proc(3Tcl)							    proc(3Tcl)

NAME    [Toc]    [Back]

     proc - Create a Tcl procedure

SYNOPSIS    [Toc]    [Back]

     proc name args body

DESCRIPTION    [Toc]    [Back]

     The proc command creates a	new Tcl	procedure named	name, replacing	any
     existing command or procedure there may have been by that name.  Whenever
     the new command is	invoked, the contents of body will be executed by the
     Tcl interpreter.  Args specifies the formal arguments to the procedure.
     It	consists of a list, possibly empty, each of whose elements specifies
     one argument.  Each argument specifier is also a list with	either one or
     two fields.  If there is only a single field in the specifier then	it is
     the name of the argument; if there	are two	fields,	then the first is the
     argument name and the second is its default value.

     When name is invoked a local variable will	be created for each of the
     formal arguments to the procedure;	its value will be the value of
     corresponding argument in the invoking command or the argument's default
     value.  Arguments with default values need	not be specified in a
     procedure invocation.  However, there must	be enough actual arguments for
     all the formal arguments that don't have defaults,	and there must not be
     any extra actual arguments.  There	is one special case to permit
     procedures	with variable numbers of arguments.  If	the last formal
     argument has the name args, then a	call to	the procedure may contain more
     actual arguments than the procedure has formals.  In this case, all of
     the actual	arguments starting at the one that would be assigned to	args
     are combined into a list (as if the list command had been used); this
     combined value is assigned	to the local variable args.

     When body is being	executed, variable names normally refer	to local
     variables,	which are created automatically	when referenced	and deleted
     when the procedure	returns.  One local variable is	automatically created
     for each of the procedure's arguments.  Global variables can only be
     accessed by invoking the global command or	the upvar command.

     The proc command returns an empty string.	When a procedure is invoked,
     the procedure's return value is the value specified in a return command.
     If	the procedure doesn't execute an explicit return, then its return
     value is the value	of the last command executed in	the procedure's	body.
     If	an error occurs	while executing	the procedure body, then the
     procedure-as-a-whole will return that same	error.

KEYWORDS    [Toc]    [Back]

     argument, procedure


									PPPPaaaaggggeeee 1111