Hello,

I newbie in C programming under Linux and would like to get some tips from you.
I have a C application running under Suse which is starting a script by using the spawn (spawnle) command.
This is working fine.
I use this script at the startup of the application to make sure that there is no other instance of my application running. If yes my new instance of the application should kill the old one.
The output of the script looks like this if 3 instance of my application are already running:
2245
3375
9967
The problem is that I don't know how to do to get back these PIDs in my C application because spawn can only get back an integer as returned value.

Could you please help me to find a solution to this problem.
Maybe there is another way to detect some another instance are running and get their PID to kill them.

Thanks in advance.

Alain

There are lots of ways to do inter-process communication. You can use a local socket. If your system supports it, you can use named pipes. If you are really stuck, you can have one process write to a file and another process read from it. What you really need is to do a little research.

Hi, Alain -

Please step back and look at the problem you're trying to solve - there might be a simpler implementation:

a) I imagine your "script" is something like "ps -C myapp|cut -d' ' -f 1", and you're trying to to parse the PIDs that are returned.

b) Rather than use "spawnle()", an easier solution might be to run the script with "popen()". That way, you could read back the PIDs (exactly as though the script output were a disk file).

c) Even easier, instead of having a separate script, you could code the "ps -C ..." directly into your "popen()" statement.

d) A final optimization: if you want to kill all instances of "myapp", which not just substitute the command "killall mypid"? And why not call it from "system()" (simply execute it), instead of "popen()" or "spawnle()"?

Just a thought ... PSM