CODEWITHSUNDEEP
expect
souser
souser

Reputation: 6120

What is the proper way to script Expect?

I am quite new to Expect and am looking for some suggestions on this one:

I am trying to ssh to the servers and execute some commands.

If the server is one that I am logging into for the first time, it prompts me whether I want to trust it. I select "yes"; this is why I have the first expect. The second expect is for the password.

  1. When I do the following, it accepts either the first prompt or the second prompt, so this does not work for me.

     expect {
    "yes/no" {
       send "yes\n"
    }
    "assword: " {
       send "$mypass\n"
    }
 }

  2. When I do the following, it works, but it waits for a very long time before it enters the password. I suspect it waits for the "yes/no" prompt for a certain amount of time, does not receive it and then moves on

     expect "yes/no" {
       send "yes\n"
    }

 expect "assword: " {
       send "$mypass\n"
    }

What is the right way to set this up?

Upvotes: 1

Views: 508

Answers (1)

glenn jackman
glenn jackman

Reputation: 246774

When you split it into two separate commands, you force the script to first look for the "yes/no" prompt. It will wait up to $timeout seconds (default 10 seconds). Only then will it look for the password prompt.

Your first idea is the right approach, but you're missing one key command:

expect {
   "yes/no" {
      send "yes\r"
      exp_continue    ;# <== this
   }
   "assword: " {
      send "$mypass\r"
   }
}

The exp_continue command essentially forces the flow of execution to remain in that Expect command so you can still match the password prompt.

A minor point: idiomatically, use \r (carriage return) as the character for "hitting Enter".

For further learning, look at the tag for more information and links to other questions and answers.

Upvotes: 1

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