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Tcl_Exit(3)			      Tcl Library Procedures			      Tcl_Exit(3)

_________________________________________________________________________________________________

NAME
       Tcl_Exit,   Tcl_Finalize,  Tcl_CreateExitHandler,  Tcl_DeleteExitHandler,  Tcl_ExitThread,
       Tcl_FinalizeThread, Tcl_CreateThreadExitHandler, Tcl_DeleteThreadExitHandler, Tcl_SetExit-
       Proc - end the application or thread (and invoke exit handlers)

SYNOPSIS
       #include <tcl.h>

       Tcl_Exit(status)

       Tcl_Finalize()

       Tcl_CreateExitHandler(proc, clientData)

       Tcl_DeleteExitHandler(proc, clientData)

       Tcl_ExitThread(status)

       Tcl_FinalizeThread()

       Tcl_CreateThreadExitHandler(proc, clientData)

       Tcl_DeleteThreadExitHandler(proc, clientData)

       Tcl_ExitProc *										  |
       Tcl_SetExitProc(proc)									  |

ARGUMENTS
       int status (in)			     Provides  information  about  why the application or
					     thread exited.  Exact meaning may	be  platform-spe-
					     cific.   0  usually means a normal exit, any nonzero
					     value usually means that an error occurred.

       Tcl_ExitProc *proc (in)		     Procedure to invoke before exiting  application,  or
					     (for  Tcl_SetExitProc) NULL to uninstall the current
					     application exit procedure.

       ClientData clientData (in)	     Arbitrary one-word value to pass to proc.
_________________________________________________________________

DESCRIPTION
       The procedures described here provide a graceful mechanism to end the execution of  a  Tcl
       application.  Exit  handlers  are invoked to cleanup the application's state before ending
       the execution of Tcl code.

       Invoke Tcl_Exit to end a Tcl application and to exit from this process. This procedure  is
       invoked	by  the  exit command, and can be invoked anyplace else to terminate the applica-
       tion.  No-one should ever invoke  the  exit  system  procedure  directly;   always  invoke
       Tcl_Exit  instead,  so  that it can invoke exit handlers.  Note that if other code invokes
       exit system procedure directly, or otherwise causes the application to  terminate  without
       calling Tcl_Exit, the exit handlers will not be run.  Tcl_Exit internally invokes the exit
       system call, thus it never returns control to its caller.  If an application exit  handler |
       has  been  installed  (see Tcl_SetExitProc), that handler is invoked with an argument con- |
       sisting of the exit status (cast to ClientData); the application exit handler  should  not |
       return control to Tcl.

       Tcl_Finalize is similar to Tcl_Exit except that it does not exit from the current process.
       It is useful for cleaning up when a process is finished using Tcl but wishes  to  continue
       executing,  and	when  Tcl  is  used in a dynamically loaded extension that is about to be
       unloaded.  On some systems Tcl is automatically notified when it is being unloaded, and it
       calls Tcl_Finalize internally; on these systems it not necessary for the caller to explic-
       itly call Tcl_Finalize.	However, to ensure portability, your code  should  always  invoke
       Tcl_Finalize  when  Tcl	is being unloaded, to ensure that the code will work on all plat-
       forms. Tcl_Finalize can be safely called more than once.

       Tcl_ExitThread is used to terminate the current thread and  invoke  per-thread  exit  han-
       dlers.	This  finalization  is done by Tcl_FinalizeThread, which you can call if you just
       want to clean up per-thread state and invoke the thread exit handlers.  Tcl_Finalize calls
       Tcl_FinalizeThread for the current thread automatically.

       Tcl_CreateExitHandler  arranges	for  proc  to  be  invoked  by Tcl_Finalize and Tcl_Exit.
       Tcl_CreateThreadExitHandler arranges for proc to  be  invoked  by  Tcl_FinalizeThread  and
       Tcl_ExitThread.	 This provides a hook for cleanup operations such as flushing buffers and
       freeing global memory.  Proc should match the type Tcl_ExitProc:
	      typedef void Tcl_ExitProc(ClientData clientData);
       The clientData parameter to proc is a copy of the clientData argument given to Tcl_Create-
       ExitHandler  or	Tcl_CreateThreadExitHandler  when  the	callback was created.  Typically,
       clientData points to a data structure containing  application-specific  information  about
       what to do in proc.

       Tcl_DeleteExitHandler  and  Tcl_DeleteThreadExitHandler	may  be called to delete a previ-
       ously-created exit handler.  It removes the handler indicated by proc  and  clientData  so
       that  no  call to proc will be made.  If no such handler exists then Tcl_DeleteExitHandler
       or Tcl_DeleteThreadExitHandler does nothing.

       Tcl_Finalize and Tcl_Exit execute all registered exit handlers, in reverse order from  the
       order  in  which they were registered.  This matches the natural order in which extensions
       are loaded and unloaded; if extension A loads extension B, it usually unloads B before  it
       itself  is  unloaded.  If extension A registers its exit handlers before loading extension
       B, this ensures that any exit handlers for B will be executed before the exit handlers for
       A.

       Tcl_Finalize  and  Tcl_Exit call Tcl_FinalizeThread and the thread exit handlers after the
       process-wide exit handlers.  This is because thread finalization shuts down the I/O  chan-
       nel  system,  so  any attempt at I/O by the global exit handlers will vanish into the bit-
       bucket.

       Tcl_SetExitProc installs an application exit handler, returning	the  previously-installed |
       application  exit handler or NULL if no application handler was installed.  If an applica- |
       tion exit handler is installed, that exit handler takes over complete  responsibility  for |
       finalization  of  Tcl's	subsystems via Tcl_Finalize at an appropriate time.  The argument |
       passed to proc when it is invoked will be the exit status code  (as  passed  to	Tcl_Exit) |
       cast to a ClientData value.

KEYWORDS
       callback, cleanup, dynamic loading, end application, exit, unloading, thread

Tcl					       8.5				      Tcl_Exit(3)
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