In this, you learned about if block conditional expressions in DOS batch programming
- if block
- if-else block
- nested if
if block example
if in the batch are used to evaluate conditional expressions and execute the lines of code based on the conditional result.
conditional expression is true, executes code.
@echo off SET active= true SET name= john if %active%==true echo active is true if %name%==eric echo name is not john
active is true
conditional expressions are evaluated to true or false and execute code based on it.
These expressions are case-sensitive.
If else in batch programs
It execute conditional express with if and else blocks
If (expressions) (codeblock1) ELSE (codeblock2)
if the expression is true, codeblock1 executes, else i.e false, codeblock2 is executed.
codeblock1 and codeblock2 wraps inside
Here is an
if else example
@echo off SET active= false if %active%==true (echo active is true) else (echo active is not true)
active is not true
The above variable is evaluated in if block and based on the result if block or else block is executed.
nested if-else blocks
nested if blocks are defined in another if blocks.
here is an syntax.
if(expression1) if (expression2) codeblock
if expression1 is true, Then expression2 is evaluated and if true, the code block is executed.
You can also include an if-else block inside if block.
Here is an exmaple
@echo off SET active= true SET name= john if %active%==true if %name%==john echo "name=john and active=true"
name=john and active=true
How to check variable exists in DOS batch programming?
if defined is used to check variable exists or not.
if defined variable code block
if variable defined, code block executes Here is an example
@echo off SET dept= sales if defined dept (echo variable dept exists) else (echo variable dept not exists)
variable dept exists
defined can be used with if block as well as nested if-else blocks