Tcl_UpVar(3)

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.

     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  vari-
                                          able,   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 refer-
                                          ences 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   pro-
                                          cedure    (or   current

Tcl                     Last change: 7.4                        1

Tcl_UpVar(3)         Tcl Library Procedures          Tcl_UpVar(3)

                                          namespace  if  no  pro-
                                          cedure 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  desti-
     nation  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                     Last change: 7.4                        2