'\" '\" Copyright (c) 1995-1996 Sun Microsystems, Inc. '\" '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" '\" RCS: @(#) Exit.3,v 1.5 2003/01/21 19:39:58 hunt Exp '\" .so man.macros .TH Tcl_Exit 3 8.1 Tcl "Tcl Library Procedures" .BS .SH NAME Tcl_Exit, Tcl_Finalize, Tcl_CreateExitHandler, Tcl_DeleteExitHandler, Tcl_ExitThread, Tcl_FinalizeThread, Tcl_CreateThreadExitHandler, Tcl_DeleteThreadExitHandler \- end the application or thread (and invoke exit handlers) .SH SYNOPSIS .nf \fB#include <tcl.h>\fR .sp \fBTcl_Exit\fR(\fIstatus\fR) .sp \fBTcl_Finalize\fR() .sp \fBTcl_CreateExitHandler\fR(\fIproc, clientData\fR) .sp \fBTcl_DeleteExitHandler\fR(\fIproc, clientData\fR) .sp \fBTcl_ExitThread\fR(\fIstatus\fR) .sp \fBTcl_FinalizeThread\fR() .sp \fBTcl_CreateThreadExitHandler\fR(\fIproc, clientData\fR) .sp \fBTcl_DeleteThreadExitHandler\fR(\fIproc, clientData\fR) .SH ARGUMENTS .AS Tcl_ExitProc clientData .AP 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. .AP Tcl_ExitProc *proc in Procedure to invoke before exiting application. .AP ClientData clientData in Arbitrary one-word value to pass to \fIproc\fR. .BE .SH DESCRIPTION .PP The procedures described here provide a graceful mechanism to end the execution of a \fBTcl\fR application. Exit handlers are invoked to cleanup the application's state before ending the execution of \fBTcl\fR code. .PP Invoke \fBTcl_Exit\fR to end a \fBTcl\fR application and to exit from this process. This procedure is invoked by the \fBexit\fR command, and can be invoked anyplace else to terminate the application. No-one should ever invoke the \fBexit\fR system procedure directly; always invoke \fBTcl_Exit\fR instead, so that it can invoke exit handlers. Note that if other code invokes \fBexit\fR system procedure directly, or otherwise causes the application to terminate without calling \fBTcl_Exit\fR, the exit handlers will not be run. \fBTcl_Exit\fR internally invokes the \fBexit\fR system call, thus it never returns control to its caller. .PP \fBTcl_Finalize\fR is similar to \fBTcl_Exit\fR except that it does not exit from the current process. It is useful for cleaning up when a process is finished using \fBTcl\fR but wishes to continue executing, and when \fBTcl\fR is used in a dynamically loaded extension that is about to be unloaded. On some systems \fBTcl\fR is automatically notified when it is being unloaded, and it calls \fBTcl_Finalize\fR internally; on these systems it not necessary for the caller to explicitly call \fBTcl_Finalize\fR. However, to ensure portability, your code should always invoke \fBTcl_Finalize\fR when \fBTcl\fR is being unloaded, to ensure that the code will work on all platforms. \fBTcl_Finalize\fR can be safely called more than once. .PP .VS \fBTcl_ExitThread\fR is used to terminate the current thread and invoke per-thread exit handlers. This finalization is done by \fBTcl_FinalizeThread\fR, which you can call if you just want to clean up per-thread state and invoke the thread exit handlers. \fBTcl_Finalize\fR calls \fBTcl_FinalizeThread\fR for the current thread automatically. .VE .PP \fBTcl_CreateExitHandler\fR arranges for \fIproc\fR to be invoked by \fBTcl_Finalize\fR and \fBTcl_Exit\fR. \fBTcl_CreateThreadExitHandler\fR arranges for \fIproc\fR to be invoked by \fBTcl_FinalizeThread\fR and \fBTcl_ExitThread\fR. This provides a hook for cleanup operations such as flushing buffers and freeing global memory. \fIProc\fR should match the type \fBTcl_ExitProc\fR: .CS typedef void Tcl_ExitProc(ClientData \fIclientData\fR); .CE The \fIclientData\fR parameter to \fIproc\fR is a copy of the \fIclientData\fR argument given to \fBTcl_CreateExitHandler\fR or \fBTcl_CreateThreadExitHandler\fR when the callback was created. Typically, \fIclientData\fR points to a data structure containing application-specific information about what to do in \fIproc\fR. .PP \fBTcl_DeleteExitHandler\fR and \fBTcl_DeleteThreadExitHandler\fR may be called to delete a previously-created exit handler. It removes the handler indicated by \fIproc\fR and \fIclientData\fR so that no call to \fIproc\fR will be made. If no such handler exists then \fBTcl_DeleteExitHandler\fR or \fBTcl_DeleteThreadExitHandler\fR does nothing. .PP .VS .PP \fBTcl_Finalize\fR and \fBTcl_Exit\fR 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 \fBA\fR loads extension \fBB\fR, it usually unloads \fBB\fR before it itself is unloaded. If extension \fBA\fR registers its exit handlers before loading extension \fBB\fR, this ensures that any exit handlers for \fBB\fR will be executed before the exit handlers for \fBA\fR. .VE .VS .PP \fBTcl_Finalize\fR and \fBTcl_Exit\fR call \fBTcl_FinalizeThread\fR and the thread exit handlers \fIafter\fR 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. .VE .SH KEYWORDS callback, cleanup, dynamic loading, end application, exit, unloading, thread