Batch Script - Empty String

An empty string can be created in DOS Scripting by assigning it no value during its initialization as shown in the following example.

Set a=

To check for an existence of an empty string, you need to encompass the variable name in square brackets and also compare it against a value in square brackets as shown in the following example.

[%a%]==[]

The following example shows how an empty string can be created and how to check for the existence of an empty string.

Example

@echo off 
SET a= 
SET b=Hello 
if [%a%]==[] echo "String A is empty" 
if [%b%]==[] echo "String B is empty "

Output

The above command produces the following output.

String A is empty