How do I get bash completion for command aliases?

Question

I am looking to get tab-completion on my command line aliases, for example, say I defined the following alias :

alias apt-inst='sudo aptitude install'

Is there a way to get the completions provided by aptitude when I hit the tab key? i.e. when I write 'sudo aptitude install gnumer' and hit tab, aptitude completes this to gnumeric, or if there was uncertainty lists all the available packages starting with gnumer. If I do it using my alias, nothing - no completion.

Answer 1

There is a great thread about this on the Ubuntu forums. Ole J proposes the following alias completion definition function:

function make-completion-wrapper () {
  local function_name="$2"
  local arg_count=$(($#-3))
  local comp_function_name="$1"
  shift 2
  local function="
    function $function_name {
      ((COMP_CWORD+=$arg_count))
      COMP_WORDS=( "$@" \${COMP_WORDS[@]:1} )
      "$comp_function_name"
      return 0
    }"
  eval "$function"
  echo $function_name
  echo "$function"
}

Use it to define a completion function for your alias, then specify that function as a completer for the alias:

make-completion-wrapper _apt_get _apt_get_install apt-get install
complete -F _apt_get_install apt-inst

I prefer to use aliases for adding always-used arguments to existing programs. For instance, with grep, I always want to skip devices and binary files, so I make an alias for grep. For adding new commands such as grepbin, I use a shell script in my ~/bin folder. If that folder is in your path, it will get autocompleted.

Answer 2

Try complete-alias, which solves this problem exactly. (Disclaimer: I am the author of complete_alias)

After install it you can use one generic function to complete many aliases like this:

complete -F _complete_alias <myalias1>
complete -F _complete_alias <myalias2>
complete -F _complete_alias <myalias3>

---

You may want to source the complete_alias file in every bash instance through .bash_profile or similar.

installation

mkdir ~/.bash_completion.d
curl https://raw.githubusercontent.com/cykerway/complete-alias/master/complete_alias \
     > ~/.bash_completion.d/complete_alias

application

source ~/.bash_completion.d/complete_alias

alias container=docker\ container
complete -F _complete_alias container

container can now be autocompleted by the original _docker() completion handler;

$ container l<Tab>
logs  ls    

$ container s<Tab>
start  stats  stop   

Answer 3

2018 answer

You must add your alias to the program 'complete'. Depending the kind of autocompletion you want to achieve, you must use -c or -F.

For package autocompletion:

complete -c name_of_your_alias

For command autocompletion:

complete -F name_of_your_alias

To check if your alias was added correctly:

complete | grep name_of_your_alias

Finally, to remove an alias from 'complete':

complete -r name_of_your_alias

In your case:

complete -c apt-inst

Answer 4

By googling this issue I ended up here, so I tried the approaches in the other answers. For various reasons I don't actually understand, they never behaved properly in my Ubuntu 16.04.

What in the end worked for me was way more trivial than expected. I wanted to use the same autocompletion as rsync has for mycommand. Hence, I looked up the autocompletion function, and then called complete accordingly.

# Lookup of name of autocompletion function used for rsync
complete -p rsync
# Returns: complete -o nospace -F _rsync rsync

# Sourcing the rsync functions before, then using the same function for 'mycommand'
. /usr/share/bash-completion/completions/rsync
complete -o nospace -F _rsync mycommand

Disclaimer: I'm not sure what's the downside of my approach compared to the others. I mainly wrote this as it could help people where this trivial approach might be enough.

Answer 5

Here's the code from Shawn J. Goff's answer with some improvements:

• Fixed syntax errors highlighted by shell-check, eg the first " of "$@" actually ended the function definition string.
• Removed the return 0 so that the return value of the underlying function can be passed back to the caller.

.

# Wraps a completion function, eg for use with an alias.
# Usage:
# make-completion-wrapper <actual completion function> <name of new func.>
#                         <command name> <list supplied arguments>
# eg.
#   alias agi='apt-get install'
#   make-completion-wrapper _apt_get _apt_get_install apt-get install
#     # defines a function called _apt_get_install (that's $2) that will
#     # complete the 'agi' alias. 
#   complete -F _apt_get_install agi
function make-completion-wrapper {
  local function_name="$2"
  local arg_count=$(( $#-3 ))
  local comp_function_name="$1"
  shift 2
  local function="function $function_name {
      (( COMP_CWORD += $arg_count ))
      COMP_WORDS=( \"\$@\" \${COMP_WORDS[@]:1} )
      \"$comp_function_name\"
    }"
  eval "$function"
  # echo "$function"
}
export -f make-completion-wrapper

Answer 6

As an extension to @Giles answer, the following convenience function auto-names the wrapper generated by make-completion-wrapper to make it possible to define completion in one line:

function complete-alias  {
    # uses make-completion-wrapper: https://unix.stackexchange.com/a/4220/50978
    # example usage
    # complete-alias _pass pshow pass show
    # complete-alias _pass pgen pass generate

    EXISTING_COMPLETION_FN=${1} && shift
    ALIAS=${1} && shift
    AUTOGEN_COMPLETION_FN="__autogen_completion_${ALIAS}"
    make-completion-wrapper ${EXISTING_COMPLETION_FN} ${AUTOGEN_COMPLETION_FN} ${*}
    complete -F ${AUTOGEN_COMPLETION_FN} ${ALIAS}
}