Regular Expressions for Not Yet Techies

The regular expressions are tools for manipulating text and data by programming languages. They are good at describing and parsing text. They are sort of a mini-language that are used by many other languages and text editors. Use regular expressions to work with documents, email, log files and CGI scripts.

You can use regular expressions to describe a chunk of text. They can help you verify form input (you'd be surprised to learn what tricks people try to play with online web forms -- if you're not careful, a hacker can crash a server or access a database through such forms.) They allow you to master your data.

For instance, a writer could use a script to change the name of their novel's main character from Mortimer to Fancy Dan. Yes, word processors can do that within a file, but novels are so long that authors usually divide them up into many separate files, and without regular expressions he'd have to open all 300 chapters and do an individual Search and Replace All process on each of all 300 files. That'd be a boring day's work.

You can also find regular expressions in such editors as Emacs, vi, Nissus Writer and Brief and in such programming environments as Delphi and Visual C++. And in such tools as lex, Expect and sed. They are often provided in programs as a power user option.

They actually date back to the early 1940s when two neurophysiologists -- Warren McCulloch and Walter Pitts -- invented the concept as their way of modeling how the nervous system works at the neuron level. Stephen Kine applied regular expressions to algebra a few years later and they became a part of algebra in the 1950s and 60s.

In 1968 Ken Thompson first documented work with applying regular expressions to text parsing, and eventually developed the editor qed which led to the Unix editor ed.

metacharacters -- such as * wildcard

literals

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