In an awk program, a function definition looks like this:

function name(argument-list) {
    statements
}

The argument-list is a list of one or more names (separated by commas) that represent argument values passed to the function. When an argument name is used in the statements of a function, it is replaced by a copy of the corresponding argument value.

For example, the following is a simple function that takes a single numeric argument N and returns a random integer between 1 and N (inclusive):

function random(N) {
    return (int(N * rand() + 1))
}