Okay, I got a log file, and I need to use a combo of the tail -f command and the grep command, but I don't want to see all the output, other than what I'm "grepping". As well I'd like it to stop tailing and searching and just return to the command line, once it finds 1 line with that string in it. Something like this:

./scriptThatGeneratesLogFile.sh; tail -f | grep RUN logfile.out

Edit:

It doesn't have to be the grep command, or even the tail command. Those are just the two I'm somewhat familiar with and use the most.

You could use a combination of comm and grep.

The logic in your script would look something like this:
- save a copy of your log file to logfile1
- wait a few minutes and save a copy of your logfile to logfile2
- comm -13 logfile1 logfile2 | grep the line your looking for
- exit if grep returns something, if it doesn't wait a few minutes.
- copy logfile2 to logfile1 and copy the new updated logfile to logfile2
- run your comm , grep command again and repeat your checks