tcl_appinit(3)
NAME
Tcl_AppInit - perform application-specific initialization
SYNOPSIS
#include <tcl.h> int Tcl_AppInit(interp)
ARGUMENTS
- Tcl_Interp *interp (in) Interpreter for the
- application.
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 pro
vided by Tcl, then link your new Tcl_AppInit with the Tcl
library.
Tcl_AppInit is invoked after 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 pro
cedure 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 applica
- tion.
- 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, inter
preter