How can I compare two variables in a batch?

Comparing two variables in a batch script can be achieved using conditional statements like IF. Here's how to do it, along with several examples and explanations.

1. Basic Equality Check

To check if two variables are equal, you can use the == operator within an IF statement.

@echo off
set VAR1=apple
set VAR2=apple

if "%VAR1%"=="%VAR2%" (
  echo Variables are equal.
) else (
  echo Variables are not equal.
)

In this example, if VAR1 and VAR2 both have the same value, the output will be "Variables are equal". If they differ, the output will be "Variables are not equal".

2. Checking for Inequality

To check if two variables are not equal, you use the NEQ operator.

@echo off
set VAR1=apple
set VAR2=banana

if "%VAR1%" NEQ "%VAR2%" (
  echo Variables are not equal.
) else (
  echo Variables are equal.
)

This script will output "Variables are not equal" because the values of VAR1 and VAR2 are different.

3. Numerical Comparisons

For comparing numerical values, use the operators EQU (equal), NEQ (not equal), LSS (less than), LEQ (less than or equal), GTR (greater than), and GEQ (greater than or equal).

@echo off
set NUM1=10
set NUM2=20

if %NUM1% LSS %NUM2% (
  echo NUM1 is less than NUM2
)

if %NUM1% GTR %NUM2% (
  echo NUM1 is greater than NUM2
) else (
  echo NUM1 is not greater than NUM2
)

In this example, since 10 is less than 20, it will first output "NUM1 is less than NUM2". And since 10 is not greater than 20 it will print "NUM1 is not greater than NUM2".

4. String Comparisons (Case-Insensitive)

By default, batch script string comparisons are case-insensitive. To force case-sensitive comparisons, you will need to use other methods or tools like PowerShell or `findstr`.

For Case-Insensitive comparison you can use `==` or `NEQ`.

Important Considerations

- When comparing strings, use double quotes around variables (e.g. `"%VAR1%"=="%VAR2%"`). This helps prevent issues with spaces in values. - When performing numerical comparisons, omit the quotes. - Be mindful of data types; ensure that numerical comparisons are made between valid numeric values to avoid unexpected results.

These examples provide a comprehensive guide to comparing variables in batch scripts, handling equality, inequality, numerical, and case-insensitive string comparisons.

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