Regular Expressions

This is really just some rough notes but is a starting point to something more... >

There is a rather good background, history and explanation of Regular Expressions on Wikipedia, see Regular expression - Wikipedia.

Regular Expression What it does
^(line)[0-9]+\: Matches lines starting “Line23:”, it looks for the word line at the start of the line and then any number of digits followed by a colon
^(Found).+$ Match lines starting “Found” and then having any number of any characters after that to the end of the line
(<)[^>]*(>) Match a “<” followed by any number of characters that are not “>” and then also match the closing “>”. This has the effect of removing all xml tags, opening and closing.
(\[|\()([a-z]|[A-Z])(\]|\)) Searches for an upper or lower case letter in round brackets ( ) or square brackets [ ]
[a-z]*(\t) Match any number of characters followed by a tab
^.*\t Match the start of the line, then any number of any character up to and including a tab
[ ]\([A][0-9]\)( - Grade) Search for " (A7) - Grade" where the number 7 can be anything between 0 and 9 inclusive

Note that the above is all Unix Regular Expressions, some tools like UltraEdit also support Perl Regular Expressions and UltraEdit also has its own format.

Useful Sites

General

There is a great visualisation and debugging tool at Debuggex: Online visual regex tester. JavaScript, Python, and PCRE., well worth a look, and you'll be able to see some issues with my expressions above! Here are some more useful sites:

If you are trying to do Regular Expression searches in Notepad ++ then see Searching | Notepad++ User Manual

Java

When working with Java, refer to Pattern (Java SE 11 & JDK 11 ) or see my demo /com/geoffdoesstuff/java/demo/RegularExpressions.java.

Python

Being a Python fan, then it is always one of my first choices, for Regular Expression information then see Regular Expression HOWTO — Python v3.3.3 documentation or the 2.x equivalent if that is your version.

PowerShell

http://dereknewton.com/2010/12/powershell-grep-equivalent/
Powershell: The many ways to use regex

Perl

It is worth noting that Perl based regular expressions are a common standard and one that UltraEdit can use. If you are working with html or xml tags then you will need to understand UltraEdit perl regex tutorial: non-greedy regular expressions, which is a helpful article.

UltraEdit

Being a very powerful and flexible editor it will hardly be a surprise that UltraEdit has three different regular expression engines built in: Perl, Unix, UltraEdit. The last two are documented at Regular expressions with find and replace. The Perl ones are described at the following:
Getting started with Perl regex in UltraEdit and UEStudio
Perl regular expressions in UltraEdit and UEStudio: Digging deeper
Perl regex backreferences in Find and Replace in UltraEdit

JavaScript

As one of the best sources of JavaScript documentation, Mozilla's MDN does not disappoint and they have both a buide and a reference for Regular Expressions in JavaScript: