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Generating Console Control Events

Terminating a process can cause problems because the terminated process cannot clean up. SEH does not help because there is no general method for one process to cause an exception in another. [1] Console control events, however, allow one process to send a console control signal, or event, to another process in certain limited circumstances. Program 4-5 illustrated how a process can set up a handler to catch such a signal, and the handler could generate an exception. In that example, the user generated a signal from the user interface.

It is possible, then, for a process to generate a signal event in another specified process or set of processes. Recall the CreateProcess creation flag value, CREATE_NEW_PROCESS_GROUP. If this flag is set, the new process ID identifies a group of processes, and the new process is the root of the group. All new processes created by the parent are in this new group until another CreateProcess call uses the CREATE_NEW_PROCESS_GROUP flag. The grouped processes are similar to UNIX process groups.

One process can generate a CTRL_C_EVENT or CTRL_BREAK_EVENT in a specified process group, identifying the group with the root process ID. The target processes must have the same console as that of the process generating the event. In particular, the calling process cannot be created with its own console (using the CREATE_NEW_CONSOLE or DETACHED_PROCESS flag).

BOOL GenerateConsoleCtrlEvent (
   DWORD dwCtrlEvent,
   DWORD dwProcessGroup)

The first parameter, then, must be one of either CTRL_C_EVENT or CTRL_BREAK_EVENT. The second parameter identifies the process group.

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