Batch Check for Empty Variables
This article explains how we can test if a variable has been set. We can use an if statement to check if a variable has been defined.
Batch check whether variables are empty
For a simpler context, we will start by defining two strings, str1 and str2. Our first string will be empty (undefined) and the second string will have a value (non-empty).
This is the script we will use.
@echo off
set str1=
set str2=Delft
::using the if statement, we will check whether str1 is an empty string.
if [%str1%]==[] echo "str1 is an empty string"
if [%str2%]==[] echo "str2 is an empty string"
pause
- We use set to get our input string where str1 has no value and str2 has the value Delft.
- We then use an if statement to test if our string is empty.
We usually use double colons ::to add comments in Batch scripts. The pause at the end will keep the CMD window until we press a key.
@echo offInstructs Command Prompt not to display the commands contained in a batch file, including itself.
Below is the output of our batch script.
As expected, our first string is empty.
In short, we can use the if statement to check if a string or variable is set, or in other words, defined. Remember to use square brackets instead of round brackets or double quotes.
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