cli

README

cli.go

cli.go is simple, fast, and fun package for building command line apps in Go. The goal is to enable developers to write fast and distributable command line applications in an expressive way.

You can view the API docs here: http://godoc.org/github.com/codegangsta/cli

Overview

Command line apps are usually so tiny that there is absolutely no reason why your code should not be self-documenting. Things like generating help text and parsing command flags/options should not hinder productivity when writing a command line app.

This is where cli.go comes into play. cli.go makes command line programming fun, organized, and expressive!

Installation

Make sure you have a working Go environment (go 1.1 is required). See the install instructions.

To install cli.go, simply run:

$ go get github.com/codegangsta/cli

Make sure your PATH includes to the $GOPATH/bin directory so your commands can be easily used:

export PATH=$PATH:$GOPATH/bin

Getting Started

One of the philosophies behind cli.go is that an API should be playful and full of discovery. So a cli.go app can be as little as one line of code in main().

package main

import (
  "os"
  "github.com/codegangsta/cli"
)

func main() {
  cli.NewApp().Run(os.Args)
}

This app will run and show help text, but is not very useful. Let's give an action to execute and some help documentation:

package main

import (
  "os"
  "github.com/codegangsta/cli"
)

func main() {
  app := cli.NewApp()
  app.Name = "boom"
  app.Usage = "make an explosive entrance"
  app.Action = func(c *cli.Context) {
    println("boom! I say!")
  }
  
  app.Run(os.Args)
}

Running this already gives you a ton of functionality, plus support for things like subcommands and flags, which are covered below.

Example

Being a programmer can be a lonely job. Thankfully by the power of automation that is not the case! Let's create a greeter app to fend off our demons of loneliness!

/* greet.go */
package main

import (
  "os"
  "github.com/codegangsta/cli"
)

func main() {
  app := cli.NewApp()
  app.Name = "greet"
  app.Usage = "fight the loneliness!"
  app.Action = func(c *cli.Context) {
    println("Hello friend!")
  }
  
  app.Run(os.Args)
}

Install our command to the $GOPATH/bin directory:

$ go install

Finally run our new command:

$ greet
Hello friend!

cli.go also generates some bitchass help text:

$ greet help
NAME:
    greet - fight the loneliness!

USAGE:
    greet [global options] command [command options] [arguments...]

VERSION:
    0.0.0

COMMANDS:
    help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS
    --version	Shows version information

Arguments

You can lookup arguments by calling the Args function on cli.Context.

...
app.Action = func(c *cli.Context) {
  println("Hello", c.Args()[0])
}
...

Flags

Setting and querying flags is simple.

...
app.Flags = []cli.Flag {
  cli.StringFlag{"lang", "english", "language for the greeting"},
}
app.Action = func(c *cli.Context) {
  name := "someone"
  if len(c.Args()) > 0 {
    name = c.Args()[0]
  }
  if c.String("lang") == "spanish" {
    println("Hola", name)
  } else {
    println("Hello", name)
  }
}
...

Alternate Names

You can set alternate (or short) names for flags by providing a comma-delimited list for the Name. e.g.

app.Flags = []cli.Flag {
  cli.StringFlag{"lang, l", "english", "language for the greeting"},
}

That flag can then be set with --lang spanish or -l spanish. Note that giving two different forms of the same flag in the same command invocation is an error.

Subcommands

Subcommands can be defined for a more git-like command line app.

...
app.Commands = []cli.Command{
  {
    Name:      "add",
    ShortName: "a",
    Usage:     "add a task to the list",
    Action: func(c *cli.Context) {
      println("added task: ", c.Args().First())
    },
  },
  {
    Name:      "complete",
    ShortName: "c",
    Usage:     "complete a task on the list",
    Action: func(c *cli.Context) {
      println("completed task: ", c.Args().First())
    },
  },
}
...

About

cli.go is written by none other than the Code Gangsta

Documentation

Overview

Package cli provides a minimal framework for creating and organizing command line Go applications. cli is designed to be easy to understand and write, the most simple cli application can be written as follows:

func main() {
  cli.NewApp().Run(os.Args)
}

Of course this application does not do much, so let's make this an actual application:

func main() {
  app := cli.NewApp()
  app.Name = "greet"
  app.Usage = "say a greeting"
  app.Action = func(c *cli.Context) {
    println("Greetings")
  }

  app.Run(os.Args)
}

Example

package main

import (
	"github.com/coreos/fleet/third_party/github.com/codegangsta/cli"
	"os"
)

func main() {
	app := cli.NewApp()
	app.Name = "todo"
	app.Usage = "task list on the command line"
	app.Commands = []cli.Command{
		{
			Name:      "add",
			ShortName: "a",
			Usage:     "add a task to the list",
			Action: func(c *cli.Context) {
				println("added task: ", c.Args().First())
			},
		},
		{
			Name:      "complete",
			ShortName: "c",
			Usage:     "complete a task on the list",
			Action: func(c *cli.Context) {
				println("completed task: ", c.Args().First())
			},
		},
	}

	app.Run(os.Args)
}

Index

• Variables
• func ShowAppHelp(c *Context)
• func ShowCommandHelp(c *Context, command string)
• func ShowVersion(c *Context)
• type App
  • func NewApp() *App
  • func (a *App) Command(name string) *Command
  • func (a *App) Run(arguments []string) error
• type Args
  • func (a Args) First() string
  • func (a Args) Get(n int) string
  • func (a Args) Present() bool
  • func (a Args) Tail() []string
• type BoolFlag
  • func (f BoolFlag) Apply(set *flag.FlagSet)
  • func (f BoolFlag) String() string
• type BoolTFlag
  • func (f BoolTFlag) Apply(set *flag.FlagSet)
  • func (f BoolTFlag) String() string
• type Command
  • func (c Command) HasName(name string) bool
  • func (c Command) Run(ctx *Context) error
• type Context
  • func NewContext(app *App, set *flag.FlagSet, globalSet *flag.FlagSet) *Context
  • func (c *Context) Args() Args
  • func (c *Context) Bool(name string) bool
  • func (c *Context) BoolT(name string) bool
  • func (c *Context) Float64(name string) float64
  • func (c *Context) GlobalBool(name string) bool
  • func (c *Context) GlobalInt(name string) int
  • func (c *Context) GlobalIntSlice(name string) []int
  • func (c *Context) GlobalString(name string) string
  • func (c *Context) GlobalStringSlice(name string) []string
  • func (c *Context) Int(name string) int
  • func (c *Context) IntSlice(name string) []int
  • func (c *Context) IsSet(name string) bool
  • func (c *Context) String(name string) string
  • func (c *Context) StringSlice(name string) []string
• type Flag
• type Float64Flag
  • func (f Float64Flag) Apply(set *flag.FlagSet)
  • func (f Float64Flag) String() string
• type IntFlag
  • func (f IntFlag) Apply(set *flag.FlagSet)
  • func (f IntFlag) String() string
• type IntSlice
  • func (f *IntSlice) Set(value string) error
  • func (f *IntSlice) String() string
  • func (f *IntSlice) Value() []int
• type IntSliceFlag
  • func (f IntSliceFlag) Apply(set *flag.FlagSet)
  • func (f IntSliceFlag) String() string
• type StringFlag
  • func (f StringFlag) Apply(set *flag.FlagSet)
  • func (f StringFlag) String() string
• type StringSlice
  • func (f *StringSlice) Set(value string) error
  • func (f *StringSlice) String() string
  • func (f *StringSlice) Value() []string
• type StringSliceFlag
  • func (f StringSliceFlag) Apply(set *flag.FlagSet)
  • func (f StringSliceFlag) String() string

Examples

• Package
• App

Variables

var AppHelpTemplate = `` /* 296-byte string literal not displayed */

The text template for the Default help topic. cli.go uses text/template to render templates. You can render custom help text by setting this variable.

var CommandHelpTemplate = `` /* 174-byte string literal not displayed */

The text template for the command help topic. cli.go uses text/template to render templates. You can render custom help text by setting this variable.

var HelpPrinter = printHelp

Prints help for the App

Functions

func ShowAppHelp

func ShowAppHelp(c *Context)

func ShowCommandHelp

func ShowCommandHelp(c *Context, command string)

Prints help for the given command

func ShowVersion

func ShowVersion(c *Context)

Prints the version number of the App

Types

type App

type App struct {
	// The name of the program. Defaults to os.Args[0]
	Name string
	// Description of the program.
	Usage string
	// Version of the program
	Version string
	// List of commands to execute
	Commands []Command
	// List of flags to parse
	Flags []Flag
	// An action to execute before any subcommands are run, but after the context is ready
	// If a non-nil error is returned, no subcommands are run
	Before func(context *Context) error
	// The action to execute when no subcommands are specified
	Action func(context *Context)
	// Compilation date
	Compiled time.Time
	// Author
	Author string
	// Author e-mail
	Email string
}

App is the main structure of a cli application. It is recomended that and app be created with the cli.NewApp() function

Example

package main

import (
	"fmt"
	"github.com/coreos/fleet/third_party/github.com/codegangsta/cli"
	"os"
)

func main() {
	// set args for examples sake
	os.Args = []string{"greet", "--name", "Jeremy"}

	app := cli.NewApp()
	app.Name = "greet"
	app.Flags = []cli.Flag{
		cli.StringFlag{Name: "name", Value: "bob", Usage: "a name to say"},
	}
	app.Action = func(c *cli.Context) {
		fmt.Printf("Hello %v\n", c.String("name"))
	}
	app.Run(os.Args)
}

Output:

Hello Jeremy

func NewApp

func NewApp() *App

Creates a new cli Application with some reasonable defaults for Name, Usage, Version and Action.

func (*App) Command

func (a *App) Command(name string) *Command

Returns the named command on App. Returns nil if the command does not exist

func (*App) Run

func (a *App) Run(arguments []string) error

Entry point to the cli app. Parses the arguments slice and routes to the proper flag/args combination

type Args

type Args []string

func (Args) First

func (a Args) First() string

Returns the first argument, or else a blank string

func (Args) Get

func (a Args) Get(n int) string

Returns the nth argument, or else a blank string

func (Args) Present

func (a Args) Present() bool

Checks if there are any arguments present

func (Args) Tail

func (a Args) Tail() []string

Return the rest of the arguments (not the first one) or else an empty string slice

type BoolFlag

type BoolFlag struct {
	Name  string
	Usage string
}

func (BoolFlag) Apply

func (f BoolFlag) Apply(set *flag.FlagSet)

func (BoolFlag) String

func (f BoolFlag) String() string

type BoolTFlag

type BoolTFlag struct {
	Name  string
	Usage string
}

func (BoolTFlag) Apply

func (f BoolTFlag) Apply(set *flag.FlagSet)

func (BoolTFlag) String

func (f BoolTFlag) String() string

type Command

type Command struct {
	// The name of the command
	Name string
	// short name of the command. Typically one character
	ShortName string
	// A short description of the usage of this command
	Usage string
	// A longer explaination of how the command works
	Description string
	// The function to call when this command is invoked
	Action func(context *Context)
	// List of flags to parse
	Flags []Flag
}

Command is a subcommand for a cli.App.

func (Command) HasName

func (c Command) HasName(name string) bool

Returns true if Command.Name or Command.ShortName matches given name

func (Command) Run

func (c Command) Run(ctx *Context) error

Invokes the command given the context, parses ctx.Args() to generate command-specific flags

type Context

type Context struct {
	App *App
	// contains filtered or unexported fields
}

Context is a type that is passed through to each Handler action in a cli application. Context can be used to retrieve context-specific Args and parsed command-line options.

func NewContext

func NewContext(app *App, set *flag.FlagSet, globalSet *flag.FlagSet) *Context

Creates a new context. For use in when invoking an App or Command action.

func (*Context) Args

func (c *Context) Args() Args

Returns the command line arguments associated with the context.

func (*Context) Bool

func (c *Context) Bool(name string) bool

Looks up the value of a local bool flag, returns false if no bool flag exists

func (*Context) BoolT

func (c *Context) BoolT(name string) bool

Looks up the value of a local boolT flag, returns false if no bool flag exists

func (*Context) Float64

func (c *Context) Float64(name string) float64

Looks up the value of a local float64 flag, returns 0 if no float64 flag exists

func (*Context) GlobalBool

func (c *Context) GlobalBool(name string) bool

Looks up the value of a global bool flag, returns false if no bool flag exists

func (*Context) GlobalInt

func (c *Context) GlobalInt(name string) int

Looks up the value of a global int flag, returns 0 if no int flag exists

func (*Context) GlobalIntSlice

func (c *Context) GlobalIntSlice(name string) []int

Looks up the value of a global int slice flag, returns nil if no int slice flag exists

func (*Context) GlobalString

func (c *Context) GlobalString(name string) string

Looks up the value of a global string flag, returns "" if no string flag exists

func (*Context) GlobalStringSlice

func (c *Context) GlobalStringSlice(name string) []string

Looks up the value of a global string slice flag, returns nil if no string slice flag exists

func (*Context) Int

func (c *Context) Int(name string) int

Looks up the value of a local int flag, returns 0 if no int flag exists

func (*Context) IntSlice

func (c *Context) IntSlice(name string) []int

Looks up the value of a local int slice flag, returns nil if no int slice flag exists

func (*Context) IsSet

func (c *Context) IsSet(name string) bool

Determines if the flag was actually set exists

func (*Context) String

func (c *Context) String(name string) string

Looks up the value of a local string flag, returns "" if no string flag exists

func (*Context) StringSlice

func (c *Context) StringSlice(name string) []string

Looks up the value of a local string slice flag, returns nil if no string slice flag exists

type Flag

type Flag interface {
	fmt.Stringer
	// Apply Flag settings to the given flag set
	Apply(*flag.FlagSet)
	// contains filtered or unexported methods
}

Flag is a common interface related to parsing flags in cli. For more advanced flag parsing techniques, it is recomended that this interface be implemented.

type Float64Flag

type Float64Flag struct {
	Name  string
	Value float64
	Usage string
}

func (Float64Flag) Apply

func (f Float64Flag) Apply(set *flag.FlagSet)

func (Float64Flag) String

func (f Float64Flag) String() string

type IntFlag

type IntFlag struct {
	Name  string
	Value int
	Usage string
}

func (IntFlag) Apply

func (f IntFlag) Apply(set *flag.FlagSet)

func (IntFlag) String

func (f IntFlag) String() string

type IntSlice

type IntSlice []int

func (*IntSlice) Set

func (f *IntSlice) Set(value string) error

func (*IntSlice) String

func (f *IntSlice) String() string

func (*IntSlice) Value

func (f *IntSlice) Value() []int

type IntSliceFlag

type IntSliceFlag struct {
	Name  string
	Value *IntSlice
	Usage string
}

func (IntSliceFlag) Apply

func (f IntSliceFlag) Apply(set *flag.FlagSet)

func (IntSliceFlag) String

func (f IntSliceFlag) String() string

type StringFlag

type StringFlag struct {
	Name  string
	Value string
	Usage string
}

func (StringFlag) Apply

func (f StringFlag) Apply(set *flag.FlagSet)

func (StringFlag) String

func (f StringFlag) String() string

type StringSlice

type StringSlice []string

func (*StringSlice) Set

func (f *StringSlice) Set(value string) error

func (*StringSlice) String

func (f *StringSlice) String() string

func (*StringSlice) Value

func (f *StringSlice) Value() []string

type StringSliceFlag

type StringSliceFlag struct {
	Name  string
	Value *StringSlice
	Usage string
}

func (StringSliceFlag) Apply

func (f StringSliceFlag) Apply(set *flag.FlagSet)

func (StringSliceFlag) String

func (f StringSliceFlag) String() string