wait-dbus-service

wait-dbus-service

#!/bin/bash
set -e

eval "$(git rev-parse --parseopt -- "$@" <<EOF || echo exit $?
${0##*/} [OPTIONS...] {SERVICE} [TIMEOUT]

Wait for {SERVICE} to be registered on the bus.
--
y,system    Connect to system bus
e,session   Connect to user bus
a,address=  Connect to bus specified by address
EOF
)"

BUS=(--session)
while getopts yea: opt; do
    case "${opt}" in
        y) BUS=(--system) ;;
        e) BUS=(--session) ;;
        a) BUS=(--address="${OPTARG}") ;;
    esac
done
shift $((OPTIND-1))
SERVICE=$1
DELAY=$2
if [[ -z ${SERVICE} ]]; then
    echo "Must provide {SERVICE}" >&2
    exit 129
fi

wait_time() {
    if [[ -n ${DELAY} ]]; then
        sleep "${DELAY}" && echo '(timeout)' >&2
        echo -
    fi
}

check_name() {
    dbus-send "${BUS[@]}" --dest=org.freedesktop.DBus --print-reply --type=method_call / org.freedesktop.DBus.ListNames |
    while IFS= read -r line; do
        read -r type value <<<${line}
        if [[ ${type} = string && ${value} = "\"$(printf %q "${SERVICE}")\"" ]]; then
            printf '%s\n' "${line}"
            break
        fi
    done
}

wait_name() {
    local connected= signal= args=() values=()
    dbus-monitor "${BUS[@]}" --monitor \
        "type='signal',sender='org.freedesktop.DBus',path_namespace='/',interface='org.freedesktop.DBus',member='NameOwnerChanged',arg0='$(printf %q "${SERVICE}")'" |
    while IFS= read -r line; do
        if [[ ${line} = signal[[:space:]]* ]]; then
            signal=$(expr match "${line}" '.*;[[:space:]]\+member=\([^[:space:]]\+\)')
            signal=${signal:-\?} args=() values=()
            if [[ ${signal} = NameAcquired && -z ${connected} ]]; then
                connected=1
                check_name
            fi
        elif [[ ${line} != [[:space:]]* ]]; then
            signal= args=() values=()
        elif [[ -n ${signal} ]]; then
            read type value <<<${line}
            args+=("${line}") values+=("${value}")
        fi
        if [[ ${signal} = NameOwnerChanged && -n ${args[2]} && ${values[2]} != '""' && ${values[2]} != "''" ]]; then
            printf '%s\n' "${args[0]}"
        fi
    done
}

trap 'kill -TERM -$$' EXIT
while IFS= read -r line; do
    if [[ -n ${line} ]]; then
        break
    fi
done < <(
    wait_time &
    wait_name
)