How do I echo stars (*) when reading password with `read`?

Question

What do I need to do for code in Bash, if I want to echo *s in place of password characters (or even just hide the characters completely) when the user types so

Answer 1

I just made this Bash-specific function based on Dennis Williamson's, Wirone's and Logan VanCuren's answers:

ask() {
  local 'args' 'char' 'charcount' 'prompt' 'reply' 'silent'

  # Basic arguments parsing
  while [[ "${1++}" ]]; do
    case "${1}" in
      ( '--silent' | '-s' )
        silent='yes'
        ;;
      ( '--' )
        args+=( "${@:2}" )
        break
        ;;
      ( * )
        args+=( "${1}" )
        ;;
    esac
    shift || break
  done

  if [[ "${silent}" == 'yes' ]]; then
    for prompt in "${args[@]}"; do
      charcount='0'
      prompt="${prompt}: "
      reply=''
      while IFS='' read -n '1' -p "${prompt}" -r -s 'char'; do
        case "${char}" in
          # Handles NULL
          ( $'\000' )
            break
            ;;
          # Handles BACKSPACE and DELETE
          ( $'\010' | $'\177' )
            if (( charcount > 0 )); then
              prompt=$'\b \b'
              reply="${reply%?}"
              (( charcount-- ))
            else
              prompt=''
            fi
            ;;
          ( * )
            prompt='*'
            reply+="${char}"
            (( charcount++ ))
            ;;
        esac
      done
      printf '\n' >&2
      printf '%s\n' "${reply}"
    done
  else
    for prompt in "${args[@]}"; do
      IFS='' read -p "${prompt}: " -r 'reply'
      printf '%s\n' "${reply}"
    done
  fi
}

It could be used like:

$ ask Username
Username: AzureDiamond
AzureDiamond

$ ask -s Password
Password: *******
hunter2

$ ask First Second Third
First: foo
foo
Second: bar
bar
Third: baz
baz

Answer 2

stty -echo
read something
stty echo

will stop user input being echoed to the screen for that read. Depending on what you are doing with prompts, you may want to add an extra echo command to generate a newline after the read.

Answer 3

If you don't care about it being interactive, you can simply do

read -s pass
echo "$pass" | sed 's/./*/g'

This will show a * for each character of the entered password after enter is pressed.

Answer 4

@nxnev's answer didn't quite work for me, at least on macOS. I simplified it a bit, and now it's flawless:

#!/bin/bash

ask() {
    charcount='0'
    prompt="${1}: "
    reply=''
    while IFS='' read -n '1' -p "${prompt}" -r -s 'char'
    do
        case "${char}" in
            # Handles NULL
            ( $'\000' )
            break
            ;;
            # Handles BACKSPACE and DELETE
            ( $'\010' | $'\177' )
            if (( charcount > 0 )); then
                prompt=$'\b \b'
                reply="${reply%?}"
                (( charcount-- ))
            else
                prompt=''
            fi
            ;;
            ( * )
            prompt='*'
            reply+="${char}"
            (( charcount++ ))
            ;;
        esac
    done
    printf '\n' >&2
    printf '%s\n' "${reply}"
}

pwd="$(ask Password)"

echo "Your password is $pwd"

Answer 5

As Mark Rushakoff pointed out, read -s will suppress the echoing of characters typed at the prompt. You can make use of that feature as part of this script to echo asterisks for each character typed:

#!/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"

Answer 6

read -s should put it in silent mode:

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

See the read section in man bash.