# A helpful idea if you're looking for something to do

**URL:** <https://www.ruby-forum.com/t/a-helpful-idea-if-youre-looking-for-something-to-do/112242>\
**Category:** Ruby\
**Created:** [August 16, 2007, 6:37pm UTC](https://www.ruby-forum.com/t/a-helpful-idea-if-youre-looking-for-something-to-do/112242 "2007-08-16T18:37:42Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![simonsaid](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/b5e925/32.png) [@simonsaid](https://www.ruby-forum.com/u/simonsaid)\
**Post date:** [August 16, 2007, 6:37pm UTC](https://www.ruby-forum.com/t/a-helpful-idea-if-youre-looking-for-something-to-do/112242/1 "2007-08-16T18:37:42Z")

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compile a whole lot of ruby regex examples, with commentary on what’s  
going on. the few websites I’ve found, and books I’ve looked through  
just touch on the basics with minimal examples and explanation, or are  
specifically for perl/etc. a nice-looking and lengthy site could be  
extremely helpful to a lot of people starting with ruby, I imagine.

- dealing with unicode?
- mingling literal " / \ etc, with their regex counterparts, in ways  
that would be daunting for the inexperienced
- just generally “higher-level” regex, leave the “intro to regex” to  
all the other places. that’s easy enough to find.

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**Author:** ![simonsaid](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/b5e925/32.png) [@simonsaid](https://www.ruby-forum.com/u/simonsaid)\
**Post date:** [August 16, 2007, 7:54pm UTC](https://www.ruby-forum.com/t/a-helpful-idea-if-youre-looking-for-something-to-do/112242/2 "2007-08-16T19:54:51Z")

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On Thursday 16 August 2007 09:36:13 am Simon S. wrote:

> all the other places. that’s easy enough to find.  
> For the most part, the ruby regex engine is perl-like. And instead of  
> having  
> to escape /s, we get stuff like %r@regex/bar@i. ZenSpider’s Ruby  
> QuickRef is a  
> great place to go for beginner help.

> **[Ruby | zenspider.com | by ryan davis](https://www.zenspider.com/ruby/)**
>
> Ruby facts, opinions, source code, links, and stuff.

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<div class="post-metadata">

**Author:** ![simonsaid](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/b5e925/32.png) [@simonsaid](https://www.ruby-forum.com/u/simonsaid)\
**Post date:** [August 16, 2007, 7:56pm UTC](https://www.ruby-forum.com/t/a-helpful-idea-if-youre-looking-for-something-to-do/112242/3 "2007-08-16T19:56:53Z")

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Simon S. wrote:

> compile a whole lot of ruby regex examples, with commentary on what’s  
> going on. the few websites I’ve found, and books I’ve looked through  
> just touch on the basics with minimal examples and explanation, or are  
> specifically for perl/etc. a nice-looking and lengthy site could be  
> extremely helpful to a lot of people starting with ruby, I imagine.
> 
> - dealing with unicode?  
> This one bothered me a lot, but the solution is simple. At the beginning  
> of the document, set  
> $KCODE = “u”

This will fix regex behavior for use with regular expressions. I assume  
the default behavior will be improved with Ruby 2.0, but I’m not using  
1.9 so can’t say for sure.

> - mingling literal " / \ etc, with their regex counterparts, in ways  
> that would be daunting for the inexperienced  
> The first think to keep in mind is that it never hurts to accidentally  
> escape something in a double quoted (soft quoted) string or regex. So if  
> you aren’t sure, “”", “’”, “\” are all okay, as are /"/, ///, and  
> %r|/| (the latter being an alternative way to specify a regex. But you  
> only need to escape characters that have special meaning. So in a  
> slash-delimited regex, a slash has special meaning, but in a %r regex,  
> it does not:  
> %{/} is the same as ///, as the former does not need to be escaped.

If you use Regexp.new(" … "), then the regexp comes from a string, and  
needs to follow the escaping rules for strings–you need to escape  
double quotes.

A single quoted string is sometimes called “hard quoted”. This means  
nothing is expanded / nothing has special meaning, so nothing needs to  
be escaped. Slash is not an escape character, here. The one exception is  
if the slash is before a single quote, in which case it will escape  
it.

Sorry if these rules are confusing. You will get used to them. The way  
to learn regular expressions is to use them. You will get comfortable  
with them when you need them.

> - just generally “higher-level” regex, leave the “intro to regex” to  
> all the other places. that’s easy enough to find.

Here’s one of mine:  
/\<a[^\>]+?href=[’"]?(.+?)[’"\s\>][^\>]_\>/im  
This matches a link. Throughout the regex I use [^\>] frequently, which  
means “any character that does not end the tag”. Think of [^\>]_ as a  
better .\*  
Interesting bits:  
-using +? says that the match is non-greedy. It will match as little as  
possible. \*? does the same think, but I find less use for it, as it  
usually matches an empty string.  
-the /i and /m at the end mean “case insensitive” and “multi-line”. You  
can mix and match from /i, /m, /x (extended–ignores whitespace in the  
regex).

I don’t know what your level is, so this may be a bit too cryptic, but  
you can probably puzzle it out if you are complaining about regex  
tutorials being too basic.

Dan