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Custom Shell Completions

Beyond the built-in ** completion trigger for standard commands, you can create fully custom fzf completions for any command.

How Shell Completion Works with fzf​

When you press <Tab> after **, fzf intercepts the completion event and calls your custom _fzf_complete_COMMAND function.

Writing a Custom Completion​

Bash Completion Function​

~/.bashrc
# Custom completion for a command called 'deploy'
_fzf_complete_deploy() {
  # $@ contains the current command line tokens
  _fzf_complete --multi --prompt="Environment> " -- "$@" < <(
    # Produce the list of completions
    echo "development"
    echo "staging"
    echo "production-us-east"
    echo "production-eu-west"
  )
}

# Register the completion
complete -F _fzf_complete_deploy deploy

Post-process the Selection​

# The _fzf_complete_deploy_post function transforms the selected value
_fzf_complete_deploy_post() {
  # Read from stdin, transform, write to stdout
  awk '{print $1}'  # take only first column
}

Real-World: kubectl Completion​

~/.bashrc
# Pick kubernetes contexts with fzf
_fzf_complete_kubectl() {
  if [[ $COMP_LINE == *"kubectl config use-context"* ]]; then
    _fzf_complete --prompt="Context> " -- "$@" < <(
      kubectl config get-contexts -o name 2>/dev/null
    )
  else
    _fzf_complete -- "$@" < <(
      kubectl get all --all-namespaces 2>/dev/null | awk '{print $1"/"$2}'
    )
  fi
}
complete -F _fzf_complete_kubectl kubectl

Real-World: SSH Completion Enhanced​

~/.bashrc
_fzf_complete_ssh() {
  _fzf_complete --prompt="Host> " -- "$@" < <(
    {
      # From known_hosts
      cat ~/.ssh/known_hosts 2>/dev/null | awk '{print $1}' | tr ',' '\n'
      # From config hosts
      grep -E "^Host " ~/.ssh/config 2>/dev/null | awk '{print $2}'
    } | grep -v '\*' | sort -u
  )
}
complete -F _fzf_complete_ssh ssh

Real-World: Git Branch Completion​

~/.bashrc
_fzf_complete_git() {
  local subcommand="${COMP_WORDS[1]}"
  case "$subcommand" in
    checkout|co|switch|merge|rebase|cherry-pick|branch)
      _fzf_complete --prompt="Branch> " -- "$@" < <(
        git branch --all 2>/dev/null | grep -v HEAD | sed 's/^[* ]*//' | sed 's#remotes/origin/##' | sort -u
      )
      ;;
    *)
      _fzf_complete_git_default "$@"
      ;;
  esac
}
complete -F _fzf_complete_git git

Zsh Custom Completions​

~/.zshrc
# Zsh: override completion for 'deploy'
_fzf_complete_deploy() {
  _fzf_complete -- "$@" < <(
    print -l development staging production
  )
}

Triggering Custom Completion​

By default, **<Tab> triggers fzf completion. Override the trigger:

~/.bashrc
export FZF_COMPLETION_TRIGGER='~~'   # Use ~~ instead of **
# Now: vim ~~<Tab> triggers fzf

What's Next​