Define input number with expect

Question

I am trying to automate the deployment of a Docker container. Three prompts need to be filled in manually in order to proceed with the deployment. However, they are not to be filled in after each other. The order in which these fields appear is very odd. First off it asks for a password and a confirmation (two fields following each other). Then, the OpenVPN script does its thing and then needs an FQDN to generate a certificate I believe.

So: I'm wondering if I can tell expect to fill in value X for field X and once the input field Y appears, fill in value Y. In other words, can I tell expect to automatically recognize input prompts and fill them in accordingly?

Answer 1

Certainly, this is what expect is for. The exp_continue command is the key here:

expect {
    "password: "   {send "$password\r"; exp_continue}
    "confirmation" {send "$confirm\r"; exp_continue}
    "FQDN"         {send "$fqdn\r"; exp_continue}
    "some other pattern"
}

Of course you'll have to change the quoted patterns so they match your actual case.

With this structure, the patterns can match in any order. The patterns don't even have to appear at all.

When "some other pattern" is seen, since there's no action block associated with it, it triggers the end of the encompassing expect command and the rest of the script can carry on.

---

For expect to be able to control a process, you must launch that process from within expect. Try this:

#!/bin/bash
port=$1
export hostname=$2
export OVPN_DATA="ovpn-data-$port"
docker volume create --name $OVPN_DATA

/usr/bin/expect <<'END_EXPECT'
    set timeout -1
    spawn docker run -v $env(OVPN_DATA):/etc/openvpn --rm kylemanna/openvpn ovpn_genconfig -u udp://$env(hostname)
    expect {
        "Enter PEM pass phrase:" {
            # this should match whether it's the initial or confirmation prompt
            send "secret\r"
            exp_continue
        }
        "Common Name" {
            send "$env(hostname)\r"
            exp_continue
        }
        eof
    }
END_EXPECT

docker run -v $OVPN_DATA:/etc/openvpn --rm -it kylemanna/openvpn ovpn_initpki
docker run -dit --restart unless-stopped --name=$port -v $OVPN_DATA:/etc/openvpn -d -p $port:1194/udp --cap-add=NET_ADMIN kylemanna/openvpn