moon.sh

#!/bin/bash
# https://smithje.github.io/bash/2013/07/08/moon-phase-prompt
get_phase_day () {
  local lp=2551443
  local now=$(date -ju +"%s")
  local newmoon=592500
  local phase=$((($now - $newmoon) % $lp))
  echo $(((phase / 86400) + 1))
}


get_moon_icon () {
  local phase_number=$(get_phase_day)
  # Multiply by 100000 so we can do integer comparison.  Go Bash!
  local phase_number_biggened=$((phase_number * 100000))

  if   [ $phase_number_biggened -lt 184566 ];  then phase_icon="🌑"  # new
  elif [ $phase_number_biggened -lt 553699 ];  then phase_icon="🌒"  # waxing crescent
  elif [ $phase_number_biggened -lt 922831 ];  then phase_icon="🌓"  # first quarter
  elif [ $phase_number_biggened -lt 1291963 ]; then phase_icon="🌔"  # waxing gibbous
  elif [ $phase_number_biggened -lt 1661096 ]; then phase_icon="🌕"  # full
  elif [ $phase_number_biggened -lt 2030228 ]; then phase_icon="🌖"  # waning gibbous
  elif [ $phase_number_biggened -lt 2399361 ]; then phase_icon="🌗"  # last quarter
  elif [ $phase_number_biggened -lt 2768493 ]; then phase_icon="🌘"  # waning crescent
  else                                     phase_icon="🌑"  # new
  fi
  echo $phase_icon

}

get_moon_icon