我想分叉一个进程,在父进程退出之前等待,在子进程中做一些事情。
# BAD WAY!
pid = os.fork()
if pid == 0:
while True:
if os.path.isdir("/proc/%s" % pid):
break
time.sleep(0.1)
# Parent is dead there.
flock()
。但这不起作用,因为子进程与父进程共享相同的锁。# Good way
read_fd, write_fd = os.pipe()
pid = os.fork()
if pid > 0:
# Close the read pipe, so that only the child is the reader.
os.close(read_fd)
# It is important to voluntarily leak write_fd there,
# so that the kernel will close it for the parent process
# when it will exit, triggering our trick.
elif pid == 0:
# Daemon ourselves first.
os.setsid()
for fd in {0, 1, 2}:
os.close(fd)
# Close the write pipe so that the parent is the only writer.
# This will make sure we then get an EOF when the only writer exits.
os.close(write_fd)
# Now, we're waiting on the read pipe for an EOF.
# PS: the assert is not necessary in production...
assert os.read(read_fd, 1) == ""
os.close(read_fd)
# At this point, the parent is dead.