Tcl_UpVar(3) Tcl Library Procedures Tcl_UpVar(3)

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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.
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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(3)