fetch variable in expect

Question

I have the following vm's running on vmhost:

[root@server ~]# virsh list
 Id    Name                           State
----------------------------------------------------
 2     vm1                            running
 3     xw-4530c                       running
 4     optaserver                     running

I'm trying to fetch the name of the virtual machine starting with "xw" with an expect script, but it gives me all kinds of errors. I've replaced single quotes with curly brackets... because of... I think tcl? :) What is wrong with the set command below? The purpose with the script is to fetch the name, to run virsh reboot $xw ...

spawn ssh -o StrictHostKeyChecking=no $user@$host
expect "password:"
send "$password\r"
expect -re $prompt

send "virsh list\r"
expect -re $prompt
set xw [exec virsh list | grep xw | awk { { print \$2 } } ]
puts $xw
expect -re $prompt

Answer 1

For awk, the "outer" braces are Tcl's non-interpolating quotes: they already prevent variable substitution, so the awk $ does not need to be escaped.

However, exec is trying to launch virsh on your local machine not on the remote host.

This is where you need the expect_out variable which buffers the text going to and fro the spawned process.

send "virsh list\r"
expect -re $prompt
regexp -expanded -- { \m xw \S+ } $expect_out(buffer) xw
puts $xw

• read about expect_out in your expect man page
• regexp is a Tcl command.
• \m is a regex assertion that matches an empty string at the start of a word;
  \S is a non-space character

---

Thanks to Donal's suggestion:

send "virsh list\r"
set xw "not found"
expect {
    -re {\m(xw\S+)} {    # using capturing parentheses
        set xw $expect_out(1,string)
        exp_continue    ;# continue to expect the prompt
    }
    -re $prompt
}
puts $xw