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Regular Expressions

Issue 109

From Issue #109
May 2003

May 01, 2003  By Giovanni Organtini
 in
For precision of text manipulation and description, it's hard to beat the power of regexps.
Conclusion

Regular expressions are by far the most powerful tool for text manipulation and description, and they are well supported under Linux on many applications. Unfortunately, they are not supported at all (to my knowledge) by the most popular search engines because of their complexities. But, can you imagine how precise your search would be if you had the ability to describe the page you are looking for with a regular expression?

email: Giovanni.Organtini@roma1.infn.it

Giovanni Organtini (g.organtini@roma1.infn.it) is a professor of Introduction to Computing and Programming for Physicists at the University of Rome. He has used Linux for years, both for fun and at work, where it is used for the simulation of the CMS experiment (cmsdoc.cern.ch) on large farms and as part of a complex data-acquisition system and machine control. Before the birth of his son, Lorenzo, he used to travel, seeking good restaurants and attending concerts and operas.

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Re: Regular Expressions

Anonymous's picture
Submitted by Anonymous on Thu, 01/15/2004 - 03:00.

"...followed by a space, followed by at most two (+) characters that could be either numeric..."

Is this a mistake? I can't see how that regexp isolates 2 characters (day of the month) without matching the space and hour as well. Surely you need something like this?

$line =~ /^([a-zA-Z]{3} [ 0-9]{2}
[0-9:]*).*logname=([a-zA-Z0-9]*).*user=
([a-zA-Z0-9]*)$/;

Otherwise you'll chew up further spaces and digits until you hit the first ':'.

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