calcweek.sh

#!/bin/bash

# calcweek.sh by dan saunders <[email protected]>

# Define some defaults
SEASONS="spring summer fall winter"
YEAR="$(date +%Y)"
DAY="$(date +%j)"

# If there is a first argument, make sure it's a season
if [[ -n "$1" ]] && [[ "$SEASONS" =~ "$1" ]]; then
    SEASON="$1"

    # Check for a second argument - a date input
    if [[ -n "$2" ]]; then
        # Do some dirty cleverness by throwing the input through date - it will complain if it is an invalid format ;)
        date +%m/%d/%Y -d "$2" > /dev/null 2>&1
        [[ "$?" -ne "0" ]] && echo "That's not a valid date format, silly!" && exit

        # Extract that stuff!
        DATE=$(date +%m/%d/%Y -d "$2" 2>/dev/null)
        YEAR="$(date -d "$DATE" +%Y)"
        DAY="$(date -d "$DATE" +%j)"
    fi
else
    # Ok, so they didn't provide a date. Time to use trial and error to search for the correct semester
    # In order to loop through a sequence of words, I had to do some dirty work using read
    SEASON=$(echo $SEASONS | while read line; do
        for word in $line; do
            [[ -f "./$word$YEAR.conf" ]] && source "./$word$YEAR.conf"
            [[ -f "/var/public/fall2015/unix/sfp0/$word$YEAR.conf" ]] && source "/var/public/fall2015/unix/sfp0/$word$YEAR.conf"
            [[ -z "$SEMESTER" ]] && continue

            if [[ "$SEMESTER_START" -le "$DAY" ]] && [[ "$DAY" -le "$SEMESTER_END" ]]; then
                echo $word
                break
            fi
        done
    done)
fi

# Load the configuration, or at least attempt to
[[ -f "./$SEASON$YEAR.conf" ]] && source "./$SEASON$YEAR.conf"
[[ -f "/var/public/fall2015/unix/sfp0/$SEASON$YEAR.conf" ]] && source "/var/public/fall2015/unix/sfp0/$SEASON$YEAR.conf"
[[ -z "$SEMESTER" ]] && echo "Could not find configuration for \"$SEASON$YEAR\". Maybe you're looking into the future?" && exit

# Is the date during the given semester?
if [[ "$DAY" -le "$SEMESTER_START" ]]; then
    # It's before, so we must return 0
    echo 0
    exit
elif [[ "$SEMESTER_END" -le "$DAY" ]]; then
    # It's after, so we must return 16
    echo 16
    exit
fi

# Check for break weeks. Since bash doesn't have a loop by index feature, use cleverness to make it
for i in "${!BREAK[@]}"; do
    # Checks every other index to determine if it's a break week; the even and odd indexes are the same - it's not one
    if [[ $((i%2)) -eq 0 ]] && [[ "${BREAK[$i]}" -le "$DAY" ]] && [[ "$DAY" -le "${BREAK[$((i+1))]}" ]] && [[ "${BREAK[$i]}" -ne "${BREAK[$((i+1))]}" ]]; then
        echo break week
        exit
    fi
done

# The final step, display the week number, and in the process remove leading zeroes that we don't need
echo $(($(date -d "$(date -d "$YEAR-01-01 + $(($DAY - 1)) days")" +%V) - $STARTWEEK))