#!/usr/bin/env python """ Wait for a certain PID to terminate and check for PID existance (POSIX). """ # Author: Giampaolo Rodola' # License: MIT import os import time import errno class TimeoutExpired(Exception): pass def pid_exists(pid): """Check whether pid exists in the current process table.""" if pid < 0: return False try: os.kill(pid, 0) except OSError, e: return e.errno == errno.EPERM else: return True def wait_pid(pid, timeout=None): """Wait for process with pid 'pid' to terminate and return its exit status code as an integer. If pid is not a children of os.getpid() (current process) just waits until the process disappears and return None. If pid does not exist at all return None immediately. Raise TimeoutExpired on timeout expired (if specified). """ def check_timeout(delay): if timeout is not None: if time.time() >= stop_at: raise TimeoutExpired time.sleep(delay) return min(delay * 2, 0.04) if timeout is not None: waitcall = lambda: os.waitpid(pid, os.WNOHANG) stop_at = time.time() + timeout else: waitcall = lambda: os.waitpid(pid, 0) delay = 0.0001 while 1: try: retpid, status = waitcall() except OSError, err: if err.errno == errno.EINTR: delay = check_timeout(delay) continue elif err.errno == errno.ECHILD: # This has two meanings: # - pid is not a child of os.getpid() in which case # we keep polling until it's gone # - pid never existed in the first place # In both cases we'll eventually return None as we # can't determine its exit status code. while 1: if pid_exists(pid): delay = check_timeout(delay) else: return else: raise else: if retpid == 0: # WNOHANG was used, pid is still running delay = check_timeout(delay) continue # process exited due to a signal; return the integer of # that signal if os.WIFSIGNALED(status): return os.WTERMSIG(status) # process exited using exit(2) system call; return the # integer exit(2) system call has been called with elif os.WIFEXITED(status): return os.WEXITSTATUS(status) else: # should never happen raise RuntimeError("unknown process exit status")