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Re: binary search in a file

From: Sorav Bansal
Subject: Re: binary search in a file
Date: Thu, 14 Jul 2005 11:54:56 -0700
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

Is there a utility to search for a value in a sorted file using binary search. The file was sorted using the 'sort' command.

Is there any reason why you want to use a binary search, except for speed?

Well, linear search on a 60GB file is likely to be many orders of magnitude slower than binary search.

Unless the lines are fixed-length, after each chop, the search program
will have to find the start-of-line character.
This is likely to negate any advantage gained from binary searches.

Just a little bit. Finding the start-of-line is easy and quite fast since it is an in-memory operation. The speed in such operations is usually limited by disk-I/Os

I'd sugest just sticking to grep. You can use the '-l' (ell) option -
this will exit when the first matching line is found, (but not display it).

I ended up writing my own binary search utility. We are discussing if it should be made a part of gnu.coreutils.


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