Date: 04 Jul 1999 14:09:47 +0200 From: Dag-Erling Smorgrav <des@flood.ping.uio.no> To: Jamie Howard <howardjp@wam.umd.edu> Cc: freebsd-hackers@FreeBSD.ORG, tech-userlevel@netbsd.org, tech@openbsd.org Subject: Re: Repalcement for grep(1) Message-ID: <xzp4sjkwr90.fsf@flood.ping.uio.no> In-Reply-To: Jamie Howard's message of "Sat, 3 Jul 1999 15:18:07 -0400 (EDT)" References: <Pine.GSO.4.10.9907031513150.17705-100000@rac9.wam.umd.edu>
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Jamie Howard <howardjp@wam.umd.edu> writes:
> I made the version in FreeBSD 4.0 my target except for -A num, -B num, -C,
> -num, and -Z. These are not required by the Single Unix Specification or
> POSIX and I felt they would bloat my code too significantly.
I find those quite useful, and I don't see how they'd bloat your code
a lot. You need a line @queue and a $toprint counter, as well as $lead
and $trail counters. $regexp is the expression to search for, and
$line is a scratch variable. Initialize by setting $lead to the -A
argument, $trail to the -B argument; if you encounter -C, set $lead
and $trail to 2; if you encounter -<num>, set $lead and $trail to
<num>. Now for the search algorithm in Perl:
$toprint = 0;
@queue = qw();
while ($line = <INPUT>) {
if ($toprint) {
print $line;
--$toprint;
} else {
shift @queue if (@queue > $lead);
push @queue, $line;
}
next unless ($line ~ m/$regexp/o);
while (@queue) {
print shift @queue;
}
$toprint = $trail;
}
This should be trivial to translate to C. The only non-trivial part of
implementing this stuff is that you have to trick getopt() to make
-<num> work. You'll have to put a : at the start of your getopt()
string and examine every argument getopt() complains about.
Hope this helps... keep up the good work!
DES
--
Dag-Erling Smorgrav - des@flood.ping.uio.no
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