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'\" Copyright (c) 1993 The Regents of the University of California.

'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.

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'\" RCS: @(#) $Id: proc.n,v 1.1.1.1 2002-01-16 10:25:25 markom Exp $

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.so man.macros

.TH proc n "" Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

proc \- Create a Tcl procedure

.SH SYNOPSIS

\fBproc \fIname args body\fR

.BE

.SH DESCRIPTION

.PP

The \fBproc\fR command creates a new Tcl procedure named

\fIname\fR, replacing

any existing command or procedure there may have been by that name.

Whenever the new command is invoked, the contents of \fIbody\fR will

be executed by the Tcl interpreter.

Normally, \fIname\fR is unqualified

(does not include the names of any containing namespaces),

and the new procedure is created in the current namespace.

If \fIname\fR includes any namespace qualifiers,

the procedure is created in the specified namespace.

\fIArgs\fR 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.

.PP

When \fIname\fR 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

\fBargs\fR, 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 \fBargs\fR are combined into

a list (as if the \fBlist\fR command had been used); this combined value

is assigned to the local variable \fBargs\fR.

.PP

When \fIbody\fR 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 \fBglobal\fR command or the \fBupvar\fR command.

Namespace variables can only be accessed by invoking

the \fBvariable\fR command or the \fBupvar\fR command.

.PP

The \fBproc\fR command returns an empty string.  When a procedure is

invoked, the procedure's return value is the value specified in a

\fBreturn\fR command.  If the procedure doesn't execute an explicit

\fBreturn\fR, 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.

.SH KEYWORDS

argument, procedure