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cli === [](https://travis-ci.org/urfave/cli) [](https://ci.appveyor.com/project/urfave/cli) [](https://godoc.org/github.com/urfave/cli) [](https://codebeat.co/projects/github-com-urfave-cli) [](https://goreportcard.com/report/urfave/cli) [](http://gocover.io/github.com/urfave/cli) / [](http://gocover.io/github.com/urfave/cli/altsrc) **Notice:** This is the library formerly known as `github.com/codegangsta/cli` -- Github will automatically redirect requests to this repository, but we recommend updating your references for clarity. cli is a 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. <!-- toc --> - [Overview](#overview) - [Installation](#installation) * [Supported platforms](#supported-platforms) * [Using the `v2` branch](#using-the-v2-branch) * [Pinning to the `v1` branch](#pinning-to-the-v1-branch) - [Getting Started](#getting-started) - [Examples](#examples) * [Arguments](#arguments) * [Flags](#flags) + [Placeholder Values](#placeholder-values) + [Alternate Names](#alternate-names) + [Values from the Environment](#values-from-the-environment) + [Values from alternate input sources (YAML, TOML, and others)](#values-from-alternate-input-sources-yaml-toml-and-others) * [Subcommands](#subcommands) * [Subcommands categories](#subcommands-categories) * [Exit code](#exit-code) * [Bash Completion](#bash-completion) + [Enabling](#enabling) + [Distribution](#distribution) + [Customization](#customization) * [Generated Help Text](#generated-help-text) + [Customization](#customization-1) * [Version Flag](#version-flag) + [Customization](#customization-2) + [Full API Example](#full-api-example) - [Contribution Guidelines](#contribution-guidelines) <!-- tocstop --> ## 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 comes into play.** cli makes command line programming fun, organized, and expressive! ## Installation Make sure you have a working Go environment. Go version 1.2+ is supported. [See the install instructions for Go](http://golang.org/doc/install.html). To install cli, simply run: ``` $ go get github.com/urfave/cli ``` Make sure your `PATH` includes the `$GOPATH/bin` directory so your commands can be easily used: ``` export PATH=$PATH:$GOPATH/bin ``` ### Supported platforms cli is tested against multiple versions of Go on Linux, and against the latest released version of Go on OS X and Windows. For full details, see [`./.travis.yml`](./.travis.yml) and [`./appveyor.yml`](./appveyor.yml). ### Using the `v2` branch **Warning**: The `v2` branch is currently unreleased and considered unstable. There is currently a long-lived branch named `v2` that is intended to land as the new `master` branch once development there has settled down. The current `master` branch (mirrored as `v1`) is being manually merged into `v2` on an irregular human-based schedule, but generally if one wants to "upgrade" to `v2` *now* and accept the volatility (read: "awesomeness") that comes along with that, please use whatever version pinning of your preference, such as via `gopkg.in`: ``` $ go get gopkg.in/urfave/cli.v2 ``` ``` go ... import ( "gopkg.in/urfave/cli.v2" // imports as package "cli" ) ... ``` ### Pinning to the `v1` branch Similarly to the section above describing use of the `v2` branch, if one wants to avoid any unexpected compatibility pains once `v2` becomes `master`, then pinning to the `v1` branch is an acceptable option, e.g.: ``` $ go get gopkg.in/urfave/cli.v1 ``` ``` go ... import ( "gopkg.in/urfave/cli.v1" // imports as package "cli" ) ... ``` ## Getting Started One of the philosophies behind cli is that an API should be playful and full of discovery. So a cli app can be as little as one line of code in `main()`. <!-- { "args": ["&#45;&#45;help"], "output": "A new cli application" } --> ``` go package main import ( "os" "github.com/urfave/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: <!-- { "output": "boom! I say!" } --> ``` go package main import ( "fmt" "os" "github.com/urfave/cli" ) func main() { app := cli.NewApp() app.Name = "boom" app.Usage = "make an explosive entrance" app.Action = func(c *cli.Context) error { fmt.Println("boom! I say!") return nil } 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. ## Examples 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! Start by creating a directory named `greet`, and within it, add a file, `greet.go` with the following code in it: <!-- { "output": "Hello friend!" } --> ``` go package main import ( "fmt" "os" "github.com/urfave/cli" ) func main() { app := cli.NewApp() app.Name = "greet" app.Usage = "fight the loneliness!" app.Action = func(c *cli.Context) error { fmt.Println("Hello friend!") return nil } app.Run(os.Args) } ``` Install our command to the `$GOPATH/bin` directory: ``` $ go install ``` Finally run our new command: ``` $ greet Hello friend! ``` cli also generates neat 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`, e.g.: <!-- { "output": "Hello \"" } --> ``` go package main import ( "fmt" "os" "github.com/urfave/cli" ) func main() { app := cli.NewApp() app.Action = func(c *cli.Context) error { fmt.Printf("Hello %q", c.Args().Get(0)) return nil } app.Run(os.Args) } ``` ### Flags Setting and querying flags is simple. <!-- { "output": "Hello Nefertiti" } --> ``` go package main import ( "fmt" "os" "github.com/urfave/cli" ) func main() { app := cli.NewApp() app.Flags = []cli.Flag { cli.StringFlag{ Name: "lang", Value: "english", Usage: "language for the greeting", }, } app.Action = func(c *cli.Context) error { name := "Nefertiti" if c.NArg() > 0 { name = c.Args().Get(0) } if c.String("lang") == "spanish" { fmt.Println("Hola", name) } else { fmt.Println("Hello", name) } return nil } app.Run(os.Args) } ``` You can also set a destination variable for a flag, to which the content will be scanned. <!-- { "output": "Hello someone" } --> ``` go package main import ( "os" "fmt" "github.com/urfave/cli" ) func main() { var language string app := cli.NewApp() app.Flags = []cli.Flag { cli.StringFlag{ Name: "lang", Value: "english", Usage: "language for the greeting",