if
Conditional execution based on boolean expressions.
Syntax
tcl
if expr1 ?then? body1 ?elseif expr2 ?then? body2 ...? ?else bodyN?Parameters
- expr1: Boolean expression evaluated with
expr - then: Optional keyword for readability
- body1: Script to execute if expr1 is true
- elseif: Keyword introducing additional conditions
- expr2: Additional condition expression
- body2: Script to execute if expr2 is true
- else: Keyword introducing the fallback branch
- bodyN: Script to execute if no conditions are true
Boolean Values
Conditions can evaluate to:
- Boolean literals:
true,false,yes,no - Integer values:
0is false, any non-zero value is true
Return Value
Returns the result of the executed body script. If no condition matches and no else clause exists, returns an empty string.
Examples
Basic if-else
Output
Multiple conditions with elseif
Output
Using optional then keyword
Output