Ubuntu – Using bash commands in expect script

bashexpect

I've tried using some bash commands in an expect script before spawning anything, and this doesn't seem to work:

#!/usr/bin/expect

sudo ifdown usb0
sudo ifup usb0

expect "[sudo] password for stud:"
send "FirstPassword\r"

spawn ssh root@10.9.8.2
expect "root@10.9.8.2's password:"
send "SecondPassword\r"

expect eof

I've tried running this with the first part of the script commented out (because it's not neccesary to do this check 100% of the time, just better), but in that case I enter the device, and literally can't do anything there. I'd like to ifdown ifup, enter pass, ssh, enter pass, and scope to that shell.

Best Answer

Nope. you can't expect to run bash commands in an expect interpreter, just like you can't run perl commands in a python interpreter -- they're different languages. If you want to run some bash commands that require user interaction (sudo), then you have to spawn bash

set prompt {\$ $}    ; # this is a regular expression that should match the
                       # *end* of you bash prompt. Alter it as required.
spawn bash
expect -re $prompt

send "sudo ifdown usb0\r"
expect {
    "[sudo] password for stud:" {
        send "FirstPassword\r"
        exp_continue
    }
    -re $prompt
}
send "sudo ifup usb0\r"
expect -re $prompt

send "ssh root@10.9.8.2\r"
expect "root@10.9.8.2's password:"
send "SecondPassword\r"
expect eof

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Ubuntu – How to execute sudo commands with Expect & send commands in bash script

set login "sasuke"
set addr "hostname"
set pw "mypasswd"
spawn ssh $login@$addr
expect "$login@$addr's password:"
send "$pw\r"
expect "#"
send {output=$(sudo virsh list --all | awk '/running/{print $2}' | tail -2)}
expect {
    password: {send "$pw\r"; exp_continue}
    "#"
}
send {sudo virsh dominfo "$output"}    ;# don't know if you need quotes there
expect {
    password: {send "$pw\r"; exp_continue}
    "#"
}

In Tcl (and, by extension, expect), curly braces act like the shell's single quotes: inhibit variable expansion.

The multi-pattern form of expect is useful for the case where you may not see a pattern. The exp_continue statement essentially "loops" within the expect so you can send the password and continue to expect the prompt. Since there is no action associated with the prompt pattern, control passes from the expect command to the next one.

I would recommend you save this as a separate script. First line should be

#!/usr/bin/expect -f

If you want to embed in a shell script:

#!/bin/sh
expect <<'END'
   # code as above
END

Note the quotes around the first "END" -- that has the effect of single quoting the entire here-document so you don't have to worry about the shell interpreting the Expect variables

Best Answer

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Ubuntu – How to execute sudo commands with Expect & send commands in bash script

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