166 lines
4.7 KiB
Markdown
166 lines
4.7 KiB
Markdown
# Cobra
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A Commander for modern go CLI interactions
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[](https://travis-ci.org/spf13/cobra)
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## Overview
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Cobra provides a simple interface to create powerful modern CLI
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interfaces similar to git & go tools.
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Cobra was inspired by go, go-Commander, gh and subcommand
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## Concepts
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There are 3 different core objects to become familiar with to use Cobra.
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To help illustrate these 3 items better use the following as an example:
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hugo server --port=1313
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### Commander
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The Commander is the head of your application. It holds the configuration
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for your application. It also is responsible for all global flags.
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In the example above 'hugo' is the commander.
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### Command
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Command is the central point of the application. Each interaction that
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the application supports will be contained in a Command. A command can
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have children commands and optionally run an action.
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In the example above 'server' is the command
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### Flags
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A flag is a way to modify the behavior of an command. Cobra supports
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fully posix compliant flags as well as remaining consistent with
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the go flag package. A Cobra command has can define flags that
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persist through to children commands and flags that are only available
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to that command.
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In the example above 'port' is the flag.
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## Usage
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### Implementing Cobra
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Using Cobra is easy. First use go get to install the latest version
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of the library.
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$ go get github.com/spf13/cobra
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Next include cobra in your application.
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import "github.com/spf13/cobra"
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Now you are ready to implement Cobra.
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Cobra works by creating a set of commands and then organizing them into a tree.
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The tree defines the structure of the application.
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Once each command is defined with it's corresponding flags, then the
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tree is assigned to the commander which is finally executed.
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In the example below we have defined three commands. Two are at the top
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level and one (cmdTimes) is a child of one of the top commands.
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We have only defined one flag for a single command.
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More documentation about flags is available at https://github.com/spf13/pflag
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## Example
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Import(
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"github.com/spf13/cobra"
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"fmt"
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"strings"
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)
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func main() {
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var echoTimes int
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var cmdPrint = &cobra.Command{
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Use: "print [string to print]",
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Short: "Print anything to the screen",
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Long: `print is for printing anything back to the screen.
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For many years people have printed back to the screen.
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`,
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Run: func(cmd *cobra.Command, args []string) {
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fmt.Println("Print: " + strings.Join(args, " "))
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},
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}
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var cmdEcho = &cobra.Command{
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Use: "echo [string to echo]",
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Short: "Echo anything to the screen",
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Long: `echo is for echoing anything back.
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Echo works a lot like print, except it has a child command.
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`,
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Run: func(cmd *cobra.Command, args []string) {
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fmt.Println("Print: " + strings.Join(args, " "))
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},
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}
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var cmdTimes = &cobra.Command{
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Use: "times [# times] [string to echo]",
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Short: "Echo anything to the screen more times",
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Long: `echo things multiple times back to the user by providing
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a count and a string.`,
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Run: func(cmd *cobra.Command, args []string) {
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for i:=0; i < echoTimes; i++ {
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fmt.Println("Echo: " + strings.Join(args, " "))
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}
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},
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}
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cmdTimes().Flags().IntVarP(&echoTimes, "times", "t", 1, "times to echo the input")
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var commander = cobra.NewCommander()
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commander.SetName("CobraExample")
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commander.AddCommand(cmdPrint, cmdEcho)
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cmdEcho.AddCommand(cmdTimes)
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commander.Execute()
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}
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## Release Notes
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* **0.7.0** Sept 24, 2013
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* Needs more eyes
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* Test suite
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* Support for automatic error messages
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* Support for help command
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* Support for printing to any io.Writer instead of os.Stderr
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* Support for persistent flags which cascade down tree
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* Ready for integration into Hugo
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* **0.1.0** Sept 3, 2013
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* Implement first draft
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## ToDo
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* More testing of non-runnable
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* More testing
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* Launch proper documentation site
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## Contributing
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1. Fork it
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2. Create your feature branch (`git checkout -b my-new-feature`)
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3. Commit your changes (`git commit -am 'Add some feature'`)
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4. Push to the branch (`git push origin my-new-feature`)
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5. Create new Pull Request
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## Contributors
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Names in no particular order:
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* [spf13](https://github.com/spf13)
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## License
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nitro is released under the Apache 2.0 license. See [LICENSE.txt](https://github.com/spf13/nitro/blob/master/LICENSE.txt)
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