How to create an else statement with the expect command?

I have the follow expect script which adds a known host if a known host does not exist.

#!/usr/bin/expect
spawn ssh user@domain "cd /home/user"
expect "Are you sure you want to continue connecting (yes/no)?"
send "yes\r"
interact

The script works fine the first time I ssh into a device however if I ssh into a device for a nth + 1 time, it throws an error

send: spawn id exp6 not open
    while executing
"send "yes\r""
    (file "./testing_spawn.sh" line 4)

presumably because it continues to expect the string Are you sure you want to continue connecting (yes/no)?

How can I tell the script to just interact if that message does not show up?

Solution 1:

Use expect_before to match the "unknown host" question only if it comes before the command prompt:

#!/usr/bin/expect
spawn ssh user@domain
expect_before "*(yes/no)?" {
    send "yes\r"
}
expect "*# "
interact