Bash Autocomplete – How to Output String Completions to stdout

I'm the one that suggested changing the completion-display-width readline variable at /r/bash, but then you didn't specify you only wanted it to work on this one completion function.

Anyway, in a completion function, you can detect whether it's triggered by TAB (COMP_TYPE == 9) or by TABTAB (COMP_TYPE == 63), and if the latter is the case, you could pad the results with spaces so they fill the entire width of the terminal. It's the least hackish thing I can think of. It would look something like this:

_foo_complete() {
    local i file files
    files=( ~/work/dev/jobs/"$2"* )
    [[ -e ${files[0]} || -L ${files[0]} ]] || return 0
    if (( COMP_TYPE == 63 )); then
        for file in "${files[@]}"; do
            printf -v 'COMPREPLY[i++]' '%*s' "-$COLUMNS" "${file##*/}"
        done
    else
        COMPREPLY=( "${files[@]##*/}" )
    fi
}
complete -F _foo_complete foo

On a side note, you really shouldn't parse ls output.

At the first time, zsh Completion System seems to be very complex and difficult to grasp. Let try an example.

First thing you need to know, zsh completion system will load completion functions from $fpath. Make sure your completions directory appear in:

print -rl -- $fpath

(If you used oh-my-zsh, there's .oh-my-zsh/completions existed in $fpath, you can just create it and put your completion functions there)

Now, you must create a completion file for your function, its name must start with underscore _, plus your function name. In your case, its name is _eb_instances.

Add theses lines to _eb_instances file:

#compdef eb_instances

_eb_instances() {
  local state

  _arguments \
    '1: :->aws_profile'\
    '*: :->eb_name'

  case $state in
    (aws_profile) _arguments '1:profiles:(cuonglm test)' ;;
              (*) compadd "$@" prod staging dev
  esac
}

_eb_instances "$@"

You are done. Save the file and start new session to test completion. You will see some thing like this:

$ eb_instances <cursor>TAB
cuonglm  test

$ eb_instances cuonglm <cursor>TAB
dev      prod     staging

You can read zsh completion system documentation about _arguments function, state variable. Also you need to change (cuonglm test) with your sed command and change prod staging dev to your eb_names function.

If you want to generate the 2nd argument base on what 1st argument passed, you can use $words[2] variable:

case $state in
  (aws_profile) _arguments '1:profiles:(cuonglm test)' ;;
            (*) compadd "$@" $(echo $words[2]) ;;
esac

Replace echo with your real function, in your case, it's $(eb_names $words[2]).

If you still feel hard to accomplish this, just define _eb_instances and eb_instances in your .zshrc then call completion as:

compdef _eb_instances eb_instances

You need to initialize completion system with:

autoload -U compinit
compinit

(If you used oh-my-zsh, it have been loaded)