i want to cron a backup script
 

I have a site that gets new users signing up every day. Some of them upload avatars for use in a forum. I need a script that will
1) create a folder named after today's date
2) do a mysqldump of selected tables to that folder with and zip it up with a filename like db_dump.sql.tgz
3) copy any NEW uploaded images from some folder (e.g., /var/www/html/assets/images/) and zip them inot the same folder created in step 1.

I have lots of PHP experience and am familiar with the command line for various things but i have NO experience shell scripting. If anyone could help me out, I'd be very grateful. Somethings I'm wondering are:
* Should I shutdown the site while I'm doing the mysql dump?
* how do you get the folder to have a name that matches the current date (e.g., 2008_03_25)
* what sort of 'gotcha' conditions should I be wary of?

The best thing about writing shell scripts is that you can run each part (usually) from the command lines to test it
1.
runs the date command setting the format to YYYY_MM_DD storing it in a variable called TODAY and if that command succedes then echoing its value back to you.
then (in the script) you can just add a line under the first (might want to add a path).
2.
I am not familure with the mySQLdump but lots of examples exist so lets assume it creates mySQL.dump
c= create
v= verbose
z= zip compression (j is for bzip)
f= file
modify the above thus
3.
I think that using "mtime 1" is a bit dodgy as its not what is new but what was modified/created in the last 1 day.
There are other ways the -print0 / xargs -0 handle bad file names.

you might be better off asking short specific questions, but please let us know how you get on.

Thanks for the help!

Perhaps we could start with shell basics:
* how do you declare a var in a shell script?
* how do you concatenate vars to form a new var?
* i've seen the if/fi statements but am wondering how to halt a script should an error occur?

variables can be created in simple ways.

PARAMS="`echo test`"
echo $PARAMS

Concatenations
PARAMS2="`echo $PARAMS| .lst`"
echo $PARAMS2

exit - to halt your script during error.

Gentoo

No.

You assign and create (declare) a shell var in one step:
PARAM="somevalue"

Concatenate by putting the vars next to each other:
t=tt
g=gg
h=${t}${g}

echo $h
ttgg

The parentheses tell the interpreter where each varname starts & finishes.

Read these docs:
http://www.tldp.org/LDP/abs/html/
http://tldp.org/LDP/Bash-Beginners-G...tml/index.html
http://rute.2038bug.com/index.html.gz