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As discussed in the previous tutorial, a batch file is an unformatted text file or script file which contains multiple batch file commands or instructions to achieve a certain task. It has extension of.bat or.cmd. Click here to go through the introduction of the batch file before learning batch file commands. Batch file commands: Windows/DOS. Fun Things to Do With Batch Files: ok script kiddies and pros alike, its time for my third instructable. Before i start, i wanna tell you guys something. I want to hear what YOU guys would like to see next. If you have a fun idea for a batch file, email it to gcolonna@sympatico.ca w.
To run a batch file, follow the steps below for where you want to run the batch file.
Running a batch file from within Windows
A batch file runs like any other executable file by double-clicking the file within Windows. However, because a batch file runs in a command line, it immediately exits when done, so you may only see a black box for a second.
TipIf the batch file is closing too fast, or you want to read the output, you can edit the batch file. Add a pause command to the end of the file at the beginning of a new line. The pause command waits for user input before continuing.
Run a batch file from the Command Prompt
To run a batch file, move to the directory containing the file and type the name of the batch file. For example, if the batch file is named 'hope.bat,' you'd type 'hope' to execute the batch file.
Additional information
- Batch Script Tutorial
- Batch Script Resources
- Selected Reading
There are two types of variables in batch files. One is for parameters which can be passed when the batch file is called and the other is done via the set command.
Command Line Arguments
Batch scripts support the concept of command line arguments wherein arguments can be passed to the batch file when invoked. The arguments can be called from the batch files through the variables %1, %2, %3, and so on.
The following example shows a batch file which accepts 3 command line arguments and echo’s them to the command line screen.
If the above batch script is stored in a file called test.bat and we were to run the batch as
Following is a screenshot of how this would look in the command prompt when the batch file is executed.
The above command produces the following output.
If we were to run the batch as
The output would still remain the same as above. However, the fourth parameter would be ignored.
Set Command
The other way in which variables can be initialized is via the ‘set’ command. Following is the syntax of the set command.
My Batch Files Batch Files Linux
Syntax
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 – This switch is used if the value needs to be numeric in nature.
The following example shows a simple way the set command can be used.
Example
In the above code snippet, a variable called message is defined and set with the value of 'Hello World'.
To display the value of the variable, note that the variable needs to be enclosed in the % sign.
Output
The above command produces the following output.
Working with Numeric Values
In batch script, it is also possible to define a variable to hold a numeric value. This can be done by using the /A switch.
The following code shows a simple way in which numeric values can be set with the /A switch.
We are first setting the value of 2 variables, a and b to 5 and 10 respectively.
We are adding those values and storing in the variable c.
Finally, we are displaying the value of the variable c.
The output of the above program would be 15.
All of the arithmetic operators work in batch files. The following example shows arithmetic operators can be used in batch files.
The above command produces the following output.
Local vs Global Variables
In any programming language, there is an option to mark variables as having some sort of scope, i.e. the section of code on which they can be accessed. Normally, variable having a global scope can be accessed anywhere from a program whereas local scoped variables have a defined boundary in which they can be accessed.
DOS scripting also has a definition for locally and globally scoped variables. By default, variables are global to your entire command prompt session. Call the SETLOCAL command to make variables local to the scope of your script. After calling SETLOCAL, any variable assignments revert upon calling ENDLOCAL, calling EXIT, or when execution reaches the end of file (EOF) in your script. The following example shows the difference when local and global variables are set in the script.
Example
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Few key things to note about the above program.
The ‘globalvar’ is defined with a global scope and is available throughout the entire script.
The ‘var‘ variable is defined in a local scope because it is enclosed between a ‘SETLOCAL’ and ‘ENDLOCAL’ block. Hence, this variable will be destroyed as soon the ‘ENDLOCAL’ statement is executed.
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Output
The above command produces the following output.
You will notice that the command echo %var% will not yield anything because after the ENDLOCAL statement, the ‘var’ variable will no longer exist.
Working with Environment Variables
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If you have variables that would be used across batch files, then it is always preferable to use environment variables. Once the environment variable is defined, it can be accessed via the % sign. The following example shows how to see the JAVA_HOME defined on a system. The JAVA_HOME variable is a key component that is normally used by a wide variety of applications.
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The output would show the JAVA_HOME directory which would depend from system to system. Following is an example of an output.