dbmathis has asked for the wisdom of the Perl Monks concerning the following question:

Hi Everyone,

I have been searching throught this sitre for any tips on matching lines on huge logfiles and I can across the following node. The script in this node works great and it's almost exactly what I need, but it only returns that text that I am searching for. When I modify it to fit my needs it slows down.


#!/usr/bin/perl -w # # Proof-of-concept for using minimal memory to search huge # files, using a sliding window, matching within the window, # and using on /gc and pos() to restart the search at the # correct spot whenever we slide the window. # # Doesn't correctly handle potential matches that overlap; # the first fragment that matches wins. # use strict; use constant BLOCKSIZE => (8 * 1024); &search("bighuge.log", sub { print $_[0], "\n" }, "<img[^>]*>"); sub search { my ($file, $callback, @fragments) = @_; local *F; open(F, "<", $file) or die "$file: $!"; binmode(F); # prime the window with two blocks (if possible) my $nbytes = read(F, my $window, 2 * BLOCKSIZE); my $re = "(" . join("|", @fragments) . ")"; while ( $nbytes > 0 ) { # match as many times as we can within the # window, remembering the position of the # final match (if any). while ( $window =~ m/$re/oigcs ) { &$callback($1); } my $pos = pos($window); # grab the next block $nbytes = read(F, my $block, BLOCKSIZE); last if $nbytes == 0; # slide the window by discarding the initial # block and appending the next. then reset # the starting position for matching. substr($window, 0, BLOCKSIZE) = ''; $window .= $block; $pos -= BLOCKSIZE; pos($window) = $pos > 0 ? $pos : 0; } close(F); }

For example the regex search doesn't search by line it searches across the entire block and then prints out matches.

I was searching for e-mail addresses in a 2 GB maillog file and when it finds the e-mail it just spits it out

So I modified:

while ( $window =~ m/$re/oigcs ) { &$callback($1); }

To look like this to capture the line (which is what I need):

while ( $window =~ m/\w{3}\s{1,2}\d{1,2}.*$re.*\n/oigc ) { &$callback($1); }

And things slowed considerably. It went for 30 secs to several minutes. How should I modify the code above to spit out the line in which the match was found in without slowing down the search time?

Here is a sample of the lines in the file:

Feb 24 04:03:47 server sendmail[]: khdkahsdad876sad8: to=<sample@colle>, delay=1+13:12:11, xdelay=00:00:00, mail er=esmtp, pri=25672345,, dsn=4.0.0, stat=Deferr +ed: Connection timed out with Feb 24 04:03:47 server sendmail[31356]: madhksadkh5574: to=<sample@iit>, delay=1+13:20:32, xdelay=00:00:00, mailer=esmtp, pri=26574dffd, [], dsn=4.3.1, sta +t=Deferred: 452 sample 4.2.1 Mailbox temporarily disabled: sample@iit

After all this is over, all that will really have mattered is how we treated each other.