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

NAME
       uplevel - Execute a script in a different stack frame

SYNOPSIS
       uupplleevveell ?level? arg ?arg ...?



DESCRIPTION
       All of the arg arguments are concatenated as if they had been passed to
       ccoonnccaatt; the result is then evaluated in the variable context  indicated
       by level.  UUpplleevveell returns the result of that evaluation.

       If level is an integer then it gives a distance (up the procedure call-
       ing stack) to move before executing the command.  If level consists  of
       ##  followed by a number then the number gives an absolute level number.
       If level is omitted then it defaults to 11.  Level cannot  be  defaulted
       if the first command argument starts with a digit or ##.

       For  example,  suppose that procedure aa was invoked from top-level, and
       that it called bb, and that bb called cc.   Suppose  that  cc  invokes  the
       uupplleevveell  command.   If  level  is 11 or ##22  or omitted, then the command
       will be executed in the variable context of bb.  If level  is  22  or  ##11
       then  the  command  will  be executed in the variable context of aa.  If
       level is 33 or ##00 then the command will be executed at  top-level  (only
       global variables will be visible).

       The uupplleevveell command causes the invoking procedure to disappear from the
       procedure calling stack while the command is being  executed.   In  the
       above example, suppose cc invokes the command
              uupplleevveell 11 {{sseett xx 4433;; dd}}
       where  dd  is  another  Tcl  procedure.  The sseett command will modify the
       variable xx in bb's context, and dd will execute at level 3, as if  called
       from bb.  If it in turn executes the command
              uupplleevveell {{sseett xx 4422}}
       then  the  sseett  command will modify the same variable xx in bb's context:
       the procedure cc does not appear to be on the call stack when dd is  exe-
       cuting.   The command ``iinnffoo lleevveell'' may be used to obtain the level of
       the current procedure.

       UUpplleevveell makes it possible to implement new control  constructs  as  Tcl
       procedures  (for  example, uupplleevveell could be used to implement the wwhhiillee
       construct as a Tcl procedure).

       nnaammeessppaaccee eevvaall is another way (besides procedure calls)  that  the  Tcl
       naming context can change.  It adds a call frame to the stack to repre-
       sent the namespace context.  This means  each  nnaammeessppaaccee  eevvaall  command
       counts as another call level for uupplleevveell and uuppvvaarr commands.  For exam-
       ple, iinnffoo lleevveell 11 will return a  list  describing  a  command  that  is
       either  the  outermost  procedure  call or the outermost nnaammeessppaaccee eevvaall
       command.  Also, uupplleevveell ##00 evaluates a script at top-level in the  out-
       ermost namespace (the global namespace).


SEE ALSO
       namespace(n), upvar(n)


KKEEYYWWOORRDDSS
       context, level, namespace, stack frame, variables



Tcl                                                                 uplevel(n)