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(bashref.info)Shell Functions

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Shell Functions
===============

   Shell functions are a way to group commands for later execution
using a single name for the group.  They are executed just like a
"regular" command.  When the name of a shell function is used as a
simple command name, the list of commands associated with that function
name is executed.  Shell functions are executed in the current shell
context; no new process is created to interpret them.

   Functions are declared using this syntax:
     [ `function' ] NAME () { COMMAND-LIST; }

   This defines a shell function named NAME.  The reserved word
`function' is optional.  If the `function' reserved word is supplied,
the parentheses are optional.  The BODY of the function is the
COMMAND-LIST between { and }.  This list is executed whenever NAME is
specified as the name of a command.  The exit status of a function is
the exit status of the last command executed in the body.

   Note that for historical reasons, the curly braces that surround the
body of the function must be separated from the body by `blank's or
newlines.  This is because the braces are reserved words and are only
recognized as such when they are separated by whitespace.  Also, the
COMMAND-LIST must be terminated with a semicolon or a newline.

   When a function is executed, the arguments to the function become
the positional parameters during its execution (Note: Positional
Parameters).  The special parameter `#' that expands to the number of
positional parameters is updated to reflect the change.  Positional
parameter `0' is unchanged.  The `FUNCNAME' variable is set to the name
of the function while the function is executing.

   If the builtin command `return' is executed in a function, the
function completes and execution resumes with the next command after
the function call.  When a function completes, the values of the
positional parameters and the special parameter `#' are restored to the
values they had prior to the function's execution.  If a numeric
argument is given to `return', that is the function's return status;
otherwise the function's return status is the exit status of the last
command executed before the `return'.

   Variables local to the function may be declared with the `local'
builtin.  These variables are visible only to the function and the
commands it invokes.

   Functions may be recursive.  No limit is placed on the number of
recursive  calls.