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| Cobra is a library for creating powerful modern CLI applications. |
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| Cobra is used in many Go projects such as [Kubernetes](https://kubernetes.io/), |
| [Hugo](https://gohugo.io), and [GitHub CLI](https://github.com/cli/cli) to |
| name a few. [This list](./projects_using_cobra.md) contains a more extensive list of projects using Cobra. |
| |
| [](https://github.com/spf13/cobra/actions?query=workflow%3ATest) |
| [](https://pkg.go.dev/github.com/spf13/cobra) |
| [](https://goreportcard.com/report/github.com/spf13/cobra) |
| [](https://gophers.slack.com/archives/CD3LP1199) |
| |
| # Overview |
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| Cobra is a library providing a simple interface to create powerful modern CLI |
| interfaces similar to git & go tools. |
| |
| Cobra provides: |
| * Easy subcommand-based CLIs: `app server`, `app fetch`, etc. |
| * Fully POSIX-compliant flags (including short & long versions) |
| * Nested subcommands |
| * Global, local and cascading flags |
| * Intelligent suggestions (`app srver`... did you mean `app server`?) |
| * Automatic help generation for commands and flags |
| * Grouping help for subcommands |
| * Automatic help flag recognition of `-h`, `--help`, etc. |
| * Automatically generated shell autocomplete for your application (bash, zsh, fish, powershell) |
| * Automatically generated man pages for your application |
| * Command aliases so you can change things without breaking them |
| * The flexibility to define your own help, usage, etc. |
| * Optional seamless integration with [viper](https://github.com/spf13/viper) for 12-factor apps |
| |
| # Concepts |
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| Cobra is built on a structure of commands, arguments & flags. |
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| **Commands** represent actions, **Args** are things and **Flags** are modifiers for those actions. |
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| The best applications read like sentences when used, and as a result, users |
| intuitively know how to interact with them. |
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| The pattern to follow is |
| `APPNAME VERB NOUN --ADJECTIVE` |
| or |
| `APPNAME COMMAND ARG --FLAG`. |
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| A few good real world examples may better illustrate this point. |
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| In the following example, 'server' is a command, and 'port' is a flag: |
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| hugo server --port=1313 |
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| In this command we are telling Git to clone the url bare. |
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| git clone URL --bare |
| |
| ## Commands |
| |
| Command is the central point of the application. Each interaction that |
| the application supports will be contained in a Command. A command can |
| have children commands and optionally run an action. |
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| In the example above, 'server' is the command. |
| |
| [More about cobra.Command](https://pkg.go.dev/github.com/spf13/cobra#Command) |
| |
| ## Flags |
| |
| A flag is a way to modify the behavior of a command. Cobra supports |
| fully POSIX-compliant flags as well as the Go [flag package](https://golang.org/pkg/flag/). |
| A Cobra command can define flags that persist through to children commands |
| and flags that are only available to that command. |
| |
| In the example above, 'port' is the flag. |
| |
| Flag functionality is provided by the [pflag |
| library](https://github.com/spf13/pflag), a fork of the flag standard library |
| which maintains the same interface while adding POSIX compliance. |
| |
| # Installing |
| Using Cobra is easy. First, use `go get` to install the latest version |
| of the library. |
| |
| ``` |
| go get -u github.com/spf13/cobra@latest |
| ``` |
| |
| Next, include Cobra in your application: |
| |
| ```go |
| import "github.com/spf13/cobra" |
| ``` |
| |
| # Usage |
| `cobra-cli` is a command line program to generate cobra applications and command files. |
| It will bootstrap your application scaffolding to rapidly |
| develop a Cobra-based application. It is the easiest way to incorporate Cobra into your application. |
| |
| It can be installed by running: |
| |
| ``` |
| go install github.com/spf13/cobra-cli@latest |
| ``` |
| |
| For complete details on using the Cobra-CLI generator, please read [The Cobra Generator README](https://github.com/spf13/cobra-cli/blob/main/README.md) |
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| For complete details on using the Cobra library, please read the [The Cobra User Guide](user_guide.md). |
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| # License |
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| Cobra is released under the Apache 2.0 license. See [LICENSE.txt](https://github.com/spf13/cobra/blob/master/LICENSE.txt) |