setuid question

[Steven J Lamb]

I have written a script which I have set with the permissions of 4755 whose
owner is root and group is root. I am attempting to use it as a way to read
my system logs from a webpage. Obviously the final result will be more
complex, but here is what I got going on


My log file has the following permissions
-rw------- root root		Huge  DATE	log.file

My script has the permissions of 
-rwsr-xr-x root root		small	DATE	test.sh

My web user is www-data 

When I su to www-data and run test.sh I get a logfile permission denied. 

Test.sh is essentially this 

grep "string" /var/log/log.file

My question that make this an setuid question is this. When I make it an
setuid I thought it ran the script as if I am its owner. So like I will
become root run my script and leave. If this is true and root owns the log
file why do I get a permission error

Thanks

Steven Lamb