Linux/Unix Shell Scripting - SHELL SCRIPT...NO IDENTIFICO LOS ERRORES EN PROGRAMA

#!/bin/bash

# by vk for INF627 (15/10/2012)

usage () {

    echo "Usage: ./datediff date1 [date2]"

    echo "Calculates the days difference between two dates"

    echo "Examples: ./datediff 20121231     # days to the New Year"

    echo "          ./datediff 20120930     # days from the beginning of the month"

    echo "          ./datediff 20121216 20120820     # days of the PUCP semester"

    echo "          ./datediff 1941-09-09 2011/10/12 # days of Dennis Ritchie"

    echo

}

if [ "$#" -eq 0 ]; then

    usage; exit 1

fi

arg1=$(date -d "$1" +%Y%j 2>/dev/null)

if [ -z "$arg1" ]; then

    echo "Invalid 1st parameter"; exit 2

fi

if [ "$#" -eq 1 ]; then

    arg2=$(date +%Y%j)

else

    arg2=$(date -d "$2" +%Y%j 2>/dev/null)

fi

if [ -z "$arg2" ]; then

    echo "Invalid 2nd parameter"; exit 3

fi

if [ "$arg1" -gt "$arg2" ]; then

    date1="$arg2"; date2="$arg1"

else

    date1="$arg1"; date2="$arg2"

fi

y1=${date1:0:4}; d1=${date1:4:3}

y2=${date2:0:4}; d2=${date2:4:3}

if [ "$y1" -eq "$y2" ]; then

    days=$(($d2 - $d1))

else

    y=$y1

    days=$(($(date +%j -d ${y}1231) - $d1))

    y=$(($y + 1))

    while [ "$y" -lt "$y2" ]

    do

        days=$(($days + $(date +%j -d ${y}1231)))

    done

    days=$(($days + $d2))

fi

# Check the algorithm

arg1=$(date -d "$1" +%Y%m%d)

if [ "$#" -eq 1 ]; then

    arg2=$(date +%Y%m%d)

else

    arg2=$(date -d "$2" +%Y%m%d)

fi

if [ "$arg1" -gt "$arg2" ]; then

    date1="$arg2"; date2="$arg1"

else

    date1="$arg1"; date2="$arg2"

fi

if [ "$(date -d "$date1 +$days days" +%Y%j)" != "$date2" ]; then

    echo "Very BAD error"; exit 4

fi

# It's ok

echo "$days"

exit 0