#!/bin/bash
#
# Read and echo a password, echoing responsive 'stars' for input characters
# Also handles: backspaces, deleted and ^U (kill-line) control-chars
#
# This is the minimal shell script to do 'star' password reading
# but it is not the best one. For the more advanced one see...
#   https://antofthy.gitlab.io/software/#askpass_stars
#
####
#
# Anthony Thyssen,  22 May 2014
#
unset PWORD
PWORD=
echo -n 'password: ' 1>&2
while IFS= read -r -n1 -s char; do
  # Convert users key press to hexadecimal character code
  # Note a 'return' or EOL, will return a empty string
  #
  #code=$( echo -n "$char" | od -An -tx1 | tr -d ' \011' )
  code=${char:+$(printf '%02x' "'$char'")} # set to nothing for EOL

  case "$code" in
  ''|0a|0d) break ;;   # EOL, newline, return
  08|7f)  # backspace or delete
      if [ -n "$PWORD" ]; then
        PWORD="$( echo "$PWORD" | sed 's/.$//' )"
        echo -n $'\b \b' 1>&2
      fi
      ;;
  15) # ^U or kill line
      echo -n "$PWORD" | sed 's/./\cH \cH/g' >&2
      PWORD=''
      ;;
  [01]?) ;; # Ignore ALL other control characters
  *)  PWORD="$PWORD$char"
      echo -n '*' 1>&2
      ;;
  esac
done
echo
echo $PWORD