How does the sudo key symbol work?

Question

I'm trying to write a script that requests the user password for some sudo-related commands. My goal is to emulate the default method that OS X uses to obtain the user's password, Password: followed by a key-like symbol, as seen in the screenshot attached below:

I tried the answer from How to get a password from a shell script without echoing over on Stack Overflow that uses read -s, but that results in Password: without the key symbol when run from a script, but displays the symbol when run from the Terminal itself . What is this key symbol, and can I find it under the Characters menu?

Answer 1

I get the key symbol when running read -s in Terminal.

As this seems to work the same for read -s as for sudo, I assume this is a feature of Terminal (to display a key symbol whenever input is requested in silent/hidden mode).

Answer 2

The simplest answer is just write the script without sudo

then tell the user to run it with sudo e.g. sudo script

the script will run with root privileges

`this has the advantage that the user knows what asks for and where the password is used, if in your script you could be taking a copy or leaving it in memory

Answer 3

I think it has something to do with whether the terminal echo option is disabled. I tried running stty -echo; cat; stty echo in my terminal and then typing something, and the key symbol showed. I then pressed Ctrl+D and it went away.