Regex cheat sheet

========================================= Anchros START
^ --- Start of line
\A --- Start of string
$ --- End of Line
\Z --- End of string
\b --- word boundary
\B --- not word boundary
\< --- start of word \> --- eof word
========================================= Anchros END
=========================================Sample patterns START
([A-Za-z0-9-]+) --- Letters numbers and hyphens
(^[1-9]{1}$|^[1-4]{1}[0-9]{1}$|^50$) -- any number from 1 to 50 inclusive
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6}) --- e-mail addresses
====================================== Sample patterns END
====================================== Pattern modifiers
g --- Global match
i -- Case-insensitive
m --- Multiple lines
s --- Treat string as single line
x -- Allow comments and white space in pattern
e --- Evaluate replacement
U --- Ungreedy pattern
====================================== Pattern modifiers
==================================================nix file glob pattern START
So to match all files except "." and ".." safely you have to use
3 patterns (if you don't have filenames like ".a" you can leave
out the first):

.[!.]* .??* *

===============================================nix file glob END
(https|http|ftp|news)\://[a-zA-Z0-9\-\.]+\.[a-zA-Z]{2,3}(:[a-zA-Z0-9]*)?/?([a-zA-Z0-9\-\._\?\,\'/\\\+&%\$#\=~])*
==========================================http links END
[^a-zA-Z] -- anything else but a letter
[^0-9] --- anything else but a digit
==========================================digits , letters

===============================match e-mail addresses
(\w+@[a-zA-Z_]+?\.[a-zA-Z]{2,6})
================================HTML TAGS
(\<(/?[^\>]+)\>)
=================================THE FOLLOWING ARE METACHARACTERS (MUST BE ESCAPED)
^ $ ( ) < . * + ? [ { \ | >
=====================================
\c - Control character
\s - White space
\S - Not white space
\d - Digit
\D - Not digit
\w - Word
\W - Not word
\x - Hexadecimal digit