Question

I’m trying to write a script to allow me to log in to a console servers 48 ports so that I can quickly determine what devices are connected to each serial line.

Essentially I want to be able to have a script that, given a list of hosts/ports, telnets to the first device in the list and leaves me in interactive mode so that I can log in and confirm the device, then when I close the telnet session, connects to the next session in the list.

The problem I’m facing is that if I start a telnet session from within an executable bash script, the session terminates immediately, rather than waiting for input.

For example, given the following code:

$ cat ./telnetTest.sh #!/bin/bash  while read line do         telnet $line done $ 

When I run the command ‘echo ‘hostname’ | testscript.sh’ I receive the following output:

$ echo 'testhost' | ./telnetTest.sh Trying 192.168.1.1... Connected to testhost (192.168.1.1). Escape character is '^]'. Connection closed by foreign host. $ 

Does anyone know of a way to stop the telnet session being closed automatically?

Answer 1

You need to redirect the Terminal input to the telnet process. This should be /dev/tty. So your script will look something like:

#!/bin/bash  for HOST in `cat` do   echo Connecting to $HOST...   telnet $HOST </dev/tty done