Regex

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

Regular expressions is used to search in text.

Standard character classes

• • A character class is created by putting things inside a []

  • So gr[ae]y match both gray and grey

  • Use a - inside to specify a range. [0-9] for a single digit between 0 and 9.

  • It's possible to specify more then one range and single characters. Ex [0-9a-fq] is 0-9, a-f or q.

  • Use a caret after the opening square to negate the class. [^0-9] will match any non number character.

Standard Character set

• • Some character sets is so common that shorthand names already exist for them

  • \d match a single character digit

  • \w Match alphanumeric characters and _.

  • \s Match white space characters.

Quantifiers

Examples

%x (\w+)

Search for %x and capture the word behind it.

%xx (.*?) %xx

Capture the text between %xx and %xx. To use the capture text in a search and replace use \1 where the number is the index of the capture group. So use <b>\1</b> as the replace text to replace %xx Hello world %xx with <b>Hello World</b>.

^@title\s+(.*)

At start of line (^) find @title, skip any number of spaces behind it (\s+) and then capture the rest of the text (.*).

^(#+)\s+(.*)

At start of line capture any number of # (#+). Skip space and then capture the rest of the text.