9.2.3.1 Writing A Function Call

Calling a function means causing the function to run and do its job. A function call is an expression and its value is the value returned by the function.

A function call consists of the function name followed by the arguments in parentheses. awk expressions are what you write in the call for the arguments. Each time the call is executed, these expressions are evaluated, and the values become the actual arguments. For example, here is a call to foo() with three arguments (the first being a string concatenation):

foo(x y, "lose", 4 * z)

CAUTION: Whitespace characters (spaces and TABs) are not allowed between the function name and the open-parenthesis of the argument list. If you write whitespace by mistake, awk might think that you mean to concatenate a variable with an expression in parentheses. However, it notices that you used a function name and not a variable name, and reports an error.