Tcl_AppInit - perform application-specific initialization
#include <tcl.h>
int
Tcl_AppInit(interp)
- Tcl_Interp *interp (in)
- Interpreter for the application.
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.
Tcl_Main(3tcl)
application, argument, command, initialization, interpreter