Hide input for a command

Question

Updated as original was unclear.

I'm setting up postfix on a computer to work with my email's SMTP.

I don't want to enter my credentials in plain text, especially when typing in public.

Is it possible to make bash not show my input for a command or two?

Example: I'm entering a series of commands and then I want to echo a username and password into a config file.

I'd like to quickly go into a mode where my input isn't shown on screen, then easily leave that mode with ctl+c.

You mean enter a password into a variable without it being seen on-screen? — Jeff Schaller, Oct 09 '17 at 14:08
@JeffSchaller kind of I'm just typing in terminal GMAIL_PASSWORD=secret maybe I should write a small script that asks for the env name and then password. — Philip Kirkbride, Oct 09 '17 at 14:13
@JeffSchaller thanks but I don't think that Q/A is at all helpful for my work-flow. I'm not writing a script. I've just noticed often I have a command or two I don't want to be seen by someone looking over my shoulder. I updated the text. — Philip Kirkbride, Oct 09 '17 at 14:21
The answers that Jeff linked to apply equally to interactive use as when used in a script. — Anthony Geoghegan, Oct 10 '17 at 08:53

score 4 · Answer 1 · answered Oct 09 '17 at 14:14

4

In bash: read is the command and the relevant option is (from man bash):

-s Silent mode. If input is coming from a terminal, characters are not echoed.

#!/bin/bash
unset password
prompt="Enter Password:"
while IFS= read -p "$prompt" -r -s -n 1 char
do
    if [[ $char == $'\0' ]]
    then
        break
    fi
    prompt='*'
    password+="$char"
done
echo
echo "Done. Password=$password"

But better to not echo anything as using asterisks allows others to see the lenght of the password.

answered Oct 09 '17 at 14:14

1

Might more directly solve the OP's problem by reading the whole variable at once. – Jeff Schaller Oct 09 '17 at 14:22
Reading in one go allows interpretation of some characters. As an specific example, the key backspace removes one character from the string. Others are also possible. One character at a time allow the most precise capture of the string of characters typed. @JeffSchaller – Oct 09 '17 at 14:56

score 3 · Accepted Answer · answered Oct 09 '17 at 19:45

3

You should use the stty command:

stty -echo

To re-enable echoing of terminal input:

stty echo

answered Oct 09 '17 at 19:45

GAD3R

66,769

Hide input for a command

2 Answers2