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Old 08-24-2021, 04:56 PM   #16
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Originally Posted by Bad Blue Bull View Post
What I need is unbuffered stdin stream.
Are you sure? I don't have a telnet server handy to test, but -u works for me in
(echo -n x; sleep 1; echo -n y; sleep 1; echo -n z) | python3 -u
works for me (whereas without the -u, there is no output for 2 seconds).
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Old 08-25-2021, 08:22 AM   #17
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It's important to note that this is only the case with the second code example in post #1 - the first example is looping/splitting on newlines and since none are received it only prints once, when the input is complete.

(For it to work with both code examples, simply don't exclude newlines from the echo, i.e remove the -n args.)

Also, an important thing to check - the original code only says "python", which is often python2. (Even when it's not, it's better to be explicit and request python3.)

Thirdly, the in-code equivalent to the -u argument is "print(...,flush=True)", so given an executable of:

#!/usr/bin/env python3

import io
import sys

input_stream = io.TextIOWrapper(
    sys.stdin.buffer, encoding='cp866', newline='\n')
while True:
    x =
    if len(x) == 0:
One can then use:
(for i in {1..5}; do echo "$i";sleep 1;done) | ./

If that isn't working with telnet, I would start by adding timestamps and seeing if that indicates whether the issue is on the Telnet side or the Python side.

Last edited by boughtonp; 08-25-2021 at 08:25 AM.
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