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Top Forums Shell Programming and Scripting omitting lines from file A that are in file B Post 302168714 by earnstaf on Tuesday 19th of February 2008 08:10:44 AM
Old 02-19-2008
Quote:
Originally Posted by gneen
Heh - the grep inside the read loop would "work" ... but I'd have to come back in a year to see the results!

For tiny files this would clearly be the way to go - but for files the size I'm dealing with this would mean one million greps into a file that was ten million lines long ... can you spell "Rip Van Winkle"?

Smilie
=Gneen
So, I made a 1M line file and 10M line file to test on... running the grep loop on a pretty beefy server (dual 2.8ghz intel xeons) and it took 170m ... so, not forever but definitely not as fast as you'd want.
 

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ZGREP(1)						      General Commands Manual							  ZGREP(1)

NAME
zgrep - search possibly compressed files for a regular expression SYNOPSIS
zgrep [ grep_options ] [ -e ] pattern filename... DESCRIPTION
Zgrep invokes grep on compressed or gzipped files. These grep options will cause zgrep to terminate with an error code: (-[drRzZ]|--di*|--exc*|--inc*|--rec*|--nu*). All other options specified are passed directly to grep. If no file is specified, then the standard input is decompressed if necessary and fed to grep. Otherwise the given files are uncompressed if necessary and fed to grep. If the GREP environment variable is set, zgrep uses it as the grep program to be invoked. EXIT CODE
2 - An option that is not supported was specified. AUTHOR
Charles Levert (charles@comm.polymtl.ca) SEE ALSO
grep(1), gzexe(1), gzip(1), zdiff(1), zforce(1), zmore(1), znew(1) ZGREP(1)
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