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Full Discussion: help in grep
Top Forums Shell Programming and Scripting help in grep Post 302136461 by varungupta on Tuesday 18th of September 2007 02:29:34 AM
Old 09-18-2007
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Quote:
Originally Posted by vino
You will not find any difference between those two grep's. Rather try these two and see the difference.

grep '$USER' /etc/passwd
grep "$USER" /etc/passwd

Open the man pages of sh or ksh and see the section on Quoting. Basically single quotes prevent variable expansion.
Adding to Vino's comment...
variables in single quotes are treated as const. string

as
1. var = 5 ;
echo '$var'

This will simply display the string $var as it is, no variable replacement by value.

2. var = 5;
echo "$var"
In double quotes variables get expansion in terms of its value.
o/p will be 5


Similarly is the case with grep '$var' and grep "$var".
But when it comes to constant string, it hardly reflects any change.

grep -w "string1 string2" file1
grep -w 'string1 string2" file1

Both are same.

Hope you get this !!Smilie
 

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XZGREP(1)							     XZ Utils								 XZGREP(1)

NAME
xzgrep - search compressed files for a regular expression SYNOPSIS
xzgrep [grep_options] [-e] pattern file... xzegrep ... xzfgrep ... lzgrep ... lzegrep ... lzfgrep ... DESCRIPTION
xzgrep invokes grep(1) on files which may be either uncompressed or compressed with xz(1), lzma(1), gzip(1), or bzip2(1). All options specified are passed directly to grep(1). If no file is specified, then standard input is decompressed if necessary and fed to grep(1). When reading from standard input, gzip(1) and bzip2(1) compressed files are not supported. If xzgrep is invoked as xzegrep or xzfgrep then egrep(1) or fgrep(1) is used instead of grep(1). The same applies to names lzgrep, lze- grep, and lzfgrep, which are provided for backward compatibility with LZMA Utils. ENVIRONMENT
GREP If the GREP environment variable is set, xzgrep uses it instead of grep(1), egrep(1), or fgrep(1). SEE ALSO
grep(1), xz(1), gzip(1), bzip2(1), zgrep(1) Tukaani 2010-09-27 XZGREP(1)
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