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markom |
'\"
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'\" Copyright (c) 1994 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: UpVar.3,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $
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'\"
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.so man.macros
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.TH Tcl_UpVar 3 7.4 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_UpVar, Tcl_UpVar2 \- link one variable to another
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.SH SYNOPSIS
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.nf
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\fB#include \fR
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.sp
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int
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\fBTcl_UpVar(\fIinterp, frameName, sourceName, destName, flags\fB)\fR
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.sp
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int
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\fBTcl_UpVar2(\fIinterp, frameName, name1, name2, destName, flags\fB)\fR
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.SH ARGUMENTS
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.AS Tcl_VarTraceProc prevClientData
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.AP Tcl_Interp *interp in
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Interpreter containing variables; also used for error reporting.
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.AP char *frameName in
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Identifies the stack frame containing source variable.
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May have any of the forms accepted by
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the \fBupvar\fR command, such as \fB#0\fR or \fB1\fR.
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.AP char *sourceName in
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Name of source variable, in the frame given by \fIframeName\fR.
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May refer to a scalar variable or to an array variable with a
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parenthesized index.
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.AP char *destName in
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Name of destination variable, which is to be linked to source
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variable so that references to \fIdestName\fR
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refer to the other variable. Must not currently exist except as
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an upvar-ed variable.
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.AP int flags in
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Either TCL_GLOBAL_ONLY or 0; if non-zero, then \fIdestName\fR is
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a global variable; otherwise it is a local to the current procedure
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(or global if no procedure is active).
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.AP char *name1 in
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First part of source variable's name (scalar name, or name of array
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without array index).
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.AP char *name2 in
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If source variable is an element of an array, gives the index of the element.
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For scalar source variables, is NULL.
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.BE
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.SH DESCRIPTION
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.PP
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\fBTcl_UpVar\fR and \fBTcl_UpVar2\fR provide the same functionality
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as the \fBupvar\fR command: they make a link from a source variable
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to a destination variable, so that references to the destination are
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passed transparently through to the source.
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The name of the source variable may be specified either as a single
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string such as \fBxyx\fR or \fBa(24)\fR (by calling \fBTcl_UpVar\fR)
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or in two parts where the array name has been separated from the
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element name (by calling \fBTcl_UpVar2\fR).
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The destination variable name is specified in a single string; it
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may not be an array element.
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.PP
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Both procedures return either TCL_OK or TCL_ERROR, and they
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leave an error message in \fIinterp->result\fR if an error
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occurs.
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.PP
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As with the \fBupvar\fR command, the source variable need not exist;
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if it does exist, unsetting it later does not destroy the link. The
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destination variable may exist at the time of the call, but if so
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it must exist as a linked variable.
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.SH KEYWORDS
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linked variable, upvar, variable
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