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Bash Completion

Introduction

Bash completion is a shell feature that allows you to auto-complete commands, options, and arguments by pressing the Tab key.
This is especially useful for CLI tools like git, docker, kubectl, and multipass where you often need to remember many commands and flags.

In this guide, we'll:

  • Install bash-completion using Homebrew.
  • Enable bash completion in your shell.
  • Set up completion for Git, Docker, kubectl, and Multipass.

Installing Bash Completion

Bash Completion comes in two major versions, and the right one for you depends on your Bash version.

Feature bash-completion v1 bash-completion v2
Compatible Bash versions Bash 3.x and above Bash 4.x and above (including 5.x)
Status Legacy, still works for older setups Recommended for modern setups
Installation path (Homebrew) /usr/local/etc/bash_completion.d/ $(brew --prefix)/etc/profile.d/
Feature set More limited Expanded features and modern completion format
macOS usage Works with macOS default Bash (3.2) Best used with newer Bash installed via Homebrew

When to choose v1:

  • You are on macOS and using the default Bash (3.2) without upgrading.
  • You need maximum compatibility with older scripts or legacy environments.

When to choose v2:

  • You have installed a newer Bash (4.x or 5.x) via Homebrew.
  • You want more up-to-date and feature-rich completions.

Installation commands:

  • v1:
brew install bash-completion
  • v2:
brew install bash-completion@2

Enabling Bash Completion

To enable bash completion globally, add the following to your ~/.bash_profile (or ~/.bashrc if you prefer):

  • If you installed bash-completion:
if [ -f $(brew --prefix)/etc/bash_completion ]; then
  . $(brew --prefix)/etc/bash_completion
fi
  • If you installed bash-completion@2:
if [ -f $(brew --prefix)/etc/profile.d/bash_completion.sh ]; then
    . $(brew --prefix)/etc/profile.d/bash_completion.sh
fi

Then reload your profile:

source ~/.bash_profile

Git Bash Completion

Git also supports bash tab completion to make typing commands and branch names faster.

Add alias g for git in your ~/.aliases file:

alias g="git"

Source the git-completion script if it exists:

if [ -f ~/.git-completion.bash ]; then
    source ~/.git-completion.bash
fi

Set up tab completion for the 'g' alias if bash completion is available:

if type _git &> /dev/null && [ -f /usr/local/etc/bash_completion.d/git-completion.bash ]; then
  complete -o default -o nospace -F _git g;
fi;

Reload your shell:

source ~/.aliases
source ~/.bash_profile

You can now type:

git <TAB>
g <TAB>

and see available commands.

Docker Bash Completion

Add alias d for docker in your ~/.aliases file:

alias d="docker"

Create a dedicated directory for Docker completions and download the script:

mkdir -p ~/.docker/completion
curl -L https://raw.githubusercontent.com/docker/cli/master/contrib/completion/bash/docker \
    -o ~/.docker/completion/docker

Source the completion script in your ~/.bash_profile:

echo 'source ~/.docker/completion/docker' >> ~/.bash_profile
echo 'complete -F _docker d' >> ~/.bash_profile # optional alias completion

or manually add these lines to your ~/.bash_profile:

source ~/.docker/completion/docker
complete -F _docker d # optional alias completion

Reload your shell:

source ~/.aliases
source ~/.bash_profile

You can now type:

docker <TAB>
d <TAB>

and see available commands.

kubectl Bash Completion

Add alias k for kubectl in your ~/.aliases file:

alias k="kubectl"

Source the completion script in your ~/.bash_profile:

echo 'source /usr/local/opt/kubernetes-cli/etc/bash_completion.d/kubectl' >> ~/.bash_profile
#echo 'source <(kubectl completion bash)' >> ~/.bash_profile # optional for dynamic completion
echo 'complete -F __start_kubectl k' >> ~/.bash_profile # optional alias completion

or manually add these lines to your ~/.bash_profile:

source /usr/local/opt/kubernetes-cli/etc/bash_completion.d/kubectl
#source <(kubectl completion bash) # optional for dynamic completion
complete -F __start_kubectl k # optional alias completion

Reload your shell:

source ~/.aliases
source ~/.bash_profile

You can now type:

kubectl <TAB>
k <TAB>

and see available commands.

Multipass Bash Completion

Add alias mp for multipass in your ~/.aliases file:

alias mp="multipass"

Source the completion script in your ~/.bash_profile:

echo 'source "/Library/Application Support/com.canonical.multipass/Resources/completions/bash/multipass"' >> ~/.bash_profile
echo 'complete -F _multipass_complete mp' >> ~/.bash_profile # optional alias completion

or manually add these lines to your ~/.bash_profile:

if [ -f "/Library/Application Support/com.canonical.multipass/Resources/completions/bash/multipass" ]; then
    source "/Library/Application Support/com.canonical.multipass/Resources/completions/bash/multipass"
    complete -F _multipass_complete mp
fi

Reload your shell:

source ~/.aliases
source ~/.bash_profile

You can now type:

multipass <TAB>
mp <TAB>

and see available commands.

Conclusion

Bash completion can dramatically speed up your workflow when working with CLI tools.
With these configurations, you now have tab-completion support for:

  • Git
  • Docker
  • kubectl
  • Multipass

No more typing long command names or guessing available flags—just hit Tab and let bash do the work.