import re
def send(s):
    RET = "@@RETURN VALUE@@"
    print(s+";echo {} $?".format(RET))
    outputs = []
    while True:
        output = input()
        if re.search("^{} ".format(RET), output):
            m = re.match("^{} (.*)".format(RET), output)
            return (int(m.groups()[0]), outputs)
        outputs.append(output)

import sys
print(send("ping www.google.co.jp -c 4"), file=sys.stderr)
print(send("ls ----"), file=sys.stderr)

$ mkfifo net
$ bash < net 2>&1 | tee /dev/stderr | python ls.py | tee net
ping www.google.co.jp -c 4;echo @@RETURN VALUE@@ $?
PING www.google.co.jp (142.250.206.195) 56(84) bytes of data.
64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=1 ttl=56 time=14.8 ms
64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=2 ttl=56 time=16.6 ms
64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=3 ttl=56 time=15.8 ms
64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=4 ttl=56 time=15.4 ms

--- www.google.co.jp ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3005ms
rtt min/avg/max/mdev = 14.760/15.666/16.645/0.681 ms
@@RETURN VALUE@@ 0
(0, ['PING www.google.co.jp (142.250.206.195) 56(84) bytes of data.', '64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=1 ttl=56 time=14.8 ms', '64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=2 ttl=56 time=16.6 ms', '64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=3 ttl=56 time=15.8 ms', '64 bytes from kix07s07-in-f3.1e100.net (142.250.206.195): icmp_seq=4 ttl=56 time=15.4 ms', '', '--- www.google.co.jp ping statistics ---', '4 packets transmitted, 4 received, 0% packet loss, time 3005ms', 'rtt min/avg/max/mdev = 14.760/15.666/16.645/0.681 ms'])
ls ----;echo @@RETURN VALUE@@ $?
ls: unrecognized option '----'
Try 'ls --help' for more information.
@@RETURN VALUE@@ 2
(2, ["ls: unrecognized option '----'", "Try 'ls --help' for more information."])

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