C - WEXITSTATUS() question

james2432 · #1 (**permalink**) 10-14-2009

I want to check if an application is still running under C. So far I've been using

Code:

int rc;
rc=WEXITSTATUS( [PID here] )

if(rc > 0)
{
   //then I exited
}

I was wondering seeing as WEXITSTATUS in man pages is close to the WAIT() if it was thread blocking and if it was how would I go about making my code non-blocking without threads?

jim mcnamara · #2 (**permalink**) 10-14-2009

Code:

pid_t waitpid(pid_t pid, int *status, int options);
// use WNOHANG as the option

This returns the pid when if the process ended, or it checks and returns right away if the child process is still active.

---------- Post updated at 11:48 ---------- Previous update was at 11:00 ----------

If it is not a child process -

try

Code:

errno=0;
if(kill(pid, 0) == 0 )
{
    printf("process running\n");
}
else

{
    if(errno==ESRCH)
        printf("process stopped\n");
    else
    {
        perror("cannot signal the process");
        exit(1);
     }
}

james2432 · #3 (**permalink**) 10-14-2009

The thing is I'm creating a daemon to check that certain applications are running(via PID) I do not initially launch them(so they are not my children) and I don't really feel like trying to kill something that I'm to prevent from stopping. would waitpid still work even though it's not my child?

frank_rizzo · #4 (**permalink**) 10-14-2009

if your just checking to see if PID exists. use kill(pid,0); see man page for details.

jim mcnamara · #5 (**permalink**) 10-16-2009

When you're writing a daemon consider using a lockfile to prevent two instacnes of the daemon from running. Otherwise the kill(pid,0) approach works fine.

More UNIX and Linux Forum Topics You Might Find Helpful
Thread	Thread Starter	Forum	Replies	Last Post
Question on order of headers and WEXITSTATUS	frequency8	High Level Programming	5	06-05-2007 10:28 PM

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes	Rate This Thread
Switch to Linear Mode Hybrid Mode Switch to Threaded Mode	Rate This Thread:


	Powered by