How to enable double tab autocompletion list in csh

Zsh has a lot of completion-related options (see man zshoptions under Completion). I think you're after setopt no_auto_menu and perhaps setopt bash_auto_list as well.

Thanks to Muru for pointing me to the solution.

Apparently my issue was that every time my function was called it always returned the full list of possible matches. I needed to only return those possible completions that match what the user has typed so far. Once I return only a single item, then bash will auto-complete the rest of the line.

This is the function that works. Before adding each possible completion, I do a quick check to see if the completion starts with the word that was typed originally. I do this using regular expressions. I also had to test to see if they haven't entered anything yet - in which case I always return everything.

I also changed it to make some more variables "local".

_use () {
    local word="${COMP_WORDS[$COMP_CWORD]}"
    local files=( `compgen -f -X "!*.use" /opt/use/` )
    local output=()
    for file in "${files[@]}"; do
        fileBaseName=`basename $file .use`
        if [[ $fileBaseName =~ ^$word.* ]] || [ "$word" == "" ]; then
            output+=("$fileBaseName")
        fi
    done
    COMPREPLY=( ${output[@]} )
}