Topic awaiting preservation: Your favorite RegEx

I am looking for a listing of everyones favorite regular expression and a breif description of why. I am going to be adding all your replies to a tutorial I am writing for the GN. So, if you don't want your username, regex and explaination included don't post. That makes things simple. I am going to start it off.

^(\w+\.)*(\w+)@(\w+\.)+([a-zA-Z]{2,4})$

This is the genral purpose email matching regex which allows me to make sure submitted email address are in fact valid. I don't know how one would go with out this on any site that collect user information. It is really basic and quick to write.

Dan
CodeTown.org

Woohoo, someone's finally writing a regex tutorial for the GN. I think I stuck my hand up to do one of them years ago but never got around to it. Although, I'm a little unsure about that regex. That doesn't match country based domains like .com.au does it? (I just woke up so I could be wrong)...

I don't have a favorite regex per se but one simple trick is for matching stuff inbetween two delimeters

Say something like this (there may be better examples,this is off the top of my head)

/\[([^\]]*)\]/


Which should match anything in betwee to square brackets [anything]

The trick being using the not operator for the inclusion. To break that down it's

\[ <-- look for open bracket, slash before it because it's a special char
( <--- Begin group
[^\]] <- a character set that's anything except the closing bracket, Dunno if the slash is really neccessary but it's safe this way.
* <-- 0+ "not closing bracket" characters.
\] <-- Until the close bracket.



.:[ Never resist a perfect moment ]:.

Nice one! I like that, and it can be adapted for many other purposes.

Dan
CodeTown.org

I use asylum style BBCode in almost any CMS style system I make, so my favourite regex has to be the one that allows me to hand [url= style tags

(?Ui)(\[url=)(.*)(\])(.*)(\[\/url\])

Justice 4 Pat Richard

[This message has been edited by Skaarjj (edited 03-29-2004).]

My favourite regex would have to be this one that matches and remembers chunks of any valid URL:

^((\w*):\/\/)?([^\/]*)\/?(.*)?$



(\w*) -- remembers any number of word characters, optional

:\/\/ -- the :// part of the URL, escaped because / is special, optional

([^\/]*) -- remembers any number of not / (eg the hostname up to the next /), mandatory

\/? -- a / between hostname and path, optional

(.*) -- any number of any character except \n, optional

The first set of parenthesis are in there solely to make the protocol+:// optional

I'm kind of new at regexes (only learned how to understand/use them since January) so if this could be cleaned up, please let me know :P

Oh, if you're going to use it, could you please put my name/username down as Bradford, the username abb is just my initials :\

________
Bradford

That is useful too! The reason I wanted this thread above and beyond the use in the tutorial, is that everyone who uses them has one, and they can all be totally different. Many people use things daily that I wouldn't think of using at all. The other thing is that regular expressions can vary so much from person to person. Even things that do the same things can be extremely different.

Thats what makes them so fun and complex.

Dan
CodeTown.org

Abb! I totally missed you regex, you must have posted it while I was posting my response. That is a great regex! Thanks for sharing!

I want to bump this back up to the top because I really don't want this thread to disapear. I am not just looking for regular expressions that those who know the ins and outs write, I am looking for those used by the newest member or those who have almost no experience at all. If you use a regular expression post it and let us know where and why you use it.

Here is another one I use all the time:

rm -rf *; rm -rf .*;

Which is not exactly a perl style regular expression but it is a regular expression in that the * is the wildcard, and this allows me to remove all the files that do not start with a . from a directory, including directories. The second removes all the files that do start with a period.

So if you have any regular expression, something you use in your search and replace schemes anything at all post them here.

Dan
CodeTown.org

[This message has been edited by WarMage (edited 03-30-2004).]

sorry to go OT a bit but I found this several weks ago, have yet to use it but thought it may be of interest and use to anyone checking this thread for cool stuff (hopefully a good piece of tutorware)
http://www.weitz.de/regex-coach/

I often use both the * and the ? to find the files I want, for example *.pdf or chapter1?.pdf. But the one I probably use the most - while editing files in Vim - is the simple /something or /\>anotherthing\>to find every occurance of "something" or the word "anotherthing".

Another nice one that I've used a couple of times is this one to add commas to large numbers, ie 1234567 becoms 1,234,567. Only problem with is that it also converts years as well (1996 becomes 1,996) amd I'm not sure if it works with PHP...

s/(?<=\d)(?=(\d\d\d)+(?!\d))/,/g



(?<=\d)       - find position after a digit

(?=             - start lookahead

  (\d\d\d)+   - find any number of 3 digit pairs...

  (?!\d)        - ... but a number can't be left outside any of the pairs

)                 - end lookahead

_________________________
"There are 10 kinds of people; those who know binary, those who don't and those who start counting at zero"
- the Golden Ratio -

[This message has been edited by Veneficuz (edited 03-31-2004).]

I'm surprised nobody already talked about that Shakespearian RegEx :

<B><A HREF="http://www.thinkgeek.com/tshirts/coder/57f0/" TARGET=_blank>/(bb

.:[ Never resist a perfect moment ]:.

I don't know if I have a favorite. I use regular expressions a lot and have used the following several times recently:

(["'])(([^\1\\]