Batch Script - Decision Making

Introduction to Decision Making in Batch Scripts

Hello there, aspiring programmers! Today, we're going to dive into the exciting world of decision making in Batch scripts. As your friendly neighborhood computer teacher, I'm here to guide you through this journey with plenty of examples and a dash of humor. So, buckle up and let's get started!

Decision making is like choosing which flavor of ice cream to eat – it's all about making choices based on certain conditions. In Batch scripting, we use these decisions to make our scripts smarter and more flexible.

The IF Statement: Your First Decision Maker

Basic IF Statement

The IF statement is the bread and butter of decision making in Batch. It's like a traffic light for your code – it tells your script when to go and when to stop.

Let's start with a simple example:

@echo off
IF EXIST "C:\MyFile.txt" echo File exists!

In this script, we're checking if a file named "MyFile.txt" exists in the C: drive. If it does, we print "File exists!". It's that simple!

IF-ELSE Statement: Two Paths to Choose From

Now, let's add an ELSE clause to our IF statement. This is like having a Plan B:

@echo off
IF EXIST "C:\MyFile.txt" (
    echo File exists!
) ELSE (
    echo File does not exist!
)

Here, if the file doesn't exist, we'll see "File does not exist!" instead. It's like asking, "Is there pizza in the fridge? If yes, eat it; if not, order some!"

Comparison Operators: The Decision-Making Toolkit

When making decisions, we often need to compare things. In Batch, we have several comparison operators to help us out. Here's a handy table of these operators:

Operator	Description
EQU	Equal to
NEQ	Not equal to
LSS	Less than
LEQ	Less than or equal to
GTR	Greater than
GEQ	Greater than or equal to

Let's use these in an example:

@echo off
SET /A age=25
IF %age% GEQ 18 (
    echo You're an adult!
) ELSE (
    echo You're still a minor.
)

In this script, we're checking if the age is greater than or equal to 18. If it is, we declare the person an adult. It's like a virtual bouncer for your code!

The GOTO Statement: Jumping Around Your Script

Sometimes, you need to jump to different parts of your script based on a decision. That's where the GOTO statement comes in handy. It's like teleportation for your code!

@echo off
SET /P choice=Enter 1 for Hello, 2 for Goodbye: 
IF %choice%==1 GOTO hello
IF %choice%==2 GOTO goodbye
GOTO end

:hello
echo Hello, World!
GOTO end

:goodbye
echo Goodbye, World!
GOTO end

:end
echo Script finished!

This script asks the user to make a choice and then jumps to the appropriate section using GOTO. It's like a "Choose Your Own Adventure" book, but in code form!

Nested IF Statements: Decisions Within Decisions

Sometimes, one decision isn't enough. We need to make decisions based on the outcome of other decisions. This is where nested IF statements come in:

@echo off
SET /P age=Enter your age: 
IF %age% GEQ 18 (
    IF %age% LSS 65 (
        echo You're an adult of working age.
    ) ELSE (
        echo You're a senior citizen.
    )
) ELSE (
    echo You're a minor.
)

This script categorizes a person based on their age, using nested IF statements. It's like a Russian doll of decision making!

The Choice Command: Interactive Decision Making

The CHOICE command allows us to create interactive menus for user input. It's like creating a multiple-choice quiz in your script:

@echo off
ECHO What's your favorite color?
ECHO 1. Red
ECHO 2. Blue
ECHO 3. Green
CHOICE /C 123 /N /M "Enter your choice (1-3):"
IF ERRORLEVEL 3 ECHO You chose Green
IF ERRORLEVEL 2 ECHO You chose Blue
IF ERRORLEVEL 1 ECHO You chose Red

This script presents a menu and reacts based on the user's choice. It's like being a mind reader, but with code!

Conclusion

And there you have it, folks! We've journeyed through the land of decision making in Batch scripts. From simple IF statements to complex nested conditions, you now have the power to make your scripts smarter and more interactive.

Remember, practice makes perfect. Try creating your own scripts using these techniques. Maybe create a script that decides what to have for dinner based on the day of the week? The possibilities are endless!

Happy scripting, and may your decisions always lead to bug-free code!

Credits: Image by storyset