bash completion for systemctl --user alias, save as '~/.local/share/bash-completion/completions/userctl'

userctl

# user(1) completion                                 -*- shell-script -*-
# SPDX-License-Identifier: LGPL-2.1-or-later

__systemctl() {
    local mode=$1; shift 1
    systemctl $mode --full --legend=no --no-pager --plain "$@" 2>/dev/null
}

__systemd_properties() {
    /usr/lib/systemd/systemd --dump-bus-properties
}

__contains_word () {
    local w word=$1; shift
    for w in "$@"; do
        [[ $w = "$word" ]] && return
    done
}

__filter_units_by_properties () {
    local mode=$1 properties=$2; shift 2
    local units=("$@")
    local props i p n
    local names= count=0

    IFS=$',' read -r -a p < <(echo "Names,$properties")
    n=${#p[*]}
    readarray -t props < \
              <(__systemctl $mode show --property "Names,$properties" -- "${units[@]}")

    for ((i=0; i < ${#props[*]}; i++)); do
        if [[ -z ${props[i]} ]]; then
            if (( count == n )) && [[ -n $names ]]; then
                echo $names
            fi
            names=
            count=0
        else
            (( count++ ))
            if [[ ${props[i]%%=*} == 'Names' ]]; then
                names=${props[i]#*=}
            fi
        fi
    done
    if (( count == n )) && [[ -n $names ]]; then
        echo $names
    fi
}

__get_all_units      () { { __systemctl $1 list-unit-files "$2*"; __systemctl $1 list-units --all "$2*"; } \
                              | { while read -r a b; do echo " $a"; done; }; }
__get_non_template_units() { { __systemctl $1 list-unit-files "$2*"; __systemctl $1 list-units --all "$2*"; } \
                                 | { while read -r a b; do [[ $a =~ @\. ]] || echo " $a"; done; }; }
__get_template_names () { __systemctl $1 list-unit-files "$2*" \
                              | { while read -r a b; do [[ $a =~ @\. ]] && echo " ${a%%@.*}@"; done; }; }
__get_active_units   () { __systemctl $1 list-units "$2*"      \
                              | { while read -r a b; do echo " $a"; done; }; }

__get_not_masked_unit_files() {
    # filter out masked, not-found, or template units.
    __systemctl $1 list-unit-files --state enabled,enabled-runtime,linked,linked-runtime,static,indirect,disabled,generated,transient "$2*" | \
        { while read -r a b; do [[ $a =~ @\. ]] || echo " $a"; done; }
}

__get_startable_units () {
    __filter_units_by_properties $1 ActiveState=inactive,CanStart=yes $(
        { __get_not_masked_unit_files $1 $2
          # get inactive template units
          __systemctl $1 list-units --state inactive,failed "$2*" | \
              { while read -r a b c; do [[ $b == "loaded" ]] && echo " $a"; done; }
        } | sort -u )
}
__get_restartable_units () {
    # filter out masked and not-found
    __filter_units_by_properties $1 CanStart=yes $(
        { __get_not_masked_unit_files $1 $2
          __get_active_units $1 $2
        } | sort -u )
}

__get_stoppable_units () {
    # filter out masked and not-found
    local units=$(
        { __get_not_masked_unit_files $1 $2
          __get_active_units $1 $2
        } | sort -u )
    __filter_units_by_properties $1 ActiveState=active,CanStop=yes $units
    __filter_units_by_properties $1 ActiveState=reloading,CanStop=yes $units
    __filter_units_by_properties $1 ActiveState=activating,CanStop=yes $units
}

__get_reloadable_units () {
    # filter out masked and not-found
    __filter_units_by_properties $1 ActiveState=active,CanReload=yes $(
        { __get_not_masked_unit_files $1 $2
          __get_active_units $1 $2
        } | sort -u )
}

__get_failed_units   () { __systemctl $1 list-units "$2*"      \
                              | { while read -r a b c d; do [[ $c == "failed"   ]] && echo " $a"; done; }; }
__get_enabled_units  () { __systemctl $1 list-unit-files "$2*" \
                              | { while read -r a b c  ; do [[ $b == "enabled"  ]] && echo " $a"; done; }; }
__get_disabled_units () { __systemctl $1 list-unit-files "$2*" \
                              | { while read -r a b c  ; do [[ $b == "disabled" ]] && echo " $a"; done; }; }
__get_masked_units   () { __systemctl $1 list-unit-files "$2*" \
                              | { while read -r a b c  ; do [[ $b == "masked"   ]] && echo " $a"; done; }; }
__get_all_unit_files () { { __systemctl $1 list-unit-files "$2*"; } | { while read -r a b; do echo " $a"; done; }; }

__get_machines() {
    local a b
    { machinectl list --full --max-addresses=0 --no-legend --no-pager 2>/dev/null; echo ".host"; } | \
	{ while read a b; do echo " $a"; done; } | \
        sort -u
}

_userctl () {
    local cur=${COMP_WORDS[COMP_CWORD]} prev=${COMP_WORDS[COMP_CWORD-1]}
    local i verb comps mode cur_orig

    local -A OPTS=(
        [STANDALONE]='--all -a --reverse --after --before --defaults --force -f --full -l --global
                             --help -h --no-ask-password --no-block --legend=no --no-pager --no-reload --no-wall --now
                             --quiet -q --system --user --version --runtime --recursive -r --firmware-setup
                             --show-types --plain --failed --value --fail --dry-run --wait --no-warn'
        [ARG]='--host -H --kill-whom --property -p --signal -s --type -t --state --job-mode --root
                             --preset-mode -n --lines -o --output -M --machine --message --timestamp --check-inhibitors'
    )

    if __contains_word "--user" ${COMP_WORDS[*]}; then
        mode=--user
    elif __contains_word "--global" ${COMP_WORDS[*]}; then
        mode=--user
    elif __contains_word "--system" ${COMP_WORDS[*]}; then
        mode=--system
    else
        mode=--user
    fi

    if __contains_word "$prev" ${OPTS[ARG]}; then
        case $prev in
            --signal|-s)
                _signals
                return
                ;;
            --type|-t)
                comps=$(__systemctl $mode -t help)
                ;;
            --state)
                comps=$(__systemctl $mode --state=help)
                ;;
            --job-mode)
                comps='fail replace replace-irreversibly isolate
                                       ignore-dependencies ignore-requirements flush'
                ;;
            --kill-whom|--kill-who)
                comps='all control main'
                ;;
            --root)
                comps=$(compgen -A directory -- "$cur" )
                compopt -o filenames
                ;;
            --host|-H)
                comps=$(compgen -A hostname)
                ;;
            --property|-p)
                comps=$(__systemd_properties)
                ;;
            --preset-mode)
                comps='full enable-only disable-only'
                ;;
            --output|-o)
                comps=$( systemctl --output=help 2>/dev/null )
                ;;
            --machine|-M)
                comps=$( __get_machines )
                ;;
            --timestamp)
                comps='pretty us µs utc us+utc µs+utc'
                ;;
            --check-inhibitors)
                comps='auto yes no'
                ;;
        esac
        COMPREPLY=( $(compgen -W '$comps' -- "$cur") )
        return 0
    fi

    if [[ "$cur" = -* ]]; then
        COMPREPLY=( $(compgen -W '${OPTS[*]}' -- "$cur") )
        return 0
    fi

    local -A VERBS=(
        [ALL_UNITS]='cat mask'
        [NONTEMPLATE_UNITS]='is-active is-failed is-enabled status show preset help list-dependencies edit set-property revert'
        [ENABLED_UNITS]='disable'
        [DISABLED_UNITS]='enable'
        [REENABLABLE_UNITS]='reenable'
        [FAILED_UNITS]='reset-failed'
        [STARTABLE_UNITS]='start'
        [STOPPABLE_UNITS]='stop condstop kill try-restart condrestart'
        [ISOLATABLE_UNITS]='isolate'
        [RELOADABLE_UNITS]='reload condreload try-reload-or-restart force-reload'
        [RESTARTABLE_UNITS]='restart reload-or-restart'
        [TARGET_AND_UNITS]='add-wants add-requires'
        [MASKED_UNITS]='unmask'
        [JOBS]='cancel'
        [ENVS]='set-environment unset-environment import-environment'
        [STANDALONE]='daemon-reexec daemon-reload default whoami
                             emergency exit halt hibernate hybrid-sleep
                             suspend-then-hibernate kexec soft-reboot list-jobs list-sockets
                             list-timers list-units list-unit-files poweroff
                             reboot rescue show-environment suspend get-default
                             is-system-running preset-all list-automounts list-paths'
        [FILE]='link switch-root bind mount-image'
        [TARGETS]='set-default'
        [MACHINES]='list-machines'
        [LOG_LEVEL]='log-level'
        [LOG_TARGET]='log-target'
        [SERVICE_WATCHDOGS]='service-watchdogs'
    )

    for ((i=0; i < COMP_CWORD; i++)); do
        if __contains_word "${COMP_WORDS[i]}" ${VERBS[*]} &&
                ! __contains_word "${COMP_WORDS[i-1]}" ${OPTS[ARG]}; then
            verb=${COMP_WORDS[i]}
            break
        fi
    done

    # When trying to match a unit name with certain special characters in its name (i.e
    # foo\x2dbar:01) they get (un)escaped by bash along the way, thus causing any possible
    # match to fail.
    # The following condition solves two cases:
    # 1) We're trying to complete an already escaped unit name part,
    #    i.e foo\\x2dba. In this case we need to unescape the name, so it
    #    gets properly matched with the systemctl output (i.e. foo\x2dba).
    #    However, we need to keep the original escaped name as well for the
    #    final match, as the completion machinery does the unescaping
    #    automagically.
    # 2) We're trying to complete an unescaped (literal) unit name part,
    #    i.e. foo\x2dba. That means we don't have to do the unescaping
    #    required for correct matching with systemctl's output, however,
    #    we need to escape the name for the final match, where the completion
    #    expects the string to be escaped.
    cur_orig=$cur
    if [[ $cur =~ '\\' ]]; then
        cur="$(echo $cur | xargs echo)"
    else
        cur_orig="$(printf '%q' $cur)"
    fi

    if [[ -z ${verb-} ]]; then
        comps="${VERBS[*]}"

    elif __contains_word "$verb" ${VERBS[ALL_UNITS]}; then
        comps=$( __get_all_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[NONTEMPLATE_UNITS]}; then
        comps=$( __get_non_template_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[ENABLED_UNITS]}; then
        comps=$( __get_enabled_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[DISABLED_UNITS]}; then
        comps=$( __get_disabled_units $mode "$cur";
                 __get_template_names $mode "$cur")
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[REENABLABLE_UNITS]}; then
        comps=$( __get_disabled_units $mode "$cur";
                 __get_enabled_units $mode "$cur";
                 __get_template_names $mode "$cur")
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[STARTABLE_UNITS]}; then
        comps=$( __get_startable_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[RESTARTABLE_UNITS]}; then
        comps=$( __get_restartable_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[STOPPABLE_UNITS]}; then
        comps=$( __get_stoppable_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[RELOADABLE_UNITS]}; then
        comps=$( __get_reloadable_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[ISOLATABLE_UNITS]}; then
        comps=$( __filter_units_by_properties $mode AllowIsolate=yes \
                                              $( __get_non_template_units $mode "$cur" ) )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[FAILED_UNITS]}; then
        comps=$( __get_failed_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[MASKED_UNITS]}; then
        comps=$( __get_masked_units $mode "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[TARGET_AND_UNITS]}; then
        if __contains_word "$prev" ${VERBS[TARGET_AND_UNITS]} \
                || __contains_word "$prev" ${OPTS[STANDALONE]}; then
            comps=$( __systemctl $mode list-unit-files --type target --all "$cur*" \
                         | { while read -r a b; do echo " $a"; done; } )
        else
            comps=$( __get_all_unit_files $mode "$cur" )
        fi
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[STANDALONE]}; then
        comps=''

    elif __contains_word "$verb" ${VERBS[JOBS]}; then
        comps=$( __systemctl $mode list-jobs | { while read -r a b; do echo " $a"; done; } )

    elif [ "$verb" = 'unset-environment' ]; then
        comps=$( __systemctl $mode show-environment \
                     | while read -r line; do echo " ${line%%=*}"; done )
        compopt -o nospace

    elif [ "$verb" = 'set-environment' ]; then
        comps=$( __systemctl $mode show-environment \
                     | while read -r line; do echo " ${line%%=*}="; done )
        compopt -o nospace

    elif [ "$verb" = 'import-environment' ]; then
        COMPREPLY=( $(compgen -A variable -- "$cur_orig") )
        return 0

    elif __contains_word "$verb" ${VERBS[FILE]}; then
        comps=$( compgen -A file -- "$cur" )
        compopt -o filenames

    elif __contains_word "$verb" ${VERBS[TARGETS]}; then
        comps=$( __systemctl $mode list-unit-files --type target --full --all "$cur*" \
                     | { while read -r a b; do echo " $a"; done; } )
    elif __contains_word "$verb" ${VERBS[LOG_LEVEL]}; then
        comps='debug info notice warning err crit alert emerg'
    elif __contains_word "$verb" ${VERBS[LOG_TARGET]}; then
        comps='console journal kmsg journal-or-kmsg null'
    elif __contains_word "$verb" ${VERBS[SERVICE_WATCHDOGS]}; then
        comps='on off'
    fi

    COMPREPLY=( $(compgen -o filenames -W '$comps' -- "$cur_orig") )
    return 0
}

complete -F _userctl userctl