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Accepted
Leonardo Petrucci
Asked: 2020-05-07 09:35:59 +0800 CST

Responding to command prompts automatically without extra packages

  • 772

I need to run a command and answer a couple of prompts the command asks. Unfortunately I can't input the prompts manually so I'm looking for a way to do that automatically.

I can't install an external package like expect or yes, I also can't move my commands into a .sh file.

I've managed to pass one answer like this:

echo 'response' | command

But I can't figure out how to send multiple prompts for the same command.

Is this possible?

EDIT:

The command is:

certbot certonly --apache
command-line 18.04

2 Answers

  1. Best Answer

    Using a loop might be helpful.

    while true; do echo yes; done | command

    With arrays:

    declare -a arr=("yes" "no" "no"); for i in "${arr[@]}"; do echo $i; done | command

    Or as @steeldriver suggested:

    printf '%s\n' yes yes no | command

    Lets say command is a script asking for inputs:

    for i in {1..3}
do
    read -p 'Yes or no' c
    echo $c
done

    The output would be: 3 yes in first case and yes, yes, no in the second one.

    • 3

  2. Additionally you could try using << EOF, some number of answers one by line, EOF construction:

    $ sudo adduser test2 << EOF
> password
> password
> test2name
> 1
> 2
> 3
> 4
> y
> EOF
[sudo] password for user: 
Adding user `test2' ...
Adding new group `test2' (1004) ...
Adding new user `test2' (1003) with group `test2' ...
Creating home directory `/home/test2' ...
Copying files from `/etc/skel' ...
New password: Retype new password: passwd: password updated successfully
Changing the user information for test2
Enter the new value, or press ENTER for the default
        Full Name []:   Room Number []:         Work Phone []:  Home Phone []:  Other []: Is the information correct? [Y/n] 

user@ubuntu:~$ finger test2
Login: test2                            Name: test2name
Directory: /home/test2                  Shell: /bin/bash
Office: 1, 2                            Home Phone: 3
Never logged in.
No mail.
No Plan.

    You could also create an answers file:

    $ cat answers 
password
password
test
1
1
1
1
y

    And then just pipe the file content using cat command:

    $ cat answers | sudo adduser test
Adding user `test' ...
Adding new group `test' (1002) ...
Adding new user `test' (1001) with group `test' ...
Creating home directory `/home/test' ...
Copying files from `/etc/skel' ...
New password: Retype new password: passwd: password updated successfully
Changing the user information for test
Enter the new value, or press ENTER for the default
        Full Name []:   Room Number []:         Work Phone []:  Home Phone []:  Other []: Use of uninitialized value $answer in chop at /usr/sbin/adduser line 621.
Use of uninitialized value $answer in pattern match (m//) at /usr/sbin/adduser line 622.
Is the information correct? [Y/n] 

user@ubuntu:~$ finger test
Login: test                             Name: test
Directory: /home/test                   Shell: /bin/bash
Office: 1, 1                            Home Phone: 1
Never logged in.
No mail.
No Plan.
    • 1