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Full Discussion: -n option with grep command
Top Forums Shell Programming and Scripting -n option with grep command Post 302458217 by frans on Thursday 30th of September 2010 05:01:24 AM
Old 09-30-2010
Nothing with grep but with string :
[ -n "String" ] returns TRUE if string is not empty.

likely [ -z "String" ] returns TRUE if string is empty.

"`grep $some_string /tmp/tmp_crontab.txt`" is a command substitution returning a string value. It can be better written "$(grep $some_string /tmp/tmp_crontab.txt)"

Example ($> stands for the prompt):
Code:
$> grep root /etc/passwd
root:x:0:0:root:/root:/bin/bash
$> STRING="$(grep root /etc/passwd)"
$> echo $STRING
root:x:0:0:root:/root:/bin/bash

 

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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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