github.com/MikolajGasior/go-mod-cli

go-mod-cli

Package MikolajGasior/go-mod-cli is meant to make handling command line interface easier.

You define commands with flags, attach a handler to it and package does all the parsing.

Install

Ensure you have your workspace directory created and run the following:

go get -u github.com/MikolajGasior/go-mod-cli

Example

Let's start with an example covering everything. First, let's create main CLI instance and commands:

func main() {
    myCLI      := cli.NewCLI("Example CLI", "Silly app", "Author <[e-mail]>")

    cmdInit    := myCLI.AddCmd("init", "Initialises the project", InitHandler)
    cmdStart   := myCLI.AddCmd("start", "Start the application", StartHandler)
}

Next, let's add flags to our commands:

    cmdInit.AddFlag("template", "t", "filepath", "Path to template file", TypePathFile|MustExist|Required, nil)
    cmdInit.AddFlag("file-output", "o", "filepath", "Output to a specific file instead of stdout", TypePathFile, nil)
    cmdInit.AddFlag("number", "n", "int", "Number necessary for initialisation", TypeInt|Required, nil)

    cmdStart.AddFlag("verbose", "v", "", "Verbose mode", TypeBool, nil)
    cmdStart.AddFlag("username", "u", "username", "Username", TypeAlphanumeric|AllowDots|AllowUnderscore|Required, nil)
    cmdStart.AddFlag("threshold", "", "1.5", "Threshold, default 1.5", TypeFloat, nil)
    cmdStart.AddArg("input", "FILE", "Path to a file", TypePathFile|Required)
    cmdStart.AddArg("difficulty", "DIFFICULTY", "Level of difficulty (1-5), default 3", TypeInt)

Fifth argument to NewCLIFlag is used to define what is the type of flag, is it required etc. It's an integer value and the following consts are available:

• TypePathFile - flag is a path to a file (string);
• MustExist - if added along with CLIFlagTypePathFile then path must exist;
• Required - flag is required (this does not work with bool flag);
• TypeString - flag is a string;
• TypeBool - flag is boolean and will have a value of "true" or "false";
• TypeAlphanumeric - flag is string and have to match [0-9a-zA-Z]+.

Check cli_flag.go for more information on flag types.

Finally, let's create functions to handle our commands. In below code, you can see that method Flag on CLI instance (passed as first argument) can be used to get a flag value.

func InitHandler(c *cli.CLI) int {
    fmt.Fprintf(os.Stdout, "Template path: %s\n", c.Flag("template"))
    return 0
}

func StartHandler(c *cli.CLI) int {
    fmt.Fprintf(os.Stdout, "Username: %s\n", c.Flag("username"))
    return 0
}

And in the end of main() func:

    os.Exit(myCLI.Run(os.Stdout, os.Stderr))