Documentation generated from fossil trunk
Tcl_UpVar, Tcl_UpVar2 -
link one variable to another
#include <tcl.h> int Tcl_UpVar(interp, frameName, sourceName, destName, flags) int Tcl_UpVar2(interp, frameName, name1, name2, destName, flags)
| Type | Name | Mode |
|---|---|---|
| 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.