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Tools for writing regular expressions

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In this video we will discuss the **basics of regular expressions and then look at some of the tools available to learn, write and test regular expressions**.
**Basics of Regular Expressions : **
Find the word expression in a given string. This will also match with the word expressions.
**expression**
To find the word "expression" as a whole word, include \b on either sides of the word expression
**\bexpression\b**
\d indicates to find a digit. To find a 5 digit number we could use the following
**\b\d\d\d\d\d\b**
We can avoid the repetition of \d by using curly braces as shown below. \d{5} means repeat \d 5 times.
**\b\d{5}\b**
The above example can also be rewritten as shown below.
**\b[0-9]{5}\b**
Find all the words with exactly 5 letters
**\b[a-zA-Z]{5}\b**
**Brackets are used to find a range of characters**
**[a-z]** - Find any of the characters between the brackets
**[0-9]** - Find any of the digits between the brackets. This is equivalent to \d
**(a|b)** - Find any of the characters a or b
The page at the following link explains the basics of regular expressions.
https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions
Expresso is one of the free tools available. Here is the link to download.
http://www.ultrapico.com/ExpressoDownload.htm
Regular Expression Library
http://regexlib.com
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