When forking a process, consider the following scenario:
1) We open two pipes for IPC bidirection communication
2) Suppose these have (3,4) and (5,6) as file descriptors.
3) We fork the process somewhere in the middle.
4) We exec the child process
Now, the thing that happens is that these two processes are completely independent of each other and the-then child process is now having it's own address space and is a completely new process.
Now, my question is, how do pipes(/file descriptor) live in an Execed processes? Because, pipes opened like this are used for the execed and the parent process to communicate.
The only way I see this could happen is when the file descriptors are global to the machine, which I think is impossible to happen, as that would be conflicting.
And in the IDE for this code:
import os from multiprocessing import Process, Pipe def sender(pipe): """ send object to parent on anonymous pipe """ pipe.send(['spam']+[42, 'eggs']) pipe.close() def talker(pipe): """ send and receive objects on a pipe """ pipe.send(dict(name = 'Bob', spam = 42)) reply = pipe.recv() print('talker got: ', reply) if __name__ == '__main__': (parentEnd, childEnd) = Pipe() Process(target = sender, args = (childEnd,)).start() print("parent got: ", parentEnd.recv()) parentEnd.close() (parentEnd, childEnd) = Pipe() child = Process(target = talker, args = (childEnd,)) ##############################from here child.start() print('From talker Parent got:', parentEnd.recv()) parentEnd.send({x * 2 for x in 'spam'}) child.join() ############################## to here print('parent exit') There are two processes run, but only the output from one process can be seen in the idle, not two processes. However, in the terminal, it's like the stdout is also shared.
