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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_Final-izeThread, Tcl_FinalizeThread,
       izeThread, Tcl_CreateThreadExitHandler, Tcl_DeleteThreadExitHandler, Tcl_SetExitProc - end the appli-cation application
       cation 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-specific.   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 application.  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 applica- |
       tion exit handler has been installed (see Tcl_SetExitProc), that handler is invoked with an  argument |
       consisting  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 explicitly call Tcl_Finalize.  However, to  ensure  porta-bility, portability,
       bility,  your  code  should always invoke Tcl_Finalize when Tcl is being unloaded, to ensure that the
       code will work on all platforms. Tcl_Finalize can be safely called more than once.

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

       Tcl_CreateExitHandler  arranges  for  proc  to  be  invoked  by  Tcl_Finalize and Tcl_Exit.  Tcl_Cre-ateThreadExitHandler Tcl_CreateThreadExitHandler
       ateThreadExitHandler 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_CreateExitHandler
       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  previously-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  han-dlers handlers
       dlers 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 channel system, so any attempt
       at I/O by the global exit handlers will vanish into the bitbucket.

       Tcl_SetExitProc  installs an application exit handler, returning the previously-installed application |
       exit handler or NULL if no application handler was installed.  If  an  application  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)