Advanced Bash−Scripting Guide

Chapter 23. Functions
Like "real" programming languages, Bash has functions, though in a somewhat limited implementation. A
function is a subroutine, a code block that implements a set of operations, a "black box" that performs a
specified task. Wherever there is repetitive code, when a task repeats with only slight variations, then consider
using a function.
function function_name {
command...
}
or
function_name () {
command...
}
This second form will cheer the hearts of C programmers (and is more portable).
As in C, the function's opening bracket may optionally appear on the second line.
function_name ()
{
command...
}
Functions are called, triggered, simply by invoking their names.
Example 23−1. Simple function
#!/bin/bash
funky ()
{
echo "This is a funky function."
echo "Now exiting funky function."
} # Function declaration must precede call.
# Now, call the function.
funky
exit 0
The function definition must precede the first call to it. There is no method of "declaring" the function, as, for
example, in C.
f1
# Will give an error message, since function "f1" not yet defined.
declare −f f1
# This doesn't help either.
Chapter 23. Functions 274