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'\"
'\" Copyright (c) 1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\" Copyright (c) 2000 Ajuba Solutions.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: @(#) $Id: Tcl_Main.3,v 1.5 2001/12/10 15:50:47 dgp Exp $
'\"
.so man.macros
.TH Tcl_Main 3 8.4 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_Main, Tcl_SetMainLoop \- main program and event loop definition for Tcl-based applications
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
\fBTcl_Main\fR(\fIargc, argv, appInitProc\fR)
.sp
\fBTcl_SetMainLoop\fR(\fImainLoopProc\fR)
.SH ARGUMENTS
.AS Tcl_AppInitProc *appInitProc
.AP int argc in
Number of elements in \fIargv\fR.
.AP char *argv[] in
Array of strings containing command-line arguments.
.AP Tcl_AppInitProc *appInitProc in
Address of an application-specific initialization procedure.
The value for this argument is usually \fBTcl_AppInit\fR.
.AP Tcl_MainLoopProc *mainLoopProc in
Address of an application-specific event loop procedure.
.BE
.SH DESCRIPTION
.PP
\fBTcl_Main\fR acts as the main program for most Tcl-based applications.
Starting with Tcl 7.4 it is not called \fBmain\fR anymore because it
is part of the Tcl library and having a function \fBmain\fR
in a library (particularly a shared library) causes problems on many
systems.
Having \fBmain\fR in the Tcl library would also make it hard to use
Tcl in C++ programs, since C++ programs must have special C++
\fBmain\fR functions.
.PP
Normally each application contains a small \fBmain\fR function that does
nothing but invoke \fBTcl_Main\fR.
\fBTcl_Main\fR then does all the work of creating and running a
\fBtclsh\fR-like application.
.PP
When it is has finished its own initialization, but before
it processes commands, \fBTcl_Main\fR calls the procedure given by
the \fIappInitProc\fR argument. This procedure provides a ``hook''
for the application to perform its own initialization, such as defining
application-specific commands. The procedure must have an interface
that matches the type \fBTcl_AppInitProc\fR:
.CS
typedef int Tcl_AppInitProc(Tcl_Interp *\fIinterp\fR);
.CE
\fIAppInitProc\fR is almost always a pointer to \fBTcl_AppInit\fR; for more
details on this procedure, see the documentation for \fBTcl_AppInit\fR.
When the \fIappInitProc\fR is finished, the startup script will be
evaluated. If none exists, then an interactive prompt is provided.
.PP
.VS 8.4
\fBTcl_SetMainLoop\fR allows setting an event loop procedure to be run.
This allows, for example, Tk to be dynamically loaded and set its event
loop. The event loop will run following the startup script. If you
are in interactive mode, setting the main loop procedure will cause the
prompt to become fileevent based and then the loop procedure is called.
The main loop procedure must have an interface that matches the type
\fBTcl_MainLoopProc\fR:
.CS
typedef void Tcl_MainLoopProc(void);
.CE
.VE 8.4
.PP
\fBTcl_Main\fR and therefore all applications based upon it, like
\fBtclsh\fR, use \fBTcl_GetStdChannel\fR to initialize the standard
channels to their default values. See \fBTcl_StandardChannels\fR for
more information.
.SH "SEE ALSO"
Tcl_GetStdChannel(3)
.SH KEYWORDS
application-specific initialization, command-line arguments, main program
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