egrep bug

[jwp at sdchema.UUCP]

There's another problem in 4.1BSD egrep that I discovered quite a while
back, but don't remember if I told anyone or not (though if you haven't
discovered it by now you probably don't have any applicatons that care).
It has to do with using the '-f' flag to get the patterns then trying
to read the data from a pipe, e.g:

	program | egrep -f patternfile ...

The inner 'if' at the 'out' label in 'main()' reads:

if(freopen(fname = *argv, "r", stdin) == NULL) {
	fprintf(stderr, "egrep: can't open %s\n", fname);
	exit(2);
}

The inner 'if' in 'nextch()' reads:

if((c = getc(stdin)) == EOF) return(0);

This bit of cleverness causes a slight problem (egrep exits after reading
all of the patterns in since stdin is really pointing at "patternfile"
and nextch() returns EOF).  I have a fix for anyone who cares and doesn't
want to work it out themselves (it's relatively straight forward - simply
use another file pointer for the pattern file).

			John Pierce, Chemistry, UC San Diego
			{ucbvax, philabs}!sdcsvax!sdchema!jwp