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Full Discussion: Big data file - sed/grep/awk?
Top Forums Shell Programming and Scripting Big data file - sed/grep/awk? Post 302204235 by era on Wednesday 11th of June 2008 03:53:08 AM
Old 06-11-2008
Just getting rid of the grep should save you some cycles. Also reading the result into backticks and then looping over the result is wasteful (although some shells probably optimize that into a loop internally).

Code:
awk -F'|' "/^\[$STARTHOUR/"'{print $4}' ANYOLDFILE |
while read results; do
  stuff
done

If you can implement "stuff" in awk you are probably as fast as this is going to get, unless of course you are in a position to sit down and write your own little C program. Anyway, the "stuff" part is probably responsible for most of the processing time, not the loop scaffolding around it.
 

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LEARN ABOUT POSIX

zgrep

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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