c++ Windows - How to get process PID from its path

Question

Similar to C++ Windows - How to get process path from its PID but the reverse: How can I get a pid from a given path?

I am trying to write an update tool, and I want to see if the exe is in use. Then if it is in use, I want to wait for the process to exit. Therefore, I want to get the process PID belonging to the file.

You have to search all live processes and see which one is running from the path you have, if any. — Some programmer dude, May 22 '14 at 18:55
Can't you just try to exclusively open the EXE file for reading once a second? When it succeeds, you're good to go. — Erik, May 22 '14 at 19:24

score 2 · Accepted Answer · answered May 22 '14 at 20:56

Here is a quick and simple way to do what you are looking for. By using the QueryFullProcessImageName, you can do a quick check.

Things that can cause the following code not to work as desired:

If you do not have permissions to view a process, you will not be able to see the information.
If the process is 64bit and you are running your application as 32 bit, you will see the process ID, but you can not open a process handle to it.

Example:

BOOL GetProcessName(LPTSTR szFilename, DWORD dwSize, DWORD dwProcID)
{
    BOOLEAN retVal = FALSE;
    HANDLE hProcess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, FALSE, dwProcID);
    DWORD dwPathSize = dwSize;
    if (hProcess == 0)
        return retVal; // You should check for error code, if you are concerned about this
    retVal = QueryFullProcessImageName(hProcess, 0, szFilename, &dwPathSize);

    CloseHandle(hProcess);

    return retVal;
}

BOOL IsProcessInUse(LPCTSTR process_name)
{
    DWORD* pProcs = NULL;
    DWORD dwSize = 0;
    DWORD dwRealSize = 0;
    TCHAR szCompareName[MAX_PATH + 1];
    int nCount = 0;
    int nResult = 0;

    dwSize = 1024;
    pProcs = new DWORD[dwSize];
    EnumProcesses(pProcs, dwSize*sizeof(DWORD), &dwRealSize);
    dwSize = dwRealSize / sizeof(DWORD);

    for (DWORD nCount = 0; nCount < dwSize; nCount++)
    {
        ZeroMemory(szCompareName, MAX_PATH + 1 * (sizeof(TCHAR)));
        if (GetProcessName(szCompareName, MAX_PATH, pProcs[nCount]))
        {
            if (_tcscmp(process_name, szCompareName) == 0)
            {
                delete[] pProcs;
                return true;
            }
        }
    }
    delete[] pProcs;
    return FALSE;
}

You would then use something simple like the following to test it:

if (IsProcessInUse(your_file))
    AfxMessageBox(_T("The process is still running"));
else
    AfxMessageBox(_T("The process has been closed"));

The above answers your indirect question. To answer your literal question, you would change the IsProcessInUse as follows:

DWORD GetNamedProcessID(LPCTSTR process_name)
{
    DWORD* pProcs = NULL;
    DWORD retVal = 0;
    DWORD dwSize = 0;
    DWORD dwRealSize = 0;
    TCHAR szCompareName[MAX_PATH + 1];
    int nCount = 0;
    int nResult = 0;

    dwSize = 1024;
    pProcs = new DWORD[dwSize];
    EnumProcesses(pProcs, dwSize*sizeof(DWORD), &dwRealSize);
    dwSize = dwRealSize / sizeof(DWORD);

    for (DWORD nCount = 0; nCount < dwSize; nCount++)
    {
        ZeroMemory(szCompareName, MAX_PATH + 1 * (sizeof(TCHAR)));
        if (GetProcessName(szCompareName, MAX_PATH, pProcs[nCount]))
        {
            if (_tcscmp(process_name, szCompareName) == 0)
            {
                retVal = pProcs[nCount];
                delete[] pProcs;
                return retVal;
            }
        }
    }
    delete[] pProcs;
    return 0;
}

One last important thing to note is the fact that this will only return a single instance (or PID) for a file, and this does not look for Modules that are used by process (so any DLL in use by process will not be identified, however, from the link you provided, you can see ways of utilizing that to get that level of functionality.

c++ Windows - How to get process PID from its path

1 Answers1