bashtime_codemath.sh

#! /bin/bash

# This is bashtime.sh
# Copyright (c) 2013 Paul Scott-Murphy (idea, initial code)
# Copyright (c) 2013 Johann Dreo (new code)

# Permission is hereby granted, free of charge, to any person obtaining a copy of
# this software and associated documentation files (the "Software"), to deal in
# the Software without restriction, including without limitation the rights to
# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
# the Software, and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:

# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
# COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


# if no args
if [[ -z "$*" ]] ; then
    # get the date as "hours(12) minutes" in a single call
    # make a bash array with it
    d=( $(date "+%I %M") )
    # separate hours and minutes
    hour=${d[0]#0} # remove leading 0 or values <10 will be interpreted as octal
    min=${d[1]#0}
else
    # get the arguments passed to the script
    hour=${1#0}
    min=${2#0}
fi

# The targeted unicode characters are the "CLOCK FACE" ones
# They are located in the codepages between:
#     U+1F550 (ONE OCLOCK) and U+1F55B (TWELVE OCLOCK), for the plain hours
#     U+1F55C (ONE-THIRTY) and U+1F567 (TWELVE-THIRTY), for the thirties
#
# Those codes may be output with unicode escapes or hexadecimal escapes,
# the later being the more portable.
#
# But we can iterate only over integers.
#
# We thus need the following conversion table:
#       utf   hex   int
# hours 50:5B 90:9b 144:155
# half  5C:67 9c:a7 156:167

# The characters being grouped bas plain/thirty, we must first now
# if we are close to the 0 or 30 minutes.
# Bash using integer arithmetic by default, we do not need rounding.
# We thus add 0 (plain hour) or 12 (half).
# Then we add 144, which is the first index (as an integer).

# (0 … 16 … 31 … 46 …) -> (0 1 2 3)
a=$(echo $(($min/15)))

# (0 1 2 3) -> (0 1 1 2)
i=$(echo $a | awk '{ print $1/1.5 }' OFMT="%.0f")

# (0 1 1 2) -> (0 12 12 -1)
j=$(( ( (i*12+1)%25 )-1 ))

# (0 12 12 -1) -> (0 12 12 1)
k=${j#-}

# start from the first code
mi=$((144+$k))

# Add the computed minutes index (144 or 156) minus 1 (because the first hour starts at 0).
hi=$(($mi+$hour-1))

# Get the hexadecimal representation of this integer
hex=$(printf "%x" $hi)

# Print the first three bytes (that are always the same) and the computed last one.
printf "\xf0\x9f\x95\x$hex"