Examples of often used regular expressions

regex-examples.md

Regular Expressions (REGEX)

Sites that let you test expressions

• regexr.com
• regextester.com

Basics

Regular expressions attempt to match characters in a string using specific symbols. Some examples:

Expression	Matches	Does not match	Description
a	a	1	Match a single a character
.	a,1,[...]	\n	Match any single character (a-z,0-9) (except line breaks)
.+	a,1a,[...]	\n	Match one or more of any character (except line breaks)
[a-z]	a,b,[...]	1a,1,2,[...]	Match any lower case single letter
[a-z]+	a,ab,[...]	1a,1,2,[...]	Match any lower case single letter one or more
([a-z]+)	a,ab,[...]	1a,1,2,[...]	Match any lower case single letter and place in capture group
([0-9a-fA-F]{6})	f0f0f0,[...]	other,words,[...]	Match hexadecimal color values
([0-9]{1,3})	123,456,[...]	1234,words,[...]	Match integers of a specific length

Examples

All of these should work in languages like Javascript and C# as well as the Find/Replace function of code editors like Atom or Visual Studio.

Find and Replace - JSON keys Live example

Find and replace a string using the matching string in the replacement. The following example adds double quotes to JSON keys by wrapping the pattern with parentheses to create a "capture group" ([a-z0-9]+(?=:)) and thus allow access to the matched string in the replacement using $1:

Example string

{
key1:"value1",
key2:"value2"
}

Pattern

([a-z0-9]+(?=:))

Replacement

"$1"

Result

{
"key1":"value1",
"key2":"value2"
}

How to use a regex in Atom

Find and Replace - Transform CSV to a C# dictionary Live example

Example string

52, Business, 0E6897
483, Sports, 253785
239, Hobbies, 5b11db

Pattern matches integer, string, hex value using capture groups

([0-9]{1,3})(, )([A-Za-z]+)(, )([0-9a-fA-F]{6})

Replacement with captured strings

{ $1, new MarketingColor{ category = "$3", colorStr = "$5" } },

To make C# dictionary

{ 52, new MarketingColor{  category = "Business", colorStr = "0E6897"} },
{ 483, new MarketingColor{  category = "Sports", colorStr = "253785"} },
{ 239, new MarketingColor{  category = "Hobbies", colorStr = "5b11db"} },

Find and Replace - Get stock symbols from a list

Example string

ACBI|Atlantic Capital Bancshares, Inc. - Common Stock|Q|N|N|100|N|N
ACCD|Accolade, Inc. - common stock|Q|N|N|100|N|N
ACER|Acer Therapeutics Inc. - Common Stock|S|N|N|100|N|N

Pattern

(^[A-Z]{1,5})+(.*)

Replacement

$1

Result

ACBI
ACCD
ACER