/etc/bash_completion.d/powerwake_completion is in powerwake 2.18-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 | # powerwake(1) completion
have powerwake &&
_powerwake()
{
    local cur prev options files targets
    COMPREPLY=()
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    options="-b --broadcast -m --method"
    files="/etc/ethers /var/cache/powerwake/ethers $HOME/.cache/ethers"
    targets="$( cat ${files} 2>/dev/null | awk '{print $2}' )"
    case "${prev}" in
        -@(b|-broadcast))
            COMPREPLY=( $( compgen -W "$( LANG=C ifconfig 2>/dev/null | \
                awk '/Bcast:/ {print $3}' | awk -F ':' '{print $2}' )" \
                -- ${cur} ) )
            return 0
            ;;
        -@(m|-method))
            COMPREPLY=( $( compgen -W "wol" -- ${cur} ) )
            return 0
            ;;
        *)
        ;;
    esac
    if [[ ${cur} == -* ]] ; then
        COMPREPLY=( $( compgen -W "${options}" -- ${cur} ) )
        return 0
    else
        COMPREPLY=( $( compgen -W "${targets}" -- ${cur} ) );
        return 0
    fi
}
complete -F _powerwake powerwake
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