I have an idiom I use a lot to do quick searches through log files or data streams, or to do a "uniq" on a file without having to sort it.

I'm wondering if someone can suggest a better way to do it, out of curiosity. If no one has a better way, then here's my way, you're welcome to use it :)

Simple "uniq" (print unique lines): 

perl -ne'print unless $seen{$_}++' filesToUniq

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(Note that I'm not using strict, not using -w. These are meant to be one-liners)

Print out all the seen values for a field (in this example, all the HTTP protocol versions used to access my web server) 

perl -ne'm[HTTP/([^"]+)] or next; print unless $seen{$1}++' access_log

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That version prints out the first line on which a given protocol is encountered. If you prefer just enumerating the protocols, use: 
perl -ne'm[HTTP/([^"]+)] or next; print "$1\n" unless $seen{$1}++' acc
+ess_log

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This is hardly "perl rocket science", obviously. But I figured it might be useful, since I wind up typing "$seen{$_}++" a lot every day...

Hmmm, maybe I should drop the 'een' and improve my golf score. Oops, wrong thread! :)
--
Mike

In reply to Better "uniq" idiom? by RMGir

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