Tcl_UpVar(3) Tcl Library Procedures Tcl_UpVar(3)
Tcl_UpVar, Tcl_UpVar2 - link one variable to another
Tcl_UpVar(interp, frameName, sourceName, destName, flags)
Tcl_UpVar2(interp, frameName, name1, name2, destName, flags)
Tcl_Interp *interp (in) Interpreter containing variables; also used for
const char *frameName (in) Identifies the stack frame containing source vari-
able. 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 frame-
Name. 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 pro-
cedure (or current namespace if no procedure is
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 vari-
ables, is NULL.
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 destina-
tion 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.
linked variable, upvar, variable
Tcl 7.4 Tcl_UpVar(3)