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Python Programming On Win32 by Mark Hammond, Andy Robinson

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Ultimate Process Control: The win32process Module

The win32process module provides the ultimate in process level control; it exposes most of the native Windows API for starting, stopping, controlling, and waiting for processes. But before we delve into the win32process module, some definitions are in order.

Handles and IDs

Every thread and process in the system can be identified by a Windows handle, and by an integer ID. A process or thread ID is a unique number allocated for the process or thread and is valid across the entire system. An ID is invariant while the thread or process is running and serves no purpose other than to uniquely identify the thread or process. IDs are reused, so while two threads or processes will never share the same ID while running, the same ID may be reused by the system once it has terminated. Further, IDs are not secure. Any user can obtain the ID for a thread or process. This is not a security problem, as the ID is not sufficient to control the thread or process.

A handle provides additional control capabilities for the thread or handle. Using a handle, you can wait for a process to terminate, force the termination of a process, or change the characteristics of a running process.

While a process can have only a single ID, there may be many handles to it. The handle to a process determines the rights a user has to perform operations on the process or thread.

Given a process ID, the function win32api.OpenProcess() can obtain a handle. The ability to use ...

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