bash script, differential backup

[erinod]

Hey guys,
I am very new to bash scripts and I realize there are ways I could have done a single backup script but the way I started out seemed to be easier to me at the time. Basically I have one script that I will run on Sunday which copies a full backup of the directory: /var/www/html/SocProjects
and places it in directory: /home/erind/socprojects_backups/$b/SocProjects.$a

a=$(date +%H:%M--%d_%m_%Y)
b=$(date +%m_%d_%Y)

Now I want to have another script that I plan to run twice a day that makes a differential copy. Im not sure how to do this. Should I use tar or rsync? Since the pathname to the full backup will change each week (since the date will change) I wasnt sure if this will be a problem when the differential is made. Also I want to do a differential rather than an incremental because size isnt much of an issue and I felt that restoring from a differential would be easier for a newbie like me.

Thanks for any help,

Erin

[Irithori]

May I suggest to use one of the already available and matured backup applications?
Imho, there is little point in reinventing the wheel, other than for learning purposes.

rdiff -backup might be fitting.
More sophisticated backup systems are amanda or bacula.
But there are many more.