Tcl7.6 C API Man Page -- UpVar (n)
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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 error reporting.
- *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.
- *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.
- *destName (in) Name of destination variable, which is to be linked to source variable so that references to dest_Name refer to the other variable. Must not currently exist except as an upvar-ed variable.
- flags (in) Either TCL_GLOBAL_ONLY or 0; if non-zero, then destName is a global variable; otherwise it is a local to the current procedure (or global if no procedure is active).
- *name1 (in) First part of source variable's name (scalar name, or name of array without array index).
- *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 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
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