aboutsummaryrefslogtreecommitdiffstats
path: root/vendor/github.com/spf13/cobra/bash_completions.md
blob: 4ac61ee132a48bebf069a27385e289e28f7c09ac (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
# Generating Bash Completions For Your Own cobra.Command

If you are using the generator you can create a completion command by running

```bash
cobra add completion
```

Update the help text show how to install the bash_completion Linux show here [Kubectl docs show mac options](https://kubernetes.io/docs/tasks/tools/install-kubectl/#enabling-shell-autocompletion)

Writing the shell script to stdout allows the most flexible use.

```go
// completionCmd represents the completion command
var completionCmd = &cobra.Command{
	Use:   "completion",
	Short: "Generates bash completion scripts",
	Long: `To load completion run

. <(bitbucket completion)

To configure your bash shell to load completions for each session add to your bashrc

# ~/.bashrc or ~/.profile
. <(bitbucket completion)
`,
	Run: func(cmd *cobra.Command, args []string) {
		rootCmd.GenBashCompletion(os.Stdout);
	},
}
```

**Note:** The cobra generator may include messages printed to stdout for example if the config file is loaded, this will break the auto complete script


## Example from kubectl

Generating bash completions from a cobra command is incredibly easy. An actual program which does so for the kubernetes kubectl binary is as follows:

```go
package main

import (
	"io/ioutil"
	"os"

	"k8s.io/kubernetes/pkg/kubectl/cmd"
	"k8s.io/kubernetes/pkg/kubectl/cmd/util"
)

func main() {
	kubectl := cmd.NewKubectlCommand(util.NewFactory(nil), os.Stdin, ioutil.Discard, ioutil.Discard)
	kubectl.GenBashCompletionFile("out.sh")
}
```

`out.sh` will get you completions of subcommands and flags. Copy it to `/etc/bash_completion.d/` as described [here](https://debian-administration.org/article/316/An_introduction_to_bash_completion_part_1) and reset your terminal to use autocompletion. If you make additional annotations to your code, you can get even more intelligent and flexible behavior.

## Creating your own custom functions

Some more actual code that works in kubernetes:

```bash
const (
        bash_completion_func = `__kubectl_parse_get()
{
    local kubectl_output out
    if kubectl_output=$(kubectl get --no-headers "$1" 2>/dev/null); then
        out=($(echo "${kubectl_output}" | awk '{print $1}'))
        COMPREPLY=( $( compgen -W "${out[*]}" -- "$cur" ) )
    fi
}

__kubectl_get_resource()
{
    if [[ ${#nouns[@]} -eq 0 ]]; then
        return 1
    fi
    __kubectl_parse_get ${nouns[${#nouns[@]} -1]}
    if [[ $? -eq 0 ]]; then
        return 0
    fi
}

__kubectl_custom_func() {
    case ${last_command} in
        kubectl_get | kubectl_describe | kubectl_delete | kubectl_stop)
            __kubectl_get_resource
            return
            ;;
        *)
            ;;
    esac
}
`)
```

And then I set that in my command definition:

```go
cmds := &cobra.Command{
	Use:   "kubectl",
	Short: "kubectl controls the Kubernetes cluster manager",
	Long: `kubectl controls the Kubernetes cluster manager.

Find more information at https://github.com/GoogleCloudPlatform/kubernetes.`,
	Run: runHelp,
	BashCompletionFunction: bash_completion_func,
}
```

The `BashCompletionFunction` option is really only valid/useful on the root command. Doing the above will cause `__kubectl_custom_func()` (`__<command-use>_custom_func()`) to be called when the built in processor was unable to find a solution. In the case of kubernetes a valid command might look something like `kubectl get pod [mypod]`. If you type `kubectl get pod [tab][tab]` the `__kubectl_customc_func()` will run because the cobra.Command only understood "kubectl" and "get." `__kubectl_custom_func()` will see that the cobra.Command is "kubectl_get" and will thus call another helper `__kubectl_get_resource()`.  `__kubectl_get_resource` will look at the 'nouns' collected. In our example the only noun will be `pod`.  So it will call `__kubectl_parse_get pod`.  `__kubectl_parse_get` will actually call out to kubernetes and get any pods.  It will then set `COMPREPLY` to valid pods!

## Have the completions code complete your 'nouns'

In the above example "pod" was assumed to already be typed. But if you want `kubectl get [tab][tab]` to show a list of valid "nouns" you have to set them. Simplified code from `kubectl get` looks like:

```go
validArgs []string = { "pod", "node", "service", "replicationcontroller" }

cmd := &cobra.Command{
	Use:     "get [(-o|--output=)json|yaml|template|...] (RESOURCE [NAME] | RESOURCE/NAME ...)",
	Short:   "Display one or many resources",
	Long:    get_long,
	Example: get_example,
	Run: func(cmd *cobra.Command, args []string) {
		err := RunGet(f, out, cmd, args)
		util.CheckErr(err)
	},
	ValidArgs: validArgs,
}
```

Notice we put the "ValidArgs" on the "get" subcommand. Doing so will give results like

```bash
# kubectl get [tab][tab]
node                 pod                    replicationcontroller  service
```

## Plural form and shortcuts for nouns

If your nouns have a number of aliases, you can define them alongside `ValidArgs` using `ArgAliases`:

```go
argAliases []string = { "pods", "nodes", "services", "svc", "replicationcontrollers", "rc" }

cmd := &cobra.Command{
    ...
	ValidArgs:  validArgs,
	ArgAliases: argAliases
}
```

The aliases are not shown to the user on tab completion, but they are accepted as valid nouns by
the completion algorithm if entered manually, e.g. in:

```bash
# kubectl get rc [tab][tab]
backend        frontend       database 
```

Note that without declaring `rc` as an alias, the completion algorithm would show the list of nouns
in this example again instead of the replication controllers.

## Mark flags as required

Most of the time completions will only show subcommands. But if a flag is required to make a subcommand work, you probably want it to show up when the user types [tab][tab].  Marking a flag as 'Required' is incredibly easy.

```go
cmd.MarkFlagRequired("pod")
cmd.MarkFlagRequired("container")
```

and you'll get something like

```bash
# kubectl exec [tab][tab][tab]
-c            --container=  -p            --pod=  
```

# Specify valid filename extensions for flags that take a filename

In this example we use --filename= and expect to get a json or yaml file as the argument. To make this easier we annotate the --filename flag with valid filename extensions.

```go
	annotations := []string{"json", "yaml", "yml"}
	annotation := make(map[string][]string)
	annotation[cobra.BashCompFilenameExt] = annotations

	flag := &pflag.Flag{
		Name:        "filename",
		Shorthand:   "f",
		Usage:       usage,
		Value:       value,
		DefValue:    value.String(),
		Annotations: annotation,
	}
	cmd.Flags().AddFlag(flag)
```

Now when you run a command with this filename flag you'll get something like

```bash
# kubectl create -f 
test/                         example/                      rpmbuild/
hello.yml                     test.json
```

So while there are many other files in the CWD it only shows me subdirs and those with valid extensions.

# Specify custom flag completion

Similar to the filename completion and filtering using cobra.BashCompFilenameExt, you can specify
a custom flag completion function with cobra.BashCompCustom:

```go
	annotation := make(map[string][]string)
	annotation[cobra.BashCompCustom] = []string{"__kubectl_get_namespaces"}

	flag := &pflag.Flag{
		Name:        "namespace",
		Usage:       usage,
		Annotations: annotation,
	}
	cmd.Flags().AddFlag(flag)
```

In addition add the `__handle_namespace_flag` implementation in the `BashCompletionFunction`
value, e.g.:

```bash
__kubectl_get_namespaces()
{
    local template
    template="{{ range .items  }}{{ .metadata.name }} {{ end }}"
    local kubectl_out
    if kubectl_out=$(kubectl get -o template --template="${template}" namespace 2>/dev/null); then
        COMPREPLY=( $( compgen -W "${kubectl_out}[*]" -- "$cur" ) )
    fi
}
```
# Using bash aliases for commands

You can also configure the `bash aliases` for the commands and they will also support completions.

```bash
alias aliasname=origcommand
complete -o default -F __start_origcommand aliasname

# and now when you run `aliasname` completion will make
# suggestions as it did for `origcommand`.

$) aliasname <tab><tab>
completion     firstcommand   secondcommand
```