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# Cobra Generator | ||
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Cobra provides its own program that will create your application and add any | ||
commands you want. It's the easiest way to incorporate Cobra into your application. | ||
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Install the cobra generator with the command `go install github.com/spf13/cobra/cobra@latest`. | ||
Go will automatically install it in your `$GOPATH/bin` directory which should be in your $PATH. | ||
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Once installed you should have the `cobra` command available. Confirm by typing `cobra` at a | ||
command line. | ||
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There are only two operations currently supported by the Cobra generator: | ||
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### cobra init | ||
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The `cobra init [app]` command will create your initial application code | ||
for you. It is a very powerful application that will populate your program with | ||
the right structure so you can immediately enjoy all the benefits of Cobra. | ||
It can also apply the license you specify to your application. | ||
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With the introduction of Go modules, the Cobra generator has been simplified to | ||
take advantage of modules. The Cobra generator works from within a Go module. | ||
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#### Initializing a module | ||
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__If you already have a module, skip this step.__ | ||
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If you want to initialize a new Go module: | ||
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1. Create a new directory | ||
2. `cd` into that directory | ||
3. run `go mod init <MODNAME>` | ||
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e.g. | ||
``` | ||
cd $HOME/code | ||
mkdir myapp | ||
cd myapp | ||
go mod init github.com/spf13/myapp | ||
``` | ||
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#### Initializing an Cobra CLI application | ||
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From within a Go module run `cobra init`. This will create a new barebones project | ||
for you to edit. | ||
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You should be able to run your new application immediately. Try it with | ||
`go run main.go`. | ||
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You will want to open up and edit 'cmd/root.go' and provide your own description and logic. | ||
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e.g. | ||
``` | ||
cd $HOME/code/myapp | ||
cobra init | ||
go run main.go | ||
``` | ||
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Cobra init can also be run from a subdirectory such as how the [cobra generator itself is organized](https://github.com/spf13/cobra). | ||
This is useful if you want to keep your application code separate from your library code. | ||
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#### Optional flags: | ||
You can provide it your author name with the `--author` flag. | ||
e.g. `cobra init --author "Steve Francia [email protected]"` | ||
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You can provide a license to use with `--license` | ||
e.g. `cobra init --license apache` | ||
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Use the `--viper` flag to automatically setup [viper](https://github.com/spf13/viper) | ||
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Viper is a companion to Cobra intended to provide easy handling of environment variables and config files and seamlessly connecting them to the application flags. | ||
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### Add commands to a project | ||
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Once a cobra application is initialized you can continue to use the Cobra generator to | ||
add additional commands to your application. The command to do this is `cobra add`. | ||
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Let's say you created an app and you wanted the following commands for it: | ||
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* app serve | ||
* app config | ||
* app config create | ||
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In your project directory (where your main.go file is) you would run the following: | ||
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``` | ||
cobra add serve | ||
cobra add config | ||
cobra add create -p 'configCmd' | ||
``` | ||
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`cobra add` supports all the same optional flags as `cobra init` does (described above). | ||
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You'll notice that this final command has a `-p` flag. This is used to assign a | ||
parent command to the newly added command. In this case, we want to assign the | ||
"create" command to the "config" command. All commands have a default parent of rootCmd if not specified. | ||
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By default `cobra` will append `Cmd` to the name provided and uses this name for the internal variable name. When specifying a parent, be sure to match the variable name used in the code. | ||
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*Note: Use camelCase (not snake_case/kebab-case) for command names. | ||
Otherwise, you will encounter errors. | ||
For example, `cobra add add-user` is incorrect, but `cobra add addUser` is valid.* | ||
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Once you have run these three commands you would have an app structure similar to | ||
the following: | ||
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``` | ||
▾ app/ | ||
▾ cmd/ | ||
config.go | ||
create.go | ||
serve.go | ||
root.go | ||
main.go | ||
``` | ||
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At this point you can run `go run main.go` and it would run your app. `go run | ||
main.go serve`, `go run main.go config`, `go run main.go config create` along | ||
with `go run main.go help serve`, etc. would all work. | ||
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You now have a basic Cobra-based application up and running. Next step is to edit the files in cmd and customize them for your application. | ||
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For complete details on using the Cobra library, please read the [The Cobra User Guide](https://github.com/spf13/cobra/blob/master/user_guide.md#using-the-cobra-library). | ||
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Have fun! | ||
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### Configuring the cobra generator | ||
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The Cobra generator will be easier to use if you provide a simple configuration | ||
file which will help you eliminate providing a bunch of repeated information in | ||
flags over and over. | ||
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An example ~/.cobra.yaml file: | ||
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```yaml | ||
author: Steve Francia <[email protected]> | ||
license: MIT | ||
viper: true | ||
``` | ||
You can also use built-in licenses. For example, **GPLv2**, **GPLv3**, **LGPL**, | ||
**AGPL**, **MIT**, **2-Clause BSD** or **3-Clause BSD**. | ||
You can specify no license by setting `license` to `none` or you can specify | ||
a custom license: | ||
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```yaml | ||
author: Steve Francia <[email protected]> | ||
year: 2020 | ||
license: | ||
header: This file is part of CLI application foo. | ||
text: | | ||
{{ .copyright }} | ||
This is my license. There are many like it, but this one is mine. | ||
My license is my best friend. It is my life. I must master it as I must | ||
master my life. | ||
``` | ||
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In the above custom license configuration the `copyright` line in the License | ||
text is generated from the `author` and `year` properties. The content of the | ||
`LICENSE` file is | ||
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``` | ||
Copyright © 2020 Steve Francia <[email protected]> | ||
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This is my license. There are many like it, but this one is mine. | ||
My license is my best friend. It is my life. I must master it as I must | ||
master my life. | ||
``` | ||
The `header` property is used as the license header files. No interpolation is | ||
done. This is the example of the go file header. | ||
``` | ||
/* | ||
Copyright © 2020 Steve Francia <[email protected]> | ||
This file is part of CLI application foo. | ||
*/ | ||
``` |
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