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authorMatthew Heon <matthew.heon@gmail.com>2017-11-01 11:24:59 -0400
committerMatthew Heon <matthew.heon@gmail.com>2017-11-01 11:24:59 -0400
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Initial checkin from CRI-O repo
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+cli
+===
+
+[![Build Status](https://travis-ci.org/urfave/cli.svg?branch=master)](https://travis-ci.org/urfave/cli)
+[![Windows Build Status](https://ci.appveyor.com/api/projects/status/rtgk5xufi932pb2v?svg=true)](https://ci.appveyor.com/project/urfave/cli)
+[![GoDoc](https://godoc.org/github.com/urfave/cli?status.svg)](https://godoc.org/github.com/urfave/cli)
+[![codebeat](https://codebeat.co/badges/0a8f30aa-f975-404b-b878-5fab3ae1cc5f)](https://codebeat.co/projects/github-com-urfave-cli)
+[![Go Report Card](https://goreportcard.com/badge/urfave/cli)](https://goreportcard.com/report/urfave/cli)
+[![top level coverage](https://gocover.io/_badge/github.com/urfave/cli?0 "top level coverage")](http://gocover.io/github.com/urfave/cli) /
+[![altsrc coverage](https://gocover.io/_badge/github.com/urfave/cli/altsrc?0 "altsrc coverage")](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` releases](#pinning-to-the-v1-releases)
+- [Getting Started](#getting-started)
+- [Examples](#examples)
+ * [Arguments](#arguments)
+ * [Flags](#flags)
+ + [Placeholder Values](#placeholder-values)
+ + [Alternate Names](#alternate-names)
+ + [Ordering](#ordering)
+ + [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` releases
+
+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 `v1` is an acceptable option, e.g.:
+
+```
+$ go get gopkg.in/urfave/cli.v1
+```
+
+``` go
+...
+import (
+ "gopkg.in/urfave/cli.v1" // imports as package "cli"
+)
+...
+```
+
+This will pull the latest tagged `v1` release (e.g. `v1.18.1` at the time of writing).
+
+## 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",
+ Destination: &language,
+ },
+ }
+
+ app.Action = func(c *cli.Context) error {
+ name := "someone"
+ if c.NArg() > 0 {
+ name = c.Args()[0]
+ }
+ if language == "spanish" {
+ fmt.Println("Hola", name)
+ } else {
+ fmt.Println("Hello", name)
+ }
+ return nil
+ }
+
+ app.Run(os.Args)
+}
+```
+
+See full list of flags at http://godoc.org/github.com/urfave/cli
+
+#### Placeholder Values
+
+Sometimes it's useful to specify a flag's value within the usage string itself.
+Such placeholders are indicated with back quotes.
+
+For example this:
+
+<!-- {
+ "args": ["&#45;&#45;help"],
+ "output": "&#45;&#45;config FILE, &#45;c FILE"
+} -->
+```go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Flags = []cli.Flag{
+ cli.StringFlag{
+ Name: "config, c",
+ Usage: "Load configuration from `FILE`",
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+Will result in help output like:
+
+```
+--config FILE, -c FILE Load configuration from FILE
+```
+
+Note that only the first placeholder is used. Subsequent back-quoted words will
+be left as-is.
+
+#### Alternate Names
+
+You can set alternate (or short) names for flags by providing a comma-delimited
+list for the `Name`. e.g.
+
+<!-- {
+ "args": ["&#45;&#45;help"],
+ "output": "&#45;&#45;lang value, &#45;l value.*language for the greeting.*default: \"english\""
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Flags = []cli.Flag {
+ cli.StringFlag{
+ Name: "lang, l",
+ Value: "english",
+ Usage: "language for the greeting",
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+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.
+
+#### Ordering
+
+Flags for the application and commands are shown in the order they are defined.
+However, it's possible to sort them from outside this library by using `FlagsByName`
+or `CommandsByName` with `sort`.
+
+For example this:
+
+<!-- {
+ "args": ["&#45;&#45;help"],
+ "output": "add a task to the list\n.*complete a task on the list\n.*\n\n.*\n.*Load configuration from FILE\n.*Language for the greeting.*"
+} -->
+``` go
+package main
+
+import (
+ "os"
+ "sort"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Flags = []cli.Flag {
+ cli.StringFlag{
+ Name: "lang, l",
+ Value: "english",
+ Usage: "Language for the greeting",
+ },
+ cli.StringFlag{
+ Name: "config, c",
+ Usage: "Load configuration from `FILE`",
+ },
+ }
+
+ app.Commands = []cli.Command{
+ {
+ Name: "complete",
+ Aliases: []string{"c"},
+ Usage: "complete a task on the list",
+ Action: func(c *cli.Context) error {
+ return nil
+ },
+ },
+ {
+ Name: "add",
+ Aliases: []string{"a"},
+ Usage: "add a task to the list",
+ Action: func(c *cli.Context) error {
+ return nil
+ },
+ },
+ }
+
+ sort.Sort(cli.FlagsByName(app.Flags))
+ sort.Sort(cli.CommandsByName(app.Commands))
+
+ app.Run(os.Args)
+}
+```
+
+Will result in help output like:
+
+```
+--config FILE, -c FILE Load configuration from FILE
+--lang value, -l value Language for the greeting (default: "english")
+```
+
+#### Values from the Environment
+
+You can also have the default value set from the environment via `EnvVar`. e.g.
+
+<!-- {
+ "args": ["&#45;&#45;help"],
+ "output": "language for the greeting.*APP_LANG"
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Flags = []cli.Flag {
+ cli.StringFlag{
+ Name: "lang, l",
+ Value: "english",
+ Usage: "language for the greeting",
+ EnvVar: "APP_LANG",
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+The `EnvVar` may also be given as a comma-delimited "cascade", where the first
+environment variable that resolves is used as the default.
+
+<!-- {
+ "args": ["&#45;&#45;help"],
+ "output": "language for the greeting.*LEGACY_COMPAT_LANG.*APP_LANG.*LANG"
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Flags = []cli.Flag {
+ cli.StringFlag{
+ Name: "lang, l",
+ Value: "english",
+ Usage: "language for the greeting",
+ EnvVar: "LEGACY_COMPAT_LANG,APP_LANG,LANG",
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+#### Values from alternate input sources (YAML, TOML, and others)
+
+There is a separate package altsrc that adds support for getting flag values
+from other file input sources.
+
+Currently supported input source formats:
+* YAML
+* TOML
+
+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:
+
+``` go
+ altsrc.NewIntFlag(cli.IntFlag{Name: "test"})
+```
+
+Initialization must also occur for these flags. Below is an example initializing
+getting data from a yaml file below.
+
+``` go
+ command.Before = altsrc.InitInputSourceWithContext(command.Flags, NewYamlSourceFromFlagFunc("load"))
+```
+
+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. It will then use that file name to initialize
+the yaml input source for any flags that are defined on that command. 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.
+
+Currently only the aboved specified formats are supported but developers can
+add support for other input sources by implementing the
+altsrc.InputSourceContext for their given sources.
+
+Here is a more complete sample of a command using YAML support:
+
+<!-- {
+ "args": ["test-cmd", "&#45;&#45;help"],
+ "output": "&#45&#45;test value.*default: 0"
+} -->
+``` go
+package notmain
+
+import (
+ "fmt"
+ "os"
+
+ "github.com/urfave/cli"
+ "github.com/urfave/cli/altsrc"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ flags := []cli.Flag{
+ altsrc.NewIntFlag(cli.IntFlag{Name: "test"}),
+ cli.StringFlag{Name: "load"},
+ }
+
+ app.Action = func(c *cli.Context) error {
+ fmt.Println("yaml ist rad")
+ return nil
+ }
+
+ app.Before = altsrc.InitInputSourceWithContext(flags, altsrc.NewYamlSourceFromFlagFunc("load"))
+ app.Flags = flags
+
+ app.Run(os.Args)
+}
+```
+
+### Subcommands
+
+Subcommands can be defined for a more git-like command line app.
+
+<!-- {
+ "args": ["template", "add"],
+ "output": "new task template: .+"
+} -->
+```go
+package main
+
+import (
+ "fmt"
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Commands = []cli.Command{
+ {
+ Name: "add",
+ Aliases: []string{"a"},
+ Usage: "add a task to the list",
+ Action: func(c *cli.Context) error {
+ fmt.Println("added task: ", c.Args().First())
+ return nil
+ },
+ },
+ {
+ Name: "complete",
+ Aliases: []string{"c"},
+ Usage: "complete a task on the list",
+ Action: func(c *cli.Context) error {
+ fmt.Println("completed task: ", c.Args().First())
+ return nil
+ },
+ },
+ {
+ Name: "template",
+ Aliases: []string{"t"},
+ Usage: "options for task templates",
+ Subcommands: []cli.Command{
+ {
+ Name: "add",
+ Usage: "add a new template",
+ Action: func(c *cli.Context) error {
+ fmt.Println("new task template: ", c.Args().First())
+ return nil
+ },
+ },
+ {
+ Name: "remove",
+ Usage: "remove an existing template",
+ Action: func(c *cli.Context) error {
+ fmt.Println("removed task template: ", c.Args().First())
+ return nil
+ },
+ },
+ },
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+### Subcommands categories
+
+For additional organization in apps that have many subcommands, you can
+associate a category for each command to group them together in the help
+output.
+
+E.g.
+
+```go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+
+ app.Commands = []cli.Command{
+ {
+ Name: "noop",
+ },
+ {
+ Name: "add",
+ Category: "template",
+ },
+ {
+ Name: "remove",
+ Category: "template",
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+Will include:
+
+```
+COMMANDS:
+ noop
+
+ Template actions:
+ add
+ remove
+```
+
+### Exit code
+
+Calling `App.Run` will not automatically call `os.Exit`, which means that by
+default the exit code will "fall through" to being `0`. An explicit exit code
+may be set by returning a non-nil error that fulfills `cli.ExitCoder`, *or* a
+`cli.MultiError` that includes an error that fulfills `cli.ExitCoder`, e.g.:
+
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ app := cli.NewApp()
+ app.Flags = []cli.Flag{
+ cli.BoolTFlag{
+ Name: "ginger-crouton",
+ Usage: "is it in the soup?",
+ },
+ }
+ app.Action = func(ctx *cli.Context) error {
+ if !ctx.Bool("ginger-crouton") {
+ return cli.NewExitError("it is not in the soup", 86)
+ }
+ return nil
+ }
+
+ app.Run(os.Args)
+}
+```
+
+### Bash Completion
+
+You can enable completion commands by setting the `EnableBashCompletion`
+flag on the `App` object. By default, this setting will only auto-complete to
+show an app's subcommands, but you can write your own completion methods for
+the App or its subcommands.
+
+<!-- {
+ "args": ["complete", "&#45;&#45;generate&#45;bash&#45;completion"],
+ "output": "laundry"
+} -->
+``` go
+package main
+
+import (
+ "fmt"
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ tasks := []string{"cook", "clean", "laundry", "eat", "sleep", "code"}
+
+ app := cli.NewApp()
+ app.EnableBashCompletion = true
+ app.Commands = []cli.Command{
+ {
+ Name: "complete",
+ Aliases: []string{"c"},
+ Usage: "complete a task on the list",
+ Action: func(c *cli.Context) error {
+ fmt.Println("completed task: ", c.Args().First())
+ return nil
+ },
+ BashComplete: func(c *cli.Context) {
+ // This will complete if no args are passed
+ if c.NArg() > 0 {
+ return
+ }
+ for _, t := range tasks {
+ fmt.Println(t)
+ }
+ },
+ },
+ }
+
+ app.Run(os.Args)
+}
+```
+
+#### Enabling
+
+Source the `autocomplete/bash_autocomplete` file in your `.bashrc` file while
+setting the `PROG` variable to the name of your program:
+
+`PROG=myprogram source /.../cli/autocomplete/bash_autocomplete`
+
+#### Distribution
+
+Copy `autocomplete/bash_autocomplete` into `/etc/bash_completion.d/` and rename
+it to the name of the program you wish to add autocomplete support for (or
+automatically install it there if you are distributing a package). Don't forget
+to source the file to make it active in the current shell.
+
+```
+sudo cp src/bash_autocomplete /etc/bash_completion.d/<myprogram>
+source /etc/bash_completion.d/<myprogram>
+```
+
+Alternatively, you can just document that users should source the generic
+`autocomplete/bash_autocomplete` in their bash configuration with `$PROG` set
+to the name of their program (as above).
+
+#### Customization
+
+The default bash completion flag (`--generate-bash-completion`) is defined as
+`cli.BashCompletionFlag`, and may be redefined if desired, e.g.:
+
+<!-- {
+ "args": ["&#45;&#45;compgen"],
+ "output": "wat\nhelp\nh"
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ cli.BashCompletionFlag = cli.BoolFlag{
+ Name: "compgen",
+ Hidden: true,
+ }
+
+ app := cli.NewApp()
+ app.EnableBashCompletion = true
+ app.Commands = []cli.Command{
+ {
+ Name: "wat",
+ },
+ }
+ app.Run(os.Args)
+}
+```
+
+### Generated Help Text
+
+The default help flag (`-h/--help`) is defined as `cli.HelpFlag` and is checked
+by the cli internals in order to print generated help text for the app, command,
+or subcommand, and break execution.
+
+#### Customization
+
+All of the help text generation may be customized, and at multiple levels. The
+templates are exposed as variables `AppHelpTemplate`, `CommandHelpTemplate`, and
+`SubcommandHelpTemplate` which may be reassigned or augmented, and full override
+is possible by assigning a compatible func to the `cli.HelpPrinter` variable,
+e.g.:
+
+<!-- {
+ "output": "Ha HA. I pwnd the help!!1"
+} -->
+``` go
+package main
+
+import (
+ "fmt"
+ "io"
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ // EXAMPLE: Append to an existing template
+ cli.AppHelpTemplate = fmt.Sprintf(`%s
+
+WEBSITE: http://awesometown.example.com
+
+SUPPORT: support@awesometown.example.com
+
+`, cli.AppHelpTemplate)
+
+ // EXAMPLE: Override a template
+ cli.AppHelpTemplate = `NAME:
+ {{.Name}} - {{.Usage}}
+USAGE:
+ {{.HelpName}} {{if .VisibleFlags}}[global options]{{end}}{{if .Commands}} command [command options]{{end}} {{if .ArgsUsage}}{{.ArgsUsage}}{{else}}[arguments...]{{end}}
+ {{if len .Authors}}
+AUTHOR:
+ {{range .Authors}}{{ . }}{{end}}
+ {{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)
+}
+```
+
+The default flag may be customized to something other than `-h/--help` by
+setting `cli.HelpFlag`, e.g.:
+
+<!-- {
+ "args": ["&#45;&#45halp"],
+ "output": "haaaaalp.*HALP"
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ cli.HelpFlag = cli.BoolFlag{
+ Name: "halp, haaaaalp",
+ Usage: "HALP",
+ EnvVar: "SHOW_HALP,HALPPLZ",
+ }
+
+ cli.NewApp().Run(os.Args)
+}
+```
+
+### Version Flag
+
+The default version flag (`-v/--version`) is defined as `cli.VersionFlag`, which
+is checked by the cli internals in order to print the `App.Version` via
+`cli.VersionPrinter` and break execution.
+
+#### Customization
+
+The default flag may be customized to something other than `-v/--version` by
+setting `cli.VersionFlag`, e.g.:
+
+<!-- {
+ "args": ["&#45;&#45print-version"],
+ "output": "partay version 19\\.99\\.0"
+} -->
+``` go
+package main
+
+import (
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+func main() {
+ cli.VersionFlag = cli.BoolFlag{
+ Name: "print-version, V",
+ Usage: "print only the version",
+ }
+
+ app := cli.NewApp()
+ app.Name = "partay"
+ app.Version = "19.99.0"
+ app.Run(os.Args)
+}
+```
+
+Alternatively, the version printer at `cli.VersionPrinter` may be overridden, e.g.:
+
+<!-- {
+ "args": ["&#45;&#45version"],
+ "output": "version=19\\.99\\.0 revision=fafafaf"
+} -->
+``` go
+package main
+
+import (
+ "fmt"
+ "os"
+
+ "github.com/urfave/cli"
+)
+
+var (
+ Revision = "fafafaf"
+)
+
+func main() {
+ cli.VersionPrinter = func(c *cli.Context) {
+ fmt.Printf("version=%s revision=%s\n", c.App.Version, Revision)
+ }
+
+ app := cli.NewApp()
+ app.Name = "partay"
+ app.Version = "19.99.0"
+ app.Run(os.Args)
+}
+```
+
+#### Full API Example
+
+**Notice**: This is a contrived (functioning) example meant strictly for API
+demonstration purposes. Use of one's imagination is encouraged.
+
+<!-- {
+ "output": "made it!\nPhew!"
+} -->
+``` go
+package main
+
+import (
+ "errors"
+ "flag"
+ "fmt"
+ "io"
+ "io/ioutil"
+ "os"
+ "time"
+
+ "github.com/urfave/cli"
+)
+
+func init() {
+ cli.AppHelpTemplate += "\nCUSTOMIZED: you bet ur muffins\n"
+ cli.CommandHelpTemplate += "\nYMMV\n"
+ cli.SubcommandHelpTemplate += "\nor something\n"
+
+ cli.HelpFlag = cli.BoolFlag{Name: "halp"}
+ cli.BashCompletionFlag = cli.BoolFlag{Name: "compgen", Hidden: true}
+ cli.VersionFlag = cli.BoolFlag{Name: "print-version, V"}
+
+ cli.HelpPrinter = func(w io.Writer, templ string, data interface{}) {
+ fmt.Fprintf(w, "best of luck to you\n")
+ }
+ cli.VersionPrinter = func(c *cli.Context) {
+ fmt.Fprintf(c.App.Writer, "version=%s\n", c.App.Version)
+ }
+ cli.OsExiter = func(c int) {
+ fmt.Fprintf(cli.ErrWriter, "refusing to exit %d\n", c)
+ }
+ cli.ErrWriter = ioutil.Discard
+ cli.FlagStringer = func(fl cli.Flag) string {
+ return fmt.Sprintf("\t\t%s", fl.GetName())
+ }
+}
+
+type hexWriter struct{}
+
+func (w *hexWriter) Write(p []byte) (int, error) {
+ for _, b := range p {
+ fmt.Printf("%x", b)
+ }
+ fmt.Printf("\n")
+
+ return len(p), nil
+}
+
+type genericType struct{
+ s string
+}
+
+func (g *genericType) Set(value string) error {
+ g.s = value
+ return nil
+}
+
+func (g *genericType) String() string {
+ return g.s
+}
+
+func main() {
+ app := cli.NewApp()
+ app.Name = "kənˈtrīv"
+ app.Version = "19.99.0"
+ app.Compiled = time.Now()
+ app.Authors = []cli.Author{
+ cli.Author{
+ Name: "Example Human",
+ Email: "human@example.com",
+ },
+ }
+ app.Copyright = "(c) 1999 Serious Enterprise"
+ app.HelpName = "contrive"
+ app.Usage = "demonstrate available API"
+ app.UsageText = "contrive - demonstrating the available API"
+ app.ArgsUsage = "[args and such]"
+ app.Commands = []cli.Command{
+ cli.Command{
+ Name: "doo",
+ Aliases: []string{"do"},
+ Category: "motion",
+ Usage: "do the doo",
+ UsageText: "doo - does the dooing",
+ Description: "no really, there is a lot of dooing to be done",
+ ArgsUsage: "[arrgh]",
+ Flags: []cli.Flag{
+ cli.BoolFlag{Name: "forever, forevvarr"},
+ },
+ Subcommands: cli.Commands{
+ cli.Command{
+ Name: "wop",
+ Action: wopAction,
+ },
+ },
+ SkipFlagParsing: false,
+ HideHelp: false,
+ Hidden: false,
+ HelpName: "doo!",
+ BashComplete: func(c *cli.Context) {
+ fmt.Fprintf(c.App.Writer, "--better\n")
+ },
+ Before: func(c *cli.Context) error {
+ fmt.Fprintf(c.App.Writer, "brace for impact\n")
+ return nil
+ },
+ After: func(c *cli.Context) error {
+ fmt.Fprintf(c.App.Writer, "did we lose anyone?\n")
+ return nil
+ },
+ Action: func(c *cli.Context) error {
+ c.Command.FullName()
+ c.Command.HasName("wop")
+ c.Command.Names()
+ c.Command.VisibleFlags()
+ fmt.Fprintf(c.App.Writer, "dodododododoodododddooooododododooo\n")
+ if c.Bool("forever") {
+ c.Command.Run(c)
+ }
+ return nil
+ },
+ OnUsageError: func(c *cli.Context, err error, isSubcommand bool) error {
+ fmt.Fprintf(c.App.Writer, "for shame\n")
+ return err
+ },
+ },
+ }
+ app.Flags = []cli.Flag{
+ cli.BoolFlag{Name: "fancy"},
+ cli.BoolTFlag{Name: "fancier"},
+ cli.DurationFlag{Name: "howlong, H", Value: time.Second * 3},
+ cli.Float64Flag{Name: "howmuch"},
+ cli.GenericFlag{Name: "wat", Value: &genericType{}},
+ cli.Int64Flag{Name: "longdistance"},
+ cli.Int64SliceFlag{Name: "intervals"},
+ cli.IntFlag{Name: "distance"},
+ cli.IntSliceFlag{Name: "times"},
+ cli.StringFlag{Name: "dance-move, d"},
+ cli.StringSliceFlag{Name: "names, N"},
+ cli.UintFlag{Name: "age"},
+ cli.Uint64Flag{Name: "bigage"},
+ }
+ app.EnableBashCompletion = true
+ app.HideHelp = false
+ app.HideVersion = false
+ app.BashComplete = func(c *cli.Context) {
+ fmt.Fprintf(c.App.Writer, "lipstick\nkiss\nme\nlipstick\nringo\n")
+ }
+ app.Before = func(c *cli.Context) error {
+ fmt.Fprintf(c.App.Writer, "HEEEERE GOES\n")
+ return nil
+ }
+ app.After = func(c *cli.Context) error {
+ fmt.Fprintf(c.App.Writer, "Phew!\n")
+ return nil
+ }
+ app.CommandNotFound = func(c *cli.Context, command string) {
+ fmt.Fprintf(c.App.Writer, "Thar be no %q here.\n", command)
+ }
+ app.OnUsageError = func(c *cli.Context, err error, isSubcommand bool) error {
+ if isSubcommand {
+ return err
+ }
+
+ fmt.Fprintf(c.App.Writer, "WRONG: %#v\n", err)
+ return nil
+ }
+ app.Action = func(c *cli.Context) error {
+ cli.DefaultAppComplete(c)
+ cli.HandleExitCoder(errors.New("not an exit coder, though"))
+ cli.ShowAppHelp(c)
+ cli.ShowCommandCompletions(c, "nope")
+ cli.ShowCommandHelp(c, "also-nope")
+ cli.ShowCompletions(c)
+ cli.ShowSubcommandHelp(c)
+ cli.ShowVersion(c)
+
+ categories := c.App.Categories()
+ categories.AddCommand("sounds", cli.Command{
+ Name: "bloop",
+ })
+
+ for _, category := range c.App.Categories() {
+ fmt.Fprintf(c.App.Writer, "%s\n", category.Name)
+ fmt.Fprintf(c.App.Writer, "%#v\n", category.Commands)
+ fmt.Fprintf(c.App.Writer, "%#v\n", category.VisibleCommands())
+ }
+
+ fmt.Printf("%#v\n", c.App.Command("doo"))
+ if c.Bool("infinite") {
+ c.App.Run([]string{"app", "doo", "wop"})
+ }
+
+ if c.Bool("forevar") {
+ c.App.RunAsSubcommand(c)
+ }
+ c.App.Setup()
+ fmt.Printf("%#v\n", c.App.VisibleCategories())
+ fmt.Printf("%#v\n", c.App.VisibleCommands())
+ fmt.Printf("%#v\n", c.App.VisibleFlags())
+
+ fmt.Printf("%#v\n", c.Args().First())
+ if len(c.Args()) > 0 {
+ fmt.Printf("%#v\n", c.Args()[1])
+ }
+ fmt.Printf("%#v\n", c.Args().Present())
+ fmt.Printf("%#v\n", c.Args().Tail())
+
+ set := flag.NewFlagSet("contrive", 0)
+ nc := cli.NewContext(c.App, set, c)
+
+ fmt.Printf("%#v\n", nc.Args())
+ fmt.Printf("%#v\n", nc.Bool("nope"))
+ fmt.Printf("%#v\n", nc.BoolT("nerp"))
+ fmt.Printf("%#v\n", nc.Duration("howlong"))
+ fmt.Printf("%#v\n", nc.Float64("hay"))
+ fmt.Printf("%#v\n", nc.Generic("bloop"))
+ fmt.Printf("%#v\n", nc.Int64("bonk"))
+ fmt.Printf("%#v\n", nc.Int64Slice("burnks"))
+ fmt.Printf("%#v\n", nc.Int("bips"))
+ fmt.Printf("%#v\n", nc.IntSlice("blups"))
+ fmt.Printf("%#v\n", nc.String("snurt"))
+ fmt.Printf("%#v\n", nc.StringSlice("snurkles"))
+ fmt.Printf("%#v\n", nc.Uint("flub"))
+ fmt.Printf("%#v\n", nc.Uint64("florb"))
+ fmt.Printf("%#v\n", nc.GlobalBool("global-nope"))
+ fmt.Printf("%#v\n", nc.GlobalBoolT("global-nerp"))
+ fmt.Printf("%#v\n", nc.GlobalDuration("global-howlong"))
+ fmt.Printf("%#v\n", nc.GlobalFloat64("global-hay"))
+ fmt.Printf("%#v\n", nc.GlobalGeneric("global-bloop"))
+ fmt.Printf("%#v\n", nc.GlobalInt("global-bips"))
+ fmt.Printf("%#v\n", nc.GlobalIntSlice("global-blups"))
+ fmt.Printf("%#v\n", nc.GlobalString("global-snurt"))
+ fmt.Printf("%#v\n", nc.GlobalStringSlice("global-snurkles"))
+
+ fmt.Printf("%#v\n", nc.FlagNames())
+ fmt.Printf("%#v\n", nc.GlobalFlagNames())
+ fmt.Printf("%#v\n", nc.GlobalIsSet("wat"))
+ fmt.Printf("%#v\n", nc.GlobalSet("wat", "nope"))
+ fmt.Printf("%#v\n", nc.NArg())
+ fmt.Printf("%#v\n", nc.NumFlags())
+ fmt.Printf("%#v\n", nc.Parent())
+
+ nc.Set("wat", "also-nope")
+
+ ec := cli.NewExitError("ohwell", 86)
+ fmt.Fprintf(c.App.Writer, "%d", ec.ExitCode())
+ fmt.Printf("made it!\n")
+ return ec
+ }
+
+ if os.Getenv("HEXY") != "" {
+ app.Writer = &hexWriter{}
+ app.ErrWriter = &hexWriter{}
+ }
+
+ app.Metadata = map[string]interface{}{
+ "layers": "many",
+ "explicable": false,
+ "whatever-values": 19.99,
+ }
+
+ app.Run(os.Args)
+}
+
+func wopAction(c *cli.Context) error {
+ fmt.Fprintf(c.App.Writer, ":wave: over here, eh\n")
+ return nil
+}
+```
+
+## 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.