trusty (3) Tcl_AppInit.3tcl.gz

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.

       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 don't 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.

KEYWORDS

       application, argument, command, initialization, interpreter