X server running ?

Question

Is there any way to find out if the current session user is running an Xserver (under Linux) ?

I'v started off with things like:

ps -e | grep X

but this doesn't work always

and one more thing I tried is checking the $DISPLAY variable

Are there any other ways to check this?

EDIT: Some people suggested using the $DISPLAY variables but what if the user fiddles with this variable ? what if he tries to do something and changes this variable and then when I check it, it no longer reflects an accurate state of the system. Is there no specific way to do this that will always return a correct answer ?

I found that it can be done programatically thus:

#include <X11/Xlib.h> 
int main()
    { exit(XOpenDisplay(NULL) ? 0 : 1);  } 

$ gcc -o xprobe xprobe.c -L/usr/X11R6/lib -lX11

But I am looking for a script way.

Answer 1

I use

pidof X && echo "yup X server is running"

pgrep and $DISPLAY are other options.

Other considerations:

su then $DISPLAY will not be set. Things that change the environment of the program running can make this not work.

I don't recommand ps -e | grep X as this will find procX, which is not the X server.

Answer 2

$DISPLAY is the standard way. That's how users communicate with programs about which X server to use, if any.

Answer 3

One trick I use to tell if X is running is:

telnet 127.0.0.1 6000

If it connects, you have an X server running and its accepting inbound TCP connections (not usually the default these days)....

Answer 4

1)

# netstat -lp|grep -i x
tcp        0      0 *:x11                   *:*                     LISTEN      2937/X          
tcp6       0      0 [::]:x11                [::]:*                  LISTEN      2937/X          
Active UNIX domain sockets (only servers)
unix  2      [ ACC ]     STREAM     LISTENING     8940     2937/X              @/tmp/.X11-unix/X0
unix  2      [ ACC ]     STREAM     LISTENING     8941     2937/X              /tmp/.X11-unix/X0
#

2) nmap

# nmap localhost|grep -i x
6000/tcp open  X11
#