system() call causes core dump

Peter Steele psteele at
Sat Oct 31 15:17:09 UTC 2009

I have an application running a number of threads. I've had recent instances where the code below is causing a core dump to occur:

char fstatCmd[200];
char *fstatOut = "/tmp/fstat.out";
sprintf(fstatCmd, "fstat | grep -v USER | wc -l >%s", fstatOut);
rc = system(fstatCmd);

The call is simply intended to get a count of the current open handles. The system call though causes a core:

#0 0x0000000801058307 in _spinunlock () from /lib/
#1 0x00000008011d0afb in _malloc_postfork () from /lib/
#2 0x000000080105c5fb in fork () from /lib/
#3 0x0000000801191aae in system () from /lib/
#4 0x00000008010553aa in system () from /lib/
#5 0x000000000040b6f9 in mythread at myapp.c:461
#6 0x0000000801056a88 in pthread_getprio () from /lib/

There appears to be some kind of thread-safe issue going on. I have a number of threads that are monitoring various items, waking up a differing intervals to do their respective tasks. Do I need to put in a global mutex so that the threads never attempt to make simultaneous system() calls? Curiously, only this particular system() call appears to be causing a core.

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