README.md

Time Calculator

Quickly calculate when it's time to leave or when something will be over.

Because the calculation of clock times is a bit cumbersome. At least if it is not carried out regularly.

Examples

Here, I want to be somewhere at 19:30 and have three things to do that take 20, 10 and 15 minutes:

$ ./timecalc.sh 19:30 -20 -10 -15
19:30
19:10 -00:20
19:00 -00:10
18:45 -00:15
18:45

So I have to start at 18:45.

Here, I want to know when I will be home after a movie that takes 128 minutes and starts at 20:00:

$ ./timecalc.sh 20 128 20
20:00
22:08 02:08
22:28 00:20
22:28

timecalc.sh

#!/usr/bin/env bash

# Print clock time of given timestamp
#
# @param 1 - timestamp
clocktime() {
	if date --version &>/dev/null
	then
		# GNU
		date -d "@$*" +%H:%M
	else
		# BSD
		date -j -f '%s' "$@" +%H:%M
	fi
}

# Print timestamp of given date and time
#
# @param ... - date and time in format 'YYYY-MM-DD HH:MM:SS'
timestamp() {
	if date --version &>/dev/null
	then
		# GNU
		date -d "$@" +%s
	else
		# BSD
		date -j -f '%Y-%m-%d %H:%M:%S' "$@" +%s
	fi
}

# Print timestamp of given time of day
#
# @param 1 - time in HH[:MM] format
hours_to_timestamp() {
	local TIME=$1
	[[ $TIME == *:* ]] || TIME=$TIME':00'
	timestamp "$(date +%Y-%m-%d) $TIME:00"
}

# Convert duration from hours and minutes into seconds
#
# @param 1 - duration in [HH:]MM format
minutes_to_seconds() {
	local D=$1
	[[ $D == *:* ]] && {
		local SIGN=
		[[ $D == -* ]] && SIGN=-
		D=$(($SIGN${D##*:} + ${D%%:*} * 60))
	}
	echo $((D * 60))
}

# Expand duration to HH:MM format
#
# @param 1 - duration in [HH:]MM format
minutes_to_clocktime() {
	local T=${1#-}
	[[ $T == *:* ]] || T=$(printf '%02d:%02d' "$((T / 60))" "$((T % 60))")
	local SIGN=
	[[ $1 == -* ]] && SIGN=-
	echo "$SIGN$T"
}

# Print time ruler
#
# @param 1 - target time in HH[:MM] format
# @param ... - time ranges in [HH:]MM format
ruler() {
	local TIME
	TIME=$(hours_to_timestamp "$1")
	clocktime "$TIME"
	shift
	for T
	do
		((TIME += $(minutes_to_seconds "$T")))
		echo "$(clocktime "$TIME")" "$(minutes_to_clocktime "$T")"
	done
	clocktime "$TIME"
}

if [ "${BASH_SOURCE[0]}" == "$0" ]
then
	if (($# < 2))
	then
		echo "usage: ${0##*/} HH[:MM] [HH:]MM..."
	else
		ruler "$@"
	fi
fi