Path: utzoo!yunexus!geac!syntron!jtsv16!uunet!peregrine!elroy!ames!ncar!mailrus!uflorida!novavax!proxftl!bill
From: bill@proxftl.UUCP (T. William Wells)
Newsgroups: comp.lang.c
Subject: Re: Question about popen and pclose
Keywords: popen,pclose
Message-ID: <577@proxftl.UUCP>
Date: 12 Aug 88 12:43:26 GMT
Article-I.D.: proxftl.577
References: <364@nynex1.UUCP>
Reply-To: bill@proxftl.UUCP (T. William Wells)
Organization: Proximity Technology, Ft. Lauderdale
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In article <364@nynex1.UUCP> tsai@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.