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Tcl_AppInit

Section: Tcl Library Procedures (3)
Updated: 7.0
Index

NAME

Tcl_AppInit - perform application-specific initialization

SYNOPSIS

#include <tcl.h>intTcl_AppInit(interp)

ARGUMENTS

Tcl_Interp *interp (in)
Interpreter for the application.

DESCRIPTION

Tcl_AppInit is a ``hook'' procedure that is invoked bythe main programs for Tcl applications such as tclsh and wish.Its purpose is to allow new Tcl applications to be created withoutmodifying the main programs provided as part of Tcl and Tk.To create a new application you write a new version ofTcl_AppInit to replace the default version provided by Tcl,then link your new Tcl_AppInit with the Tcl library.

Tcl_AppInit is invoked after by Tcl_Main and Tk_Mainafter their own initialization and before entering the main loopto process commands.Here are some examples of things that Tcl_AppInit might do:

[1]: Call initialization procedures for various packages used bythe application.Each initialization procedure adds new commands to interpfor its package and performs other package-specific initialization.
[2]: Process command-line arguments, which can be accessed from theTcl variables argv and argv0 in interp.
[3]: Invoke a startup script to initialize the application.

Tcl_AppInit returns TCL_OK or TCL_ERROR.If it returns TCL_ERROR then it must leave an error message ininterp->result; otherwise the result is ignored.

In addition to Tcl_AppInit, your application should also containa procedure main that calls Tcl_Main as follows:

Tcl_Main(argc, argv, Tcl_AppInit);

The third argument to Tcl_Main gives the address of theapplication-specific initialization procedure to invoke.This means that you don't have to use the name Tcl_AppInitfor the procedure, but in practice the name is nearly alwaysTcl_AppInit (in versions before Tcl 7.4 the name Tcl_AppInitwas implicit; there was no way to specify the procedure explicitly).The best way to get started is to make a copy of the filetclAppInit.c from the Tcl library or source directory.It already contains a main procedure and a template forTcl_AppInit that you can modify for your application.

KEYWORDS

application, argument, command, initialization, interpreter

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