Find and replace.

Regular expressions are useful for extracting information from any text by searching one or more matches of a specific pattern.

A regex usually comes within this form /abc/ where the search pattern is delimited by two slash characters /.

Anchors

	
^The
	
matches any string that starts with The


	
end$
	
matches a string that ends with end


	
^The end$
	
exact string match (starts and ends with The end)


	
long
	
matches any string that has the text long in it

Quantifiers

	
abc*
	
matches a string that has ab followed by zero or more c


	
abc+
	
matches a string that has ab followed by one or more c


	
abc?
	
matches a string that has ab followed by zero or one c

Character classes

User uppercase to negate.

	
\d*
	
matches a single character that is a digit


	
\w*
	
matches a word character (alphanumeric character plus underscore)


	
\s*
	
matches a whitespace character (includes tabs and line breaks)


	
.*
	
matches any character

Escaping

In order to be taken literally, you must escape the characters ^.[$()|*+?{\ with a backslash \ as they have special meaning.

Flags

	
g
	
global
	
does not return after the first match, restarting the subsequent searches from the end of the previous match


	
m
	
multi-line
	
when enabled ^ and $ will match the start and end of a line, instead of the whole string


	
i
	
insensitive
	
makes the whole expression case-insensitive (for instance /aBc/i would match AbC)