catch output from linux telnet to a python script

Question

Hello. My problem is that i want to do something like this in linux console

telnet 192.168.255.28 > process.py i.e i would like to do some transformation with console telnet output using python script. I'm see Popen in python for this case, but i can't understand how can i get input from telnet if it do not stop all time.. Pleas any ideas.

Answer 1

Have you considered telnetlib? It seems like pretty much exactly what you're looking for?

Answer 2

If you can adapt your solution, telnetlib seems like the right way to do it -- +1 to xitrium.

That said, though, if you're dead set on piping the output of telnet into your Python script, it'll be coming in on standard in. That means you can do something like this:

try:
    while True:
        line = raw_input()
        do_stuff(line)
except EOFError:
    pass    # the telnet process finished; there's no more input

which will grab the output from telnet, one line at a time. If you want finer control, you can get the input using sys.stdin.read().

Important: In your question, you said (for example) telnet 192.168.255.28 > process.py. This is wrong; instead of piping the output from telnet into your script, it will save the output to file, overwriting your script. What you want is a pipe: telnet 192.168.255.28 | process.py.

Answer 3

As xitrium mentioned, it would be better if you used telnetlib. You can dispense with the whole mess of shell redirection etc.

If you do something like telnet foo | process.py, you can read your programs stdin (sys.stdin) to get the output of the telnet program. When you're happy, you can exit and terminate the pipeline. subprocess.Popen would be used if you're trying to open the telnet program as a subprocess of the interpreter. I'm not sure you wanted that.

In any case, telnetlib is the right way to go it seems. If you simply want an output text processor, consider perl. It's strengths lean in that direction.

Answer 4

Ok, thanks for all, i will try to use telnetlib.