doy

#!/bin/bash
#-----------------------------------------------------
# NAME
#   doy - print Serial Day of Year
#
# SYNOPSIS
#   doy [date] | [--help] |
#
# VERSION
#	0.2
#   1.0     Parse more common date formats (yp)
#
# AUTHOR
#	Yaswant Pradhan
#-----------------------------------------------------
version=1.0

usage()
{
cat <<EOF

NAME
    ${0##*/} - show serial day of year

SYNOPSIS
    ${0##*/} date
    Valid date formats:
        CCYY-MM-DD
        CCYY/MM/DD
        CCYYMMDD
        CCYY MM DD
        DD-MM-CCYY (- can be any character in this form)
        DDMMCCYY
        DD MM YYYY


DESCRIPTION
    Display the Serial Day of Year for a given day month year in DD MM YYYY
    FORMAT, or for the system date.

    -h -? --help    print this message and exit
    -v    --version prints version information and exit

Examples:
   doy              Return Serial Day of Year for the current date
   doy 29 06 2003   Returns DOY for 29th June 2003, which is 180

EOF
}

#------------------------------------------------------------------------------
# Parse arguments
#------------------------------------------------------------------------------
while [[ $1 == -* ]]; do
    case $1 in
	    -v|--version)
	        echo -e "\n${0##*/}: v-$version\n"
	        shift 1 ;;

        -h|--help|-?|*)
            usage
	        exit ;;
    esac
done


#------------------------------------------------------------------------------
# Parse input date and return doy
#------------------------------------------------------------------------------
case $# in
    0)  # Current system doy
        date +'%j'; exit $?;;
    1)  #echo "1 arg"
        case ${#1} in
            8)  #echo "len=8"
                ret=$(date -d $1 +'%j' 2>/dev/null)
                case $? in
                    0)  echo $ret; exit 0;;
                    ?)  # Get Day Month Year in reverse order
                        y=$(echo $1 |cut -c5-8)
                        m=$(echo $1 |cut -c3-4)
                        d=$(echo $1 |cut -c1-2)
                        date -d $y$m$d +'%j'
                        exit $? ;;
                esac
                ;;

            10) #echo "len=10"
                ret=$(date -d $1 +'%j' 2>/dev/null)
                case $? in
                    0)  echo $ret; exit 0;;
                    ?)
                        y=$(echo $1 |cut -c7-10)
                        m=$(echo $1 |cut -c4-5)
                        d=$(echo $1 |cut -c1-2)
                        ret=$(date -d $y$m$d +'%j' 2>/dev/null)
                        [[ $? -eq 0 ]] && echo $ret || \
                        (echo "invalid date format" && exit 1)
                        exit $?;;
                esac
                ;;
            *)  echo "invalid date"; usage; exit 1;;
        esac
        ;;
    3)  #echo "3 args"
        case ${#1} in
            2) date -d $3$2$1 +'%j'; exit $?;;
            4) date -d $1$2$3 +'%j'; exit $?;;
            ?) echo "invalid date"; usage; exit 1;;
        esac
        ;;
    *)  usage; exit ;;
esac