Registering a Control Handler Function
This section shows an example of the
SetConsoleCtrlHandler function that is used to install a control handler.
When a CTRL+C signal is received, the control handler returns TRUE, indicating that it has
handled the signal. Doing this prevents other control handlers from being
called.
When a CTRL_CLOSE_EVENT signal is received, the control handler returns TRUE,
causing the system to display a dialog box that gives the user the choice of
terminating the process and closing the console or allowing the process to
continue execution. If the user chooses not to terminate the process, the system
closes the console when the process finally terminates.
When a CTRL+BREAK, CTRL_LOGOFF_EVENT, or CTRL_SHUTDOWN_EVENT signal is received, the control
handler returns FALSE. Doing this causes the signal to be passed to the next
control handler function. If no other control handlers have been registered or none
of the registered handlers returns TRUE, the default handler will be used,
resulting in the process being terminated.
BOOL CtrlHandler(DWORD fdwCtrlType) {
switch (fdwCtrlType) {
/* Handle the CTRL+C signal. */
case CTRL_C_EVENT:
Beep(1000, 1000);
return TRUE;
/* CTRL+CLOSE: confirm that the user wants to exit. */
case CTRL_CLOSE_EVENT:
return TRUE;
/* Pass other signals to the next handler. */
case CTRL_BREAK_EVENT:
case CTRL_LOGOFF_EVENT:
case CTRL_SHUTDOWN_EVENT:
default:
return FALSE;
}
}
VOID main(void) {
BOOL fSuccess;
fSuccess = SetConsoleCtrlHandler(
(PHANDLER_ROUTINE) CtrlHandler, /* handler function */
TRUE); /* add to list */
if (! fSuccess)
MyErrorExit("Could not set control handler");
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