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.

       const 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.

       const 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.

       const char *destName (in)            Name of destination variable,  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)                       One  of TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY or 0;  if non-zero, then
                                            destName is a global or namespace variable;  otherwise it  is  local
                                            to  the  current  procedure (or current namespace if no procedure is
                                            active).

       const char *name1 (in)               First part of source variable's name (scalar name, or name of  array
                                            without array index).

       const char *name2 (in)               If source variable is an element of an array, gives the index of the
                                            element.  For scalar source variables, is NULL.
________________________________________________________________________________________________________________

DESCRIPTION

       Tcl_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 transparently
       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  the  interpreter's
       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 destination 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(3tcl)