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Full Discussion: Need help writing a small script
Top Forums Shell Programming and Scripting Need help writing a small script Post 302204823 by mschwage on Thursday 12th of June 2008 03:06:36 PM
Old 06-12-2008
Quote:
Originally Posted by llsmr777
thank you for the reply!

can you expand on this? please bear with me I'm just learning:

grep -q "2007"; if [ $? -eq 0 ];

-q is option for what again?

[ $? -eq 0 ]; what does this break down to?
The man pages are your friends. Try
Code:
man grep

Specifically, in this case it means to be quiet. No output will be produced- the default is to print to the screen what grep finds. In your case, you don't want to see what it found, you just want to know what it found, and report it. The -q option is perfect for that.

Regardless, grep exits with a code. If it finds something, it exits with code 0 (which perhaps paradoxically means "success" in UNIX shell-land). That number is put into the "$?" variable. Also, the [ is the shell command "test". So
Code:
[ $? -eq 0 ]

means "Test the $? variable and see if it's equal to 0". If so, the test command will exit with code 0 (success). The "if" command checks the exit code of the command it is given- in this instance, the "test" command. So if the test is successful, then do the "then" clause.
-mschwage
 

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LEARN ABOUT ULTRIX

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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