3.4. Auxiliary functions

General syntax:

function <name>[:<type>] ( <arg1>[:<type>], ... ) { <stmts> }

SystemTap scripts may define subroutines to factor out common work. Functions may take any number of scalar arguments, and must return a single scalar value. Scalars in this context are integers or strings. For more information on scalars, see Section Section 3.3, “Variables” and Section Section 5.2, “Data types”. The following is an example function declaration.

function thisfn (arg1, arg2) {
return arg1 + arg2
}

Note the general absence of type declarations, which are inferred by the translator. If desired, a function definition may include explicit type declarations for its return value, its arguments, or both. This is helpful for embedded-C functions. In the following example, the type inference engine need only infer the type of arg2, a string.

function thatfn:string(arg1:long, arg2) {
return sprintf("%d%s", arg1, arg2)
}

Functions may call others or themselves recursively, up to a fixed nesting limit. See Section Section 1.6, “Safety and security”.