[Question] How to use the Expect.BufStr()?

[samuel-phan]

Description

I don't understand how to use the Expect.BufStr().

Let's say I have this command that prints this:

Here are your choices:
1) Go to Smith valley
2) Go to Victoria street
3) Go home
Your choice:  <-- wait for input here

If I write this in my code:

exp, _ := expect.NewExpect(myCmd)
exp.Expect("Your choice: ")
// exp.BufStr() is already empty at this line because the exp.Expect() matched and reset the buffer
// I can't parse my choices then

Question

How can I read the choices after the exp.Expect() call?

Environment

• OS: macOS Big Sur 11.2.3
• Shell: zsh

[samuel-phan]

@grrtrr I saw that you contributed quite a bit in your fork. Do you have an idea how this could be achieved?

[grrtrr]

Not immediately, this is some time ago. Here are some examples, hope they may be of help: grrtrr@7603f50

[leemcloughlin]

Hi

I think you should be looking for a choice line matching inputs like:

1. Go to Smith valley
   and
   Your choice

Something like this should match a choice line:
\d).*\n

Do that in a loop till you get "Your choice"

[samuel-phan]

Hi guys, and thanks for your quick reply. Got a busy week, I couldn't take a look sooner.

@leemcloughlin I see what you mean, and it's true that I can make it work this way. But I think it'd be simpler to have a buffer from the last matched expect.

Let's look through a more concrete example:

Choose your authentication:  ^
1) Send phone text message   | this part is asked only once per day
2) Send push                 |
Authentication choice: 2     v

Choose your credentials:
1) Account: foo Credentials: admin
2) Account: foo Credentials: readonly
3) Account: bar Credentials: storage
4) Account: bar Credentials: readonly
Credentials choice: 3

I could totally do this:

var pushChoice int
pushRE := regexp.MustCompile(`(\d+)\).*push$`)
credentialsMap = make(map[string][]string)
credentialRE := regexp.MustCompile(`(\d+)\) Acccount: (\w+) Credentials: (\w+)`)
for {
    index, buff, _ := exp.Expect("Authentication choice: ", pushRE, "Credentials choice: ", credentialsRE)
    switch index {
    case 0:
        break
    case 1:
        // Use pushRE regexp to extract choice number
        pushChoice := pushRE.FindStringSubmatch(string(buff))[1]
    case 2:
        break
    case 3:
        // Use credentialRE regexp to extract choice and infos
        matches := credentialRE.FindStringSubmatch(string(buf))
        credentialsMap[matches[2]] = append(credentialsMap[matches[2]], buff)  // store it for example
    }
}

but it sounds more natural to me to try to detect first the prompt and use a buffer for the past lines to extract the choices now that I know what I am being asked (which is what we do as human):

index, _, _ := exp.Expect("Authentication choice: ", "Credentials choice: ")
if index == 0 {
    // read the exp.Buffer to extract the authentiation choices
} else if index == 1 {
    // read the exp.Buffer to extract the credentials choices
} 

What do you think?