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proc(n)                                     Tcl Built-In Commands                                    proc(n)



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NAME
       proc - Create a Tcl procedure

SYNOPSIS
       proc name args body
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DESCRIPTION
       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.  Normally, name is unqualified (does not include the names of any
       containing namespaces), and the new procedure is created in the current namespace.  If name  includes
       any  namespace  qualifiers,  the procedure is created in the specified namespace.  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 proce-dure; procedure;
       dure; 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.  How-ever, However,
       ever, 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 automat-ically automatically
       ically  created  for  each  of  the  procedure's arguments.  Global variables can only be accessed by
       invoking the global command or the upvar command.  Namespace variables can only be accessed by invok-ing invoking
       ing the variable 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.


SEE ALSO
       info(n), unknown(n)


KEYWORDS
       argument, procedure



Tcl                                                                                                  proc(n)