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Tutorial Reference

Batch Script Variables

How to use command-line arguments, set variables with the set command, perform arithmetic operations, and manage local/global scope in Windows batch scripting.

Types of Variables

There are two types of variables in batch files. One is for parameters that can be passed when the batch file is called, and the other is done through the set command.

Command Line Arguments

Batch scripts support the concept of command-line arguments, in which arguments can be passed to the batch file when it is invoked.

The arguments can be called from the batch files through the variables %1, %2, %3, and so on.

For example, the batch script below accepts 3 command line arguments and echo's them to the command line screen:

parameter-test.batbatch
@echo off
echo %1
echo %2
echo %3

If the above batch script is stored in a file called parameter-test.bat and we were to run the batch as:

C:\my\path>parameter-test.bat 1 2 3

And the above command produces the following output:

Outputplaintext
1
2
3

set Command

The other way to initialize variables is the set command. The syntax of the set command is as follows.

set /A variable_name=value

where:

  • variable_name is the name of the variable you want to set.
  • value is the value which needs to be set against the variable.
  • /A is used if the value needs to be numeric.

For example, in this script a variable called message is defined and set with the value of "Hello World".

set-example.batbatch
@echo off
set message=Hello World
echo %message%

And the above command produces the following output:

Outputplaintext
Hello World

Numeric Variables

It is possible to define a variable to hold a numeric value. This can be done by using the /A switch (also known as flag).

For example:

numeric-example.batbatch
@echo off
SET /A a = 5
SET /A b = 10
SET /A c = %a% + %b%
echo %c%

where:

  • we assign the values 5 and 10 to two variables a and b respectively.
  • we sum these values and store the result in the variable c.
  • Finally, we display the value of the variable c.

The output of the above script is 15.

Arithmetic Operators

All the arithmetic operators work in batch files.

For example:

arithmetic-example.batbatch
@echo off
SET /A a = 5
SET /A b = 10
SET /A c = %a% + %b%
echo %c%
SET /A c = %a% - %b%
echo %c%
SET /A c = %b% / %a%
echo %c%
SET /A c = %b% * %a%
echo %c%

And the output is:

Outputplaintext
15
-5
2
50

Local and Global Variables

In Batch Scripting there are variables with local and global scope.

By default, variables are global to your entire command prompt session.

Call the SETLOCAL command to make variables local to the scope of the script. After calling SETLOCAL, any variable assignment is cancelled when ENDLOCAL, EXIT or when execution reaches the end of file (EOF) in the script is called.

The difference between setting local and global variables is shown in the following script:

@echo off
set globalvar = 5
SETLOCAL
set var = 13145
set /A var = %var% + 5
echo %var%
echo %globalvar%
ENDLOCAL

Environment Variables

Environment Variables are preferable when there are variables that would be used across batch files.

The following example shows how to see the JAVA_HOME defined on a system.

@echo off 
echo %JAVA_HOME%
Outputplaintext
C:\mypath\JAVA5.0\jre
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