and # marking an end-of-line comment. Adding single quotes around text keeps spaces in that text from being treated as word separators and also disables environment variable expansion. Inside a single-quoted block of text, a repeated single quote indicates a literal single quote, as in: A line beginning with # is a comment and conventionally explains what is being done or tested at the start of a new phase in the script. A special form of environment variable syntax can be used to quote regexp metacharacters inside environment variables. The "@R" suffix is special, and indicates that the variable should be quoted. The command prefix ! indicates that the command on the rest of the line (typically go or a matching predicate) must fail, not succeed. Only certain commands support this prefix. They are indicated below by [!] in the synopsis. The command prefix [cond] indicates that the command on the rest of the line should only run when the condition is satisfied. The predefined conditions are: Any known values of GOOS and GOARCH can also be used as conditions. They will be satisfied if the target OS or architecture match the specified value. For example, the condition [darwin] is true if GOOS=darwin, and [amd64] is true if GOARCH=amd64. A condition can be negated: [!short] means to run the rest of the line when testing.Short() is false. Additional conditions can be added by passing a function to Params.Condition. The predefined commands are: cd dir Change to the given directory for future commands. chmod perm path... Change the permissions of the files or directories named by the path arguments to the given octal mode (000 to 777). [!] cmp file1 file2 Check that the named files have (or do not have) the same content. By convention, file1 is the actual data and file2 the expected data. File1 can be "stdout" or "stderr" to use the standard output or standard error from the most recent exec or wait command. (If the files have differing content and the command is not negated, the failure prints a diff.) [!] cmpenv file1 file2 Like cmp, but environment variables in file2 are substituted before the comparison. For example, $GOOS is replaced by the target GOOS. cp src... dst Copy the listed files to the target file or existing directory. src can include "stdout" or "stderr" to use the standard output or standard error from the most recent exec or go command. env [key=value...] With no arguments, print the environment (useful for debugging). Otherwise add the listed key=value pairs to the environment. [!] exec program [args...] [&] Run the given executable program with the arguments. It must (or must not) succeed. Note that 'exec' does not terminate the script (unlike in Unix shells). If the last token is '&', the program executes in the background. The standard output and standard error of the previous command is cleared, but the output of the background process is buffered — and checking of its exit status is delayed — until the next call to 'wait', 'skip', or 'stop' or the end of the test. At the end of the test, any remaining background processes are terminated using os.Interrupt (if supported) or os.Kill. If the last token is '&word&` (where "word" is alphanumeric), the command runs in the background but has a name, and can be waited for specifically by passing the word to 'wait'. Standard input can be provided using the stdin command; this will be cleared after exec has been called. [!] exists [-readonly] file... Each of the listed files or directories must (or must not) exist. If -readonly is given, the files or directories must be unwritable. [!] grep [-count=N] pattern file The file's content must (or must not) match the regular expression pattern. For positive matches, -count=N specifies an exact number of matches to require. mkdir path... Create the listed directories, if they do not already exists. mv path1 path2 Rename path1 to path2. OS-specific restrictions may apply when path1 and path2 are in different directories. rm file... Remove the listed files or directories. skip [message] Mark the test skipped, including the message if given. [!] stderr [-count=N] pattern Apply the grep command (see above) to the standard error from the most recent exec or wait command. stdin file Set the standard input for the next exec command to the contents of the given file. File can be "stdout" or "stderr" to use the standard output or standard error from the most recent exec or wait command. [!] stdout [-count=N] pattern Apply the grep command (see above) to the standard output from the most recent exec or wait command. stop [message] Stop the test early (marking it as passing), including the message if given. symlink file -> target Create file as a symlink to target. The -> (like in ls -l output) is required. wait [command] Wait for all 'exec' and 'go' commands started in the background (with the '&' token) to exit, and display success or failure status for them. After a call to wait, the 'stderr' and 'stdout' commands will apply to the concatenation of the corresponding streams of the background commands, in the order in which those commands were started. If an argument is specified, it waits for just that command. When TestScript runs a script and the script fails, by default TestScript shows the execution of the most recent phase of the script (since the last # comment) and only shows the # comments for earlier phases. For example, here is a multi-phase script with a bug in it (TODO: make this example less go-command specific): The bug is that the final phase installs p11 instead of p1. The test failure looks like: Note that the commands in earlier phases have been hidden, so that the relevant commands are more easily found, and the elapsed time for a completed phase is shown next to the phase heading. To see the entire execution, use "go test -v", which also adds an initial environment dump to the beginning of the log. Note also that in reported output, the actual name of the per-script temporary directory has been consistently replaced with the literal string $WORK. If Params.TestWork is true, it causes each test to log the name of its $WORK directory and other environment variable settings and also to leave that directory behind when it exits, for manual debugging of failing tests:

Package utter implements a deep pretty printer for Go data structures to aid data snapshotting. A quick overview of the additional features utter provides over the built-in printing facilities for Go data types are as follows: The approach utter allows for dumping Go data structures is less flexible than its parent tool. It has just a: This section demonstrates how to quickly get started with utter. See the sections below for further details on formatting and configuration options. To dump a variable with full newlines, indentation, type, and pointer information use Dump, Fdump, or Sdump: Configuration of utter is handled by fields in the ConfigState type. For convenience, all of the top-level functions use a global state available via the utter.Config global. It is also possible to create a ConfigState instance that provides methods equivalent to the top-level functions. This allows concurrent configuration options. See the ConfigState documentation for more details. The following configuration options are available: Indent String to use for each indentation level for Dump functions. It is a single space by default. A popular alternative is "\t". NumericWidth NumericWidth specifies the number of columns to use when dumping a numeric slice or array (including bool). Zero specifies all entries on one line. StringWidth StringWidth specifies the number of columns to use when dumping a string slice or array. Zero specifies all entries on one line. BytesWidth Number of byte columns to use when dumping byte slices and arrays. CommentBytes Specifies whether ASCII comment annotations are attached to byte slice and array dumps. CommentPointers CommentPointers specifies whether pointer information will be added as comments. IgnoreUnexported Specifies that unexported fields should be ignored. ElideType ElideType specifies that type information defined by context should not be printed in a dump. SortKeys Specifies map keys should be sorted before being printed. Use this to have a more deterministic, diffable output. Note that only native types (bool, int, uint, floats, uintptr and string) are supported with other types sorted according to the reflect.Value.String() output which guarantees display stability. Natural map order is used by default. Simply call utter.Dump with a list of variables you want to dump: You may also call utter.Fdump if you would prefer to output to an arbitrary io.Writer. For example, to dump to standard error: A third option is to call utter.Sdump to get the formatted output as a string: See the Dump example for details on the setup of the types and variables being shown here. Byte (and uint8) arrays and slices are displayed uniquely, similar to the hexdump -C command as shown.

Package cgi implements the common gateway interface (CGI) for Caddy, a modern, full-featured, easy-to-use web server. This plugin lets you generate dynamic content on your website by means of command line scripts. To collect information about the inbound HTTP request, your script examines certain environment variables such as PATH_INFO and QUERY_STRING. Then, to return a dynamically generated web page to the client, your script simply writes content to standard output. In the case of POST requests, your script reads additional inbound content from standard input. The advantage of CGI is that you do not need to fuss with server startup and persistence, long term memory management, sockets, and crash recovery. Your script is called when a request matches one of the patterns that you specify in your Caddyfile. As soon as your script completes its response, it terminates. This simplicity makes CGI a perfect complement to the straightforward operation and configuration of Caddy. The benefits of Caddy, including HTTPS by default, basic access authentication, and lots of middleware options extend easily to your CGI scripts. CGI has some disadvantages. For one, Caddy needs to start a new process for each request. This can adversely impact performance and, if resources are shared between CGI applications, may require the use of some interprocess synchronization mechanism such as a file lock. Your server’s responsiveness could in some circumstances be affected, such as when your web server is hit with very high demand, when your script’s dependencies require a long startup, or when concurrently running scripts take a long time to respond. However, in many cases, such as using a pre-compiled CGI application like fossil or a Lua script, the impact will generally be insignificant. Another restriction of CGI is that scripts will be run with the same permissions as Caddy itself. This can sometimes be less than ideal, for example when your script needs to read or write files associated with a different owner. Serving dynamic content exposes your server to more potential threats than serving static pages. There are a number of considerations of which you should be aware when using CGI applications. CGI SCRIPTS SHOULD BE LOCATED OUTSIDE OF CADDY’S DOCUMENT ROOT. Otherwise, an inadvertent misconfiguration could result in Caddy delivering the script as an ordinary static resource. At best, this could merely confuse the site visitor. At worst, it could expose sensitive internal information that should not leave the server. MISTRUST THE CONTENTS OF PATH_INFO, QUERY_STRING AND STANDARD INPUT. Most of the environment variables available to your CGI program are inherently safe because they originate with Caddy and cannot be modified by external users. This is not the case with PATH_INFO, QUERY_STRING and, in the case of POST actions, the contents of standard input. Be sure to validate and sanitize all inbound content. If you use a CGI library or framework to process your scripts, make sure you understand its limitations. An error in a CGI application is generally handled within the application itself and reported in the headers it returns. Additionally, if the Caddy errors directive is enabled, any content the application writes to its standard error stream will be written to the error log. This can be useful to diagnose problems with the execution of the CGI application. Your CGI application can be executed directly or indirectly. In the direct case, the application can be a compiled native executable or it can be a shell script that contains as its first line a shebang that identifies the interpreter to which the file’s name should be passed. Caddy must have permission to execute the application. On Posix systems this will mean making sure the application’s ownership and permission bits are set appropriately; on Windows, this may involve properly setting up the filename extension association. In the indirect case, the name of the CGI script is passed to an interpreter such as lua, perl or python. The basic cgi directive lets you associate a single pattern with a particular script. The directive can be repeated any reasonable number of times. Here is the basic syntax: For example: When a request such as https://example.com/report or https://example.com/report/weekly arrives, the cgi middleware will detect the match and invoke the script named /usr/local/cgi-bin/report. The current working directory will be the same as Caddy itself. Here, it is assumed that the script is self-contained, for example a pre-compiled CGI application or a shell script. Here is an example of a standalone script, similar to one used in the cgi plugin’s test suite: The environment variables PATH_INFO and QUERY_STRING are populated and passed to the script automatically. There are a number of other standard CGI variables included that are described below. If you need to pass any special environment variables or allow any environment variables that are part of Caddy’s process to pass to your script, you will need to use the advanced directive syntax described below. The values used for the script name and its arguments are subject to placeholder replacement. In addition to the standard Caddy placeholders such as {method} and {host}, the following placeholder substitutions are made: - {.} is replaced with Caddy’s current working directory - {match} is replaced with the portion of the request that satisfies the match directive - {root} is replaced with Caddy’s specified root directory You can include glob wildcards in your matches. Basically, an asterisk represents a sequence of zero or more non-slash characters and a question mark represents a single non-slash character. These wildcards can be used multiple times in a match expression. See the documentation for path/Match in the Go standard library for more details about glob matching. Here is an example directive: In this case, the cgi middleware will match requests such as https://example.com/report/weekly.lua and https://example.com/report/report.lua/weekly but not https://example.com/report.lua. The use of the asterisk expands to any character sequence within a directory. For example, if the request is made, the following command is executed: Note that the portion of the request that follows the match is not included. That information is conveyed to the script by means of environment variables. In this example, the Lua interpreter is invoked directly from Caddy, so the Lua script does not need the shebang that would be needed in a standalone script. This method facilitates the use of CGI on the Windows platform. In order to specify custom environment variables, pass along one or more environment variables known to Caddy, or specify more than one match pattern for a given rule, you will need to use the advanced directive syntax. That looks like this: For example, With the advanced syntax, the exec subdirective must appear exactly once. The match subdirective must appear at least once. The env, pass_env, empty_env, and except subdirectives can appear any reasonable number of times. pass_all_env, dir may appear once. The dir subdirective specifies the CGI executable’s working directory. If it is not specified, Caddy’s current working directory is used. The except subdirective uses the same pattern matching logic that is used with the match subdirective except that the request must match a rule fully; no request path prefix matching is performed. Any request that matches a match pattern is then checked with the patterns in except, if any. If any matches are made with the except pattern, the request is rejected and passed along to subsequent handlers. This is a convenient way to have static file resources served properly rather than being confused as CGI applications. The empty_env subdirective is used to pass one or more empty environment variables. Some CGI scripts may expect the server to pass certain empty variables rather than leaving them unset. This subdirective allows you to deal with those situations. The values associated with environment variable keys are all subject to placeholder substitution, just as with the script name and arguments. If your CGI application runs properly at the command line but fails to run from Caddy it is possible that certain environment variables may be missing. For example, the ruby gem loader evidently requires the HOME environment variable to be set; you can do this with the subdirective pass_env HOME. Another class of problematic applications require the COMPUTERNAME variable. The pass_all_env subdirective instructs Caddy to pass each environment variable it knows about to the CGI excutable. This addresses a common frustration that is caused when an executable requires an environment variable and fails without a descriptive error message when the variable cannot be found. These applications often run fine from the command prompt but fail when invoked with CGI. The risk with this subdirective is that a lot of server information is shared with the CGI executable. Use this subdirective only with CGI applications that you trust not to leak this information. If you protect your CGI application with the Caddy JWT middleware, your program will have access to the token’s payload claims by means of environment variables. For example, the following token claims will be available with the following environment variables All values are conveyed as strings, so some conversion may be necessary in your program. No placeholder substitutions are made on these values. If you run into unexpected results with the CGI plugin, you are able to examine the environment in which your CGI application runs. To enter inspection mode, add the subdirective inspect to your CGI configuration block. This is a development option that should not be used in production. When in inspection mode, the plugin will respond to matching requests with a page that displays variables of interest. In particular, it will show the replacement value of {match} and the environment variables to which your CGI application has access. For example, consider this example CGI block: When you request a matching URL, for example, the Caddy server will deliver a text page similar to the following. The CGI application (in this case, wapptclsh) will not be called. This information can be used to diagnose problems with how a CGI application is called. To return to operation mode, remove or comment out the inspect subdirective. In this example, the Caddyfile looks like this: Note that a request for /show gets mapped to a script named /usr/local/cgi-bin/report/gen. There is no need for any element of the script name to match any element of the match pattern. The contents of /usr/local/cgi-bin/report/gen are: The purpose of this script is to show how request information gets communicated to a CGI script. Note that POST data must be read from standard input. In this particular case, posted data gets stored in the variable POST_DATA. Your script may use a different method to read POST content. Secondly, the SCRIPT_EXEC variable is not a CGI standard. It is provided by this middleware and contains the entire command line, including all arguments, with which the CGI script was executed. When a browser requests the response looks like When a client makes a POST request, such as with the following command the response looks the same except for the following lines: The fossil distributed software management tool is a native executable that supports interaction as a CGI application. In this example, /usr/bin/fossil is the executable and /home/quixote/projects.fossil is the fossil repository. To configure Caddy to serve it, use a cgi directive something like this in your Caddyfile: In your /usr/local/cgi-bin directory, make a file named projects with the following single line: The fossil documentation calls this a command file. When fossil is invoked after a request to /projects, it examines the relevant environment variables and responds as a CGI application. If you protect /projects with basic HTTP authentication, you may wish to enable the ALLOW REMOTE_USER AUTHENTICATION option when setting up fossil. This lets fossil dispense with its own authentication, assuming it has an account for the user. The agedu utility can be used to identify unused files that are taking up space on your storage media. Like fossil, it can be used in different modes including CGI. First, use it from the command line to generate an index of a directory, for example In your Caddyfile, include a directive that references the generated index: You will want to protect the /agedu resource with some sort of access control, for example HTTP Basic Authentication. This small example demonstrates how to write a CGI program in Go. The use of a bytes.Buffer makes it easy to report the content length in the CGI header. When this program is compiled and installed as /usr/local/bin/servertime, the following directive in your Caddy file will make it available: The cgit application provides an attractive and useful web interface to git repositories. Here is how to run it with Caddy. After compiling cgit, you can place the executable somewhere out of Caddy’s document root. In this example, it is located in /usr/local/cgi-bin. A sample configuration file is included in the project’s cgitrc.5.txt file. You can use it as a starting point for your configuration. The default location for this file is /etc/cgitrc but in this example the location /home/quixote/caddy/cgitrc. Note that changing the location of this file from its default will necessitate the inclusion of the environment variable CGIT_CONFIG in the Caddyfile cgi directive. When you edit the repository stanzas in this file, be sure each repo.path item refers to the .git directory within a working checkout. Here is an example stanza: Also, you will likely want to change cgit’s cache directory from its default in /var/cache (generally accessible only to root) to a location writeable by Caddy. In this example, cgitrc contains the line You may need to create the cgit subdirectory. There are some static cgit resources (namely, cgit.css, favicon.ico, and cgit.png) that will be accessed from Caddy’s document tree. For this example, these files are placed in a directory named cgit-resource. The following lines are part of the cgitrc file: Additionally, you will likely need to tweak the various file viewer filters such source-filter and about-filter based on your system. The following Caddyfile directive will allow you to access the cgit application at /cgit: Feeling reckless? You can run PHP in CGI mode. In general, FastCGI is the preferred method to run PHP if your application has many pages or a fair amount of database activity. But for small PHP programs that are seldom used, CGI can work fine. You’ll need the php-cgi interpreter for your platform. This may involve downloading the executable or downloading and then compiling the source code. For this example, assume the interpreter is installed as /usr/local/bin/php-cgi. Additionally, because of the way PHP operates in CGI mode, you will need an intermediate script. This one works in Posix environments: This script can be reused for multiple cgi directives. In this example, it is installed as /usr/local/cgi-bin/phpwrap. The argument following -c is your initialization file for PHP. In this example, it is named /home/quixote/.config/php/php-cgi.ini. Two PHP files will be used for this example. The first, /usr/local/cgi-bin/sample/min.php, looks like this: The second, /usr/local/cgi-bin/sample/action.php, follows: The following directive in your Caddyfile will make the application available at sample/min.php: This examples demonstrates printing a CGI rule

Package billingconductor provides the API client, operations, and parameter types for AWSBillingConductor. Amazon Web Services Billing Conductor is a fully managed service that you can use to customize a proformaversion of your billing data each month, to accurately show or chargeback your end customers. Amazon Web Services Billing Conductor doesn't change the way you're billed by Amazon Web Services each month by design. Instead, it provides you with a mechanism to configure, generate, and display rates to certain customers over a given billing period. You can also analyze the difference between the rates you apply to your accounting groupings relative to your actual rates from Amazon Web Services. As a result of your Amazon Web Services Billing Conductor configuration, the payer account can also see the custom rate applied on the billing details page of the Amazon Web Services Billing console, or configure a cost and usage report per billing group. This documentation shows how you can configure Amazon Web Services Billing Conductor using its API. For more information about using the Amazon Web Services Billing Conductoruser interface, see the Amazon Web Services Billing Conductor User Guide.

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialzied. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/google/jsonapi

Package goncurses is a new curses (ncurses) library for the Go programming language. It implements all the ncurses extension libraries: form, menu and panel. Minimal operation would consist of initializing the display: It is important to always call End() before your program exits. If you fail to do so, the terminal will not perform properly and will either need to be reset or restarted completely. CAUTION: Calls to ncurses functions are normally not atomic nor reentrant and therefore extreme care should be taken to ensure ncurses functions are not called concurrently. Specifically, never write data to the same window concurrently nor accept input and send output to the same window as both alter the underlying C data structures in a non safe manner. Ideally, you should structure your program to ensure all ncurses related calls happen in a single goroutine. This is probably most easily achieved via channels and Go's built-in select. Alternatively, or additionally, you can use a mutex to protect any calls in multiple goroutines from happening concurrently. Failure to do so will result in unpredictable and undefined behaviour in your program. The examples directory contains demonstrations of many of the capabilities goncurses can provide.

Package goncurses is a new curses (ncurses) library for the Go programming language. It implements all the ncurses extension libraries: form, menu and panel. Minimal operation would consist of initializing the display: It is important to always call End() before your program exits. If you fail to do so, the terminal will not perform properly and will either need to be reset or restarted completely. CAUTION: Calls to ncurses functions are normally not atomic nor reentrant and therefore extreme care should be taken to ensure ncurses functions are not called concurrently. Specifically, never write data to the same window concurrently nor accept input and send output to the same window as both alter the underlying C data structures in a non safe manner. Ideally, you should structure your program to ensure all ncurses related calls happen in a single goroutine. This is probably most easily achieved via channels and Go's built-in select. Alternatively, or additionally, you can use a mutex to protect any calls in multiple goroutines from happening concurrently. Failure to do so will result in unpredictable and undefined behaviour in your program. The examples directory contains demontrations of many of the capabilities goncurses can provide.

Package ql implements a pure Go embedded SQL database engine. QL is a member of the SQL family of languages. It is less complex and less powerful than SQL (whichever specification SQL is considered to be). 2017-01-10: Release v1.1.0 fixes some bugs and adds a configurable WAL headroom. 2016-07-29: Release v1.0.6 enables alternatively using = instead of == for equality operation. 2016-07-11: Release v1.0.5 undoes vendoring of lldb. QL now uses stable lldb (github.com/cznic/lldb). 2016-07-06: Release v1.0.4 fixes a panic when closing the WAL file. 2016-04-03: Release v1.0.3 fixes a data race. 2016-03-23: Release v1.0.2 vendors github.com/cznic/exp/lldb and github.com/camlistore/go4/lock. 2016-03-17: Release v1.0.1 adjusts for latest goyacc. Parser error messages are improved and changed, but their exact form is not considered a API change. 2016-03-05: The current version has been tagged v1.0.0. 2015-06-15: To improve compatibility with other SQL implementations, the count built-in aggregate function now accepts * as its argument. 2015-05-29: The execution planner was rewritten from scratch. It should use indices in all places where they were used before plus in some additional situations. It is possible to investigate the plan using the newly added EXPLAIN statement. The QL tool is handy for such analysis. If the planner would have used an index, but no such exists, the plan includes hints in form of copy/paste ready CREATE INDEX statements. The planner is still quite simple and a lot of work on it is yet ahead. You can help this process by filling an issue with a schema and query which fails to use an index or indices when it should, in your opinion. Bonus points for including output of `ql 'explain <query>'`. 2015-05-09: The grammar of the CREATE INDEX statement now accepts an expression list instead of a single expression, which was further limited to just a column name or the built-in id(). As a side effect, composite indices are now functional. However, the values in the expression-list style index are not yet used by other statements or the statement/query planner. The composite index is useful while having UNIQUE clause to check for semantically duplicate rows before they get added to the table or when such a row is mutated using the UPDATE statement and the expression-list style index tuple of the row is thus recomputed. 2015-05-02: The Schema field of table __Table now correctly reflects any column constraints and/or defaults. Also, the (*DB).Info method now has that information provided in new ColumInfo fields NotNull, Constraint and Default. 2015-04-20: Added support for {LEFT,RIGHT,FULL} [OUTER] JOIN. 2015-04-18: Column definitions can now have constraints and defaults. Details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. 2015-03-06: New built-in functions formatFloat and formatInt. Thanks urandom! (https://github.com/urandom) 2015-02-16: IN predicate now accepts a SELECT statement. See the updated "Predicates" section. 2015-01-17: Logical operators || and && have now alternative spellings: OR and AND (case insensitive). AND was a keyword before, but OR is a new one. This can possibly break existing queries. For the record, it's a good idea to not use any name appearing in, for example, [7] in your queries as the list of QL's keywords may expand for gaining better compatibility with existing SQL "standards". 2015-01-12: ACID guarantees were tightened at the cost of performance in some cases. The write collecting window mechanism, a formerly used implementation detail, was removed. Inserting rows one by one in a transaction is now slow. I mean very slow. Try to avoid inserting single rows in a transaction. Instead, whenever possible, perform batch updates of tens to, say thousands of rows in a single transaction. See also: http://www.sqlite.org/faq.html#q19, the discussed synchronization principles involved are the same as for QL, modulo minor details. Note: A side effect is that closing a DB before exiting an application, both for the Go API and through database/sql driver, is no more required, strictly speaking. Beware that exiting an application while there is an open (uncommitted) transaction in progress means losing the transaction data. However, the DB will not become corrupted because of not closing it. Nor that was the case before, but formerly failing to close a DB could have resulted in losing the data of the last transaction. 2014-09-21: id() now optionally accepts a single argument - a table name. 2014-09-01: Added the DB.Flush() method and the LIKE pattern matching predicate. 2014-08-08: The built in functions max and min now accept also time values. Thanks opennota! (https://github.com/opennota) 2014-06-05: RecordSet interface extended by new methods FirstRow and Rows. 2014-06-02: Indices on id() are now used by SELECT statements. 2014-05-07: Introduction of Marshal, Schema, Unmarshal. 2014-04-15: Added optional IF NOT EXISTS clause to CREATE INDEX and optional IF EXISTS clause to DROP INDEX. 2014-04-12: The column Unique in the virtual table __Index was renamed to IsUnique because the old name is a keyword. Unfortunately, this is a breaking change, sorry. 2014-04-11: Introduction of LIMIT, OFFSET. 2014-04-10: Introduction of query rewriting. 2014-04-07: Introduction of indices. QL imports zappy[8], a block-based compressor, which speeds up its performance by using a C version of the compression/decompression algorithms. If a CGO-free (pure Go) version of QL, or an app using QL, is required, please include 'purego' in the -tags option of go {build,get,install}. For example: If zappy was installed before installing QL, it might be necessary to rebuild zappy first (or rebuild QL with all its dependencies using the -a option): The syntax is specified using Extended Backus-Naur Form (EBNF) Lower-case production names are used to identify lexical tokens. Non-terminals are in CamelCase. Lexical tokens are enclosed in double quotes "" or back quotes “. The form a … b represents the set of characters from a through b as alternatives. The horizontal ellipsis … is also used elsewhere in the spec to informally denote various enumerations or code snippets that are not further specified. QL source code is Unicode text encoded in UTF-8. The text is not canonicalized, so a single accented code point is distinct from the same character constructed from combining an accent and a letter; those are treated as two code points. For simplicity, this document will use the unqualified term character to refer to a Unicode code point in the source text. Each code point is distinct; for instance, upper and lower case letters are different characters. Implementation restriction: For compatibility with other tools, the parser may disallow the NUL character (U+0000) in the statement. Implementation restriction: A byte order mark is disallowed anywhere in QL statements. The following terms are used to denote specific character classes The underscore character _ (U+005F) is considered a letter. Lexical elements are comments, tokens, identifiers, keywords, operators and delimiters, integer, floating-point, imaginary, rune and string literals and QL parameters. Line comments start with the character sequence // or -- and stop at the end of the line. A line comment acts like a space. General comments start with the character sequence /* and continue through the character sequence */. A general comment acts like a space. Comments do not nest. Tokens form the vocabulary of QL. There are four classes: identifiers, keywords, operators and delimiters, and literals. White space, formed from spaces (U+0020), horizontal tabs (U+0009), carriage returns (U+000D), and newlines (U+000A), is ignored except as it separates tokens that would otherwise combine into a single token. The formal grammar uses semicolons ";" as separators of QL statements. A single QL statement or the last QL statement in a list of statements can have an optional semicolon terminator. (Actually a separator from the following empty statement.) Identifiers name entities such as tables or record set columns. An identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter. For example No identifiers are predeclared, however note that no keyword can be used as an identifier. Identifiers starting with two underscores are used for meta data virtual tables names. For forward compatibility, users should generally avoid using any identifiers starting with two underscores. For example The following keywords are reserved and may not be used as identifiers. Keywords are not case sensitive. The following character sequences represent operators, delimiters, and other special tokens Operators consisting of more than one character are referred to by names in the rest of the documentation An integer literal is a sequence of digits representing an integer constant. An optional prefix sets a non-decimal base: 0 for octal, 0x or 0X for hexadecimal. In hexadecimal literals, letters a-f and A-F represent values 10 through 15. For example A floating-point literal is a decimal representation of a floating-point constant. It has an integer part, a decimal point, a fractional part, and an exponent part. The integer and fractional part comprise decimal digits; the exponent part is an e or E followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided. For example An imaginary literal is a decimal representation of the imaginary part of a complex constant. It consists of a floating-point literal or decimal integer followed by the lower-case letter i. For example A rune literal represents a rune constant, an integer value identifying a Unicode code point. A rune literal is expressed as one or more characters enclosed in single quotes. Within the quotes, any character may appear except single quote and newline. A single quoted character represents the Unicode value of the character itself, while multi-character sequences beginning with a backslash encode values in various formats. The simplest form represents the single character within the quotes; since QL statements are Unicode characters encoded in UTF-8, multiple UTF-8-encoded bytes may represent a single integer value. For instance, the literal 'a' holds a single byte representing a literal a, Unicode U+0061, value 0x61, while 'ä' holds two bytes (0xc3 0xa4) representing a literal a-dieresis, U+00E4, value 0xe4. Several backslash escapes allow arbitrary values to be encoded as ASCII text. There are four ways to represent the integer value as a numeric constant: \x followed by exactly two hexadecimal digits; \u followed by exactly four hexadecimal digits; \U followed by exactly eight hexadecimal digits, and a plain backslash \ followed by exactly three octal digits. In each case the value of the literal is the value represented by the digits in the corresponding base. Although these representations all result in an integer, they have different valid ranges. Octal escapes must represent a value between 0 and 255 inclusive. Hexadecimal escapes satisfy this condition by construction. The escapes \u and \U represent Unicode code points so within them some values are illegal, in particular those above 0x10FFFF and surrogate halves. After a backslash, certain single-character escapes represent special values All other sequences starting with a backslash are illegal inside rune literals. For example A string literal represents a string constant obtained from concatenating a sequence of characters. There are two forms: raw string literals and interpreted string literals. Raw string literals are character sequences between back quotes “. Within the quotes, any character is legal except back quote. The value of a raw string literal is the string composed of the uninterpreted (implicitly UTF-8-encoded) characters between the quotes; in particular, backslashes have no special meaning and the string may contain newlines. Carriage returns inside raw string literals are discarded from the raw string value. Interpreted string literals are character sequences between double quotes "". The text between the quotes, which may not contain newlines, forms the value of the literal, with backslash escapes interpreted as they are in rune literals (except that \' is illegal and \" is legal), with the same restrictions. The three-digit octal (\nnn) and two-digit hexadecimal (\xnn) escapes represent individual bytes of the resulting string; all other escapes represent the (possibly multi-byte) UTF-8 encoding of individual characters. Thus inside a string literal \377 and \xFF represent a single byte of value 0xFF=255, while ÿ, \u00FF, \U000000FF and \xc3\xbf represent the two bytes 0xc3 0xbf of the UTF-8 encoding of character U+00FF. For example These examples all represent the same string If the statement source represents a character as two code points, such as a combining form involving an accent and a letter, the result will be an error if placed in a rune literal (it is not a single code point), and will appear as two code points if placed in a string literal. Literals are assigned their values from the respective text representation at "compile" (parse) time. QL parameters provide the same functionality as literals, but their value is assigned at execution time from an expression list passed to DB.Run or DB.Execute. Using '?' or '$' is completely equivalent. For example Keywords 'false' and 'true' (not case sensitive) represent the two possible constant values of type bool (also not case sensitive). Keyword 'NULL' (not case sensitive) represents an untyped constant which is assignable to any type. NULL is distinct from any other value of any type. A type determines the set of values and operations specific to values of that type. A type is specified by a type name. Named instances of the boolean, numeric, and string types are keywords. The names are not case sensitive. Note: The blob type is exchanged between the back end and the API as []byte. On 32 bit platforms this limits the size which the implementation can handle to 2G. A boolean type represents the set of Boolean truth values denoted by the predeclared constants true and false. The predeclared boolean type is bool. A duration type represents the elapsed time between two instants as an int64 nanosecond count. The representation limits the largest representable duration to approximately 290 years. A numeric type represents sets of integer or floating-point values. The predeclared architecture-independent numeric types are The value of an n-bit integer is n bits wide and represented using two's complement arithmetic. Conversions are required when different numeric types are mixed in an expression or assignment. A string type represents the set of string values. A string value is a (possibly empty) sequence of bytes. The case insensitive keyword for the string type is 'string'. The length of a string (its size in bytes) can be discovered using the built-in function len. A time type represents an instant in time with nanosecond precision. Each time has associated with it a location, consulted when computing the presentation form of the time. The following functions are implicitly declared An expression specifies the computation of a value by applying operators and functions to operands. Operands denote the elementary values in an expression. An operand may be a literal, a (possibly qualified) identifier denoting a constant or a function or a table/record set column, or a parenthesized expression. A qualified identifier is an identifier qualified with a table/record set name prefix. For example Primary expression are the operands for unary and binary expressions. For example A primary expression of the form denotes the element of a string indexed by x. Its type is byte. The value x is called the index. The following rules apply - The index x must be of integer type except bigint or duration; it is in range if 0 <= x < len(s), otherwise it is out of range. - A constant index must be non-negative and representable by a value of type int. - A constant index must be in range if the string a is a literal. - If x is out of range at run time, a run-time error occurs. - s[x] is the byte at index x and the type of s[x] is byte. If s is NULL or x is NULL then the result is NULL. Otherwise s[x] is illegal. For a string, the primary expression constructs a substring. The indices low and high select which elements appear in the result. The result has indices starting at 0 and length equal to high - low. For convenience, any of the indices may be omitted. A missing low index defaults to zero; a missing high index defaults to the length of the sliced operand The indices low and high are in range if 0 <= low <= high <= len(a), otherwise they are out of range. A constant index must be non-negative and representable by a value of type int. If both indices are constant, they must satisfy low <= high. If the indices are out of range at run time, a run-time error occurs. Integer values of type bigint or duration cannot be used as indices. If s is NULL the result is NULL. If low or high is not omitted and is NULL then the result is NULL. Given an identifier f denoting a predeclared function, calls f with arguments a1, a2, … an. Arguments are evaluated before the function is called. The type of the expression is the result type of f. In a function call, the function value and arguments are evaluated in the usual order. After they are evaluated, the parameters of the call are passed by value to the function and the called function begins execution. The return value of the function is passed by value when the function returns. Calling an undefined function causes a compile-time error. Operators combine operands into expressions. Comparisons are discussed elsewhere. For other binary operators, the operand types must be identical unless the operation involves shifts or untyped constants. For operations involving constants only, see the section on constant expressions. Except for shift operations, if one operand is an untyped constant and the other operand is not, the constant is converted to the type of the other operand. The right operand in a shift expression must have unsigned integer type or be an untyped constant that can be converted to unsigned integer type. If the left operand of a non-constant shift expression is an untyped constant, the type of the constant is what it would be if the shift expression were replaced by its left operand alone. Expressions of the form yield a boolean value true if expr2, a regular expression, matches expr1 (see also [6]). Both expression must be of type string. If any one of the expressions is NULL the result is NULL. Predicates are special form expressions having a boolean result type. Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be comparable as defined in "Comparison operators". Another form of the IN predicate creates the expression list from a result of a SelectStmt. The SelectStmt must select only one column. The produced expression list is resource limited by the memory available to the process. NULL values produced by the SelectStmt are ignored, but if all records of the SelectStmt are NULL the predicate yields NULL. The select statement is evaluated only once. If the type of expr is not the same as the type of the field returned by the SelectStmt then the set operation yields false. The type of the column returned by the SelectStmt must be one of the simple (non blob-like) types: Expressions of the form are equivalent, including NULL handling, to The types of involved expressions must be ordered as defined in "Comparison operators". Expressions of the form yield a boolean value true if expr does not have a specific type (case A) or if expr has a specific type (case B). In other cases the result is a boolean value false. Unary operators have the highest precedence. There are five precedence levels for binary operators. Multiplication operators bind strongest, followed by addition operators, comparison operators, && (logical AND), and finally || (logical OR) Binary operators of the same precedence associate from left to right. For instance, x / y * z is the same as (x / y) * z. Note that the operator precedence is reflected explicitly by the grammar. Arithmetic operators apply to numeric values and yield a result of the same type as the first operand. The four standard arithmetic operators (+, -, *, /) apply to integer, rational, floating-point, and complex types; + also applies to strings; +,- also applies to times. All other arithmetic operators apply to integers only. sum integers, rationals, floats, complex values, strings difference integers, rationals, floats, complex values, times product integers, rationals, floats, complex values / quotient integers, rationals, floats, complex values % remainder integers & bitwise AND integers | bitwise OR integers ^ bitwise XOR integers &^ bit clear (AND NOT) integers << left shift integer << unsigned integer >> right shift integer >> unsigned integer Strings can be concatenated using the + operator String addition creates a new string by concatenating the operands. A value of type duration can be added to or subtracted from a value of type time. Times can subtracted from each other producing a value of type duration. For two integer values x and y, the integer quotient q = x / y and remainder r = x % y satisfy the following relationships with x / y truncated towards zero ("truncated division"). As an exception to this rule, if the dividend x is the most negative value for the int type of x, the quotient q = x / -1 is equal to x (and r = 0). If the divisor is a constant expression, it must not be zero. If the divisor is zero at run time, a run-time error occurs. If the dividend is non-negative and the divisor is a constant power of 2, the division may be replaced by a right shift, and computing the remainder may be replaced by a bitwise AND operation The shift operators shift the left operand by the shift count specified by the right operand. They implement arithmetic shifts if the left operand is a signed integer and logical shifts if it is an unsigned integer. There is no upper limit on the shift count. Shifts behave as if the left operand is shifted n times by 1 for a shift count of n. As a result, x << 1 is the same as x*2 and x >> 1 is the same as x/2 but truncated towards negative infinity. For integer operands, the unary operators +, -, and ^ are defined as follows For floating-point and complex numbers, +x is the same as x, while -x is the negation of x. The result of a floating-point or complex division by zero is not specified beyond the IEEE-754 standard; whether a run-time error occurs is implementation-specific. Whenever any operand of any arithmetic operation, unary or binary, is NULL, as well as in the case of the string concatenating operation, the result is NULL. For unsigned integer values, the operations +, -, *, and << are computed modulo 2n, where n is the bit width of the unsigned integer's type. Loosely speaking, these unsigned integer operations discard high bits upon overflow, and expressions may rely on “wrap around”. For signed integers with a finite bit width, the operations +, -, *, and << may legally overflow and the resulting value exists and is deterministically defined by the signed integer representation, the operation, and its operands. No exception is raised as a result of overflow. An evaluator may not optimize an expression under the assumption that overflow does not occur. For instance, it may not assume that x < x + 1 is always true. Integers of type bigint and rationals do not overflow but their handling is limited by the memory resources available to the program. Comparison operators compare two operands and yield a boolean value. In any comparison, the first operand must be of same type as is the second operand, or vice versa. The equality operators == and != apply to operands that are comparable. The ordering operators <, <=, >, and >= apply to operands that are ordered. These terms and the result of the comparisons are defined as follows - Boolean values are comparable. Two boolean values are equal if they are either both true or both false. - Complex values are comparable. Two complex values u and v are equal if both real(u) == real(v) and imag(u) == imag(v). - Integer values are comparable and ordered, in the usual way. Note that durations are integers. - Floating point values are comparable and ordered, as defined by the IEEE-754 standard. - Rational values are comparable and ordered, in the usual way. - String values are comparable and ordered, lexically byte-wise. - Time values are comparable and ordered. Whenever any operand of any comparison operation is NULL, the result is NULL. Note that slices are always of type string. Logical operators apply to boolean values and yield a boolean result. The right operand is evaluated conditionally. The truth tables for logical operations with NULL values Conversions are expressions of the form T(x) where T is a type and x is an expression that can be converted to type T. A constant value x can be converted to type T in any of these cases: - x is representable by a value of type T. - x is a floating-point constant, T is a floating-point type, and x is representable by a value of type T after rounding using IEEE 754 round-to-even rules. The constant T(x) is the rounded value. - x is an integer constant and T is a string type. The same rule as for non-constant x applies in this case. Converting a constant yields a typed constant as result. A non-constant value x can be converted to type T in any of these cases: - x has type T. - x's type and T are both integer or floating point types. - x's type and T are both complex types. - x is an integer, except bigint or duration, and T is a string type. Specific rules apply to (non-constant) conversions between numeric types or to and from a string type. These conversions may change the representation of x and incur a run-time cost. All other conversions only change the type but not the representation of x. A conversion of NULL to any type yields NULL. For the conversion of non-constant numeric values, the following rules apply 1. When converting between integer types, if the value is a signed integer, it is sign extended to implicit infinite precision; otherwise it is zero extended. It is then truncated to fit in the result type's size. For example, if v == uint16(0x10F0), then uint32(int8(v)) == 0xFFFFFFF0. The conversion always yields a valid value; there is no indication of overflow. 2. When converting a floating-point number to an integer, the fraction is discarded (truncation towards zero). 3. When converting an integer or floating-point number to a floating-point type, or a complex number to another complex type, the result value is rounded to the precision specified by the destination type. For instance, the value of a variable x of type float32 may be stored using additional precision beyond that of an IEEE-754 32-bit number, but float32(x) represents the result of rounding x's value to 32-bit precision. Similarly, x + 0.1 may use more than 32 bits of precision, but float32(x + 0.1) does not. In all non-constant conversions involving floating-point or complex values, if the result type cannot represent the value the conversion succeeds but the result value is implementation-dependent. 1. Converting a signed or unsigned integer value to a string type yields a string containing the UTF-8 representation of the integer. Values outside the range of valid Unicode code points are converted to "\uFFFD". 2. Converting a blob to a string type yields a string whose successive bytes are the elements of the blob. 3. Converting a value of a string type to a blob yields a blob whose successive elements are the bytes of the string. 4. Converting a value of a bigint type to a string yields a string containing the decimal decimal representation of the integer. 5. Converting a value of a string type to a bigint yields a bigint value containing the integer represented by the string value. A prefix of “0x” or “0X” selects base 16; the “0” prefix selects base 8, and a “0b” or “0B” prefix selects base 2. Otherwise the value is interpreted in base 10. An error occurs if the string value is not in any valid format. 6. Converting a value of a rational type to a string yields a string containing the decimal decimal representation of the rational in the form "a/b" (even if b == 1). 7. Converting a value of a string type to a bigrat yields a bigrat value containing the rational represented by the string value. The string can be given as a fraction "a/b" or as a floating-point number optionally followed by an exponent. An error occurs if the string value is not in any valid format. 8. Converting a value of a duration type to a string returns a string representing the duration in the form "72h3m0.5s". Leading zero units are omitted. As a special case, durations less than one second format using a smaller unit (milli-, micro-, or nanoseconds) to ensure that the leading digit is non-zero. The zero duration formats as 0, with no unit. 9. Converting a string value to a duration yields a duration represented by the string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h". 10. Converting a time value to a string returns the time formatted using the format string When evaluating the operands of an expression or of function calls, operations are evaluated in lexical left-to-right order. For example, in the evaluation of the function calls and evaluation of c happen in the order h(), i(), j(), c. Floating-point operations within a single expression are evaluated according to the associativity of the operators. Explicit parentheses affect the evaluation by overriding the default associativity. In the expression x + (y + z) the addition y + z is performed before adding x. Statements control execution. The empty statement does nothing. Alter table statements modify existing tables. With the ADD clause it adds a new column to the table. The column must not exist. With the DROP clause it removes an existing column from a table. The column must exist and it must be not the only (last) column of the table. IOW, there cannot be a table with no columns. For example When adding a column to a table with existing data, the constraint clause of the ColumnDef cannot be used. Adding a constrained column to an empty table is fine. Begin transactions statements introduce a new transaction level. Every transaction level must be eventually balanced by exactly one of COMMIT or ROLLBACK statements. Note that when a transaction is roll-backed because of a statement failure then no explicit balancing of the respective BEGIN TRANSACTION is statement is required nor permitted. Failure to properly balance any opened transaction level may cause dead locks and/or lose of data updated in the uppermost opened but never properly closed transaction level. For example A database cannot be updated (mutated) outside of a transaction. Statements requiring a transaction A database is effectively read only outside of a transaction. Statements not requiring a transaction The commit statement closes the innermost transaction nesting level. If that's the outermost level then the updates to the DB made by the transaction are atomically made persistent. For example Create index statements create new indices. Index is a named projection of ordered values of a table column to the respective records. As a special case the id() of the record can be indexed. Index name must not be the same as any of the existing tables and it also cannot be the same as of any column name of the table the index is on. For example Now certain SELECT statements may use the indices to speed up joins and/or to speed up record set filtering when the WHERE clause is used; or the indices might be used to improve the performance when the ORDER BY clause is present. The UNIQUE modifier requires the indexed values tuple to be index-wise unique or have all values NULL. The optional IF NOT EXISTS clause makes the statement a no operation if the index already exists. A simple index consists of only one expression which must be either a column name or the built-in id(). A more complex and more general index is one that consists of more than one expression or its single expression does not qualify as a simple index. In this case the type of all expressions in the list must be one of the non blob-like types. Note: Blob-like types are blob, bigint, bigrat, time and duration. Create table statements create new tables. A column definition declares the column name and type. Table names and column names are case sensitive. Neither a table or an index of the same name may exist in the DB. For example The optional IF NOT EXISTS clause makes the statement a no operation if the table already exists. The optional constraint clause has two forms. The first one is found in many SQL dialects. This form prevents the data in column DepartmentName to be NULL. The second form allows an arbitrary boolean expression to be used to validate the column. If the value of the expression is true then the validation succeeded. If the value of the expression is false or NULL then the validation fails. If the value of the expression is not of type bool an error occurs. The optional DEFAULT clause is an expression which, if present, is substituted instead of a NULL value when the colum is assigned a value. Note that the constraint and/or default expressions may refer to other columns by name: When a table row is inserted by the INSERT INTO statement or when a table row is updated by the UPDATE statement, the order of operations is as follows: 1. The new values of the affected columns are set and the values of all the row columns become the named values which can be referred to in default expressions evaluated in step 2. 2. If any row column value is NULL and the DEFAULT clause is present in the column's definition, the default expression is evaluated and its value is set as the respective column value. 3. The values, potentially updated, of row columns become the named values which can be referred to in constraint expressions evaluated during step 4. 4. All row columns which definition has the constraint clause present will have that constraint checked. If any constraint violation is detected, the overall operation fails and no changes to the table are made. Delete from statements remove rows from a table, which must exist. For example If the WHERE clause is not present then all rows are removed and the statement is equivalent to the TRUNCATE TABLE statement. Drop index statements remove indices from the DB. The index must exist. For example The optional IF EXISTS clause makes the statement a no operation if the index does not exist. Drop table statements remove tables from the DB. The table must exist. For example The optional IF EXISTS clause makes the statement a no operation if the table does not exist. Insert into statements insert new rows into tables. New rows come from literal data, if using the VALUES clause, or are a result of select statement. In the later case the select statement is fully evaluated before the insertion of any rows is performed, allowing to insert values calculated from the same table rows are to be inserted into. If the ColumnNameList part is omitted then the number of values inserted in the row must be the same as are columns in the table. If the ColumnNameList part is present then the number of values per row must be same as the same number of column names. All other columns of the record are set to NULL. The type of the value assigned to a column must be the same as is the column's type or the value must be NULL. For example If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. Explain statement produces a recordset consisting of lines of text which describe the execution plan of a statement, if any. For example, the QL tool treats the explain statement specially and outputs the joined lines: The explanation may aid in uderstanding how a statement/query would be executed and if indices are used as expected - or which indices may possibly improve the statement performance. The create index statements above were directly copy/pasted in the terminal from the suggestions provided by the filter recordset pipeline part returned by the explain statement. If the statement has nothing special in its plan, the result is the original statement. To get an explanation of the select statement of the IN predicate, use the EXPLAIN statement with that particular select statement. The rollback statement closes the innermost transaction nesting level discarding any updates to the DB made by it. If that's the outermost level then the effects on the DB are as if the transaction never happened. For example The (temporary) record set from the last statement is returned and can be processed by the client. In this case the rollback is the same as 'DROP TABLE tmp;' but it can be a more complex operation. Select from statements produce recordsets. The optional DISTINCT modifier ensures all rows in the result recordset are unique. Either all of the resulting fields are returned ('*') or only those named in FieldList. RecordSetList is a list of table names or parenthesized select statements, optionally (re)named using the AS clause. The result can be filtered using a WhereClause and orderd by the OrderBy clause. For example If Recordset is a nested, parenthesized SelectStmt then it must be given a name using the AS clause if its field are to be accessible in expressions. A field is an named expression. Identifiers, not used as a type in conversion or a function name in the Call clause, denote names of (other) fields, values of which should be used in the expression. The expression can be named using the AS clause. If the AS clause is not present and the expression consists solely of a field name, then that field name is used as the name of the resulting field. Otherwise the field is unnamed. For example The SELECT statement can optionally enumerate the desired/resulting fields in a list. No two identical field names can appear in the list. When more than one record set is used in the FROM clause record set list, the result record set field names are rewritten to be qualified using the record set names. If a particular record set doesn't have a name, its respective fields became unnamed. The optional JOIN clause, for example is mostly equal to except that the rows from a which, when they appear in the cross join, never made expr to evaluate to true, are combined with a virtual row from b, containing all nulls, and added to the result set. For the RIGHT JOIN variant the discussed rules are used for rows from b not satisfying expr == true and the virtual, all-null row "comes" from a. The FULL JOIN adds the respective rows which would be otherwise provided by the separate executions of the LEFT JOIN and RIGHT JOIN variants. For more thorough OUTER JOIN discussion please see the Wikipedia article at [10]. Resultins rows of a SELECT statement can be optionally ordered by the ORDER BY clause. Collating proceeds by considering the expressions in the expression list left to right until a collating order is determined. Any possibly remaining expressions are not evaluated. All of the expression values must yield an ordered type or NULL. Ordered types are defined in "Comparison operators". Collating of elements having a NULL value is different compared to what the comparison operators yield in expression evaluation (NULL result instead of a boolean value). Below, T denotes a non NULL value of any QL type. NULL collates before any non NULL value (is considered smaller than T). Two NULLs have no collating order (are considered equal). The WHERE clause restricts records considered by some statements, like SELECT FROM, DELETE FROM, or UPDATE. It is an error if the expression evaluates to a non null value of non bool type. The GROUP BY clause is used to project rows having common values into a smaller set of rows. For example Using the GROUP BY without any aggregate functions in the selected fields is in certain cases equal to using the DISTINCT modifier. The last two examples above produce the same resultsets. The optional OFFSET clause allows to ignore first N records. For example The above will produce only rows 11, 12, ... of the record set, if they exist. The value of the expression must a non negative integer, but not bigint or duration. The optional LIMIT clause allows to ignore all but first N records. For example The above will return at most the first 10 records of the record set. The value of the expression must a non negative integer, but not bigint or duration. The LIMIT and OFFSET clauses can be combined. For example Considering table t has, say 10 records, the above will produce only records 4 - 8. After returning record #8, no more result rows/records are computed. 1. The FROM clause is evaluated, producing a Cartesian product of its source record sets (tables or nested SELECT statements). 2. If present, the JOIN cluase is evaluated on the result set of the previous evaluation and the recordset specified by the JOIN clause. (... JOIN Recordset ON ...) 3. If present, the WHERE clause is evaluated on the result set of the previous evaluation. 4. If present, the GROUP BY clause is evaluated on the result set of the previous evaluation(s). 5. The SELECT field expressions are evaluated on the result set of the previous evaluation(s). 6. If present, the DISTINCT modifier is evaluated on the result set of the previous evaluation(s). 7. If present, the ORDER BY clause is evaluated on the result set of the previous evaluation(s). 8. If present, the OFFSET clause is evaluated on the result set of the previous evaluation(s). The offset expression is evaluated once for the first record produced by the previous evaluations. 9. If present, the LIMIT clause is evaluated on the result set of the previous evaluation(s). The limit expression is evaluated once for the first record produced by the previous evaluations. Truncate table statements remove all records from a table. The table must exist. For example Update statements change values of fields in rows of a table. For example Note: The SET clause is optional. If any of the columns of the table were defined using the optional constraints clause or the optional defaults clause then those are processed on a per row basis. The details are discussed in the "Constraints and defaults" chapter below the CREATE TABLE statement documentation. To allow to query for DB meta data, there exist specially named tables, some of them being virtual. Note: Virtual system tables may have fake table-wise unique but meaningless and unstable record IDs. Do not apply the built-in id() to any system table. The table __Table lists all tables in the DB. The schema is The Schema column returns the statement to (re)create table Name. This table is virtual. The table __Colum lists all columns of all tables in the DB. The schema is The Ordinal column defines the 1-based index of the column in the record. This table is virtual. The table __Colum2 lists all columns of all tables in the DB which have the constraint NOT NULL or which have a constraint expression defined or which have a default expression defined. The schema is It's possible to obtain a consolidated recordset for all properties of all DB columns using The Name column is the column name in TableName. The table __Index lists all indices in the DB. The schema is The IsUnique columns reflects if the index was created using the optional UNIQUE clause. This table is virtual. Built-in functions are predeclared. The built-in aggregate function avg returns the average of values of an expression. Avg ignores NULL values, but returns NULL if all values of a column are NULL or if avg is applied to an empty record set. The column values must be of a numeric type. The built-in function contains returns true if substr is within s. If any argument to contains is NULL the result is NULL. The built-in aggregate function count returns how many times an expression has a non NULL values or the number of rows in a record set. Note: count() returns 0 for an empty record set. For example Date returns the time corresponding to in the appropriate zone for that time in the given location. The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1. A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which. A location maps time instants to the zone in use at that time. Typically, the location represents the collection of time offsets in use in a geographical area, such as "CEST" and "CET" for central Europe. "local" represents the system's local time zone. "UTC" represents Universal Coordinated Time (UTC). The month specifies a month of the year (January = 1, ...). If any argument to date is NULL the result is NULL. The built-in function day returns the day of the month specified by t. If the argument to day is NULL the result is NULL. The built-in function formatTime returns a textual representation of the time value formatted according to layout, which defines the format by showing how the reference time, would be displayed if it were the value; it serves as an example of the desired output. The same display rules will then be applied to the time value. If any argument to formatTime is NULL the result is NULL. NOTE: The string value of the time zone, like "CET" or "ACDT", is dependent on the time zone of the machine the function is run on. For example, if the t value is in "CET", but the machine is in "ACDT", instead of "CET" the result is "+0100". This is the same what Go (time.Time).String() returns and in fact formatTime directly calls t.String(). returns on a machine in the CET time zone, but may return on a machine in the ACDT zone. The time value is in both cases the same so its ordering and comparing is correct. Only the display value can differ. The built-in functions formatFloat and formatInt format numbers to strings using go's number format functions in the `strconv` package. For all three functions, only the first argument is mandatory. The default values of the rest are shown in the examples. If the first argument is NULL, the result is NULL. returns returns returns Unlike the `strconv` equivalent, the formatInt function handles all integer types, both signed and unsigned. The built-in function hasPrefix tests whether the string s begins with prefix. If any argument to hasPrefix is NULL the result is NULL. The built-in function hasSuffix tests whether the string s ends with suffix. If any argument to hasSuffix is NULL the result is NULL. The built-in function hour returns the hour within the day specified by t, in the range [0, 23]. If the argument to hour is NULL the result is NULL. The built-in function hours returns the duration as a floating point number of hours. If the argument to hours is NULL the result is NULL. The built-in function id takes zero or one arguments. If no argument is provided, id() returns a table-unique automatically assigned numeric identifier of type int. Ids of deleted records are not reused unless the DB becomes completely empty (has no tables). For example If id() without arguments is called for a row which is not a table record then the result value is NULL. For example If id() has one argument it must be a table name of a table in a cross join. For example The built-in function len takes a string argument and returns the lentgh of the string in bytes. The expression len(s) is constant if s is a string constant. If the argument to len is NULL the result is NULL. The built-in aggregate function max returns the largest value of an expression in a record set. Max ignores NULL values, but returns NULL if all values of a column are NULL or if max is applied to an empty record set. The expression values must be of an ordered type. For example The built-in aggregate function min returns the smallest value of an expression in a record set. Min ignores NULL values, but returns NULL if all values of a column are NULL or if min is applied to an empty record set. For example The column values must be of an ordered type. The built-in function minute returns the minute offset within the hour specified by t, in the range [0, 59]. If the argument to minute is NULL the result is NULL. The built-in function minutes returns the duration as a floating point number of minutes. If the argument to minutes is NULL the result is NULL. The built-in function month returns the month of the year specified by t (January = 1, ...). If the argument to month is NULL the result is NULL. The built-in function nanosecond returns the nanosecond offset within the second specified by t, in the range [0, 999999999]. If the argument to nanosecond is NULL the result is NULL. The built-in function nanoseconds returns the duration as an integer nanosecond count. If the argument to nanoseconds is NULL the result is NULL. The built-in function now returns the current local time. The built-in function parseTime parses a formatted string and returns the time value it represents. The layout defines the format by showing how the reference time, would be interpreted if it were the value; it serves as an example of the input format. The same interpretation will then be made to the input string. Elements omitted from the value are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored. In the absence of a time zone indicator, parseTime returns a time in UTC. When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location, then parseTime uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset. When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parses and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset. If any argument to parseTime is NULL the result is NULL. The built-in function second returns the second offset within the minute specified by t, in the range [0, 59]. If the argument to second is NULL the result is NULL. The built-in function seconds returns the duration as a floating point number of seconds. If the argument to seconds is NULL the result is NULL. The built-in function since returns the time elapsed since t. It is shorthand for now()-t. If the argument to since is NULL the result is NULL. The built-in aggregate function sum returns the sum of values of an expression for all rows of a record set. Sum ignores NULL values, but returns NULL if all values of a column are NULL or if sum is applied to an empty record set. The column values must be of a numeric type. The built-in function timeIn returns t with the location information set to loc. For discussion of the loc argument please see date(). If any argument to timeIn is NULL the result is NULL. The built-in function weekday returns the day of the week specified by t. Sunday == 0, Monday == 1, ... If the argument to weekday is NULL the result is NULL. The built-in function year returns the year in which t occurs. If the argument to year is NULL the result is NULL. The built-in function yearDay returns the day of the year specified by t, in the range [1,365] for non-leap years, and [1,366] in leap years. If the argument to yearDay is NULL the result is NULL. Three functions assemble and disassemble complex numbers. The built-in function complex constructs a complex value from a floating-point real and imaginary part, while real and imag extract the real and imaginary parts of a complex value. The type of the arguments and return value correspond. For complex, the two arguments must be of the same floating-point type and the return type is the complex type with the corresponding floating-point constituents: complex64 for float32, complex128 for float64. The real and imag functions together form the inverse, so for a complex value z, z == complex(real(z), imag(z)). If the operands of these functions are all constants, the return value is a constant. If any argument to any of complex, real, imag functions is NULL the result is NULL. For the numeric types, the following sizes are guaranteed Portions of this specification page are modifications based on work[2] created and shared by Google[3] and used according to terms described in the Creative Commons 3.0 Attribution License[4]. This specification is licensed under the Creative Commons Attribution 3.0 License, and code is licensed under a BSD license[5]. Links from the above documentation This section is not part of the specification. WARNING: The implementation of indices is new and it surely needs more time to become mature. Indices are used currently used only by the WHERE clause. The following expression patterns of 'WHERE expression' are recognized and trigger index use. The relOp is one of the relation operators <, <=, ==, >=, >. For the equality operator both operands must be of comparable types. For all other operators both operands must be of ordered types. The constant expression is a compile time constant expression. Some constant folding is still a TODO. Parameter is a QL parameter ($1 etc.). Consider tables t and u, both with an indexed field f. The WHERE expression doesn't comply with the above simple detected cases. However, such query is now automatically rewritten to which will use both of the indices. The impact of using the indices can be substantial (cf. BenchmarkCrossJoin*) if the resulting rows have low "selectivity", ie. only few rows from both tables are selected by the respective WHERE filtering. Note: Existing QL DBs can be used and indices can be added to them. However, once any indices are present in the DB, the old QL versions cannot work with such DB anymore. Running a benchmark with -v (-test.v) outputs information about the scale used to report records/s and a brief description of the benchmark. For example Running the full suite of benchmarks takes a lot of time. Use the -timeout flag to avoid them being killed after the default time limit (10 minutes).

Package sessions provides cookie and filesystem sessions and infrastructure for custom session backends. The key features are: Let's start with an example that shows the sessions API in a nutshell: First we initialize a session store calling NewCookieStore() and passing a secret key used to authenticate the session. Inside the handler, we call store.Get() to retrieve an existing session or a new one. Then we set some session values in session.Values, which is a map[interface{}]interface{}. And finally we call session.Save() to save the session in the response. Note that in production code, we should check for errors when calling session.Save(r, w), and either display an error message or otherwise handle it. Save must be called before writing to the response, otherwise the session cookie will not be sent to the client. That's all you need to know for the basic usage. Let's take a look at other options, starting with flash messages. Flash messages are session values that last until read. The term appeared with Ruby On Rails a few years back. When we request a flash message, it is removed from the session. To add a flash, call session.AddFlash(), and to get all flashes, call session.Flashes(). Here is an example: Flash messages are useful to set information to be read after a redirection, like after form submissions. There may also be cases where you want to store a complex datatype within a session, such as a struct. Sessions are serialised using the encoding/gob package, so it is easy to register new datatypes for storage in sessions: As it's not possible to pass a raw type as a parameter to a function, gob.Register() relies on us passing it a value of the desired type. In the example above we've passed it a pointer to a struct and a pointer to a custom type representing a map[string]interface. (We could have passed non-pointer values if we wished.) This will then allow us to serialise/deserialise values of those types to and from our sessions. Note that because session values are stored in a map[string]interface{}, there's a need to type-assert data when retrieving it. We'll use the Person struct we registered above: By default, session cookies last for a month. This is probably too long for some cases, but it is easy to change this and other attributes during runtime. Sessions can be configured individually or the store can be configured and then all sessions saved using it will use that configuration. We access session.Options or store.Options to set a new configuration. The fields are basically a subset of http.Cookie fields. Let's change the maximum age of a session to one week: Sometimes we may want to change authentication and/or encryption keys without breaking existing sessions. The CookieStore supports key rotation, and to use it you just need to set multiple authentication and encryption keys, in pairs, to be tested in order: New sessions will be saved using the first pair. Old sessions can still be read because the first pair will fail, and the second will be tested. This makes it easy to "rotate" secret keys and still be able to validate existing sessions. Note: for all pairs the encryption key is optional; set it to nil or omit it and and encryption won't be used. Multiple sessions can be used in the same request, even with different session backends. When this happens, calling Save() on each session individually would be cumbersome, so we have a way to save all sessions at once: it's sessions.Save(). Here's an example: This is possible because when we call Get() from a session store, it adds the session to a common registry. Save() uses it to save all registered sessions.

Package router 0.6.5 provides fast HTTP request router. The router matches incoming requests by the request method and the path. If a handle is registered for this path and method, the router delegates the request to defined handler. The router package is useful to prepare a RESTful API for Go services. It has JSON output, which bind automatically for relevant type of data. The router has timer feature to display duration of request handling in the header Simplest example (serve static route): Check it: Serve dynamic route with parameter: Checks JSON Content-Type automatically: Custom handler with "Access-Control-Allow" options and compact JSON: Use google json style `https://google.github.io/styleguide/jsoncstyleguide.xml` Go Router

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Stop() function is called or when Ctrl-C is pressed. If we have a primitive which consumes key presses, we call the application's SetFocus() function to redirect all key presses to that primitive. Most primitives then offer ways to install handlers that allow you to react to any actions performed on them. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, colors are specified using the tcell.Color type. Functions such as tcell.GetColor(), tcell.NewHexColor(), and tcell.NewRGBColor() can be used to create colors from W3C color names or RGB values. Almost all strings which are displayed can contain color tags. Color tags are W3C color names or six hexadecimal digits following a hash tag, wrapped in square brackets. Examples: A color tag changes the color of the characters following that color tag. This applies to almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. Color tags may contain not just the foreground (text) color but also the background color and additional flags. In fact, the full definition of a color tag is as follows: Each of the three fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered color tags.) Colors that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags (some flags may not be supported by your terminal): Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. This package supports unicode characters including wide characters. Many functions in this package are not thread-safe. For many applications, this may not be an issue: If your code makes changes in response to key events, it will execute in the main goroutine and thus will not cause any race conditions. If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate() or Application.QueueUpdateDraw() (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw() from any goroutine without having to wrap it in QueueUpdate(). And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use QueueUpdate() as that may lead to deadlocks. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. All widgets also implement the Primitive interface. There is also the Focusable interface which is used to override functions in subclassing types. The tview package is based on https://github.com/gdamore/tcell. It uses types and constants from that package (e.g. colors and keyboard values). This package does not process mouse input (yet).

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialzied. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/google/jsonapi

Package spew implements a deep pretty printer for Go data structures to aid in debugging. A quick overview of the additional features spew provides over the built-in printing facilities for Go data types are as follows: There are two different approaches spew allows for dumping Go data structures: This section demonstrates how to quickly get started with spew. See the sections below for further details on formatting and configuration options. To dump a variable with full newlines, indentation, type, and pointer information use Dump, Fdump, or Sdump: Alternatively, if you would prefer to use format strings with a compacted inline printing style, use the convenience wrappers Printf, Fprintf, etc with %v (most compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types and pointer addresses): Configuration of spew is handled by fields in the ConfigState type. For convenience, all of the top-level functions use a global state available via the spew.Config global. It is also possible to create a ConfigState instance that provides methods equivalent to the top-level functions. This allows concurrent configuration options. See the ConfigState documentation for more details. The following configuration options are available: Indent String to use for each indentation level for Dump functions. It is a single space by default. A popular alternative is "\t". MaxDepth Maximum number of levels to descend into nested data structures. There is no limit by default. DisableMethods Disables invocation of error and Stringer interface methods. Method invocation is enabled by default. DisablePointerMethods Disables invocation of error and Stringer interface methods on types which only accept pointer receivers from non-pointer variables. Pointer method invocation is enabled by default. DisablePointerAddresses DisablePointerAddresses specifies whether to disable the printing of pointer addresses. This is useful when diffing data structures in tests. DisableCapacities DisableCapacities specifies whether to disable the printing of capacities for arrays, slices, maps and channels. This is useful when diffing data structures in tests. ContinueOnMethod Enables recursion into types after invoking error and Stringer interface methods. Recursion after method invocation is disabled by default. SortKeys Specifies map keys should be sorted before being printed. Use this to have a more deterministic, diffable output. Note that only native types (bool, int, uint, floats, uintptr and string) and types which implement error or Stringer interfaces are supported with other types sorted according to the reflect.Value.String() output which guarantees display stability. Natural map order is used by default. SpewKeys Specifies that, as a last resort attempt, map keys should be spewed to strings and sorted by those strings. This is only considered if SortKeys is true. Simply call spew.Dump with a list of variables you want to dump: You may also call spew.Fdump if you would prefer to output to an arbitrary io.Writer. For example, to dump to standard error: A third option is to call spew.Sdump to get the formatted output as a string: See the Dump example for details on the setup of the types and variables being shown here. Byte (and uint8) arrays and slices are displayed uniquely like the hexdump -C command as shown. Spew provides a custom formatter that implements the fmt.Formatter interface so that it integrates cleanly with standard fmt package printing functions. The formatter is useful for inline printing of smaller data types similar to the standard %v format specifier. The custom formatter only responds to the %v (most compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb combinations. Any other verbs such as %x and %q will be sent to the the standard fmt package for formatting. In addition, the custom formatter ignores the width and precision arguments (however they will still work on the format specifiers not handled by the custom formatter). The simplest way to make use of the spew custom formatter is to call one of the convenience functions such as spew.Printf, spew.Println, or spew.Printf. The functions have syntax you are most likely already familiar with: See the Index for the full list convenience functions. Double pointer to a uint8: Pointer to circular struct with a uint8 field and a pointer to itself: See the Printf example for details on the setup of variables being shown here. Since it is possible for custom Stringer/error interfaces to panic, spew detects them and handles them internally by printing the panic information inline with the output. Since spew is intended to provide deep pretty printing capabilities on structures, it intentionally does not return any errors.

Package sessions provides cookie and filesystem sessions and infrastructure for custom session backends. The key features are: Let's start with an example that shows the sessions API in a nutshell: First we initialize a session store calling NewCookieStore() and passing a secret key used to authenticate the session. Inside the handler, we call store.Get() to retrieve an existing session or a new one. Then we set some session values in session.Values, which is a map[interface{}]interface{}. And finally we call session.Save() to save the session in the response. Note that in production code, we should check for errors when calling session.Save(r, w), and either display an error message or otherwise handle it. Save must be called before writing to the response, otherwise the session cookie will not be sent to the client. That's all you need to know for the basic usage. Let's take a look at other options, starting with flash messages. Flash messages are session values that last until read. The term appeared with Ruby On Rails a few years back. When we request a flash message, it is removed from the session. To add a flash, call session.AddFlash(), and to get all flashes, call session.Flashes(). Here is an example: Flash messages are useful to set information to be read after a redirection, like after form submissions. There may also be cases where you want to store a complex datatype within a session, such as a struct. Sessions are serialised using the encoding/gob package, so it is easy to register new datatypes for storage in sessions: As it's not possible to pass a raw type as a parameter to a function, gob.Register() relies on us passing it a value of the desired type. In the example above we've passed it a pointer to a struct and a pointer to a custom type representing a map[string]interface. (We could have passed non-pointer values if we wished.) This will then allow us to serialise/deserialise values of those types to and from our sessions. Note that because session values are stored in a map[string]interface{}, there's a need to type-assert data when retrieving it. We'll use the Person struct we registered above: By default, session cookies last for a month. This is probably too long for some cases, but it is easy to change this and other attributes during runtime. Sessions can be configured individually or the store can be configured and then all sessions saved using it will use that configuration. We access session.Options or store.Options to set a new configuration. The fields are basically a subset of http.Cookie fields. Let's change the maximum age of a session to one week: Sometimes we may want to change authentication and/or encryption keys without breaking existing sessions. The CookieStore supports key rotation, and to use it you just need to set multiple authentication and encryption keys, in pairs, to be tested in order: New sessions will be saved using the first pair. Old sessions can still be read because the first pair will fail, and the second will be tested. This makes it easy to "rotate" secret keys and still be able to validate existing sessions. Note: for all pairs the encryption key is optional; set it to nil or omit it and and encryption won't be used. Multiple sessions can be used in the same request, even with different session backends. When this happens, calling Save() on each session individually would be cumbersome, so we have a way to save all sessions at once: it's sessions.Save(). Here's an example: This is possible because when we call Get() from a session store, it adds the session to a common registry. Save() uses it to save all registered sessions.

Package ppsarama instruments the Shopify/sarama package (https://github.com/Shopify/sarama). This package instruments Kafka consumers and producers. To instrument a Kafka consumer, use ConsumeMessageContext. In order to display the kafka broker on the pinpoint screen, a context with broker addresses must be created and delivered using NewContext. ConsumePartition example: ConsumerGroupHandler example: ConsumeMessageContext passes a context added pinpoint.Tracer to HandlerContextFunc. In HandlerContextFunc, this tracer can be obtained by using the pinpoint.FromContext function. To instrument a Kafka producer, use NewSyncProducer or NewAsyncProducer. It is necessary to pass the context containing the pinpoint.Tracer to sarama.SyncProducer (or sarama.AsyncProducer) using WithContext function. The WithContext function() function is not thread-safe, so use the SendMessageContext function() if you have a data trace.

Elastic Guardian is a tiny reverse proxy that can offer authentication (using HTTP Basic Auth) as well as authorization. While it was originally meant as a thin layer between Elasticsearch (which has no builtin authentication/authorization) and the World, there is nothing specific to Elasticsearch (other than a few defaults which can be changed via command line flags). The generic use case for Elastic Guardian is to restrict access to a HTTP API with HTTP Basic Auth and authorization rules. It currently offers: It currently supports loading the authentication and authorization data from two different backends: Whether the external files are used or not can be controled (at compile time) via AllowAuthFromFiles constant. See that constant definition for further details. Please see authentication and authorization packages for further details. Commandline help can be accessed with: That will also display the default values for all flags. Log output will go to console (stdout) by default.

Package iris provides a beautifully expressive and easy to use foundation for your next website, API, or distributed app. Source code and other details for the project are available at GitHub: 8.5.9 Final The only requirement is the Go Programming Language, at least version 1.8 but 1.9 is highly recommended. Iris takes advantage of the vendor directory feature wisely: https://docs.google.com/document/d/1Bz5-UB7g2uPBdOx-rw5t9MxJwkfpx90cqG9AFL0JAYo. You get truly reproducible builds, as this method guards against upstream renames and deletes. A simple copy-paste and `go get ./...` to resolve two dependencies: https://github.com/kataras/golog and the https://github.com/iris-contrib/httpexpect will work for ever even for older versions, the newest version can be retrieved by `go get` but this file contains documentation for an older version of Iris. Follow the instructions below: 1. install the Go Programming Language: https://golang.org/dl 2. clear yours previously `$GOPATH/src/github.com/kataras/iris` folder or create new 3. download the Iris v8.5.9 (final): https://github.com/kataras/iris/archive/v8.zip 4. extract the contents of the `iris-v8` folder that's inside the downloaded zip file to your `$GOPATH/src/github.com/kataras/iris` 5. navigate to your `$GOPATH/src/github.com/kataras/iris` folder if you're not already there and open a terminal/command prompt, execute the command: `go get ./...` and you're ready to GO:) Example code: You can start the server(s) listening to any type of `net.Listener` or even `http.Server` instance. The method for initialization of the server should be passed at the end, via `Run` function. Below you'll see some useful examples: UNIX and BSD hosts can take advandage of the reuse port feature. Example code: That's all with listening, you have the full control when you need it. Let's continue by learning how to catch CONTROL+C/COMMAND+C or unix kill command and shutdown the server gracefully. In order to manually manage what to do when app is interrupted, we have to disable the default behavior with the option `WithoutInterruptHandler` and register a new interrupt handler (globally, across all possible hosts). Example code: Access to all hosts that serve your application can be provided by the `Application#Hosts` field, after the `Run` method. But the most common scenario is that you may need access to the host before the `Run` method, there are two ways of gain access to the host supervisor, read below. First way is to use the `app.NewHost` to create a new host and use one of its `Serve` or `Listen` functions to start the application via the `iris#Raw` Runner. Note that this way needs an extra import of the `net/http` package. Example Code: Second, and probably easier way is to use the `host.Configurator`. Note that this method requires an extra import statement of "github.com/kataras/iris/core/host" when using go < 1.9, if you're targeting on go1.9 then you can use the `iris#Supervisor` and omit the extra host import. All common `Runners` we saw earlier (`iris#Addr, iris#Listener, iris#Server, iris#TLS, iris#AutoTLS`) accept a variadic argument of `host.Configurator`, there are just `func(*host.Supervisor)`. Therefore the `Application` gives you the rights to modify the auto-created host supervisor through these. Example Code: Read more about listening and gracefully shutdown by navigating to: All HTTP methods are supported, developers can also register handlers for same paths for different methods. The first parameter is the HTTP Method, second parameter is the request path of the route, third variadic parameter should contains one or more iris.Handler executed by the registered order when a user requests for that specific resouce path from the server. Example code: In order to make things easier for the user, iris provides functions for all HTTP Methods. The first parameter is the request path of the route, second variadic parameter should contains one or more iris.Handler executed by the registered order when a user requests for that specific resouce path from the server. Example code: A set of routes that are being groupped by path prefix can (optionally) share the same middleware handlers and template layout. A group can have a nested group too. `.Party` is being used to group routes, developers can declare an unlimited number of (nested) groups. Example code: iris developers are able to register their own handlers for http statuses like 404 not found, 500 internal server error and so on. Example code: With the help of iris's expressionist router you can build any form of API you desire, with safety. Example code: Iris has first-class support for the MVC pattern, you'll not find these stuff anywhere else in the Go world. Example Code: Iris web framework supports Request data, Models, Persistence Data and Binding with the fastest possible execution. Characteristics: All HTTP Methods are supported, for example if want to serve `GET` then the controller should have a function named `Get()`, you can define more than one method function to serve in the same Controller struct. Persistence data inside your Controller struct (share data between requests) via `iris:"persistence"` tag right to the field or Bind using `app.Controller("/" , new(myController), theBindValue)`. Models inside your Controller struct (set-ed at the Method function and rendered by the View) via `iris:"model"` tag right to the field, i.e User UserModel `iris:"model" name:"user"` view will recognise it as `{{.user}}`. If `name` tag is missing then it takes the field's name, in this case the `"User"`. Access to the request path and its parameters via the `Path and Params` fields. Access to the template file that should be rendered via the `Tmpl` field. Access to the template data that should be rendered inside the template file via `Data` field. Access to the template layout via the `Layout` field. Access to the low-level `iris.Context` via the `Ctx` field. Get the relative request path by using the controller's name via `RelPath()`. Get the relative template path directory by using the controller's name via `RelTmpl()`. Flow as you used to, `Controllers` can be registered to any `Party`, including Subdomains, the Party's begin and done handlers work as expected. Optional `BeginRequest(ctx)` function to perform any initialization before the method execution, useful to call middlewares or when many methods use the same collection of data. Optional `EndRequest(ctx)` function to perform any finalization after any method executed. Inheritance, recursively, see for example our `mvc.SessionController/iris.SessionController`, it has the `mvc.Controller/iris.Controller` as an embedded field and it adds its logic to its `BeginRequest`. Source file: https://github.com/kataras/iris/blob/v8/mvc/session_controller.go. Read access to the current route via the `Route` field. Support for more than one input arguments (map to dynamic request path parameters). Register one or more relative paths and able to get path parameters, i.e Response via output arguments, optionally, i.e Where `any` means everything, from custom structs to standard language's types-. `Result` is an interface which contains only that function: Dispatch(ctx iris.Context) and Get where HTTP Method function(Post, Put, Delete...). Iris has a very powerful and blazing fast MVC support, you can return any value of any type from a method function and it will be sent to the client as expected. * if `string` then it's the body. * if `string` is the second output argument then it's the content type. * if `int` then it's the status code. * if `bool` is false then it throws 404 not found http error by skipping everything else. * if `error` and not nil then (any type) response will be omitted and error's text with a 400 bad request will be rendered instead. * if `(int, error)` and error is not nil then the response result will be the error's text with the status code as `int`. * if `custom struct` or `interface{}` or `slice` or `map` then it will be rendered as json, unless a `string` content type is following. * if `mvc.Result` then it executes its `Dispatch` function, so good design patters can be used to split the model's logic where needed. The example below is not intended to be used in production but it's a good showcase of some of the return types we saw before; Another good example with a typical folder structure, that many developers are used to work, can be found at: https://github.com/kataras/iris/tree/v8/_examples/mvc/overview. By creating components that are independent of one another, developers are able to reuse components quickly and easily in other applications. The same (or similar) view for one application can be refactored for another application with different data because the view is simply handling how the data is being displayed to the user. If you're new to back-end web development read about the MVC architectural pattern first, a good start is that wikipedia article: https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller. Follow the examples at: https://github.com/kataras/iris/tree/v8/_examples/#mvc At the previous example, we've seen static routes, group of routes, subdomains, wildcard subdomains, a small example of parameterized path with a single known parameter and custom http errors, now it's time to see wildcard parameters and macros. iris, like net/http std package registers route's handlers by a Handler, the iris' type of handler is just a func(ctx iris.Context) where context comes from github.com/kataras/iris/context. Iris has the easiest and the most powerful routing process you have ever meet. At the same time, iris has its own interpeter(yes like a programming language) for route's path syntax and their dynamic path parameters parsing and evaluation, We call them "macros" for shortcut. How? It calculates its needs and if not any special regexp needed then it just registers the route with the low-level path syntax, otherwise it pre-compiles the regexp and adds the necessary middleware(s). Standard macro types for parameters: if type is missing then parameter's type is defaulted to string, so {param} == {param:string}. If a function not found on that type then the "string"'s types functions are being used. i.e: Besides the fact that iris provides the basic types and some default "macro funcs" you are able to register your own too!. Register a named path parameter function: at the func(argument ...) you can have any standard type, it will be validated before the server starts so don't care about performance here, the only thing it runs at serve time is the returning func(paramValue string) bool. Example Code: A path parameter name should contain only alphabetical letters, symbols, containing '_' and numbers are NOT allowed. If route failed to be registered, the app will panic without any warnings if you didn't catch the second return value(error) on .Handle/.Get.... Last, do not confuse ctx.Values() with ctx.Params(). Path parameter's values goes to ctx.Params() and context's local storage that can be used to communicate between handlers and middleware(s) goes to ctx.Values(), path parameters and the rest of any custom values are separated for your own good. Run Static Files Example code: More examples can be found here: https://github.com/kataras/iris/tree/v8/_examples/beginner/file-server Middleware is just a concept of ordered chain of handlers. Middleware can be registered globally, per-party, per-subdomain and per-route. Example code: iris is able to wrap and convert any external, third-party Handler you used to use to your web application. Let's convert the https://github.com/rs/cors net/http external middleware which returns a `next form` handler. Example code: Iris supports 5 template engines out-of-the-box, developers can still use any external golang template engine, as `context/context#ResponseWriter()` is an `io.Writer`. All of these five template engines have common features with common API, like Layout, Template Funcs, Party-specific layout, partial rendering and more. Example code: View engine supports bundled(https://github.com/jteeuwen/go-bindata) template files too. go-bindata gives you two functions, asset and assetNames, these can be setted to each of the template engines using the `.Binary` func. Example code: A real example can be found here: https://github.com/kataras/iris/tree/v8/_examples/view/embedding-templates-into-app. Enable auto-reloading of templates on each request. Useful while developers are in dev mode as they no neeed to restart their app on every template edit. Example code: Note: In case you're wondering, the code behind the view engines derives from the "github.com/kataras/iris/view" package, access to the engines' variables can be granded by "github.com/kataras/iris" package too. Each one of these template engines has different options located here: https://github.com/kataras/iris/tree/v8/view . This example will show how to store and access data from a session. You don’t need any third-party library, but If you want you can use any session manager compatible or not. In this example we will only allow authenticated users to view our secret message on the /secret page. To get access to it, the will first have to visit /login to get a valid session cookie, which logs him in. Additionally he can visit /logout to revoke his access to our secret message. Example code: Running the example: Sessions persistence can be achieved using one (or more) `sessiondb`. Example Code: More examples: In this example we will create a small chat between web sockets via browser. Example Server Code: Example Client(javascript) Code: Running the example: But you should have a basic idea of the framework by now, we just scratched the surface. If you enjoy what you just saw and want to learn more, please follow the below links: Examples: Middleware: Home Page:

Package iris provides a beautifully expressive and easy to use foundation for your next website, API, or distributed app. Source code and other details for the project are available at GitHub: 11.1.1 The only requirement is the Go Programming Language, at least version 1.8 but 1.11.1 and above is highly recommended. Example code: You can start the server(s) listening to any type of `net.Listener` or even `http.Server` instance. The method for initialization of the server should be passed at the end, via `Run` function. Below you'll see some useful examples: UNIX and BSD hosts can take advantage of the reuse port feature. Example code: That's all with listening, you have the full control when you need it. Let's continue by learning how to catch CONTROL+C/COMMAND+C or unix kill command and shutdown the server gracefully. In order to manually manage what to do when app is interrupted, we have to disable the default behavior with the option `WithoutInterruptHandler` and register a new interrupt handler (globally, across all possible hosts). Example code: Access to all hosts that serve your application can be provided by the `Application#Hosts` field, after the `Run` method. But the most common scenario is that you may need access to the host before the `Run` method, there are two ways of gain access to the host supervisor, read below. First way is to use the `app.NewHost` to create a new host and use one of its `Serve` or `Listen` functions to start the application via the `iris#Raw` Runner. Note that this way needs an extra import of the `net/http` package. Example Code: Second, and probably easier way is to use the `host.Configurator`. Note that this method requires an extra import statement of "github.com/kataras/iris/core/host" when using go < 1.9, if you're targeting on go1.9 then you can use the `iris#Supervisor` and omit the extra host import. All common `Runners` we saw earlier (`iris#Addr, iris#Listener, iris#Server, iris#TLS, iris#AutoTLS`) accept a variadic argument of `host.Configurator`, there are just `func(*host.Supervisor)`. Therefore the `Application` gives you the rights to modify the auto-created host supervisor through these. Example Code: Read more about listening and gracefully shutdown by navigating to: All HTTP methods are supported, developers can also register handlers for same paths for different methods. The first parameter is the HTTP Method, second parameter is the request path of the route, third variadic parameter should contains one or more iris.Handler executed by the registered order when a user requests for that specific resouce path from the server. Example code: In order to make things easier for the user, iris provides functions for all HTTP Methods. The first parameter is the request path of the route, second variadic parameter should contains one or more iris.Handler executed by the registered order when a user requests for that specific resouce path from the server. Example code: A set of routes that are being groupped by path prefix can (optionally) share the same middleware handlers and template layout. A group can have a nested group too. `.Party` is being used to group routes, developers can declare an unlimited number of (nested) groups. Example code: iris developers are able to register their own handlers for http statuses like 404 not found, 500 internal server error and so on. Example code: With the help of iris's expressionist router you can build any form of API you desire, with safety. Example code: At the previous example, we've seen static routes, group of routes, subdomains, wildcard subdomains, a small example of parameterized path with a single known parameter and custom http errors, now it's time to see wildcard parameters and macros. iris, like net/http std package registers route's handlers by a Handler, the iris' type of handler is just a func(ctx iris.Context) where context comes from github.com/kataras/iris/context. Iris has the easiest and the most powerful routing process you have ever meet. At the same time, iris has its own interpeter(yes like a programming language) for route's path syntax and their dynamic path parameters parsing and evaluation, We call them "macros" for shortcut. How? It calculates its needs and if not any special regexp needed then it just registers the route with the low-level path syntax, otherwise it pre-compiles the regexp and adds the necessary middleware(s). Standard macro types for parameters: if type is missing then parameter's type is defaulted to string, so {param} == {param:string}. If a function not found on that type then the "string"'s types functions are being used. i.e: Besides the fact that iris provides the basic types and some default "macro funcs" you are able to register your own too!. Register a named path parameter function: at the func(argument ...) you can have any standard type, it will be validated before the server starts so don't care about performance here, the only thing it runs at serve time is the returning func(paramValue string) bool. Example Code: Last, do not confuse ctx.Values() with ctx.Params(). Path parameter's values goes to ctx.Params() and context's local storage that can be used to communicate between handlers and middleware(s) goes to ctx.Values(), path parameters and the rest of any custom values are separated for your own good. Run Static Files Example code: More examples can be found here: https://github.com/kataras/iris/tree/master/_examples/beginner/file-server Middleware is just a concept of ordered chain of handlers. Middleware can be registered globally, per-party, per-subdomain and per-route. Example code: iris is able to wrap and convert any external, third-party Handler you used to use to your web application. Let's convert the https://github.com/rs/cors net/http external middleware which returns a `next form` handler. Example code: Iris supports 5 template engines out-of-the-box, developers can still use any external golang template engine, as `context/context#ResponseWriter()` is an `io.Writer`. All of these five template engines have common features with common API, like Layout, Template Funcs, Party-specific layout, partial rendering and more. Example code: View engine supports bundled(https://github.com/shuLhan/go-bindata) template files too. go-bindata gives you two functions, asset and assetNames, these can be setted to each of the template engines using the `.Binary` func. Example code: A real example can be found here: https://github.com/kataras/iris/tree/master/_examples/view/embedding-templates-into-app. Enable auto-reloading of templates on each request. Useful while developers are in dev mode as they no neeed to restart their app on every template edit. Example code: Note: In case you're wondering, the code behind the view engines derives from the "github.com/kataras/iris/view" package, access to the engines' variables can be granded by "github.com/kataras/iris" package too. Each one of these template engines has different options located here: https://github.com/kataras/iris/tree/master/view . This example will show how to store and access data from a session. You don’t need any third-party library, but If you want you can use any session manager compatible or not. In this example we will only allow authenticated users to view our secret message on the /secret page. To get access to it, the will first have to visit /login to get a valid session cookie, which logs him in. Additionally he can visit /logout to revoke his access to our secret message. Example code: Running the example: Sessions persistence can be achieved using one (or more) `sessiondb`. Example Code: More examples: In this example we will create a small chat between web sockets via browser. Example Server Code: Example Client(javascript) Code: Running the example: Iris has first-class support for the MVC pattern, you'll not find these stuff anywhere else in the Go world. Example Code: // GetUserBy serves // Method: GET // Resource: http://localhost:8080/user/{username:string} // By is a reserved "keyword" to tell the framework that you're going to // bind path parameters in the function's input arguments, and it also // helps to have "Get" and "GetBy" in the same controller. // // func (c *ExampleController) GetUserBy(username string) mvc.Result { // return mvc.View{ // Name: "user/username.html", // Data: username, // } // } Can use more than one, the factory will make sure that the correct http methods are being registered for each route for this controller, uncomment these if you want: Iris web framework supports Request data, Models, Persistence Data and Binding with the fastest possible execution. Characteristics: All HTTP Methods are supported, for example if want to serve `GET` then the controller should have a function named `Get()`, you can define more than one method function to serve in the same Controller. Register custom controller's struct's methods as handlers with custom paths(even with regex parametermized path) via the `BeforeActivation` custom event callback, per-controller. Example: Persistence data inside your Controller struct (share data between requests) by defining services to the Dependencies or have a `Singleton` controller scope. Share the dependencies between controllers or register them on a parent MVC Application, and ability to modify dependencies per-controller on the `BeforeActivation` optional event callback inside a Controller, i.e Access to the `Context` as a controller's field(no manual binding is neede) i.e `Ctx iris.Context` or via a method's input argument, i.e Models inside your Controller struct (set-ed at the Method function and rendered by the View). You can return models from a controller's method or set a field in the request lifecycle and return that field to another method, in the same request lifecycle. Flow as you used to, mvc application has its own `Router` which is a type of `iris/router.Party`, the standard iris api. `Controllers` can be registered to any `Party`, including Subdomains, the Party's begin and done handlers work as expected. Optional `BeginRequest(ctx)` function to perform any initialization before the method execution, useful to call middlewares or when many methods use the same collection of data. Optional `EndRequest(ctx)` function to perform any finalization after any method executed. Session dynamic dependency via manager's `Start` to the MVC Application, i.e Inheritance, recursively. Access to the dynamic path parameters via the controller's methods' input arguments, no binding is needed. When you use the Iris' default syntax to parse handlers from a controller, you need to suffix the methods with the `By` word, uppercase is a new sub path. Example: Register one or more relative paths and able to get path parameters, i.e Response via output arguments, optionally, i.e Where `any` means everything, from custom structs to standard language's types-. `Result` is an interface which contains only that function: Dispatch(ctx iris.Context) and Get where HTTP Method function(Post, Put, Delete...). Iris has a very powerful and blazing fast MVC support, you can return any value of any type from a method function and it will be sent to the client as expected. * if `string` then it's the body. * if `string` is the second output argument then it's the content type. * if `int` then it's the status code. * if `bool` is false then it throws 404 not found http error by skipping everything else. * if `error` and not nil then (any type) response will be omitted and error's text with a 400 bad request will be rendered instead. * if `(int, error)` and error is not nil then the response result will be the error's text with the status code as `int`. * if `custom struct` or `interface{}` or `slice` or `map` then it will be rendered as json, unless a `string` content type is following. * if `mvc.Result` then it executes its `Dispatch` function, so good design patters can be used to split the model's logic where needed. Examples with good patterns to follow but not intend to be used in production of course can be found at: https://github.com/kataras/iris/tree/master/_examples/#mvc. By creating components that are independent of one another, developers are able to reuse components quickly and easily in other applications. The same (or similar) view for one application can be refactored for another application with different data because the view is simply handling how the data is being displayed to the user. If you're new to back-end web development read about the MVC architectural pattern first, a good start is that wikipedia article: https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller. But you should have a basic idea of the framework by now, we just scratched the surface. If you enjoy what you just saw and want to learn more, please follow the below links: Examples: Middleware: Home Page: Book (in-progress):

Package geomaps provides the API client, operations, and parameter types for Amazon Location Service Maps V2. Capabilities include: Access to comprehensive base map data, allowing you to tailor the map display to your specific needs. Multiple pre-designed map styles suited for various application types, such as navigation, logistics, or data visualization. Generation of static map images for scenarios where interactive maps aren't suitable, such as: Embedding in emails or documents Displaying in low-bandwidth environments Creating printable maps Enhancing application performance by reducing client-side rendering

Package spew implements a deep pretty printer for Go data structures to aid in debugging. A quick overview of the additional features spew provides over the built-in printing facilities for Go data types are as follows: There are two different approaches spew allows for dumping Go data structures: This section demonstrates how to quickly get started with spew. See the sections below for further details on formatting and configuration options. To dump a variable with full newlines, indentation, type, and pointer information use Dump, Fdump, or Sdump: Alternatively, if you would prefer to use format strings with a compacted inline printing style, use the convenience wrappers Printf, Fprintf, etc with %v (most compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types and pointer addresses): Configuration of spew is handled by fields in the ConfigState type. For convenience, all of the top-level functions use a global state available via the spew.Config global. It is also possible to create a ConfigState instance that provides methods equivalent to the top-level functions. This allows concurrent configuration options. See the ConfigState documentation for more details. The following configuration options are available: Indent String to use for each indentation level for Dump functions. It is a single space by default. A popular alternative is "\t". MaxDepth Maximum number of levels to descend into nested data structures. There is no limit by default. DisableMethods Disables invocation of error and Stringer interface methods. Method invocation is enabled by default. DisablePointerMethods Disables invocation of error and Stringer interface methods on types which only accept pointer receivers from non-pointer variables. Pointer method invocation is enabled by default. DisablePointerAddresses DisablePointerAddresses specifies whether to disable the printing of pointer addresses. This is useful when diffing data structures in tests. DisableCapacities DisableCapacities specifies whether to disable the printing of capacities for arrays, slices, maps and channels. This is useful when diffing data structures in tests. ContinueOnMethod Enables recursion into types after invoking error and Stringer interface methods. Recursion after method invocation is disabled by default. SortKeys Specifies map keys should be sorted before being printed. Use this to have a more deterministic, diffable output. Note that only native types (bool, int, uint, floats, uintptr and string) and types which implement error or Stringer interfaces are supported with other types sorted according to the reflect.Value.String() output which guarantees display stability. Natural map order is used by default. SpewKeys Specifies that, as a last resort attempt, map keys should be spewed to strings and sorted by those strings. This is only considered if SortKeys is true. Simply call spew.Dump with a list of variables you want to dump: You may also call spew.Fdump if you would prefer to output to an arbitrary io.Writer. For example, to dump to standard error: A third option is to call spew.Sdump to get the formatted output as a string: See the Dump example for details on the setup of the types and variables being shown here. Byte (and uint8) arrays and slices are displayed uniquely like the hexdump -C command as shown. Spew provides a custom formatter that implements the fmt.Formatter interface so that it integrates cleanly with standard fmt package printing functions. The formatter is useful for inline printing of smaller data types similar to the standard %v format specifier. The custom formatter only responds to the %v (most compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb combinations. Any other verbs such as %x and %q will be sent to the the standard fmt package for formatting. In addition, the custom formatter ignores the width and precision arguments (however they will still work on the format specifiers not handled by the custom formatter). The simplest way to make use of the spew custom formatter is to call one of the convenience functions such as spew.Printf, spew.Println, or spew.Printf. The functions have syntax you are most likely already familiar with: See the Index for the full list convenience functions. Double pointer to a uint8: Pointer to circular struct with a uint8 field and a pointer to itself: See the Printf example for details on the setup of variables being shown here. Since it is possible for custom Stringer/error interfaces to panic, spew detects them and handles them internally by printing the panic information inline with the output. Since spew is intended to provide deep pretty printing capabilities on structures, it intentionally does not return any errors.

Package cgi implements the common gateway interface (CGI) for Caddy 2, a modern, full-featured, easy-to-use web server. It has been forked from the fantastic work of Kurt Jung who wrote that plugin for Caddy 1. This plugin lets you generate dynamic content on your website by means of command line scripts. To collect information about the inbound HTTP request, your script examines certain environment variables such as PATH_INFO and QUERY_STRING. Then, to return a dynamically generated web page to the client, your script simply writes content to standard output. In the case of POST requests, your script reads additional inbound content from standard input. The advantage of CGI is that you do not need to fuss with server startup and persistence, long term memory management, sockets, and crash recovery. Your script is called when a request matches one of the patterns that you specify in your Caddyfile. As soon as your script completes its response, it terminates. This simplicity makes CGI a perfect complement to the straightforward operation and configuration of Caddy. The benefits of Caddy, including HTTPS by default, basic access authentication, and lots of middleware options extend easily to your CGI scripts. CGI has some disadvantages. For one, Caddy needs to start a new process for each request. This can adversely impact performance and, if resources are shared between CGI applications, may require the use of some interprocess synchronization mechanism such as a file lock. Your server's responsiveness could in some circumstances be affected, such as when your web server is hit with very high demand, when your script's dependencies require a long startup, or when concurrently running scripts take a long time to respond. However, in many cases, such as using a pre-compiled CGI application like fossil or a Lua script, the impact will generally be insignificant. Another restriction of CGI is that scripts will be run with the same permissions as Caddy itself. This can sometimes be less than ideal, for example when your script needs to read or write files associated with a different owner. Serving dynamic content exposes your server to more potential threats than serving static pages. There are a number of considerations of which you should be aware when using CGI applications. CGI scripts should be located outside of Caddy's document root. Otherwise, an inadvertent misconfiguration could result in Caddy delivering the script as an ordinary static resource. At best, this could merely confuse the site visitor. At worst, it could expose sensitive internal information that should not leave the server. Mistrust the contents of PATH_INFO, QUERY_STRING and standard input. Most of the environment variables available to your CGI program are inherently safe because they originate with Caddy and cannot be modified by external users. This is not the case with PATH_INFO, QUERY_STRING and, in the case of POST actions, the contents of standard input. Be sure to validate and sanitize all inbound content. If you use a CGI library or framework to process your scripts, make sure you understand its limitations. An error in a CGI application is generally handled within the application itself and reported in the headers it returns. Your CGI application can be executed directly or indirectly. In the direct case, the application can be a compiled native executable or it can be a shell script that contains as its first line a shebang that identifies the interpreter to which the file's name should be passed. Caddy must have permission to execute the application. On Posix systems this will mean making sure the application's ownership and permission bits are set appropriately; on Windows, this may involve properly setting up the filename extension association. In the indirect case, the name of the CGI script is passed to an interpreter such as lua, perl or python. - This module needs to be installed (obviously). - The directive needs to be registered in the Caddyfile: The basic cgi directive lets you add a handler in the current caddy router location with a given script and optional arguments. The matcher is a default caddy matcher that is used to restrict the scope of this directive. The directive can be repeated any reasonable number of times. Here is the basic syntax: For example: When a request such as https://example.com/report or https://example.com/report/weekly arrives, the cgi middleware will detect the match and invoke the script named /usr/local/cgi-bin/report. The current working directory will be the same as Caddy itself. Here, it is assumed that the script is self-contained, for example a pre-compiled CGI application or a shell script. Here is an example of a standalone script, similar to one used in the cgi plugin's test suite: The environment variables PATH_INFO and QUERY_STRING are populated and passed to the script automatically. There are a number of other standard CGI variables included that are described below. If you need to pass any special environment variables or allow any environment variables that are part of Caddy's process to pass to your script, you will need to use the advanced directive syntax described below. Beware that in Caddy v2 it is (currently) not possible to separate the path left of the matcher from the full URL. Therefore if you require your CGI program to know the SCRIPT_NAME, make sure to pass that explicitly: In order to specify custom environment variables, pass along one or more environment variables known to Caddy, or specify more than one match pattern for a given rule, you will need to use the advanced directive syntax. That looks like this: For example, The script_name subdirective helps the cgi module to separate the path to the script from the (virtual) path afterwards (which shall be passed to the script). env can be used to define a list of key=value environment variable pairs that shall be passed to the script. pass_env can be used to define a list of environment variables of the Caddy process that shall be passed to the script. If your CGI application runs properly at the command line but fails to run from Caddy it is possible that certain environment variables may be missing. For example, the ruby gem loader evidently requires the HOME environment variable to be set; you can do this with the subdirective pass_env HOME. Another class of problematic applications require the COMPUTERNAME variable. The pass_all_env subdirective instructs Caddy to pass each environment variable it knows about to the CGI excutable. This addresses a common frustration that is caused when an executable requires an environment variable and fails without a descriptive error message when the variable cannot be found. These applications often run fine from the command prompt but fail when invoked with CGI. The risk with this subdirective is that a lot of server information is shared with the CGI executable. Use this subdirective only with CGI applications that you trust not to leak this information. buffer_limit is used when a http request has Transfer-Endcoding: chunked. The Go CGI Handler refused to handle these kinds of requests, see https://github.com/golang/go/issues/5613. In order to work around this the chunked request is buffered by caddy and sent to the CGI application as a whole with the correct CONTENT_LENGTH set. The buffer_limit setting marks a threshold between buffering in memory and using a temporary file. Every request body smaller than the buffer_limit is buffered in-memory. It accepts all formats supported by go-humanize. Default: 4MiB. (An example of this is git push if the objects to push are larger than the http.postBuffer) With the unbuffered_output subdirective it is possible to instruct the CGI handler to flush output from the CGI script as soon as possible. By default, the output is buffered into chunks before it is being written to optimize the network usage and allow to determine the Content-Length. When unbuffered, bytes will be written as soon as possible. This will also force the response to be written in chunked encoding. If you run into unexpected results with the CGI plugin, you are able to examine the environment in which your CGI application runs. To enter inspection mode, add the subdirective inspect to your CGI configuration block. This is a development option that should not be used in production. When in inspection mode, the plugin will respond to matching requests with a page that displays variables of interest. In particular, it will show the replacement value of {match} and the environment variables to which your CGI application has access. For example, consider this example CGI block: When you request a matching URL, for example, the Caddy server will deliver a text page similar to the following. The CGI application (in this case, wapptclsh) will not be called. This information can be used to diagnose problems with how a CGI application is called. To return to operation mode, remove or comment out the inspect subdirective. In this example, the Caddyfile looks like this: Note that a request for /show gets mapped to a script named /usr/local/cgi-bin/report/gen. There is no need for any element of the script name to match any element of the match pattern. The contents of /usr/local/cgi-bin/report/gen are: The purpose of this script is to show how request information gets communicated to a CGI script. Note that POST data must be read from standard input. In this particular case, posted data gets stored in the variable POST_DATA. Your script may use a different method to read POST content. Secondly, the SCRIPT_EXEC variable is not a CGI standard. It is provided by this middleware and contains the entire command line, including all arguments, with which the CGI script was executed. When a browser requests the response looks like When a client makes a POST request, such as with the following command the response looks the same except for the following lines: This small example demonstrates how to write a CGI program in Go. The use of a bytes.Buffer makes it easy to report the content length in the CGI header. When this program is compiled and installed as /usr/local/bin/servertime, the following directive in your Caddy file will make it available: The module is written in a way that it expects the scripts you want it to execute to actually exist. A non-existing or non-executable file is considered a setup error and will yield a HTTP 500. If you want to make sure, only existing scripts are executed, use a more specific matcher, as explained in the Caddy docs. Example: When calling a url like /cgi/foo/bar.pl it will check if the local file ./app/foo/bar.pl exists and only then it will proceed with calling the CGI.

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Stop() function is called or when Ctrl-C is pressed. If we have a primitive which consumes key presses, we call the application's SetFocus() function to redirect all key presses to that primitive. Most primitives then offer ways to install handlers that allow you to react to any actions performed on them. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, colors are specified using the tcell.Color type. Functions such as tcell.GetColor(), tcell.NewHexColor(), and tcell.NewRGBColor() can be used to create colors from W3C color names or RGB values. Almost all strings which are displayed can contain color tags. Color tags are W3C color names or six hexadecimal digits following a hash tag, wrapped in square brackets. Examples: A color tag changes the color of the characters following that color tag. This applies to almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. Color tags may contain not just the foreground (text) color but also the background color and additional flags. In fact, the full definition of a color tag is as follows: Each of the three fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered color tags.) Colors that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags (some flags may not be supported by your terminal): Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. This package supports unicode characters including wide characters. Many functions in this package are not thread-safe. For many applications, this may not be an issue: If your code makes changes in response to key events, it will execute in the main goroutine and thus will not cause any race conditions. If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate() or Application.QueueUpdateDraw() (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw() from any goroutine without having to wrap it in QueueUpdate(). And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use QueueUpdate() as that may lead to deadlocks. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. All widgets also implement the Primitive interface. The tview package is based on https://github.com/gdamore/tcell. It uses types and constants from that package (e.g. colors and keyboard values). This package does not process mouse input (yet).

Package tview implements rich widgets for terminal based user interfaces. The widgets provided with this package are useful for data exploration and data entry. The package implements the following widgets: The package also provides Application which is used to poll the event queue and draw widgets on screen. The following is a very basic example showing a box with the title "Hello, world!": First, we create a box primitive with a border and a title. Then we create an application, set the box as its root primitive, and run the event loop. The application exits when the application's Application.Stop function is called or when Ctrl-C is pressed. You will find more demos in the "demos" subdirectory. It also contains a presentation (written using tview) which gives an overview of the different widgets and how they can be used. Throughout this package, styles are specified using the tcell.Style type. Styles specify colors with the tcell.Color type. Functions such as tcell.GetColor, tcell.NewHexColor, and tcell.NewRGBColor can be used to create colors from W3C color names or RGB values. The tcell.Style type also allows you to specify text attributes such as "bold" or "underline" or a URL which some terminals use to display hyperlinks. Almost all strings which are displayed may contain style tags. A style tag's content is always wrapped in square brackets. In its simplest form, a style tag specifies the foreground color of the text. Colors in these tags are W3C color names or six hexadecimal digits following a hash tag. Examples: A style tag changes the style of the characters following that style tag. There is no style stack and no nesting of style tags. Style tags are used in almost everything from box titles, list text, form item labels, to table cells. In a TextView, this functionality has to be switched on explicitly. See the TextView documentation for more information. A style tag's full format looks like this: Each of the four fields can be left blank and trailing fields can be omitted. (Empty square brackets "[]", however, are not considered style tags.) Fields that are not specified will be left unchanged. A field with just a dash ("-") means "reset to default". You can specify the following flags to turn on certain attributes (some flags may not be supported by your terminal): Use uppercase letters to turn off the corresponding attribute, for example, "B" to turn off bold. Uppercase letters have no effect if the attribute was not previously set. Setting a URL allows you to turn a piece of text into a hyperlink in some terminals. Specify a dash ("-") to specify the end of the hyperlink. Hyperlinks must only contain single-byte characters (e.g. ASCII) and they may not contain bracket characters ("[" or "]"). Examples: In the rare event that you want to display a string such as "[red]" or "[#00ff1a]" without applying its effect, you need to put an opening square bracket before the closing square bracket. Note that the text inside the brackets will be matched less strictly than region or colors tags. I.e. any character that may be used in color or region tags will be recognized. Examples: You can use the Escape() function to insert brackets automatically where needed. When primitives are instantiated, they are initialized with colors taken from the global Styles variable. You may change this variable to adapt the look and feel of the primitives to your preferred style. Note that most terminals will not report information about their color theme. This package therefore does not support using the terminal's color theme. The default style is a dark theme and you must change the Styles variable to switch to a light (or other) theme. This package supports all unicode characters supported by your terminal. If your terminal supports mouse events, you can enable mouse support for your application by calling Application.EnableMouse. Note that this may interfere with your terminal's default mouse behavior. Mouse support is disabled by default. Many functions in this package are not thread-safe. For many applications, this is not an issue: If your code makes changes in response to key events, the corresponding callback function will execute in the main goroutine and thus will not cause any race conditions. (Exceptions to this are documented.) If you access your primitives from other goroutines, however, you will need to synchronize execution. The easiest way to do this is to call Application.QueueUpdate or Application.QueueUpdateDraw (see the function documentation for details): One exception to this is the io.Writer interface implemented by TextView. You can safely write to a TextView from any goroutine. See the TextView documentation for details. You can also call Application.Draw from any goroutine without having to wrap it in Application.QueueUpdate. And, as mentioned above, key event callbacks are executed in the main goroutine and thus should not use Application.QueueUpdate as that may lead to deadlocks. It is also not necessary to call Application.Draw from such callbacks as it will be called automatically. All widgets listed above contain the Box type. All of Box's functions are therefore available for all widgets, too. Please note that if you are using the functions of Box on a subclass, they will return a *Box, not the subclass. This is a Golang limitation. So while tview supports method chaining in many places, these chains must be broken when using Box's functions. Example: You will need to call Box.SetBorder separately: All widgets also implement the Primitive interface. The tview package's rendering is based on version 2 of https://github.com/ales999/tcell. It uses types and constants from that package (e.g. colors, styles, and keyboard values).

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialized. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/google/jsonapi

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialized. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/google/jsonapi

Package template implements data-driven templates for generating textual output. To generate HTML output, see html/template, which has the same interface as this package but automatically secures HTML output against certain attacks. Templates are executed by applying them to a data structure. Annotations in the template refer to elements of the data structure (typically a field of a struct or a key in a map) to control execution and derive values to be displayed. Execution of the template walks the structure and sets the cursor, represented by a period '.' and called "dot", to the value at the current location in the structure as execution proceeds. The input text for a template is UTF-8-encoded text in any format. "Actions"--data evaluations or control structures--are delimited by "{{" and "}}"; all text outside actions is copied to the output unchanged. Once parsed, a template may be executed safely in parallel, although if parallel executions share a Writer the output may be interleaved. Here is a trivial example that prints "17 items are made of wool". More intricate examples appear below. By default, all text between actions is copied verbatim when the template is executed. For example, the string " items are made of " in the example above appears on standard output when the program is run. However, to aid in formatting template source code, if an action's left delimiter (by default "{{") is followed immediately by a minus sign and white space, all trailing white space is trimmed from the immediately preceding text. Similarly, if the right delimiter ("}}") is preceded by white space and a minus sign, all leading white space is trimmed from the immediately following text. In these trim markers, the white space must be present: "{{- 3}}" is like "{{3}}" but trims the immediately preceding text, while "{{-3}}" parses as an action containing the number -3. For instance, when executing the template whose source is the generated output would be For this trimming, the definition of white space characters is the same as in Go: space, horizontal tab, carriage return, and newline. Here is the list of actions. "Arguments" and "pipelines" are evaluations of data, defined in detail in the corresponding sections that follow. An argument is a simple value, denoted by one of the following. A boolean, string, character, integer, floating-point, imaginary or complex constant in Go syntax. These behave like Go's untyped constants. Note that, as in Go, whether a large integer constant overflows when assigned or passed to a function can depend on whether the host machine's ints are 32 or 64 bits. The keyword nil, representing an untyped Go nil. The character '.' (period): . The result is the value of dot. A variable name, which is a (possibly empty) alphanumeric string preceded by a dollar sign, such as $piOver2 or $ The result is the value of the variable. Variables are described below. The name of a field of the data, which must be a struct, preceded by a period, such as .Field The result is the value of the field. Field invocations may be chained: .Field1.Field2 Fields can also be evaluated on variables, including chaining: $x.Field1.Field2 The name of a key of the data, which must be a map, preceded by a period, such as .Key The result is the map element value indexed by the key. Key invocations may be chained and combined with fields to any depth: .Field1.Key1.Field2.Key2 Although the key must be an alphanumeric identifier, unlike with field names they do not need to start with an upper case letter. Keys can also be evaluated on variables, including chaining: $x.key1.key2 The name of a niladic method of the data, preceded by a period, such as .Method The result is the value of invoking the method with dot as the receiver, dot.Method(). Such a method must have one return value (of any type) or two return values, the second of which is an error. If it has two and the returned error is non-nil, execution terminates and an error is returned to the caller as the value of Execute. Method invocations may be chained and combined with fields and keys to any depth: .Field1.Key1.Method1.Field2.Key2.Method2 Methods can also be evaluated on variables, including chaining: $x.Method1.Field The name of a niladic function, such as fun The result is the value of invoking the function, fun(). The return types and values behave as in methods. Functions and function names are described below. A parenthesized instance of one the above, for grouping. The result may be accessed by a field or map key invocation. print (.F1 arg1) (.F2 arg2) (.StructValuedMethod "arg").Field Arguments may evaluate to any type; if they are pointers the implementation automatically indirects to the base type when required. If an evaluation yields a function value, such as a function-valued field of a struct, the function is not invoked automatically, but it can be used as a truth value for an if action and the like. To invoke it, use the call function, defined below. A pipeline is a possibly chained sequence of "commands". A command is a simple value (argument) or a function or method call, possibly with multiple arguments: A pipeline may be "chained" by separating a sequence of commands with pipeline characters '|'. In a chained pipeline, the result of each command is passed as the last argument of the following command. The output of the final command in the pipeline is the value of the pipeline. The output of a command will be either one value or two values, the second of which has type error. If that second value is present and evaluates to non-nil, execution terminates and the error is returned to the caller of Execute. A pipeline inside an action may initialize a variable to capture the result. The initialization has syntax where $variable is the name of the variable. An action that declares a variable produces no output. Variables previously declared can also be assigned, using the syntax If a "range" action initializes a variable, the variable is set to the successive elements of the iteration. Also, a "range" may declare two variables, separated by a comma: in which case $index and $element are set to the successive values of the array/slice index or map key and element, respectively. Note that if there is only one variable, it is assigned the element; this is opposite to the convention in Go range clauses. A variable's scope extends to the "end" action of the control structure ("if", "with", or "range") in which it is declared, or to the end of the template if there is no such control structure. A template invocation does not inherit variables from the point of its invocation. When execution begins, $ is set to the data argument passed to Execute, that is, to the starting value of dot. Here are some example one-line templates demonstrating pipelines and variables. All produce the quoted word "output": During execution functions are found in two function maps: first in the template, then in the global function map. By default, no functions are defined in the template but the Funcs method can be used to add them. Predefined global functions are named as follows. The boolean functions take any zero value to be false and a non-zero value to be true. There is also a set of binary comparison operators defined as functions: For simpler multi-way equality tests, eq (only) accepts two or more arguments and compares the second and subsequent to the first, returning in effect (Unlike with || in Go, however, eq is a function call and all the arguments will be evaluated.) The comparison functions work on any values whose type Go defines as comparable. For basic types such as integers, the rules are relaxed: size and exact type are ignored, so any integer value, signed or unsigned, may be compared with any other integer value. (The arithmetic value is compared, not the bit pattern, so all negative integers are less than all unsigned integers.) However, as usual, one may not compare an int with a float32 and so on. Each template is named by a string specified when it is created. Also, each template is associated with zero or more other templates that it may invoke by name; such associations are transitive and form a name space of templates. A template may use a template invocation to instantiate another associated template; see the explanation of the "template" action above. The name must be that of a template associated with the template that contains the invocation. When parsing a template, another template may be defined and associated with the template being parsed. Template definitions must appear at the top level of the template, much like global variables in a Go program. The syntax of such definitions is to surround each template declaration with a "define" and "end" action. The define action names the template being created by providing a string constant. Here is a simple example: This defines two templates, T1 and T2, and a third T3 that invokes the other two when it is executed. Finally it invokes T3. If executed this template will produce the text By construction, a template may reside in only one association. If it's necessary to have a template addressable from multiple associations, the template definition must be parsed multiple times to create distinct *Template values, or must be copied with Template.Clone or Template.AddParseTree. Parse may be called multiple times to assemble the various associated templates; see ParseFiles, ParseGlob, Template.ParseFiles and Template.ParseGlob for simple ways to parse related templates stored in files. A template may be executed directly or through Template.ExecuteTemplate, which executes an associated template identified by name. To invoke our example above, we might write, or to invoke a particular template explicitly by name,

Package jsonapi provides a serializer and deserializer for jsonapi.org spec payloads. You can keep your model structs as is and use struct field tags to indicate to jsonapi how you want your response built or your request deserialized. What about my relationships? jsonapi supports relationships out of the box and will even side load them in your response into an "included" array--that contains associated objects. jsonapi uses StructField tags to annotate the structs fields that you already have and use in your app and then reads and writes jsonapi.org output based on the instructions you give the library in your jsonapi tags. Example structs using a Blog > Post > Comment structure, jsonapi Tag Reference Value, primary: "primary,<type field output>" This indicates that this is the primary key field for this struct type. Tag value arguments are comma separated. The first argument must be, "primary", and the second must be the name that should appear in the "type" field for all data objects that represent this type of model. Value, attr: "attr,<key name in attributes hash>[,<extra arguments>]" These fields' values should end up in the "attribute" hash for a record. The first argument must be, "attr', and the second should be the name for the key to display in the "attributes" hash for that record. The following extra arguments are also supported: "omitempty": excludes the fields value from the "attribute" hash. "iso8601": uses the ISO8601 timestamp format when serialising or deserialising the time.Time value. Value, relation: "relation,<key name in relationships hash>" Relations are struct fields that represent a one-to-one or one-to-many to other structs. jsonapi will traverse the graph of relationships and marshal or unmarshal records. The first argument must be, "relation", and the second should be the name of the relationship, used as the key in the "relationships" hash for the record. Use the methods below to Marshal and Unmarshal jsonapi.org json payloads. Visit the readme at https://github.com/companyinfo/jsonapi

Package telnet provides TELNET and TELNETS client and server implementations in a style similar to the "net/http" library that is part of the Go standard library, including support for "middleware"; TELNETS is secure TELNET, with the TELNET protocol over a secured TLS (or SSL) connection. ListenAndServe starts a (un-secure) TELNET server with a given address and handler. ListenAndServeTLS starts a (secure) TELNETS server with a given address and handler, using the specified "cert.pem" and "key.pem" files. Example TELNET Client: DialToAndCall creates a (un-secure) TELNET client, which connects to a given address using the specified caller. Example TELNETS Client: DialToAndCallTLS creates a (secure) TELNETS client, which connects to a given address using the specified caller. If you are communicating over the open Internet, you should be using (the secure) TELNETS protocol and ListenAndServeTLS. If you are communicating just on localhost, then using just (the un-secure) TELNET protocol and telnet.ListenAndServe may be OK. If you are not sure which to use, use TELNETS and ListenAndServeTLS. The previous 2 exaple servers were very very simple. Specifically, they just echoed back whatever you submitted to it. If you typed: ... it would send back: (Exactly the same data you sent it.) A more useful TELNET server can be made using the "github.com/karimrc/go-telnet/telsh" sub-package. The `telsh` sub-package provides "middleware" that enables you to create a "shell" interface (also called a "command line interface" or "CLI") which most people would expect when using TELNET OR TELNETS. For example: Note that in the example, so far, we have registered 2 commands: `date` and `animate`. For this to actually work, we need to have code for the `date` and `animate` commands. The actual implemenation for the `date` command could be done like the following: Note that your "real" work is in the `dateHandlerFunc` func. And the actual implementation for the `animate` command could be done as follows: Again, note that your "real" work is in the `animateHandlerFunc` func. If you are using the telnet.ListenAndServeTLS func or the telnet.Server.ListenAndServeTLS method, you will need to supply "cert.pem" and "key.pem" files. If you do not already have these files, the Go soure code contains a tool for generating these files for you. It can be found at: So, for example, if your `$GOROOT` is the "/usr/local/go" directory, then it would be at: If you run the command: ... then you get the help information for "generate_cert.go". Of course, you would replace or set `$GOROOT` with whatever your path actually is. Again, for example, if your `$GOROOT` is the "/usr/local/go" directory, then it would be: To demonstrate the usage of "generate_cert.go", you might run the following to generate certificates that were bound to the hosts `127.0.0.1` and `localhost`: If you are not sure where "generate_cert.go" is on your computer, on Linux and Unix based systems, you might be able to find the file with the command: (If it finds it, it should output the full path to this file.) You can make a simple (un-secure) TELNET client with code like the following: You can make a simple (secure) TELNETS client with code like the following: The TELNET protocol is best known for providing a means of connecting to a remote computer, using a (text-based) shell interface, and being able to interact with it, (more or less) as if you were sitting at that computer. (Shells are also known as command-line interfaces or CLIs.) Although this was the original usage of the TELNET protocol, it can be (and is) used for other purposes as well. The TELNET protocol came from an era in computing when text-based shell interface where the common way of interacting with computers. The common interface for computers during this era was a keyboard and a monochromatic (i.e., single color) text-based monitors called "video terminals". (The word "video" in that era of computing did not refer to things such as movies. But instead was meant to contrast it with paper. In particular, the teletype machines, which were typewriter like devices that had a keyboard, but instead of having a monitor had paper that was printed onto.) In that era, in the early days of office computers, it was rare that an individual would have a computer at their desk. (A single computer was much too expensive.) Instead, there would be a single central computer that everyone would share. The style of computer used (for the single central shared computer) was called a "mainframe". What individuals would have at their desks, instead of their own compuer, would be some type of video terminal. The different types of video terminals had named such as: • VT52 • VT100 • VT220 • VT240 ("VT" in those named was short for "video terminal".) To understand this era, we need to go back a bit in time to what came before it: teletypes. Terminal codes (also sometimes called 'terminal control codes') are used to issue various kinds of commands to the terminal. (Note that 'terminal control codes' are a completely separate concept for 'TELNET commands', and the two should NOT be conflated or confused.) The most common types of 'terminal codes' are the 'ANSI escape codes'. (Although there are other types too.) ANSI escape codes (also sometimes called 'ANSI escape sequences') are a common type of 'terminal code' used to do things such as: • moving the cursor, • erasing the display, • erasing the line, • setting the graphics mode, • setting the foregroup color, • setting the background color, • setting the screen resolution, and • setting keyboard strings. One of the abilities of ANSI escape codes is to set the foreground color. Here is a table showing codes for this: (Note that in the `[]byte` that the first `byte` is the number `27` (which is the "escape" character) where the third and fouth characters are the **not** number literals, but instead character literals `'3'` and whatever.) Another of the abilities of ANSI escape codes is to set the background color. (Note that in the `[]byte` that the first `byte` is the number `27` (which is the "escape" character) where the third and fouth characters are the **not** number literals, but instead character literals `'4'` and whatever.) In Go code, if I wanted to use an ANSI escape code to use a blue background, a white foreground, and bold, I could do that with the ANSI escape code: Note that that start with byte value 27, which we have encoded as hexadecimal as \x1b. Followed by the '[' character. Coming after that is the sub-string "44", which is the code that sets our background color to blue. We follow that with the ';' character (which separates codes). And the after that comes the sub-string "37", which is the code that set our foreground color to white. After that, we follow with another ";" character (which, again, separates codes). And then we follow it the sub-string "1", which is the code that makes things bold. And finally, the ANSI escape sequence is finished off with the 'm' character. To show this in a more complete example, our `dateHandlerFunc` from before could incorporate ANSI escape sequences as follows: Note that in that example, in addition to using the ANSI escape sequence "\x1b[44;37;1m" to set the background color to blue, set the foreground color to white, and make it bold, we also used the ANSI escape sequence "\x1b[0m" to reset the background and foreground colors and boldness back to "normal".