Tcl_UpVar manual page - Tcl Library Procedures

Tcl Documentation > Tcl C API > UpVar

Tcl Applications | Tcl Commands | Tcl C API

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

DESCRIPTION

KEYWORDS

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.

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