rakyll / command

CLI subcommands for Go

command

command is a tiny package that helps you to add cli subcommands to your Go program with no effort, and prints a pretty guide if needed.

Usage: program <command>

where <command> is one of:
  version   prints the version
  command1  some description about command1
  command2  some description about command2

available flags:
  -exec-path="": a custom path to executable

program <command> -h for subcommand help

Usage

In order to start, go get this repository:

go get github.com/rakyll/command

This package allows you to use flags package as you used to do, and provides additional parsing for subcommands and subcommand flags.

import "github.com/rakyll/command"

// register any global flags
var flagExecPath = flag.String("exec-path", "", "a custom path to executable")

type VersionCommand struct{
	flagVerbose *bool
}

func (cmd *VersionCommand) Flags(fs *flag.FlagSet) *flag.FlagSet {
	// define subcommand's flags
	cmd.flagVerbose = fs.Bool("v", false, "provides verbose output")
	return fs
}

func (cmd *VersionCommand) Run(args []string) {
	// implement the main body of the subcommand here
  // required and optional arguments are found in args
}

// register version as a subcommand
command.On("version", "prints the version", &VersionCommand{}, []string{"<required-arg>"})
command.On("command1", "some description about command1", ..., []string{})
command.On("command2", "some description about command2", ..., []string{})
command.Parse()
// ...
command.Run()

The program above will handle the registered commands and invoke the matching command's Run or print subcommand help if -h is set.

$ program -exec-path=/home/user/bin/someexec version -v=true history

will output the version of the program in a verbose way requring an argument (history), and will set the exec path to the provided path. If arguments doesn't match any subcommand or illegal arguments are provided, it will print the usage guide.

License

Copyright 2013 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

command's Issues

Check required flags are set or not

Current logic is merged without a proper code review, it doesn't look like it actually checks if flags are set or not.

git / kubectl like pugin system.

It would be nice to be able to specify a prefix and if a subcommand is not found look for an executable in the PATH that matches prefix-subcommand and execute it if found, passing any args and flags to that executable. Like git and kubectl do.

Maybe this could be implemented through #4 .

Required args should be called required flags

Allow catchall handler if no subcommand matches