Ask for a password in POSIX-compliant shell?

read_password() {
  REPLY="$(
    # always read from the tty even when redirected:
    exec < /dev/tty || exit # || exit only needed for bash

    # save current tty settings:
    tty_settings=$(stty -g) || exit

    # schedule restore of the settings on exit of that subshell
    # or on receiving SIGINT or SIGTERM:
    trap 'stty "$tty_settings"' EXIT INT TERM

    # disable terminal local echo
    stty -echo || exit

    # prompt on tty
    printf "Password: " > /dev/tty

    # read password as one line, record exit status
    IFS= read -r password; ret=$?

    # display a newline to visually acknowledge the entered password
    echo > /dev/tty

    # return the password for $REPLY
    printf '%s\n' "$password"
    exit "$ret"
  )"
}

Note that for those shells (mksh) where printf is not builtin, the password will appear in clear in the ps output (for a few microseconds) or may show up in some audit logs if all command invocations with their parameters are audited.

read -s is not in POSIX. If you want to be POSIX-compliant use the stty -echo. stty and its echo parameter are defined in POSIX.

#!/bin/bash
stty -echo
printf "Password: "
read PASSWORD
stty echo
printf "\n"

This will work on all shells that conform to POSIX.

Source