bash tab completion with spaces

Question

I\'m having a problem with bash-completion when the possible options may contain spaces.

Let\'s say I want a function which echoes the first argument:

fu         


        

Answer 1

Okay, this crazy contraption draws heavily on rici’s solution, and not only fully works, but also quotes any completions that need it, and only those.

pink() {
    # simulating actual awk output
    echo "nick mason"
    echo "syd-barrett"
    echo "david_gilmour"
    echo "roger waters"
    echo "richard wright"
}

_test() {
  cur=${COMP_WORDS[COMP_CWORD]}
  mapfile -t patterns < <( pink )
  mapfile -t COMPREPLY < <( compgen -W "$( printf '%q ' "${patterns[@]}" )" -- "$cur" | awk '/ / { print "\""$0"\"" } /^[^ ]+$/ { print $0 }' )
}

complete -F _test test

So as far as I could test it, it fully implements ls-like behavior, minus the path-specific parts.

Verbose example

Here’s a more verbose version of the _test function, so it becomes a bit more understandable:

_test() {
  local cur escapedPatterns
  cur=${COMP_WORDS[COMP_CWORD]}
  mapfile -t patterns < <( pink )
  escapedPatterns="$( printf '%q ' "${patterns[@]}" )"
  mapfile -t COMPREPLY < <( compgen -W "$escapedPatterns" -- "$cur" | quoteIfNeeded )
}

quoteIfNeeded() {
  # Only if it contains spaces. Otherwise return as-is.
  awk '/ / { print "\""$0"\"" } /^[^ ]+$/ { print $0 }'
}

None of this is even remotely optimized for efficiency. Then again, this is only tab completion, and it’s not causing a noticeable delay for any reasonably large list of completions.

It works by:

1. Pulling the awk output into an array, using mapfile.
2. Escaping the array and putting it into a string.
3. Having a single space behind the %q as a separation marker.
4. Quoting $cur, Very important!
5. Quoting the output of compgen. And only if it contains spaces.
6. Feeding that output into COMPREPLY, using another mapfile call.
7. Not using -o filenames.

And it only works with all those tricks. It fails if even a single one is missing. Trust me; I’ve tried. ;)