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

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.

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"

I really liked the answer that Wirone gave, but I didn't like that the backspacing would continue removing characters even back into the "Enter password: " prompt.

I also had some issues where pressing keys too rapidly would cause some of the characters to actually print on the screen... never a good thing when prompting for a password. =)

The following is my modified version of Wirone's answer which addresses these issues:

#!/bin/bash

unset PASSWORD
unset CHARCOUNT

echo -n "Enter password: "

stty -echo

CHARCOUNT=0
while IFS= read -p "$PROMPT" -r -s -n 1 CHAR
do
    # Enter - accept password
    if [[ $CHAR == $'\0' ]] ; then
        break
    fi
    # Backspace
    if [[ $CHAR == $'\177' ]] ; then
        if [ $CHARCOUNT -gt 0 ] ; then
            CHARCOUNT=$((CHARCOUNT-1))
            PROMPT=$'\b \b'
            PASSWORD="${PASSWORD%?}"
        else
            PROMPT=''
        fi
    else
        CHARCOUNT=$((CHARCOUNT+1))
        PROMPT='*'
        PASSWORD+="$CHAR"
    fi
done

stty echo

echo $PASSWORD