how to check the variable values is blank

Shell Programming and Scripting
1

HI ,
I have to check the values of variable is blank or not.
exm :
###test
test1

var=`cate filename | head -1 | cut -c1-3`
I need to check the first three character of 1st line . if it is blank .then exit or we need to process .

Thanks in advance .

2

Something like the following should work

if [[ -z $var ]]
then
      echo "Empty var"
      exit 1
fi
3

unrelated but I would suggest changing the

var=`cate filename | head -1 | cut -c1-3`

line to

var=`head -1 filename| cut -c1-3`

There is no reason to read the entire file when you only need the first line.