Tcl_UpVar(3) Tcl Library Procedures Tcl_UpVar(3)______________________________________________________________________________NAME
Tcl_UpVar, Tcl_UpVar2 - link one variable to another
SYNOPSIS
#include <tcl.h>
int
Tcl_UpVar(interp, frameName, sourceName, destName, flags)
int
Tcl_UpVar2(interp, frameName, name1, name2, destName, flags)
ARGUMENTS
Tcl_Interp *interp (in) Interpreter containing
variables; also used for
error reporting.
char *frameName (in) Identifies the stack
frame containing source
variable. May have any
of the forms accepted by
the upvar command, such
as #0 or 1.
char *sourceName (in) Name of source variable,
in the frame given by
frameName. May refer to
a scalar variable or to
an array variable with a
parenthesized index.
char *destName (in) Name of destination vari‐
able, which is to be
linked to source variable
so that references to
destName refer to the
other variable. Must not
currently exist except as
an upvar-ed variable.
int flags (in) Either TCL_GLOBAL_ONLY or
0; if non-zero, then
destName is a global
variable; otherwise it
is a local to the current
procedure (or global if
no procedure is active).
char *name1 (in) First part of source
variable's name (scalar
name, or name of array
without array index).
char *name2 (in) If source variable is an
element of an array,
gives the index of the
element. For scalar
source variables, is
NULL.
_________________________________________________________________DESCRIPTIONTcl_UpVar and Tcl_UpVar2 provide the same functionality as the upvar
command: they make a link from a source variable to a destination
variable, so that references to the destination are passed transpar‐
ently through to the source. The name of the source variable may be
specified either as a single string such as xyx or a(24) (by calling
Tcl_UpVar) or in two parts where the array name has been separated from
the element name (by calling Tcl_UpVar2). The destination variable
name is specified in a single string; it may not be an array element.
Both procedures return either TCL_OK or TCL_ERROR, and they leave an
error message in interp->result if an error occurs.
As with the upvar command, the source variable need not exist; if it
does exist, unsetting it later does not destroy the link. The destina‐
tion variable may exist at the time of the call, but if so it must
exist as a linked variable.
KEYWORDS
linked variable, upvar, variable
Tcl 7.4 Tcl_UpVar(3)