If condition to check null variable

Shell Programming and Scripting
1

Guys,

Please help me on the below

 
sample.cfg
var=NULL

 
sample.sh
#!/bin/sh
. /sample.cfg
if [ $var -eq NULL ];then
1 st command here
else
2 nd command here 
fi

Now i want the first command to be exectuted if the variable is NUll. If i specify the variable name, the second command to be executed.
Please advise

Thanks

2

put NULL in double quotes.. and if you are equating string better use = than -eq

3 
#!/bin/sh

. ./sample.cfg

if [ "$var" = "NULL" ]; then
        echo first
else
        echo second
fi

exit 0
4

Be aware:-

#!/bin/bash
nulltest()
{
if [ ${#var} -eq 0 ]
then
	echo "NULL, empty string..."
else
	echo "Not an empty string..."
fi
}
var=""
nulltest
var=NULL
nulltest

Gives results:-

Last login: Thu Jul 11 07:58:36 on ttys000
AMIGA:barrywalker~> ./null.sh
NULL, empty string...
Not an empty string...
AMIGA:barrywalker~>