winapi - Waiting for grandchild processes in windows

Question

Is it possible to wait for all processes launched by a child process in Windows? I can't modify the child or grandchild processes.

Specifically, here's what I want to do. My process launches uninstallA.exe. The process uninistallA.exe launches uninstallB.exe and immediately exits, and uninstallB.exe runs for a while. I'd like to wait for uninstallB.exe to exit so that I can know when the uninstall is finished.

Answer 1

Create a Job Object with CreateJobObject. Use CreateProcess to start UninstallA.exe in a suspended state. Assign that new process to your job object with AssignProcessToJobObject. Start UninstallA.exe running by calling ResumeThread on the handle of the thread you got back from CreateProcess.

Then the hard part: wait for the job object to complete its execution. Unfortunately, this is quite a bit more complex than anybody would reasonably hope for. The basic idea is that you create an I/O completion port, then you create the object object, associate it with the I/O completion port, and finally wait on the I/O completion port (getting its status with GetQueuedCompletionStatus). Raymond Chen has a demonstration (and explanation of how this came about) on his blog.