637 lines
16 KiB
Markdown
637 lines
16 KiB
Markdown
[](https://travis-ci.org/urfave/cli)
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[](https://godoc.org/github.com/urfave/cli)
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[](https://codebeat.co/projects/github-com-urfave-cli)
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[](https://goreportcard.com/report/urfave/cli)
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[](http://gocover.io/github.com/urfave/cli) /
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[](http://gocover.io/github.com/urfave/cli/altsrc)
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# cli
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**Notice:** This is the library formally known as
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`github.com/codegangsta/cli` -- Github will automatically redirect requests
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to this repository, but we recommend updating your references for clarity.
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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.
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## Overview
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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.
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**This is where cli comes into play.** cli makes command line programming fun, organized, and expressive!
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## Installation
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Make sure you have a working Go environment. Go version 1.1+ is required for
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core cli, whereas use of the [`./altsrc`](./altsrc) input extensions requires Go
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version 1.2+. [See the install
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instructions](http://golang.org/doc/install.html).
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To install cli, simply run:
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```
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$ go get github.com/urfave/cli
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```
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Make sure your `PATH` includes to the `$GOPATH/bin` directory so your commands can be easily used:
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```
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export PATH=$PATH:$GOPATH/bin
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```
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### Using the `v2` branch
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There is currently a long-lived branch named `v2` that is intended to land as
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the new `master` branch once development there has settled down. The current
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`master` branch (mirrored as `v1`) is being manually merged into `v2` on
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an irregular human-based schedule, but generally if one wants to "upgrade" to
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`v2` *now* and accept the volatility (read: "awesomeness") that comes along with
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that, please use whatever version pinning of your preference, such as via
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`gopkg.in`:
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```
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$ go get gopkg.in/urfave/cli.v2
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```
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``` go
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...
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import (
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"gopkg.in/urfave/cli.v2" // imports as package "cli"
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)
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...
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```
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### Pinning to the `v1` branch
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Similarly to the section above describing use of the `v2` branch, if one wants
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to avoid any unexpected compatibility pains once `v2` becomes `master`, then
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pinning to the `v1` branch is an acceptable option, e.g.:
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```
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$ go get gopkg.in/urfave/cli.v1
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```
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``` go
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...
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import (
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"gopkg.in/urfave/cli.v1" // imports as package "cli"
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)
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...
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```
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## Getting Started
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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()`.
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``` go
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package main
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import (
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"os"
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"github.com/urfave/cli"
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)
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func main() {
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cli.NewApp().Run(os.Args)
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}
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```
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This app will run and show help text, but is not very useful. Let's give an action to execute and some help documentation:
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<!-- {
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"output": "boom! I say!"
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} -->
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``` go
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package main
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import (
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"fmt"
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"os"
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"github.com/urfave/cli"
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)
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func main() {
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app := cli.NewApp()
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app.Name = "boom"
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app.Usage = "make an explosive entrance"
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app.Action = func(c *cli.Context) error {
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fmt.Println("boom! I say!")
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return nil
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}
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app.Run(os.Args)
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}
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```
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Running this already gives you a ton of functionality, plus support for things like subcommands and flags, which are covered below.
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## Example
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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!
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Start by creating a directory named `greet`, and within it, add a file, `greet.go` with the following code in it:
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<!-- {
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"output": "Hello friend!"
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} -->
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``` go
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package main
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import (
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"fmt"
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"os"
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"github.com/urfave/cli"
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)
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func main() {
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app := cli.NewApp()
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app.Name = "greet"
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app.Usage = "fight the loneliness!"
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app.Action = func(c *cli.Context) error {
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fmt.Println("Hello friend!")
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return nil
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}
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app.Run(os.Args)
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}
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```
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Install our command to the `$GOPATH/bin` directory:
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```
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$ go install
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```
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Finally run our new command:
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```
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$ greet
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Hello friend!
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```
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cli also generates neat help text:
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```
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$ greet help
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NAME:
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greet - fight the loneliness!
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USAGE:
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greet [global options] command [command options] [arguments...]
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VERSION:
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0.0.0
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COMMANDS:
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help, h Shows a list of commands or help for one command
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GLOBAL OPTIONS
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--version Shows version information
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```
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### Arguments
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You can lookup arguments by calling the `Args` function on `cli.Context`.
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``` go
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...
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app.Action = func(c *cli.Context) error {
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fmt.Println("Hello", c.Args()[0])
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return nil
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}
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...
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```
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### Flags
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Setting and querying flags is simple.
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``` go
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...
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app.Flags = []cli.Flag {
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cli.StringFlag{
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Name: "lang",
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Value: "english",
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Usage: "language for the greeting",
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},
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}
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app.Action = func(c *cli.Context) error {
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name := "someone"
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if c.NArg() > 0 {
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name = c.Args()[0]
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}
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if c.String("lang") == "spanish" {
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fmt.Println("Hola", name)
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} else {
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fmt.Println("Hello", name)
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}
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return nil
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}
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...
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```
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You can also set a destination variable for a flag, to which the content will be scanned.
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``` go
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...
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var language string
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app.Flags = []cli.Flag {
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cli.StringFlag{
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Name: "lang",
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Value: "english",
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Usage: "language for the greeting",
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Destination: &language,
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},
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}
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app.Action = func(c *cli.Context) error {
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name := "someone"
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if c.NArg() > 0 {
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name = c.Args()[0]
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}
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if language == "spanish" {
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fmt.Println("Hola", name)
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} else {
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fmt.Println("Hello", name)
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}
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return nil
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}
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...
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```
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See full list of flags at http://godoc.org/github.com/urfave/cli
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#### Placeholder Values
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Sometimes it's useful to specify a flag's value within the usage string itself. Such placeholders are
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indicated with back quotes.
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For example this:
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```go
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cli.StringFlag{
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Name: "config, c",
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Usage: "Load configuration from `FILE`",
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}
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```
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Will result in help output like:
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```
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--config FILE, -c FILE Load configuration from FILE
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```
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Note that only the first placeholder is used. Subsequent back-quoted words will be left as-is.
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#### Alternate Names
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You can set alternate (or short) names for flags by providing a comma-delimited list for the `Name`. e.g.
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``` go
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app.Flags = []cli.Flag {
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cli.StringFlag{
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Name: "lang, l",
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Value: "english",
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Usage: "language for the greeting",
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},
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}
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```
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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.
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#### Values from the Environment
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You can also have the default value set from the environment via `EnvVar`. e.g.
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``` go
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app.Flags = []cli.Flag {
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cli.StringFlag{
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Name: "lang, l",
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Value: "english",
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Usage: "language for the greeting",
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EnvVar: "APP_LANG",
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},
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}
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```
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The `EnvVar` may also be given as a comma-delimited "cascade", where the first environment variable that resolves is used as the default.
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``` go
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app.Flags = []cli.Flag {
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cli.StringFlag{
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Name: "lang, l",
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Value: "english",
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Usage: "language for the greeting",
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EnvVar: "LEGACY_COMPAT_LANG,APP_LANG,LANG",
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},
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}
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```
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#### Values from alternate input sources (YAML and others)
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There is a separate package altsrc that adds support for getting flag values from other input sources like YAML.
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In order to get values for a flag from an alternate input source the following code would be added to wrap an existing cli.Flag like below:
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``` go
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altsrc.NewIntFlag(cli.IntFlag{Name: "test"})
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```
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Initialization must also occur for these flags. Below is an example initializing getting data from a yaml file below.
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``` go
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command.Before = altsrc.InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
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```
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The code above will use the "load" string as a flag name to get the file name of a yaml file from the cli.Context.
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It will then use that file name to initialize the yaml input source for any flags that are defined on that command.
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As a note the "load" flag used would also have to be defined on the command flags in order for this code snipped to work.
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Currently only YAML files are supported but developers can add support for other input sources by implementing the
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altsrc.InputSourceContext for their given sources.
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Here is a more complete sample of a command using YAML support:
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``` go
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command := &cli.Command{
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Name: "test-cmd",
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Aliases: []string{"tc"},
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Usage: "this is for testing",
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Description: "testing",
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Action: func(c *cli.Context) error {
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// Action to run
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return nil
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},
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Flags: []cli.Flag{
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NewIntFlag(cli.IntFlag{Name: "test"}),
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cli.StringFlag{Name: "load"}},
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}
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command.Before = InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
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err := command.Run(c)
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```
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### Subcommands
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Subcommands can be defined for a more git-like command line app.
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```go
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...
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app.Commands = []cli.Command{
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{
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Name: "add",
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Aliases: []string{"a"},
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Usage: "add a task to the list",
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Action: func(c *cli.Context) error {
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fmt.Println("added task: ", c.Args().First())
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return nil
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},
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},
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{
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Name: "complete",
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Aliases: []string{"c"},
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Usage: "complete a task on the list",
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Action: func(c *cli.Context) error {
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fmt.Println("completed task: ", c.Args().First())
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return nil
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},
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},
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{
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Name: "template",
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Aliases: []string{"r"},
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Usage: "options for task templates",
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Subcommands: []cli.Command{
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{
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Name: "add",
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Usage: "add a new template",
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Action: func(c *cli.Context) error {
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fmt.Println("new task template: ", c.Args().First())
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return nil
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},
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},
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{
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Name: "remove",
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Usage: "remove an existing template",
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Action: func(c *cli.Context) error {
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fmt.Println("removed task template: ", c.Args().First())
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return nil
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},
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},
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},
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},
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}
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...
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```
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### Subcommands categories
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For additional organization in apps that have many subcommands, you can
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associate a category for each command to group them together in the help
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output.
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E.g.
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```go
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...
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app.Commands = []cli.Command{
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{
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Name: "noop",
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},
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{
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Name: "add",
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Category: "template",
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},
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{
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Name: "remove",
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Category: "template",
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},
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}
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...
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```
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Will include:
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```
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...
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COMMANDS:
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noop
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Template actions:
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add
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remove
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...
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```
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### Exit code
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Calling `App.Run` will not automatically call `os.Exit`, which means that by
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default the exit code will "fall through" to being `0`. An explicit exit code
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may be set by returning a non-nil error that fulfills `cli.ExitCoder`, *or* a
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`cli.MultiError` that includes an error that fulfills `cli.ExitCoder`, e.g.:
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``` go
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package main
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import (
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"os"
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"github.com/urfave/cli"
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)
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func main() {
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app := cli.NewApp()
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app.Flags = []cli.Flag{
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cli.BoolTFlag{
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Name: "ginger-crouton",
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Usage: "is it in the soup?",
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},
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}
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app.Action = func(ctx *cli.Context) error {
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if !ctx.Bool("ginger-crouton") {
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return cli.NewExitError("it is not in the soup", 86)
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}
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return nil
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}
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app.Run(os.Args)
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}
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```
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### Bash Completion
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You can enable completion commands by setting the `EnableBashCompletion`
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flag on the `App` object. By default, this setting will only auto-complete to
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show an app's subcommands, but you can write your own completion methods for
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the App or its subcommands.
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```go
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...
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var tasks = []string{"cook", "clean", "laundry", "eat", "sleep", "code"}
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app := cli.NewApp()
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app.EnableBashCompletion = true
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app.Commands = []cli.Command{
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{
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Name: "complete",
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Aliases: []string{"c"},
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Usage: "complete a task on the list",
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Action: func(c *cli.Context) error {
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fmt.Println("completed task: ", c.Args().First())
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return nil
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},
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BashComplete: func(c *cli.Context) {
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// This will complete if no args are passed
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if c.NArg() > 0 {
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return
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}
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for _, t := range tasks {
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fmt.Println(t)
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}
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},
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}
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}
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...
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```
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#### To Enable
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Source the `autocomplete/bash_autocomplete` file in your `.bashrc` file while
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setting the `PROG` variable to the name of your program:
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`PROG=myprogram source /.../cli/autocomplete/bash_autocomplete`
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#### To Distribute
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Copy `autocomplete/bash_autocomplete` into `/etc/bash_completion.d/` and rename
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it to the name of the program you wish to add autocomplete support for (or
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automatically install it there if you are distributing a package). Don't forget
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to source the file to make it active in the current shell.
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```
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sudo cp src/bash_autocomplete /etc/bash_completion.d/<myprogram>
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source /etc/bash_completion.d/<myprogram>
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```
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Alternatively, you can just document that users should source the generic
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`autocomplete/bash_autocomplete` in their bash configuration with `$PROG` set
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to the name of their program (as above).
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### Generated Help Text Customization
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All of the help text generation may be customized, and at multiple levels. The
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templates are exposed as variables `AppHelpTemplate`, `CommandHelpTemplate`, and
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`SubcommandHelpTemplate` which may be reassigned or augmented, and full override
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is possible by assigning a compatible func to the `cli.HelpPrinter` variable,
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e.g.:
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<!-- {
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"output": "Ha HA. I pwnd the help!!1"
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} -->
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``` go
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package main
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|
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import (
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"fmt"
|
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"io"
|
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"os"
|
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|
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"github.com/urfave/cli"
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)
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func main() {
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// EXAMPLE: Append to an existing template
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cli.AppHelpTemplate = fmt.Sprintf(`%s
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WEBSITE: http://awesometown.example.com
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SUPPORT: support@awesometown.example.com
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`, cli.AppHelpTemplate)
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// EXAMPLE: Override a template
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cli.AppHelpTemplate = `NAME:
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{{.Name}} - {{.Usage}}
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USAGE:
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{{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command
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[command options]{{end}} {{if
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.ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}
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{{if len .Authors}}
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AUTHOR(S):
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{{range .Authors}}{{ . }}{{end}}
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|
{{end}}{{if .Commands}}
|
|
COMMANDS:
|
|
{{range .Commands}}{{if not .HideHelp}} {{join .Names ", "}}{{ "\t"
|
|
}}{{.Usage}}{{ "\n" }}{{end}}{{end}}{{end}}{{if .VisibleFlags}}
|
|
GLOBAL OPTIONS:
|
|
{{range .VisibleFlags}}{{.}}
|
|
{{end}}{{end}}{{if .Copyright }}
|
|
COPYRIGHT:
|
|
{{.Copyright}}
|
|
{{end}}{{if .Version}}
|
|
VERSION:
|
|
{{.Version}}
|
|
{{end}}
|
|
`
|
|
|
|
// EXAMPLE: Replace the `HelpPrinter` func
|
|
cli.HelpPrinter = func(w io.Writer, templ string, data interface{}) {
|
|
fmt.Println("Ha HA. I pwnd the help!!1")
|
|
}
|
|
|
|
cli.NewApp().Run(os.Args)
|
|
}
|
|
```
|
|
|
|
## Contribution Guidelines
|
|
|
|
Feel free to put up a pull request to fix a bug or maybe add a feature. I will
|
|
give it a code review and make sure that it does not break backwards
|
|
compatibility. If I or any other collaborators agree that it is in line with
|
|
the vision of the project, we will work with you to get the code into
|
|
a mergeable state and merge it into the master branch.
|
|
|
|
If you have contributed something significant to the project, we will most
|
|
likely add you as a collaborator. As a collaborator you are given the ability
|
|
to merge others pull requests. It is very important that new code does not
|
|
break existing code, so be careful about what code you do choose to merge.
|
|
|
|
If you feel like you have contributed to the project but have not yet been
|
|
added as a collaborator, we probably forgot to add you, please open an issue.
|