I'm need to connect to another host in a script using the telnet command. How do I pass the login and password to be able to connect to the other host from within the script?

When you open a telnet session in a script you must read the session prompts and write the replies. For example, you open a telnet session in a script and read the session and when you match the word 'Login' (or whatever) you write the user id. The same for password.

In other words, you automate in the script what you manually do at the keyboard. When you do it from the keyboard, you telnet, then wait for the login prompt. When you get the login prompt, you type the login. etc.

Writing a script is the same for telnet sessions, however instead of the keyboard, you echo (or write) in the script. Instead of seeing the login problem, you match the pattern in the script (your eyes, so to speak).

I understand the concept very well. I have tried to automate it in my script but it doesn't take the login and password. Do you have an example?

I don't have an example handy, but as I recall the working construct is based on this form of code fragment:

while {

#put conditional logic here

} telnet 111.222.333.444

Thanks Neo, I'm also trying to telnet into hundreds of routers, which is why I need the telnet command (because of port 23) When I get it right I will post it.

Great. When you get it working for TELNET, the same idea will work for SSH. If you are using Cisco, they now support SSH. As PxT points out, this might be a good future revision if you require a more secure solution.

Telnet is a good first step. Cisco has SSH built into the recent IOS releases.

You can use a pipe to send the output to telnet. Something like:

#!/bin/ksh
( echo open hostname
  sleep 5
  echo username
  sleep 1
  echo password
  sleep 1
  echo some more output, etc. ) | telnet