macos: Check if screen is locked from shell script

macos-is-screen-locked.sh

#!/bin/sh

# screen_is_locked is based on work by Joel Bruner:
# https://stackoverflow.com/a/66723000
#
# For an Objective-C implementation, see:
# https://stackoverflow.com/a/76241560
#
# This version avoids creating temporary files (via '<<<') by using plutil.
#
# Returns 0 if screen is locked.
screen_is_locked() {
  [ "$(/usr/sbin/ioreg -n Root -d1 -a \
    | /usr/bin/plutil \
      -extract 'IOConsoleUsers.0.CGSSessionScreenIsLocked' \
      raw -)" \
    == 'true' ]

  return $?
}

# Example:
if screen_is_locked
then
  echo "screen is locked"
else
  echo "screen is -not- locked"
fi