ps_exists_win32.py

import ctypes

import win32event, winerror

            
class ExitCodeProcess(ctypes.Structure):
    _fields_ = [
        ('hProcess', ctypes.c_void_p),  # HANDLE
        ('lpExitCode', ctypes.POINTER(ctypes.c_ulong))  # LPDWORD
    ]


def pid_exists(pid):
    """Check whether a process with the given pid exists. Works on Windows only. 
    Works even if the process is not owned by the current user."""
    kernel32 = ctypes.windll.kernel32

    process = kernel32.OpenProcess(win32event.SYNCHRONIZE, 0, pid)
    if not process:
        if kernel32.GetLastError() == winerror.ERROR_ACCESS_DENIED:
            # Access is denied. This means the process exists!
            return True
        return False

    ec = ExitCodeProcess()
    out = kernel32.GetExitCodeProcess(process, ctypes.byref(ec))
    if not out:
        if kernel32.GetLastError() == winerror.ERROR_ACCESS_DENIED:
            # Access is denied. This means the process exists!
            kernel32.CloseHandle(process)
            return True
        kernel32.CloseHandle(process)
        return False
    elif bool(ec.lpExitCode):
        # There is an exit code, it quit
        kernel32.CloseHandle(process)
        return False
    # No exit code, it's running.
    kernel32.CloseHandle(process)
    return True
   
print(pid_exists(14444))

@ociule
the code does not always, if a process is launched by subprocess with detached mode, or shell=True, and then killing the process using task manager, will still show pid exists and returns true.

The below is the code i used to invoke pid_exits()

def check_parent_alive(proc_path=""):
    global pid_to_monitor
    while 1:
        process = pid_exists(pid_to_monitor)
        if process:
            print("[++] Process exists")
        else:
            print("Looks like process killed ... ", pid_to_monitor)
            proc = subprocess.Popen(['python', "example.py"],  # shell=True, start_new_session=True)
                                    creationflags=0x0000000)

            pid_to_monitor = proc.pid
        sleep(2)

which peridically checks if pid_to_monitor exits, if it does not then it launches example.py using subprocess, but then if the launched process is killed, it still detects process is running.

Sounds like a bug somewhere. I do not do much work nowadays with the win32 API so I'm not able to debug it, sorry. Hope you find a good solution to your issue.