Looking for PCRE resource

bunner_bob

I finally got a handle on regexps as used by functions like ereg(), but now that I know it's better to use preg_match() and the other Perl-compatible regexp functions, I need a READABLE (i.e. aimed at a mid-level techie, not code-god) bit of info on proper syntax, what the various parts are, etc. I've found lots on non-Perl but not much so far on Perl. The PHP manual is no help at all

For instance - when do I use forward slashes at the beginning and end? What characters are "special" and need to be escaped? How do I combine chunks of code - with a period as in non-Perl, or another way?

Any suggestions for a not-bleedingly-technical source for this kind of info?

Thanks!

iceraider

Heres some stuff

\	Quote the next metacharacter
^	Match the beginning of the line
.	Match any character (except newline)
$	Match the end of the line (or before newline at the end)
|	Alternation
()	Grouping
[]	Character class  
*	   Match 0 or more times
+	   Match 1 or more times
?	   Match 1 or 0 times
{n}    Match exactly n times
{n,}   Match at least n times
{n,m}  Match at least n but not more than m times 
*?	   Match 0 or more times
+?	   Match 1 or more times
??	   Match 0 or 1 time
{n}?   Match exactly n times
{n,}?  Match at least n times
{n,m}? Match at least n but not more than m times  
\t		tab                   (HT, TAB)
\n		newline               (LF, NL)
\r		return                (CR)
\f		form feed             (FF)
\a		alarm (bell)          (BEL)
\e		escape (think troff)  (ESC)
\033	octal char (think of a PDP-11)
\x1B	hex char
\c[		control char
\l		lowercase next char (think vi)
\u		uppercase next char (think vi)
\L		lowercase till \E (think vi)
\U		uppercase till \E (think vi)
\E		end case modification (think vi)
\Q		quote (disable) pattern metacharacters till \E  
\w	Match a "word" character (alphanumeric plus "_")
\W	Match a non-word character
\s	Match a whitespace character
\S	Match a non-whitespace character
\d	Match a digit character
\D	Match a non-digit character  
\b	Match a word boundary
\B	Match a non-(word boundary)
\A	Match only at beginning of string
\Z	Match only at end of string, or before newline at the end
\z	Match only at end of string
\G	Match only where previous m//g left off (works only with /g)

Heres more info on perl regulare expressions

http://www.perldoc.com/perl5.005_03/pod/perlre.html#Regular-Expressions

bunner_bob

Thanks Iceraider - actually I already found that site. It has a lot of good meat but doesn't explain it all that well.

For instance, what is a "metacharacter"? How about examples of a "greedy subpattern" re. using "?" with quantified subpatterns? That is, why use ? rather than .

I've definitely bookmarked this page. I was just hoping for a more user-friendly walk-through, one that starts with simple examples and works to more complex ones.

Weedpacket

O'Reilly have a book, "Mastering Regular Expressions".

A metacharacter is a character that has a special meaning in a regular expression - in other words, something like +*()?| etc.

The difference between greediness and nongreediness is usually explained when the use of ? is explained.

But there must be plenty of sites that describe Perl regular expressions.

128kb_com

Yeah, I have the O'Reilly book also, good book. If you looking for some info on pcre for php theres some good info in the manual at:

http://www.php.net/manual/en/pcre.pattern.syntax.php

Weedpacket

There's also a tutorial on the older POSIX regexps on this site - there's none of the interesting stuff that makes PCRE regexps more powerful, but the basics are there. (In fact, in my opinion, most of the tutorial sites I've seen on this subject don't get into the powerful stuff.)