Use variable in search pattern in awk

Passing a variable to awk and using it in the search pattern.



awk -v string="$STRING" -f  script.awk  [filename]

Script extract:

$0 ~ string {
      
       print $0;
}

Note:

        On Solaris use nawk.

Variable assigments

Validating positional parameters.

The below example will print a usage message if there is no 2nd position paramaeter.

PACKAGE=${2:?$(usage ${SERVERLIST} [Package name:Version:Package file[:Dependent service]])}

Shell Scripting: basename variable

"${0##*/}" is the equivalent of "basename $0".
I.e. From /usr/bin/sh we get just sh.


Also try this to execute commands $(shell command)

Shell scripting: Testing empty variables

$V="xNotEmpty"

if [ x$V = "xNotEmpty" ]
then
       echo "\$V not empty"
else
       echo"\$V is empty"
fi

Or:

if [ "$V" = "" ]
then
      echo "\$V is empty
fi

Shell Scripting: Special Variables

$?        Exit status or return code of last command.
$#        Number of arguments.
$@        Argument 1 thru n with Input Field Separator.
$*        "$1" $2" ... $n.
$!        Process id of last background process.
$$        Process id of shell running this script.
$-        The current shell flags.