Expect is a tool for automating interactive applications. Expect was constructed using Tcl, a language library designed to be embedded into applications.

Example code :

# Assume $remote_server, $my_user_id, $my_password, and $my_command were read in earlier
# in the script.
# Open a telnet session to a remote server, and wait for a username prompt.
spawn telnet $remote_server
expect "username:"
# Send the username, and then wait for a password prompt.
send "$my_user_id\r"
expect "password:"
# Send the password, and then wait for a shell prompt.
send "$my_password\r"

Reference : https://en.wikipedia.org/wiki/Expect