Expect script to open an ssh connection and execute comand does not work.

jstechg · July 2018

I need to connect from a machine with Centos 7 to a switch using ssh and in the same execute the command "sh vlan 110"

I have tried it in several ways:

1) I have written a script to expect with which I connect to the switch automatically and then manually enter the indicated command:

ssh_script.sh :

#!/usr/bin/expect

spawn ssh [email protected]

expect "assword:"

send "key_pass\r"

interact

After the connection is established with this expect script, I type the "sh vlan 110" command and it works fine.

2) Next, I added a pair of lines to the previous script in order to automatically execute the sh command on the switch:

ssh_script_v2.sh :

#!/usr/bin/expect

spawn ssh [email protected]

expect "assword:"

send "key_pass\r"

expect "prompt>"

sleep 5

send -- "sh vlan 110\r"

This new version of the script connects successfully to the switch, but when after five seconds it writes the command "sh vlan 100" it does not show itself nor does it appear any screen output and the connection is closed by ssh to the switch, as if we had written "exit", but without having written anything.

In order to show debug information I have executed this script with the command:

expect -d ssh_script_v2.sh

I get the output I show at the end of this message.

3) I directly execute the following command from the linux prompt:

ssh [email protected] '( sh vlan 110 )' > file

I manually enter the password that ssh requests when establishing the connection and the following error is shown:

imish: invalid option -'c'

Try `imish -“help' for more information.

I comment this in case it provides some additional information, but what I want is that the expect script works properly.