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Full Discussion: need help deciphering this if statement
Top Forums Shell Programming and Scripting need help deciphering this if statement Post 302477837 by Straitsfan on Monday 6th of December 2010 01:19:36 PM
Old 12-06-2010
actuall I did forget the single quote, but it isn't referring to a negative number. It's part of a sample script. I should have included the whole thing.

Code:
if [ -n "$(echo $1 | grep '^-[0-9][0-9]*$')" ]; then
    howmany=$1
    shift
elif [ -n "$(echo $1 | grep '^-')" ] ;then
     print 'usage: highest [-N] filename'
     exit 1
else
     howmany="-10"
fi
 
filename=$1
sort -nr $filename |head $howmany

what I wanted to know was how the * and $ mean what my book says it means, because I don't see it (particularly the dollar sign at the end of the grep expression; I know what it means in reference to the positional parameter).
 

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LEARN ABOUT LINUX

bzegrep

BZGREP(1)						      General Commands Manual							 BZGREP(1)

NAME

       bzgrep, bzfgrep, bzegrep - search possibly bzip2 compressed files for a regular expression

SYNOPSIS

       bzgrep [ grep_options ] [ -e ] pattern filename...
       bzegrep [ egrep_options ] [ -e ] pattern filename...
       bzfgrep [ fgrep_options ] [ -e ] pattern filename...

DESCRIPTION

       Bzgrep  is  used to invoke the grep on bzip2-compressed files. All 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  bzgrep  is  invoked as bzegrep or bzfgrep then egrep or fgrep is used instead of grep.  If the GREP environment variable is set, bzgrep
       uses it as the grep program to be invoked. For example:

	   for sh:  GREP=fgrep	bzgrep string files
	   for csh: (setenv GREP fgrep; bzgrep string files)

AUTHOR

       Charles Levert (charles@comm.polymtl.ca). Adapted to bzip2 by Philippe Troin <phil@fifi.org> for Debian GNU/Linux.

SEE ALSO

       grep(1), egrep(1), fgrep(1), bzdiff(1), bzmore(1), bzless(1), bzip2(1)

																	 BZGREP(1)
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