Tcl_AppInit(3) Tcl Library Procedures Tcl_AppInit(3)

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NAME

Tcl_AppInit - perform application-specific initialization

SYNOPSIS

#include <tcl.h>

int
Tcl_AppInit(interp)

ARGUMENTS

Tcl_Interp *interp (in) Interpreter for the application.
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DESCRIPTION

Tcl_AppInit is a "hook" procedure that is invoked by the main
programs for Tcl applications such as tclsh and wish. Its purpose is
to allow new Tcl applications to be created without modifying the
main programs provided as part of Tcl and Tk. To create a new
application you write a new version of Tcl_AppInit to replace the
default version provided by Tcl, then link your new Tcl_AppInit with
the Tcl library.

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

[1] Call initialization procedures for various packages used by
the application. Each initialization procedure adds new
commands to interp for its package and performs other package-
specific initialization.

[2] Process command-line arguments, which can be accessed from the
Tcl variables argv and argv0 in interp.

[3] Invoke a startup script to initialize the application.

[4] Use the routines Tcl_SetStartupScript and Tcl_GetStartupScript
to set or query the file and encoding that the active Tcl_Main
or Tk_Main routine will use as a startup script.

Tcl_AppInit returns TCL_OK or TCL_ERROR. If it returns TCL_ERROR
then it must leave an error message in for the interpreter's result;
otherwise the result is ignored.

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

Tcl_Main(argc, argv, Tcl_AppInit);

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

SEE ALSO

Tcl_Main(3)

KEYWORDS

application, argument, command, initialization, interpreter

Tcl 7.0 Tcl_AppInit(3)