Eudora Tip #199/01-Oct-2003
Matching Joe Cool 2

Example 2

Let’s make Joe Cool’s situation a little more complex. Say that, in addition to the two addresses mentioned in Part One, he sometimes sends out mail from <joe_c@example.edu> and <joe@bigserver.eng.example.edu>. How do you set up a filter to catch Joe’s messages? You could simply have it look for “example.edu” in the return address, but what if you know other people at the school who send you e-mail? In that case, your next move might be to set up a couple of filters, or maybe a single filter with multiple match criteria. However, with a single regular expression, we can cover all of Joe’s possible addresses. To put this together, let’s break it into steps, which is a good way to construct regular expressions until you get the hang of them (and then, still a good way when putting together complex expressions):

An expression to match “joe_c@” or “joe@”: joe(_c)*@

This is directly taken from Example 1, so you already know how it works.

An expression to match “cs.example.edu” or “example.edu” or “bigserver.eng.example.edu”: [A-Za-z.]*edu

Here, square brackets are used to say “match a pattern that consists of any character in the range a-z, or in the range A-Z, or that’s a period”, the * says to repeat that pattern any number of times, and the edu part says the whole pattern has to conclude with ‘edu’. Thus, the pattern will match any series of letters and periods followed by ‘edu’.

Combine the above two for our final regular expression: joe(_c)*@[A-Za-z.]*edu

Robert E. Williams, Jr.

President, TriVectus, LC www.trivectus.com

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