Shell Programming and Scripting

#!/bin/bash
# Rab
# 30th June 2010
# Template script for working out if a job is
# a weekly or monthly one.

#############################
# THE VARIABLES
#############################

# Days between monthly backups
betweenbkups=28

# Day of year of last backup from text file
lastbkup=$(cat lastbkup)

# Next backup day of year
nxtbkup=$(($lastbkup + $betweenbkups))

# Todays day of year. Sed removes first 0
today=$(date +%j | sed 's/^0*//')

# This year in format YYYY
year=$(date +%Y)

# Number of days in the year
no_of_days=$(cal $year |egrep "^[ 0-9][0-9]| [ 0-9][0-9]$" |wc -w)


#############################
# THE GUTS
#############################

# Testing for leap year
if [[ $no_of_days -eq 365 ]]

# If it is not a leap year 365 days in the year
then
        # If the next backup will be past the year mark
        if [ $nxtbkup -gt 365 ]
        then
                # Take away 365 to get true value for the new year
                nxtbkup=`expr $nxtbkup - 365`
                # If it's a Saturday and today is the same as next backup
                if [ $(date +%u) -eq 6 ] && [ $today = $nxtbkup ];
                        then echo Monthly Backup Ran >> date4.log
                             echo on a non leap year with days over 365 >> date4.log
                             echo $nxtbkup > lastbkup
                             else echo Weekly Backup Ran  >> date4.log
                             echo on a non leap year with days over 365 >> date4.log
                             echo $nxtbkup > lastbkup
                fi
        else
        # If the next backup will be within the year and if it's a
        # Saturday and today is the same as next backup
                if [ $(date +%u) -eq 6 ] && [ $today = $nxtbkup ];
                        then echo Monthly Backup Ran >> date4.log
                             echo on a non leap year with days less than 365 >> date4.log
                             echo $nxtbkup > lastbkup
                        else echo Weekly Backup Ran >> date4.log
                             echo on a non leap year with days less than 365 >> date4.log
                             echo $nxtbkup > lastbkup
                fi
        fi

# If it is a leap year (366 days in the year)
else
        # If the next backup will be past the year mark
        if [ $nxtbkup -gt 366 ]
        then
                # Take away 366 to get true value for the new year
                nxtbkup=`expr $nxtbkup - 366`
                # If it's a Saturday and today is the same as next backup
                if [ $(date +%u) -eq 6 ] && [ $today = $nxtbkup ];
                        then echo Monthly Backup Ran >> date4.log
                             echo on a leap year with days more than 366 >> date4.log
                             echo $nxtbkup > lastbkup
                        else echo Weekly Backup Ran >> date4.log
                             echo on a leap year with days more than 366 >> date4.log
                             echo $nxtbkup > lastbkup
                fi
        else
        # If the next backup will be within the year and if it's a
        # Saturday and today is the same as next backup
                if [ $(date +%u) -eq 6 ] && [ $today = $nxtbkup ];
                        then echo Monthly Backup Ran >> date4.log
                             echo on a leap year with days less than 366 >> date4.log
                             echo $nxtbkup > lastbkup
                        else echo Weekly Backup Ran >> date4.log
                             echo on a leap year with days less than 366 >> date4.log
                             echo $nxtbkup > lastbkup
                fi
        fi
fi