how to check null variable

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Check null values column

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Guys, Please help me on the below sample.cfg var=NULL sample.sh #!/bin/sh . /sample.cfg if ;then 1 st command here else 2 nd command here fi

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check for null

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Check for null values in a column

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check for NULL variable

Hello I want to check for NULL variable.. but this is not working..please help thanks in advance esham

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escape

escape(1)							Mail Avenger 0.8.3							 escape(1)

NAME

       escape - escape shell special characters in a string

SYNOPSIS

       escape string

DESCRIPTION

       escape prepends a "" character to all shell special characters in string, making it safe to compose a shell command with the result.

EXAMPLES

       The following is a contrived example showing how one can unintentionally end up executing the contents of a string:

	   $ var='; echo gotcha!'
	   $ eval echo hi $var
	   hi
	   gotcha!
	   $

       Using escape, one can avoid executing the contents of $var:

	   $ eval echo hi `escape "$var"`
	   hi ; echo gotcha!
	   $

       A less contrived example is passing arguments to Mail Avenger bodytest commands containing possibly unsafe environment variables.  For
       example, you might write a hypothetical reject_bcc script to reject mail not explicitly addressed to the recipient:

	   #!/bin/sh
	   formail -x to -x cc -x resent-to -x resent-cc 
	       | fgrep "$1" > /dev/null 
		   && exit 0
	   echo "<$1>.. address does not accept blind carbon copies"
	   exit 100

       To invoke this script, passing it the recipient address as an argument, you would need to put the following in your Mail Avenger rcpt
       script:

	   bodytest reject_bcc `escape "$RECIPIENT"`

SEE ALSO

       avenger(1),

       The Mail Avenger home page: <http://www.mailavenger.org/>.

BUGS

       escape is designed for the Bourne shell, which is what Mail Avenger scripts use.  escape might or might not work with other shells.

AUTHOR

       David Mazieres

Mail Avenger 0.8.3						    2012-04-05								 escape(1)

Shell Programming and Scripting