Search code examples
linuxbashtelnet

Linux script to write data from telnet message into a file while a period

I am connecting to a telnet listener. Telnet server sends some data for every second. I want to read the messages while X seconds and write it into a file (we'll take 6 seconds for the example).

Note: The IP address has been changed to 'IP' for the example. Same for 'Port'.

I already tried some things:

#!/bin/bash
#myScript.sh

telnet IP Port >> myFile.txt
sleep 6
pkill myScript.sh

This solution write in my file but my script never ends.

Here my 2nd proposition:

#!/bin/bash
#myScript.sh

timeout 6 telnet IP Port >> myFile.txt

Here, it's another issue, timeout is respected, the script ends after 6 seconds but in 'myFile.txt', I have

Trying IP...
Connected to IP.
Escape character is '^]'

How can I make this script right?

Note: I must use Telnet.

Solution

    1. In your first solution you could try try:

      telnet IP Port 2>&1 | tee myFile.txt &
sleep 6
exit

    This will send the telnet command to a background process and then exit after 6 seconds.

    1. In your second solution you could try:

      timeout 6 telnet IP Port 2>&1 | tee myFile.txt

    This sends stderr and stdoutt to myFile.txt

    https://www.gnu.org/software/libc/manual/html_node/Standard-Streams.html

    1. Or, as others have suggested, use netcat:

      timeout 6 nc -vz IP Port 2>&1 | tee myFile.txt

    http://netcat.sourceforge.net/