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* Fix flag completion

The flag completion functions should not be stored in the root cmd.
There is no requirement that the root cmd should be the same when
`RegisterFlagCompletionFunc` was called. Storing the flags there does
not work when you add the the flags to your cmd struct before you add the
cmd to the parent/root cmd. The flags can no longer be found in the rigth
place when the completion command is called and thus the flag completion
does not work.

Also #1423 claims that this would be thread safe but we still have a map
which will fail when accessed concurrently. To truly fix this issue use a

Fixes #1437
Fixes #1320

Signed-off-by: Paul Holzinger <>

* Fix trailing whitespaces in fish comp scripts

Signed-off-by: Paul Holzinger <>

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Feb 10, 2021

cobra logo

Cobra is both a library for creating powerful modern CLI applications as well as a program to generate applications and command files.

Cobra is used in many Go projects such as Kubernetes, Hugo, and Github CLI to name a few. This list contains a more extensive list of projects using Cobra.

GoDoc Go Report Card Slack

Table of Contents


Cobra is a library providing a simple interface to create powerful modern CLI interfaces similar to git & go tools.

Cobra is also an application that will generate your application scaffolding to rapidly develop a Cobra-based application.

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
  • Easy generation of applications & commands with cobra init appname & cobra add cmdname
  • Intelligent suggestions (app srver... did you mean app server?)
  • Automatic help generation for commands and flags
  • 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 tight integration with viper for 12-factor apps


Cobra is built on a structure of commands, arguments & flags.

Commands represent actions, Args are things and Flags are modifiers for those actions.

The best applications read like sentences when used, and as a result, users intuitively know how to interact with them.


A few good real world examples may better illustrate this point.

In the following example, 'server' is a command, and 'port' is a flag:

hugo server --port=1313

In this command we are telling Git to clone the url bare.

git clone URL --bare


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.

In the example above, 'server' is the command.

More about cobra.Command


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. 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, a fork of the flag standard library which maintains the same interface while adding POSIX compliance.


Using Cobra is easy. First, use go get to install the latest version of the library. This command will install the cobra generator executable along with the library and its dependencies:

go get -u

Next, include Cobra in your application:

import ""


See User Guide.


Cobra is released under the Apache 2.0 license. See LICENSE.txt