Shell Programming and Scripting

I have a script which searches a huge log file for the existence of a specified string and if the string is not present i receive an alert mail.
Here's an extract:

STRING=$(grep 'warning' logfile | tail -1 | wc -l)

if (( ${STRING} > 0 ));

then

print -- "---- Warning etc. --------------------" >> ${FILE}

fi



This works well but now I want to search for the existence of 50 unique strings within this log file.
I can do this by writing a script 50 times the size of the above but seems like overkill to me is there any more efficient way of doing this.

Write all the unique pattern to a file.
Then read the file in a loop and grep for the pattern.

>mail_body.txt
for i in `cat file_with_search_patterns`
do
echo $i
j=`grep -c "${i}" file_to_grep`
echo $j
if [ $j -eq 0 ]
then
echo $i >> mail_body.txt
fi
done
cat mail_body.txt | mailx -s "Patterns not found" 'abc@xyz.com'

Writing all the patterns to a file is a great tip.
Thanks sudhamacs it works perfectly.

What about:

Code:

grep -E "string1|string2|string3|string4|string..."