How to use expect with optional prompts?

linux bash expect
joshualan picture joshualan · Jul 12, 2013 · Viewed 12.3k times · Source

Let's say I am trying to write an expect script for a test.sh that has three prompts: prompt1, prompt2, prompt3.

My code is like this:

spawn test.sh
expect "prompt1"
send "pass1"
expect "prompt2"
send "pass2"
expect "prompt3"
send "pass3"

However, prompt2 only occurs half the time. If prompt2 doesn't show up, the expect script breaks. How would I write expect code that skips over prompt2 if it doesn't show up?

EDIT:

Fixed my code:

/usr/bin/expect -c '
spawn ./test.sh
expect {
      "prompt1" {
          send "pass1\r"
          exp_continue
      }
      "prompt2" {
          send "pass2\r"
          exp_continue
      }
      "prompt3" {
          send "pass3\r"
          exp_continue
      }
}
interact return
'

This way, the rest of the script executes and provides output.

Answer

jbtule picture jbtule · Oct 19, 2018

As long as you have a case that will be always be expected to hit and don't include an exp_continue in that case, you can can remove duplication and handle optional prompts easily:

expect "prompt1"
send "pass1"
expect { 
    "prompt2" { 
        send "pass2"
        exp_continue
    }
    "prompt3" {
        send "pass3"
    }
}

Related questions

Use Expect in a Bash script to provide a password to an SSH command

I'm trying to use Expect in a Bash script to provide the SSH password. Providing the password works, but I don't end up in the SSH session as I should. It goes back strait to Bash. My script: #!/bin/bash …

Read More
How to pass argument in Expect through the command line in a shell script

I am passing argument in Expect through the command line in a shell script. I tried this #!/usr/bin/expect -f set arg1 [lindex $argv 0] spawn lockdis -p expect "password:" {send "$arg1\r"} expect "password:" {send "$arg1\r"} expect "$ " But …

Read More
How to get the exit code of spawned process in expect shell script?

I am trying to execute a script that executes an EXPECT script and a spawned process which has exit code in it. But I'm unable to get the exit code of the spawned process to main script. I'm always getting …

Read More