This is where the “Exit” command becomes crucial. The “Exit” command plays a central role in ensuring that your batch scripts operate smoothly and effectively. Without it, a batch script will keep running until it finishes all its commands, regardless of whether there are errors or if the intended task is complete. Unintended effects may result from this lack of control, especially in complex programs. This article explores why the “Exit” command is vital and learn how to wield it effectively.
Syntax of Exit Command:
Here is the basic syntax for utilizing the “Exit” command in batch scripts:
Here, “/b” is an optional switch that specifies the exit of the current batch script only, not the entire command prompt session. Whereas the “exitCode” is an optional numeric value that can be used to indicate the exit status of your script. By convention, a zero (0) exit code typically signifies success, while non-zero codes indicate an error.
Now, let’s explore some common use cases of the “Exit” command and how to employ it effectively in your batch scripts.
Example 1: Normal Script Termination
Normal script termination refers to the standard way of ending a batch script after it has completed its tasks successfully. In other words, when everything in our script has been executed without any errors or issues, we want to ensure that it finishes its job gracefully and stops running.
To achieve this, we utilize the “Exit” command. Using the “Exit” command without any special instructions or exit codes simply means “terminate the script”.
Here is an illustration on how the normal script termination could be used in a batch script:
Open the text editor and save the file with the “.bat” extension after writing the script.
exit
In this script, we use two commands: “echo” and “exit”. The “echo” command is responsible for displaying a message on the command prompt. In our case, the message being exhibited is “Our script completed successfully!”
The purpose of this line is to provide feedback to the user or script operator, letting them know that the script is executed without encountering any errors.
The batch script is ended using the “exit” command. When we use “exit” without specifying an exit code, it tells the script to exit gracefully, indicating that the script has finished its tasks successfully.
So, when this script is executed, it first displays the “Script completed successfully!” message on the screen, indicating that the script has finished its tasks without any issues. Then, it immediately terminates, effectively ending the execution of the batch script.
Example 2: Error Handling
Error handling in programming is about anticipating and dealing with problems that might occur while a program or script is running.
Errors like “file not found” and “permissions denied” are frequently encountered by batch programs. We can use the “Exit” command to gracefully exit the script and provide an informative exit code when an error occurs.
Let’s carry out an example to understand this:
echo Error: newdata.txt not found!
exit 1
)
In this piece of code, we use the “if not exist newdata.txt” script. We check to see if a file named “newdata.txt” file exists. If the “newdata.txt” file doesn’t exist, we want to know that there’s a problem. An error message is shown on the command line using the “echo” command. The message it displays is “Error: newdata.txt not found!” which means that we expect to find this file, but it’s not there.
If we find that the “newdata.txt” file does not exist, we don’t want our program to keep running in vain. So, we use the “exit” command to stop our program and give it an exit code of “1”. Exit codes are like signals that can indicate different things. In this case, “1” often means that there is some kind of error.
So, in simpler terms, this code helps us avoid doing anything with a file that doesn’t exist. If we can’t find the “newdata.txt” file, we let the computer know that there’s an issue by showing an error message and giving it a code to understand its problem.
We do not have such a file, so the error message is displayed on the command prompt:
Example 3: Conditional Exits
Conditional exits refer to the practice of ending a script based on certain conditions or criteria that we specified.
Here is an example:
if %var% == 0 (
echo Variable is zero. Exiting.
exit
)
echo Variable is not zero. Continuing...
We assign the value of “8” to the “var” variable in this script. In the next step, we check if the value of “var” is equal to zero using the if-condition. If the value of the “var” is equal to zero, a “Variable is zero. Exiting” message is displayed on the command prompt. Then, it exits the script. However, if “var” is not zero, it prints a message stating “Variable is not zero. Continuing…” and the script proceeds with further instructions. Essentially, this script serves as a decision-making point in a script, enabling it to execute various actions depending on the value of the “var” variable.
In other words, it shows how to build a conditional exit point into a script that determines whether to continue or end the script depending on the value of a variable.
The generated output by executing this script is given as follows:
Conclusion
This article demonstrated the utilization of the “Exit” command to terminate our batch scripts when needed. The initial section of the article provided the introduction to the “Exit” command. Then, we created three examples to comprehend the utilization of the “Exit” command in a batch script. All the examples are explained in detail and provided the outputs as well.