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Tcl_UpVar(3)         Tcl Library Procedures                   7.4



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)


Tcl_Interp *interp (in) Interpreter containing variables; also used for error report- ing. char *frameName (in) Identifies the stack frame containing source vari- able. May have any of the forms accepted by the upvar com- mand, such as #0 or 1. char *sourceName (in) Name of source variable, in the frame given by frameName. May refer to a scalar vari- able or to an array variable with a parenthesized index. char *destName (in) Name of desti- nation vari- able, which is to be linked to source Tcl 1 Tcl_UpVar(3) Tcl Library Procedures 7.4 variable so that refer- ences to dest- Name refer to the other variable. Must not currently exist except as an upvar-ed variable. int flags (in) Either TCL_GLOBAL_ONLY or 0; if non-zero, then destName is a global vari- able; other- wise it is a local to the current pro- cedure (or global if no procedure is active). char *name1 (in) First part of source variable's name (scalar name, or name of array without array index). 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 Tcl 2 Tcl_UpVar(3) Tcl Library Procedures 7.4 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 interp->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 3 Prepared by Ready-to-Run Software, Inc.


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