perl: Launch process with system(), then check if its running under a specific display number

I have a locked down "kiosk" terminal server.

This terminal server has a perl script as its .Xsession, and launches a Tk interface. When that Tk interface is done, the perl script launches "process2" and lets the user interact with "process2" (which is a graphical application).

If a user tampers with "process2", and make it crash, the user might be able to access the underlying desktop, therefore I would want to check if "process2" is running, and if "process2" is not running on $display, I would want to just execute logout (which would logout the display the perl script is currently running as).

Since the system is running 10 instances of "process2" to 10 different users simultanuosly, I cant just check if "process2" is running on the system with "ps" or someting like that. I need to check if "process2" is running under that specific display $display. Note that all 10 users log on as the same username in all sessions, so I cannot check all processes run by a specific user, that would return all 10 instances too.

Like:

system("process2 &");
while(1) {
  sleep(1);
  if (is_it_running("process2", $display) == false) {
    system("logout &");
  }
}

Its the function "is_it_running" that I need to get to know how it should look. $display can either contain t开发者_如何学编程he raw display number, like this: ":1.0", or it can contain the display number parsed out, like this: "1".

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If you use fork and exec instead of system("...&"), you can store the Process IDs of your child processes and more directly check their status. See also perlipc.

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Why not just run process2 in the foreground? Then your perl script won't get control back until it's done executing, at which point it can exit:

system("process2");
system("logout");

Of course, if that's the entire script, maybe a bash script would make more sense.

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I solved it after many attempts.

Did a piped open

$pidofcall = open(HANDLE, "process2|");

Then I did whatever I did need to do, and I made the server send a signal to me if it loses connection with process2. If I did need to bang out, I simply did a "goto killprocess;" Then I simply had:

killprocess:
kill(9,$pidofcall);
close(HANDLE);
$mw->destroy;
system("logout");