NINJA-REGEX

This is mainly for my understanding of Regex as well as its functions and uses predominantly in Python3 as well as in its use in BASH shell scripts and UNIX grep, awk and sed

Resources

Regular Expressions - Net Ninja Regular Expressions 101 Tutorial - regular-expressions.info/tutorial.html https://www.rexegg.com/

Character Sets [ ]

Any first character from [a-z]inja will match as below. However any capitals are ignored

The range a-z can be written as [a-z]inja. Dont have to include all the way to 'z' but a-f or s-w, or whatever we require. [a-zA-Z0-9]inja will match the first charachter from a-z or A-Z or 0-9

Telephone number: 11 numbers [0-9]{11} - This will match 11 numbers exactly Between 5-8 numbers [0-9]{5,8}. If you want AT LEAST 5 numbers [0-9]{5,} --we just leave the comma with nothing after and close the braces

Metacharacters and Escaping

Special Characters

There are 12 characters with special meanings and are called "METACHARACTERS". These metacharacters add more functionality and meaning when matching strings. They are:

METACHARACTERS	DESCRIPTION	EXAMPLE
\ Backslash	Signals a special sequence (can also be used to escape special characters)	\d
^ Caret	Starts with	^hello
$ Dollar Sign	Ends with	world$
. Period	Any character (except newline character)	h..o
| Pipe	Either or	stay | go
? Question Mark	Preceding character is optional	colou?r matches color and colour
* Asterix	Zero or more occurrences	aix*
+ Plus	One or more occurrences	aix+
( ) Parenthesis	Capture and Group
[ ] Square Bracket	A set of characters	[a-m]
{ } Curly brace	Exactly the specified number of characters	{2,4}