Parameter Checking

Shell Programming and Scripting
1

Hi all,

My script has 2 mandatory and 1 optional paramter. If the third parameter\(optional\) one is null the it should take a default value say 3. Can any one please write a simple code.

sh test.sh 1 2 3

var1=$1
var2=$2

if [ -z $3 ]
then
var3=3
fi

echo " the third variable $var3"

But this is erroring out saying " test.sh: test: argument expected"

Thanks in advance
Ammu

2 
var1=$1
var2=$2

if [ -z "$3" ]
then
var3=3
fi

echo " the third variable $var3"

or

var1=$1
var2=$2
var3=${var3:-3}
echo " the third variable $var3"

Jean-Pierre.