youtube-dl/devscripts/bash-completion.in

__youtube_dl()
{
    local cur prev opts fileopts diropts keywords
    COMPREPLY=()
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    opts="{{flags}}"
    keywords=":ytfavorites :ytrecommended :ytsubscriptions :ytwatchlater :ythistory"
    fileopts="-a|--batch-file|--download-archive|--cookies"
    diropts="--cache-dir"

    if [[ ${prev} =~ ${fileopts} ]]; then
        COMPREPLY=( $(compgen -f -- ${cur}) )
        return 0
    elif [[ ${prev} =~ ${diropts} ]]; then
        COMPREPLY=( $(compgen -d -- ${cur}) )
        return 0
    fi

    if [[ ${cur} =~ : ]]; then
        COMPREPLY=( $(compgen -W "${keywords}" -- ${cur}) )
        return 0
    elif [[ ${cur} == * ]] ; then
        COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
        return 0
    fi
}

complete -F __youtube_dl youtube-dl