Как установить из скрипта, запущен X server или нет?

#!/bin/bash
#
# chkconfig: - 91 35
# description: Starts and stops vncserver. \
#           used to provide remote X administration services.

# Source function library.
. /etc/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0

unset VNCSERVERARGS
VNCSERVERS=""
[ -f /etc/sysconfig/vncservers ] && . /etc/sysconfig/vncservers

prog=$"VNC server"

start() {
    echo -n $"Starting $prog: "
    ulimit -S -c 0 >/dev/null 2>&1
    RETVAL=0
    if [ ! -d /tmp/.X11-unix ]
    then
        mkdir -m 1777 /tmp/.X11-unix || :
        restorecon /tmp/.X11-unix 2>/dev/null || :
    fi
    NOSERV=1
    for display in ${VNCSERVERS}
    do
        NOSERV=
        echo -n "${display} "
    unset BASH_ENV ENV
    DISP="${display%%:*}"
    export USER="${display##*:}"
    export VNCUSERARGS="${VNCSERVERARGS[${DISP}]}"
        runuser -l ${USER} -c "cd ~${USER} && [ -f .vnc/passwd ] && vncserver :${DISP} ${VNCUSERARGS}"
        RETVAL=$?
        [ "$RETVAL" -ne 0 ] && break
    done
    if test -n "$NOSERV"; then echo -n "no displays configured "; fi
    [ "$RETVAL" -eq 0 ] && success $"vncserver startup" || \
        failure $"vncserver start"
    echo
    [ "$RETVAL" -eq 0 ] && touch /var/lock/subsys/vncserver
}

stop() {
    echo -n $"Shutting down $prog: "
    for display in ${VNCSERVERS}
    do
        echo -n "${display} "
    unset BASH_ENV ENV
    export USER="${display##*:}"
    runuser ${USER} -c "vncserver -kill :${display%%:*}" >/dev/null 2>&1
    done
    RETVAL=$?
    [ "$RETVAL" -eq 0 ] && success $"vncserver shutdown" || \
        failure $"vncserver shutdown"
    echo
    [ "$RETVAL" -eq 0 ] && rm -f /var/lock/subsys/vncserver
}

# See how we were called.
case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  restart|reload)
    stop
    sleep 3
    start
    ;;
  condrestart)
    if [ -f /var/lock/subsys/vncserver ]; then
        stop
        sleep 3
        start
    fi
    ;;
  status)
    status Xvnc
    ;;
  *)
    echo $"Usage: $0 {start|stop|restart|condrestart|status}"
    exit 1
esac