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Full Discussion: Using AWK to match CSV files with duplicate patterns
Top Forums Shell Programming and Scripting Using AWK to match CSV files with duplicate patterns Post 302597415 by isuewing on Friday 10th of February 2012 08:49:50 AM
Old 02-10-2012
Thanks @ahamed101.

I did try grep -f, and there are two problems. I found that a pattern file with duplicate entries found unique matches, thus destroying the order of File1.csv, which I am trying to preserve. The other issue is that grep is notoriously inefficient for this task. For 173k patterns I would need to split File1.csv into chunks in a loop, and use each chunk to search against File2.csv. Even in this case, using grep to search >10k patterns begins to take several seconds. Other posts have profiled similar performance. While this second consideration is not a total deal-breaker, (a) I am going to have to perform a large number of these kinds of matches, (b) with bigger pattern files, awk is *fast*, so it would be great if I could find a more efficient solution.

-i
 

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LEARN ABOUT NETBSD

zfgrep

ZGREP(1)						    BSD General Commands Manual 						  ZGREP(1)

NAME

     zgrep, zegrep, zfgrep -- print lines matching a pattern in gzip-compressed files

SYNOPSIS

     zgrep [grep-flags] [--] pattern [files ...]

     zegrep [grep-flags] [--] pattern [file ...]

     zfgrep [grep-flags] [--] pattern [file ...]

DESCRIPTION

     zgrep runs grep(1) on files or stdin, if no files argument is given, after decompressing them with zcat(1).

     The grep-flags and pattern arguments are passed on to grep(1).  If an -e flag is found in the grep-flags, zgrep will not look for a pattern
     argument.

     zegrep calls egrep(1), while zfgrep calls fgrep(1).

EXIT STATUS

     In case of missing arguments or missing pattern, 1 will be returned, otherwise 0.

SEE ALSO

     egrep(1), fgrep(1), grep(1), gzip(1), zcat(1)

AUTHORS

     Thomas Klausner <wiz@NetBSD.org>

BSD
								 December 28, 2003							       BSD
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