Day 1 Highlights: Lincoln's Cool Tricks and Regexp

Aug 18, 1998 by Brent Michalski

Monday’s Highlights

The first day of The Perl Conference is behind us and the knowledge sharing is in high gear.

Today I attended two excellent tutorials. The first was called Cool Tricks with Perl and Apache by Lincoln Stein and the second was Understanding Perl Regular Expressions by Jeffrey Friedl.

Cool Tricks with Perl and Apache

Cool Tricks with Perl and Apache was the ideal seminar for anyone running a web server. Yes, the seminar was geared toward the Apache web server but the concepts and most of the code that Lincoln provided is useful for any webmaster/developer.

Lincoln talked extensively about how to manage and process log files. This may seem like a trivial task on the surface, but managing an ever-growing file is not as easy as working with just any file. Lincoln provided useful tips and code to help.

My favorite example that Lincoln talked about was how to set up an Apache web server to log to a mySQL database instead of the standard text files. By doing this, you are able to perform ad-hoc queries on the data on anything we choose. Since the log files are in a SQL database, to get at the data you simply use SQL to select and manipulate the data that you are looking for.

A very humorous moment, although unintended, according to Lincoln, occurred when he was talking about using Perl to monitor a remote server. The script he was demonstrating connected to a site and used the LWP libraries head command. The site Lincoln referred to was the White House. Since the latest White House scandal is still on everyone’s mind, this struck the crowd as very funny and several other funny comments followed (none of which I wish to discuss here). See the kind of fun you miss if you don’t come to the conference?

Understanding Regular Expressions

The Understanding Perl Regular Expressions was an excellent seminar by Jeffrey Friedl. Jeffrey did a wonderful job of explaining some of the details of how Perl handles regular expressions.

Trying to explain regular expressions in a three-hour seminar is no easy task. Heck, trying to explain regular expressions in a fifty-hour seminar would be hard!

Having been out of Jeffrey’s seminar for several hours now, still my head is spinning. If you think you have regular expressions under control, and can write them with your hands tied behind your back… think again! Jeffery show several examples of simple regular expressions that looked harmful enough, but didn’t work anything like you would expect!

One quick example: If you pass the string ab ab ab ab into this regular expression: /a*((ab)*|b*)/ what would you expect it to match? Well, the b* will never ever be evaluated because the asterisks inside the parenthesis make it always match. Also, since the a matches and then we hit an asterisk, this regular expression really only matches the a and then exits! Remember, the asterisk means match zero or more times.

Jeffrey had many more examples that looked innocent enough, but were basically regular expression death-traps. The examples provided in the seminar are too detailed to explain here, but if/when I get the links to the seminar notes, I will post the URL where you can find them.

Suds

After today’s conference, it was buy-Randal-beer night. How do these guys get such great nights named after them? Anyway, several of us had an enjoyable evening at the Tied House Brewery and Cafe talking about Perl and visiting with Randal. When is buy-Brent-beer night? ;-)

Tuesday promises to be an exciting day also. I will be at the Advanved Perl Fundamentals seminar by Randal Schwartz. It is an all-day seminar that promises to be an awesome learning experience! I will let you know about it tomorrow.

It is not too late to get here and get a lot out of the conference! Larry Wall gives his “State of the Onion” address Wednesday morning.