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Re: Parsing Logs

by mbethke (Hermit)
on Oct 05, 2012 at 17:03 UTC ( #997518=note: print w/replies, xml ) Need Help??

in reply to Parsing Logs

Hi mdotpl,
it would probably help if you included a few lines of the format you're trying to parse. So here's just some general advice:

It hardly ever makes sense to read files in foreach(). It evaluates <> in list context, causing the whole file to be read into memory at once even if you only want to keep a small part of it. That's particularly important with log files that tend to be large.

The other thing is that you probably want a hash instead of an array there, to save the loop that searches for a matching ID later and speed up everything by orders of magnitude. So the first part should be:

while(<AUTH>) { chomp; if(/<my-regex-goes-here>/i) { $sessionID{$4} = 1; } }

Also note that if the session ID is in your fourth capture and you're not using the other three (or more), it would make sense not to capture in the first place. It reads easier and is faster.

With the hash, the rest can simply look like this (I've also renamed @list to reflect its purpose---"@list" doesn't really say anything as at-foo is always a list):

open(MSG) or die("couldn't open msg log"); while(<MSG>) { chomp; if(my ($id) =~ /<my-regex-goes-here(<capture the id>)>/i)) { push @matching_lines, $_ if $sessionID{$id}; } } close(MSG); print $_, "\n" foreach (@matching_lines);

If you don't need to do anything else with the lines, you could also omit the chomp (the regex will match anyway) and make the last bit a simple "print @lines"

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[Corion]: Ow, "but you're not supposed to do that" ;)
[chacham]: with google, you kinda just gotta do what it recomends.

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