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Full Discussion: Command execution in grep
Top Forums UNIX for Dummies Questions & Answers Command execution in grep Post 302459988 by agama on Tuesday 5th of October 2010 09:23:31 PM
Old 10-05-2010
What turk451 said is correct. To add just a bit more.....

You need to ultimately pass \\t to grep. If the search string given to grep has \t then grep will match a tab. Passing the double slant to grep is necessary to escape it such that grep treats it as a two character pattern.

Quote:
Code:
grep -l "\t" foo

However, the double quotes don't save backslashes so the \t turns into just the character t which means now it is simply looking for that.
In this case the shell is passing the backslant, but it is grep that is interpreting it as a tab rather than two characters.

As for why you need three backslants...
When the shell sees \\\t it replaces the first two with a single slant, and because \t isn't a special case it leaves it alone resulting in \\t being passed to grep which is exactly what you need.
Last edited by agama; 10-05-2010 at 10:24 PM.. Reason: typo
 

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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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