cmdflag : command support to the standard library flag package

Overview

Building on top of the excellent flag package from the standard library, cmdflag adds a simple way of specifying nested commands. Its intent is to blend with the usage of flag by keeping its idioms and simply augment it with commands.

Install

go get github.com/pierrec/cmdflag

Usage

A Command is a set of flags (flag.FlagSet) with a (potentially empty) set of other Commands (sometimes referred to as subcommands). To define a subcommand, Command.Add an Application defining its properties:

• Name - the subcommand name
• Descr - a short desciption of the subcommand
• Args - the list of arguments expected by the subcommand
• Help - a long description of the subcommand
• Err - what to do in case of error (same as in the flag package)
• Init - the function to be run once the subcommand is encountered (lazily initialized)

Nested commands are supported, so a subcommand can also have its own subcommands.

Example

./chef cook -toppings cheese,mushrooms pizza

c := cmdflag.New(nil)
c.Add(cmdflag.Application{
    Name: "cook",
    Init: func(fs *flag.FlagSet) cmdflag.Handler {
        var toppings string
        fs.StringVar(&toppings, "toppings", "", "coma separated list of toppings")
        
        return func(args ...string) (int, error) {
            fmt.Printf("courses: %v\n", args)
            fmt.Printf("toppings: %v\n", strings.Split(toppings, ","))
            return len(args), nil
        }
    }
}

Extra features

To make life easier, a few common uses of a command line library are provided and can be easily activated:

• flags: defining them as a flag activates them
  • -version - see VersionBoolFlag
  • -fullversion - see FullVersionBoolFlag
  • the standard -h and -help flags are supported to display the usage of the command they apply to
• commands:
  • help - provides a way to display Application.Help for a given command (activated by Command.AddHelp)

Contributing

Contributions welcome via pull requests. Please provide tests.