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	Fri, 6 May 2011 19:54:42 -0500 (CDT)
Date: Fri, 6 May 2011 19:54:42 -0500 (CDT)
From: Robert Bonomi <bonomi@mail.r-bonomi.com>
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To: freebsd-questions@freebsd.org, listreader@lazlarlyricon.com
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Cc: 
Subject: Re: Comparing two lists
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> From owner-freebsd-questions@freebsd.org  Fri May  6 19:27:54 2011
> Date: Sat, 07 May 2011 02:09:26 +0200
> From: Rolf Nielsen <listreader@lazlarlyricon.com>
> To: FreeBSD <freebsd-questions@freebsd.org>
> Subject: Comparing two lists
>
> Hello all,
>
> I have two text files, quite extensive ones. They have some lines in 
> common and some lines are unique to one of the files. The lines that do 
> exist in both files are not necessarily in the same location. Now I need 
> to compare the files and output a list of lines that exist in both 
> files. Is there a simple way to do this? diff? awk? sed? cmp? Or a 
> combination of two or more of them?


If the files have only 'minor' differences -- i.e. no long runs of lines
that are in only one fie -- *and* the common lines are  in the same order
in each file, you can use diff(1), without any other shennigans.

If the above is -not- true, and If you need _only_ the common lines, AND 
order is not important, then sort(1) both files, and use diff(1) on the 
two sorted versions.


Beyond that it depends on what you mean by 'extensive' ones.  megabytes?
Gigabytes? or what??