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(3tcl)

KEYWORDS

       application, argument, command, initialization, interpreter