has the special effect of matching " any one character " so if you're looking for a period, then you really want to look for the \. When you want to find characters that have a special effect without "triggering" that special effect, you put a "\" in front of them:Īnd since the character " \ " has the special effect of removing the special effect of a character that has a special effect.
Now, what if you need to find characters like ^, or *? "look for any string that has a r followed by a e followed by zero or more characters that are not a space." So, our above simple regular expression re * means: → * means " zero or more of what just came" → r means r and e means e, " " means a space. Most characters represent themselves in regular expressions (regex), like a "normal" search. If you start from the top of the paragraph, you should have 8 "matches". Hit Next and see what you get, then hit Cmd+G and see what you get. R followed by e followed by a group of characters that are not a space, or by nothing. You should see colors appearing while you type the search terms. Paste that paragraph in your favorite regular expressions supporting text editor (I use Textwrangler for all the descriptions so you might want to use it too) then call the search window, check the "grep" box at its bottom and search for: This document uses its first two paragraphs (the paragraphs in italics, above) as a test ground. They can find simple patterns like the word "pattern" in this text, or more complex patterns like "a string that starts with ' pa', followed by a letter that's repeated twice, followed by any three characters that are neither ' space' nor ' or ' ^' and followed by a space". Regular expressions were created to find patterns in strings. Regular expressions are a "search" function on steroids. BBedit Lite has now been replaced by Textwrangler and just like its predecessor, Textwrangler can be used without paying a user license fee *. At the time, the editor of choice on the Mac was BBEdit from Barebones Software, but its free and "lite" version "BBEdit Lite" was also immensely popular. I discovered them at the end of the 90' when I was working on the conversion of a database output to a set of about 6000 static HTML pages. The technology that had the most impact on my workflow is definitely "regular expressions". In a recent project I had created a 872 characters long regular expression that described 71 different tags.Īs of February 2018, OmegaT also allows for replacements with capture groups as described below:Īnd you can also use regular expressions to search for empty segments, as I document in this article: OmegaT allows you to create "tags" that can be protected and checked during the translation by using regular expressions. OmegaT uses the Java flavor of regular expressions: In OmegaT, you lose a lot if you're not familiar with regular expressions.
Regular expressions for Aquamacs but also for Emacs are documented in the Emacs manual available here: I mention Aquamacs at the end of the article.
BBEdit "free mode" is a better TextWrangler and also happens to be a 64 bits application compatible with High Sierra.
Textwrangler has now been replaced by BBEdit that offers a free trial and then turns into a BBEdit "free mode".