Question about popen and pclose

[T. William Wells]

In article <364 at nynex1.UUCP> tsai at nynex1.UUCP (Nelson Tsai) writes:
: Then, after executed about 20 times, it caused segmentation fault
: (core dumped).  Why is that ?  Why reading from the pipe cause the
: segmentation fault ?

That's an easy one.  You ran out of fd's and the popen call
failed.  It returned a null pointer and fgets tried to
dereference it.  Thus the core dump.  When you didn't include the
fgets, the pointer was never dereferenced, hence no core dump.