getopt

Description

The getopt Ruby library is a simple command line parsing library. It implements a Getopt::Std class for basic command line parsing, as well as a Getopt::Long class for more advanced command line parsing.

Installation

gem install getopt

Synopsis

Getopt::Std

require 'getopt/std'

# Look for -o with argument, and -I and -D boolean arguments
opt = Getopt::Std.getopts("o:ID")

if opt["I"]
  # Do something if -I passed
  
if opt["D"]
  # Do something if -D passed
  
if opt["o"]
  case opt["o"]
    # blah, blah, blah
  end
end

Getopt::Long

require 'getopt/long'

opt = Getopt::Long.getopts(
  ["--foo", "-f", Getopt::BOOLEAN],
  ["--bar", "-b", Getopt::REQUIRED]
)
 
# Or, to save your fingers some typing:
#
# require "getopt/long"
# include Getopt
# opt = Long.getopts(
#    ["--foo", "-f", BOOLEAN],
#    ["--bar", "-b", REQUIRED]
# )

if opt["foo"]
  # Do something if --foo or -f passed
end

if opt["b"]
  # Do something if --bar or -b passed
end

Singleton Methods

Std.getopts(switches)

Takes a series of single character switches that can be accepted on the command line. Any characters followed by a ":" require an argument. The rest are considered boolean switches.

The method returns a hash, with the switches as the key (minus the leading '-'). For boolean switches, the value is either true or false. Switches that were not passed on the command line do not appear in the hash.

In the event that a switch which accepts an argument appears multiple times the value for that key becomes an array of values.

Long.getopts(switches)

Takes an array of switches beginning with "--" followed by one or more alphanumeric or hyphen characters, or "-" followed by a single character. The type of argument, if any, can be specified as BOOLEAN, OPTIONAL, REQUIRED or INCREMENT.

The array should be in the form:

# long form, short form (alias), option type
["--long", "-l", Getopt::OPTION]

Note that only the long form is required. If the short form is not specified, it will automatically be set to the first letter of the long switch. If multiple long switches with the same first character are listed without short switches, only the first long switch gets the short switch alias.

If the argument type is not specified, the default is BOOLEAN.

For the truly lazy, you can also pass a string of long switches (with no short switches or argument types).

See the 'examples' directory for more examples.

Getopt::Long argument types

REQUIRED

If the option is specified on the command line, it must be followed by a non-blank argument. This argument cannot be another switch. If this switch appears multiple times, the values are collected into an array.

BOOLEAN

If the option is specified on the command line, its value is set to true. It must not be followed by a non-blank argument, excluding other switches. Attempting to pass a boolean switch more than once will raise an error.

OPTIONAL

If the option is specified on the command line, it may or may not accept an argument, excluding other valid switches. If an argument is present, it's value is set to that argument. If an argument is not present, it's value is set to nil.

INCREMENT

If the option is specified on the command line, its value is incremented by one for each appearance on the command line, or set to 1 if it appears only once.

Future Plans

• Add support for negatable options so that you can do "--no-foo", for example.

• Add support for numeric types, so that you don't have to manually convert strings to numbers.

• Allow shortcut characters for the option types, e.g. "?" for BOOLEAN, "+" for INCREMENT, etc.

Known Issues

Getopt::Std

You cannot squish switches that require arguments with the argument itself. For example, if you do Getopt::Std.getopts("o:ID"), it will not parse "-IDohello" properly. Instead, you must do "-IDo hello". Or, you can just separate the argument, e.g. "-I -D -o hello".

Getopt::Long

If you mix and match compressed switches with separate, optional switches the optional switch will be set to true instead of nil if it separated from the compressed switches.

Reporting Issues

If you find any other issues, please log them on the project page at https://github.com/djberg96/getopt.

Other Stuff

Neither class attempts to be POSIX compliant in any way, shape or form.

And I don't care!

Notes From the Author

My main gripe with the getoptlong library currently in the standard library is that it doesn't return a hash, yet gives you partial hash behavior. This was both confusing and annoying, since the first thing I do (along with everyone else) is collect the results into a hash for later processing.

My main gripe with the optparse library (also in the standard library) is that it treats command line processing like event processing. It's too complex, when most of the time all you want to do is slurp the command line options into a hash.

So, I did something utterly novel with this library. I collected the command line options ... (wait for it) ... into a hash! Then I give that hash to you, aliases and all. I did get some ideas from Perl's Getopt::Long library, but this is in no way a port of that module (which supports POSIX parsing, GNU parsing, more option types, etc). My goal was to provide the functionality that I felt would cover the vast majority of common cases, yet still provide a little extra spice with switch types (REQUIRED, OPTIONAL, etc).

There are a few extra things I plan to add (see the 'Future Plans' above) but I do not plan on this library ever becoming as feature rich as, say, Perl's Getopt::Long module.

If you plan to write a full fledged command line application, e.g. you plan on implementing a full help system, gobs of command line options and tons of switches, consider Jim Freeze's commandline gem.

Warranty

This package is provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose.

License

Apache-2.0

Copyright

(C) 2005-2021, Daniel J. Berger All Rights Reserved

Author

Daniel J. Berger