#!/bin/bash
# Stephen Becker, 11/7/07  srbecker@acm.caltech.edu
# You may modify and distribute this script
# This script comes with no guarantees
#
# This script is intended to be run by cron
# e.g. have cron run it every hour, or every day, ...
#
# Every time the script is run, it checks a email folder
# (by default, the "Trash" folder)
# if this folder has changed, it will back it up
#  (Note: this is actually a filesystem file, not a folder)
# You can chose to keep up to N+1 backup copies
# Backups are kept in the BACKUP folder, with names
#   Folder, Folder.1, ..., Folder.N
# Every time a new backup is made, the oldest copy is deleted
#
# You probably want to set permissions on the backup directory to 700
#
# Basic crontab instructions:
#  (for ACM users: first, ssh to ACM, NOT your local machine)
# See current cron jobs with "crontab -l"
# To add a new job, use "crontab -e" which puts you into an editor
# syntax is: min hour day_of_month month day_of_week commandName
# and special options for the dates are @reboot, @yearly, @annually,
#  @monthly, @weekly, @daily, @midnight, @hourly
# so, you might want to add:  @hourly /home/[username]/mailBackupScript.sh

#### PARAMETERS TO CONFIGURE ####
MAILDIR="/home/srbecker/mail"
FOLDER="Trash"
BACKUP="/home/srbecker/mail_backup"
N=10

#### MAIN SCRIPT ################
if [ ! -r $MAILDIR/$FOLDER ]; then
    echo "Error: $MAILDIR/$FOLDER doesn't exist"
    exit
fi
if [ ! -s $MAILDIR/$FOLDER ]; then
    #echo "Folder has size 0, so nothing to do"
    exit
fi
# see if it's newer than most recent backup copy
if [ $MAILDIR/$FOLDER -nt $BACKUP/$FOLDER ]; then
    cd $BACKUP
    if [ -e $FOLDER.1 ]; then
        # get a list of all files in the backup directory:
        backups=`\ls -1r $FOLDER.*`

        for file in $backups
        do
            pre=`echo "$file" | cut -d"." -f1`
            post=`echo "$file" | cut -d"." -f2`
            x=$(($post + 1))
            if [ $x -lt $N ]; then
                mv $file $pre.$x
            else
                rm $file
            fi
        done
        mv $FOLDER $FOLDER.1
    fi
    cp $MAILDIR/$FOLDER $BACKUP/$FOLDER
fi