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Full Discussion: Grep -v -f and sort|diff which way is faster
Top Forums Shell Programming and Scripting Grep -v -f and sort|diff which way is faster Post 302922969 by MadeInGermany on Wednesday 29th of October 2014 01:28:58 PM
Old 10-29-2014
The file after the -f is read into memory, so it should be
Code:
grep -v -f smallfile bigfile

Some grep versions are rather slow on this, and even the faster full-line-match is not a race car:
Code:
grep -v -x -f smallfile bigfile

In this case consider replacing it by awk:
Code:
awk 'FILENAME=="-" {s[$0]; next} !($0 in s)' - bigfile <smallfile

This User Gave Thanks to MadeInGermany For This Post:
ken6503
 

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LEARN ABOUT BSD

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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