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Full Discussion: Faster command to remove headers for files in a directory
Top Forums Shell Programming and Scripting Faster command to remove headers for files in a directory Post 302730409 by jim mcnamara on Monday 12th of November 2012 08:17:26 PM
Old 11-12-2012
Did sed win? Or did file caching speed up sed? Modern controllers and RAM cache - HPUX - can cache 100 MB of a single file without really using up system resources.

I vote for caching. The only fair test is two separate files.

BTW: programs like sed, awk, head, tail, grep are all highly optimized for their respective jobs. There are several of external factors like: caching, I/O load (I/O request queue length), SAN vs disk, that distort these kinds of tests. So, by the time you have runs some tests, any time differences between the commands will likely have been eaten up by testing.

Your best bet is to parallelize, use the cpu and disk I/O to the max. With a quad core maybe you want to consider 4 simultaneous child processes, for example:

Code:
cd /directory
cnt=1
for fname in $(find . -type f)
do
   (awk 'FNR>1' $fname > tmp.${cnt}; mv tmp.${cnt} $fname)  &
   cnt=$(( $cnt + 1  ))
   [  $(( $cnt % 4 )) -eq 0 ]  && wait
done
wait

 

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DH_INSTALLDEB(1)						     Debhelper							  DH_INSTALLDEB(1)

NAME

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SYNOPSIS

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DESCRIPTION

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FILES

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	   Inside the scripts, the token #DEBHELPER# is replaced with shell script snippets generated by other debhelper commands.

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SEE ALSO

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AUTHOR

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8.9.0ubuntu2.1							    2012-06-12							  DH_INSTALLDEB(1)
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