import os
r, w = os.pipe()
print(r, w)
pid = os.fork()
print("hello", pid)
if not pid:
print("pid:", os.getpid())
os.close(r)
os.write(w, "from child")
os._exit(0)
else:
os.close(w)
print(os.read(r, 100))
print(os.waitpid(pid, 0))