Non-blocking stdin with python using epoll
I was playing with epoll and was curious whether I can use it to monitor
sys.stdin. The biggest issue was that sys.stdin.read() is blocking and I
had no way to figure out whether I read the descriptor fully or not (making the
epoll useless pretty much). Until I changed it to non-blocking with fcntl.
import os
import sys
import fcntl
import select
fd = sys.stdin.fileno()
fl = fcntl.fcntl(fd, fcntl.F_GETFL)
fcntl.fcntl(fd, fcntl.F_SETFL, fl | os.O_NONBLOCK)
epoll = select.epoll()
epoll.register(fd, select.EPOLLIN)
try:
while True:
events = epoll.poll(1)
for fileno, event in events:
data = ""
while True:
l = sys.stdin.read(64)
if not l:
break
data += l
print(data.upper(), end="")
finally:
epoll.unregister(fd)
epoll.close()
Sample usage:
$ python3 cat.py
asdqwe
ASDQWE
zxcasd
ZXCASD
^CTraceback (most recent call last):
File "cat.py", line 15, in <module>
events = epoll.poll(1)
KeyboardInterrupt