Calculate time spent on an activity which starts and ends the same day

time_between_times.sh

#!/bin/bash -e

# This script calculates time spent on an activity which starts and ends the same day.

APPLICATION_NAME=$0

printHelp() {
  echo "usage: $APPLICATION_NAME <start_time> <end_time> [<break_in_minutes>]"
  echo "    start_time                   e.g. 8:00. Also valid: 08:00, 8"
  echo "    end_time                     e.g. 17:00. Also valid: 17"
  echo "    break_in_minutes             e.g. Default: 50"
  echo "Example call: $APPLICATION_NAME 8:30 17:30"
  exit 1
}

if [[ -z "$2" ]]; then
   printHelp
fi

START_TIME=$1
END_TIME=$2
BREAK_IN_MINUTES=${3:-50}

START_DATE=$(date -d "$START_TIME $BREAK_IN_MINUTES minutes" '+%s')
END_DATE=$(date -d "$END_TIME" '+%s')
SECONDS_BETWEEN_DATES=$(($END_DATE-$START_DATE))

RESULT_HOURS=$(($SECONDS_BETWEEN_DATES/3600))
RESULT_MINUTES=$(($SECONDS_BETWEEN_DATES%3600/60))

echo "Elapsed time:"
printf '%0dh %0dm' $RESULT_HOURS $RESULT_MINUTES
echo " (${RESULT_HOURS}$(echo "scale=2; $RESULT_MINUTES/60" | bc -l )h)"