How to catch quit message from another process? - c++

Question

I want to "listen" some other application and decide what to do when it has been terminated.
How?
Edit: The two programs are run on same computer, and i want to know when i close the other program. And then do action in the other program. I cant modify the other program code. I may or may not start the app B from app A. I could identify the app B by its full path to the exe.

Answer 1

As Abyx wrote, WaitForSingleObject (or possibly WaitForMulipleObjects) is the API function you need.
Create an event
Start a (worker) thread
Pass the event handle to the thread -> HANDLE1
Get handle for the process to be watched. See How can I get a process handle by its name in C++? -> HANDLE2
In your thread function call WaitForMulipleObjects and wait for the two handles.
If HANDLE2 fires, do whatever action you want... and possibly terminate the thread.
If HANDLE1 fires, leave the thread. This is for a graceful termination of your application: Before exiting the main (GUI) thread you set the event.

Answer 2

WaitForSingleObject(hProcess, INFINITE);

Answer 3

If you start yourself, the process which termination you want wait for, for example with respect of the CreateProcess, the waiting for the process end is very simple
WaitForSingleObject(pi.hProcess, INFINITE);
If the process, which termination you want wait for, is started before you should find the process id dwProcessId of the process and then do following
HANDLE hProcess = OpenProcess (SYNCHRONIZE, FALSE, dwProcessId);
WaitForSingleObject(hProcess, INFINITE);
The searching of the process id can be implemented in different ways depend on which information you know about the process and the knowledge how many instances of the process can be running simultaneously.
For example if you know the filename of the process which is currently running you can use EnumProcesses, OpenProcess and GetProcessImageFileName. Here is the corresponding code in a simplified form:
#include <Windows.h>
#include <stdio.h>
#include <tchar.h>
#include <Psapi.h>
#include <shlwapi.h>
#pragma comment (lib, "Psapi.lib")
#pragma comment (lib, "shlwapi.lib")
int _tmain (int argc, LPCTSTR argv[])
{
DWORD arProcessIds[1024], cbNeeded, i, dwStatus;
HANDLE hProcess = NULL;
LPCTSTR pszProcessName = NULL;
if (argc != 2) {
_tprintf (TEXT("USAGE:\n")
TEXT(" \"%s\" ExeName\n\n")
TEXT("Examples:\n")
TEXT(" \"%s\" TaskMgr.exe\n"),
argv[0], argv[0]);
return 1; // error
}
pszProcessName = argv[1];
if (!EnumProcesses (arProcessIds, sizeof(arProcessIds), &cbNeeded)) {
// here shold be allocated array dynamically
return 1; // error
}
for (i = 0; i < cbNeeded/sizeof(DWORD); i++ ) {
if (arProcessIds[i] != 0) {
TCHAR szFileName[MAX_PATH];
hProcess = OpenProcess (PROCESS_QUERY_INFORMATION | SYNCHRONIZE, FALSE, arProcessIds[i]);
if (hProcess != NULL) {
dwStatus = GetProcessImageFileName (hProcess, szFileName, sizeof(szFileName)/sizeof(TCHAR));
if (dwStatus > 0 ) {
LPCTSTR pszFileName = PathFindFileName (szFileName);
//_tprintf(TEXT("Process: %s\n"),szFileName);
if (StrCmpI(pszFileName, pszProcessName) == 0) {
break;
}
}
CloseHandle (hProcess);
hProcess = NULL;
}
}
}
//hProcess = OpenProcess (SYNCHRONIZE, FALSE, dwProcessId);
if (hProcess == NULL) {
_tprintf(TEXT("The process \"%s\" is not found.\n"), pszProcessName);
return 1;
}
_tprintf(TEXT("Start waiting for the end of the process %s\n"), pszProcessName);
WaitForSingleObject(hProcess, INFINITE);
_tprintf(TEXT("The process is terminated"));
CloseHandle (hProcess);
return 0;
}

Answer 4

you can just get the process list from OS in intervals you want and take appropriate action