Mastering Regular Expressions, 3rd Edition

Chapter 1

† If you have a TiVo, you already know the feeling!

† “Regular expressions are easy!” A somewhat humorous comment about this: as Chapter 3 explains, the term regular expression originally comes from formal algebra. When people ask me what my book is about, the answer “regular expressions” draws a blank face if they are not already familiar with the concept. The Japanese word for regular expression, , means as little to the average Japanese as its English counterpart, but my reply in Japanese usually draws a bit more than a blank stare. You see, the “regular” part is unfortunately pronounced identically to a much more common word, a medical term for “reproductive organs.” You can only imagine what flashes through their minds until I explain!

† The command shell is the part of the system that accepts your typed commands and actually executes the programs you request. With the shell I use, the single quotes serve to group the command argument, telling the shell not to pay too much attention to what’s inside. If I didn’t use them, the shell might think, for example, a ‘*’ that I intended to be part of the regular expression was really part of a filename pattern that it should interpret. I don’t want that to happen, so I use the quotes to “hide” the metacharacters from the shell. Windows users of COMMAND.COM or CMD.EXE should probably use double quotes instead.

† Once, in fourth ...