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!
Start by creating a directory named greet
, and within it, add a file, greet.go
with the following code in it:
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{
Name: "lang",
Value: "english",
Usage: "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{
Name: "lang, l",
Value: "english",
Usage: "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.
Values from the Environment
You can also have the default value set from the environment via EnvVar
. e.g.
app.Flags = []cli.Flag {
cli.StringFlag{
Name: "lang, l",
Value: "english",
Usage: "language for the greeting",
EnvVar: "APP_LANG",
},
}
The EnvVar
may also be given as a comma-delimited "cascade", where the first environment variable that resolves is used as the default.
app.Flags = []cli.Flag {
cli.StringFlag{
Name: "lang, l",
Value: "english",
Usage: "language for the greeting",
EnvVar: "LEGACY_COMPAT_LANG,APP_LANG,LANG",
},
}
Subcommands
Subcommands can be defined for a more git-like command line app.
...
app.Commands = []cli.Command{
{
Name: "add",
Aliases: []string{"a"},
Usage: "add a task to the list",
Action: func(c *cli.Context) {
println("added task: ", c.Args().First())
},
},
{
Name: "complete",
Aliases: []string{"c"},
Usage: "complete a task on the list",
Action: func(c *cli.Context) {
println("completed task: ", c.Args().First())
},
},
{
Name: "template",
Aliases: []string{"r"},
Usage: "options for task templates",
Subcommands: []cli.Command{
{
Name: "add",
Usage: "add a new template",
Action: func(c *cli.Context) {
println("new task template: ", c.Args().First())
},
},
{
Name: "remove",
Usage: "remove an existing template",
Action: func(c *cli.Context) {
println("removed task template: ", c.Args().First())
},
},
},
},
}
...
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.
...
var 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) {
println("completed task: ", c.Args().First())
},
BashComplete: func(c *cli.Context) {
// This will complete if no args are passed
if len(c.Args()) > 0 {
return
}
for _, t := range tasks {
fmt.Println(t)
}
},
}
}
...
To Enable
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
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, I 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 have any questions feel free to link @codegangsta to the issue in question and we can review it together.
If you feel like you have contributed to the project but have not yet been added as a collaborator, I probably forgot to add you. Hit @codegangsta up over email and we will get it figured out.
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) }
Index ¶
- Variables
- func DefaultAppComplete(c *Context)
- func ShowAppHelp(c *Context)
- func ShowCommandCompletions(ctx *Context, command string)
- func ShowCommandHelp(c *Context, command string)
- func ShowCompletions(c *Context)
- func ShowSubcommandHelp(c *Context)
- func ShowVersion(c *Context)
- type App
- type Args
- type Author
- type BoolFlag
- type BoolTFlag
- type Command
- type Context
- func (c *Context) Args() Args
- func (c *Context) Bool(name string) bool
- func (c *Context) BoolT(name string) bool
- func (c *Context) Duration(name string) time.Duration
- func (c *Context) FlagNames() (names []string)
- func (c *Context) Float64(name string) float64
- func (c *Context) Generic(name string) interface{}
- func (c *Context) GlobalBool(name string) bool
- func (c *Context) GlobalDuration(name string) time.Duration
- func (c *Context) GlobalFlagNames() (names []string)
- func (c *Context) GlobalGeneric(name string) interface{}
- func (c *Context) GlobalInt(name string) int
- func (c *Context) GlobalIntSlice(name string) []int
- func (c *Context) GlobalIsSet(name string) bool
- 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) NumFlags() int
- func (c *Context) String(name string) string
- func (c *Context) StringSlice(name string) []string
- type DurationFlag
- type Flag
- type Float64Flag
- type Generic
- type GenericFlag
- type IntFlag
- type IntSlice
- type IntSliceFlag
- type StringFlag
- type StringSlice
- type StringSliceFlag
Examples ¶
Constants ¶
This section is empty.
Variables ¶
var AppHelpTemplate = `` /* 386-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 BashCompletionFlag = BoolFlag{
Name: "generate-bash-completion",
}
This flag enables bash-completion for all commands and subcommands
var CommandHelpTemplate = `` /* 242-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 HelpFlag = BoolFlag{
Name: "help, h",
Usage: "show help",
}
This flag prints the help for all commands and subcommands Set to the zero value (BoolFlag{}) to disable flag -- keeps subcommand unless HideHelp is set to true)
var HelpPrinter helpPrinter = nil
var SubcommandHelpTemplate = `` /* 264-byte string literal not displayed */
The text template for the subcommand help topic. cli.go uses text/template to render templates. You can render custom help text by setting this variable.
var VersionFlag = BoolFlag{
Name: "version, v",
Usage: "print the version",
}
This flag prints the version for the application
var VersionPrinter = printVersion
Prints version for the App
Functions ¶
func DefaultAppComplete ¶
func DefaultAppComplete(c *Context)
Prints the list of subcommands as the default app completion method
func ShowAppHelp ¶
func ShowAppHelp(c *Context)
func ShowCommandCompletions ¶
Prints the custom completions for a given command
func ShowCommandHelp ¶
Prints help for the given command
func ShowCompletions ¶
func ShowCompletions(c *Context)
Prints the lists of commands within a given context
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 // Boolean to enable bash completion commands EnableBashCompletion bool // Boolean to hide built-in help command HideHelp bool // Boolean to hide built-in version flag HideVersion bool // An action to execute when the bash-completion flag is set BashComplete func(context *Context) // 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 // An action to execute after any subcommands are run, but after the subcommand has finished // It is run even if Action() panics After func(context *Context) error // The action to execute when no subcommands are specified Action func(context *Context) // Execute this function if the proper command cannot be found CommandNotFound func(context *Context, command string) // Compilation date Compiled time.Time // List of all authors who contributed Authors []Author // Name of Author (Note: Use App.Authors, this is deprecated) Author string // Email of Author (Note: Use App.Authors, this is deprecated) Email string // Writer writer to write output to Writer io.Writer }
App is the main structure of a cli application. It is recomended that and app be created with the cli.NewApp() function
func NewApp ¶
func NewApp() *App
Creates a new cli Application with some reasonable defaults for Name, Usage, Version and Action.
func (*App) Run ¶
Entry point to the cli app. Parses the arguments slice and routes to the proper flag/args combination
func (*App) RunAndExitOnError ¶
func (a *App) RunAndExitOnError()
Another entry point to the cli app, takes care of passing arguments and error handling
func (*App) RunAsSubcommand ¶
Invokes the subcommand given the context, parses ctx.Args() to generate command-specific flags
type Command ¶
type Command struct { // The name of the command Name string // short name of the command. Typically one character (deprecated, use `Aliases`) ShortName string // A list of aliases for the command Aliases []string // A short description of the usage of this command Usage string // A longer explanation of how the command works Description string // The function to call when checking for bash command completions BashComplete func(context *Context) // An action to execute before any sub-subcommands are run, but after the context is ready // If a non-nil error is returned, no sub-subcommands are run Before func(context *Context) error // An action to execute after any subcommands are run, but after the subcommand has finished // It is run even if Action() panics After func(context *Context) error // The function to call when this command is invoked Action func(context *Context) // List of child commands Subcommands []Command // List of flags to parse Flags []Flag // Treat all flags as normal arguments if true SkipFlagParsing bool // Boolean to hide built-in help command HideHelp bool }
Command is a subcommand for a cli.App.
type Context ¶
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 ¶
Creates a new context. For use in when invoking an App or Command action.
func (*Context) Bool ¶
Looks up the value of a local bool flag, returns false if no bool flag exists
func (*Context) BoolT ¶
Looks up the value of a local boolT flag, returns false if no bool flag exists
func (*Context) Duration ¶
Looks up the value of a local time.Duration flag, returns 0 if no time.Duration flag exists
func (*Context) Float64 ¶
Looks up the value of a local float64 flag, returns 0 if no float64 flag exists
func (*Context) Generic ¶
Looks up the value of a local generic flag, returns nil if no generic flag exists
func (*Context) GlobalBool ¶
Looks up the value of a global bool flag, returns false if no bool flag exists
func (*Context) GlobalDuration ¶
Looks up the value of a global time.Duration flag, returns 0 if no time.Duration flag exists
func (*Context) GlobalFlagNames ¶
Returns a slice of global flag names used by the app.
func (*Context) GlobalGeneric ¶
Looks up the value of a global generic flag, returns nil if no generic flag exists
func (*Context) GlobalInt ¶
Looks up the value of a global int flag, returns 0 if no int flag exists
func (*Context) GlobalIntSlice ¶
Looks up the value of a global int slice flag, returns nil if no int slice flag exists
func (*Context) GlobalIsSet ¶
Determines if the global flag was actually set
func (*Context) GlobalString ¶
Looks up the value of a global string flag, returns "" if no string flag exists
func (*Context) GlobalStringSlice ¶
Looks up the value of a global string slice flag, returns nil if no string slice flag exists
func (*Context) IntSlice ¶
Looks up the value of a local int slice flag, returns nil if no int slice flag exists
func (*Context) String ¶
Looks up the value of a local string flag, returns "" if no string flag exists
func (*Context) StringSlice ¶
Looks up the value of a local string slice flag, returns nil if no string slice flag exists
type DurationFlag ¶
func (DurationFlag) Apply ¶
func (f DurationFlag) Apply(set *flag.FlagSet)
func (DurationFlag) String ¶
func (f DurationFlag) String() string
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 ¶
func (Float64Flag) Apply ¶
func (f Float64Flag) Apply(set *flag.FlagSet)
func (Float64Flag) String ¶
func (f Float64Flag) String() string
type GenericFlag ¶
GenericFlag is the flag type for types implementing Generic
func (GenericFlag) Apply ¶
func (f GenericFlag) Apply(set *flag.FlagSet)
Apply takes the flagset and calls Set on the generic flag with the value provided by the user for parsing by the flag
func (GenericFlag) String ¶
func (f GenericFlag) String() string
String returns the string representation of the generic flag to display the help text to the user (uses the String() method of the generic flag to show the value)
type IntSliceFlag ¶
func (IntSliceFlag) Apply ¶
func (f IntSliceFlag) Apply(set *flag.FlagSet)
func (IntSliceFlag) String ¶
func (f IntSliceFlag) String() string
type StringFlag ¶
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 EnvVar string }
func (StringSliceFlag) Apply ¶
func (f StringSliceFlag) Apply(set *flag.FlagSet)
func (StringSliceFlag) String ¶
func (f StringSliceFlag) String() string