Why is [[ ]] different then [ ]? Post: 302280873

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Top Forums Shell Programming and Scripting Why is [[ ]] different then [ ]? Post 302280873 by jim mcnamara on Tuesday 27th of January 2009 05:38:26 PM

01-27-2009

Registered User

Quoting the "${CHECK1}" construct would create a zero length string if the variable was null, yes, that is correct. So [ ] would work for that.

I use ksh with [[ ]] -- simply to avoid problems like this. And any time I work with string variables I try to enclose them in double quotes so they are "seen" correctly by the shell.

jim mcnamara

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zegrep

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)