Posix shell script to convert between time in human form and seconds

humandate

#! /bin/sh

#  Posix shell script to convert between time in human form and date
#  Copyright (C) 2011 Matous J. Fialka, <http://mjf.cz/>
#  Released under the terms of The MIT License

if humantime=`humantime -f $@`
then
    date -d "$humantime seconds" '+%F %T'
fi

humantime

#! /bin/sh

#  Posix shell script to convert between time in human form and seconds
#  Copyright (C) 2011 Matous J. Fialka, <http://mjf.cz/>
#  Released under the terms of The MIT License

is_number()
{
	[ -n "$1" -a $1 -eq $1 ] 2>/dev/null
}

human_time_to_seconds()
{
	local arg1
	local arg2
	local ago
	local result

	ago=0

	while [ -n "$1" ]
	do
		local saved="$1"

		if is_number "$1"
		then
			if [ $1 -lt 0 ]
			then
				printf -- "use 'ago' for past\n" 1>&2

				exit 1
			fi

			arg1=$1

			shift
		else
			arg1=1
		fi

		arg2="$1"

		if [ -n "$1" ]
		then
			shift
		fi

		case "$arg2" in

		s|sec|secs|second|seconds)

			result=$(( result + arg1 ))
			;;

		m|min|mins|minute|minutes)

			result=$(( result + 60 * arg1 ))
			;;

		h|hr|hrs|hour|hours)

			result=$(( result + 3600 * arg1 ))
			;;

		d|day|days)

			result=$(( result + 86400 * arg1 ))
			;;

		w|week|weeks)

			result=$(( result + 604800 * arg1 ))
			;;

		a|ago)

			if is_number "$saved"
			then
				printf -- 'bad syntax\n' 1>&2

				exit 1
			fi

			if [ $ago -eq 0 ]
			then
				ago=1
			fi
			;;

		*)
			printf -- 'bad syntax\n' 1>&2

			exit 1
		esac

		unset saved
	done

	unset arg1
	unset arg2

	if [ $ago -eq 1 ]
	then
		result=$(( -result ))
	fi

	unset ago

	printf -- '%d\n' $result

	unset result

	return 0
}

seconds_to_human_time()
{
	if ! is_number "$1"
	then
		printf -- 'seconds expected\n' 1>&2

		exit 1
	fi

	if [ $1 -eq 0 ]
	then
		printf -- '0 seconds\n'

		return 0
	fi

	local ago=0
	local arg=$1

	if [ $arg -lt 0 ]
	then
		ago=1
		arg=$(( -arg ))
	fi

	local field_order='week day hour minute second'
	local first_field_passed=0
	local result=0

	for field in $field_order
	do
		if [ $first_field_passed -ne 0 ]
		then
			if [ $result -ne 0 ]
			then
				printf -- ' '
			fi
		else
			first_field_passed=1
		fi

		case $field in
	
		second)

			result=$(( arg % 60 ))
			;;

		minute)

			result=$(( arg / 60 % 60 ))
			;;

		hour)

			result=$(( arg / 3600 % 24 ))
			;;

		day)

			result=$(( arg / 86400 % 7 ))
			;;

		week)

			result=$(( arg / 604800 ))
		esac

		if [ $result -ne 0 ]
		then

			printf -- '%d %s' $result $field

			if [ $result -ne 1 -a $result -ne -1 ]
			then
				printf -- 's'
			fi
		fi
	done

	if [ $ago -eq 1 ]
	then
		printf -- ' ago'
	fi

	unset ago
	unset field_order
	unset first_field_passed
	unset result

	printf -- '\n'

	return 0
}


case "$1" in

-h)
	printf -- 'usage: humantime [-hf] <time>\n'
	;;

-f)
	shift

	if [ $# -eq 0 ]
	then
		printf -- 'human form expected\n' 1>&2

		exit 1
	fi

	human_time_to_seconds $@
	;;

*)
	while :
	do
		seconds_to_human_time "$1"

		if [ -z "$2" ]
		then
			break
		fi

		shift
	done
esac

exit 0

If only Gauss had had it!

$ humantime `seq 1 100` |xargs humantime -f
5050

OK, let's be more serious about it.

Example usage:

$ humantime 10 -100 1000 -10000 100000 -6478000
10 seconds
1 minute 40 seconds ago
16 minutes 40 seconds
2 hours 46 minutes 40 seconds ago
1 day 3 hours 46 minutes 40 seconds
10 weeks 4 days 23 hours 26 minutes 40 seconds ago

Well, do some more tests...

$ humantime -f 10 weeks 100 hours 1000 minutes 10000 seconds ago
-6478000

$ humantime -6478000
10 weeks 4 days 23 hours 26 minutes 40 seconds ago

Confused? Test it more further!

$ humantime -f 10 weeks 4 days 23 hours 26 minutes 40 seconds ago
-6478000

Everything looks just fine. Love it or hate it...

The other, simple, script called "humandate" works as follows.

Example usage:

$ humandate 10 weeks 5 hours 2 seconds ago
2011-05-06 03:43:08