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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
bexpressionb
d indicates to find a digit. To find a 5 digit number we could use the following
bdddddb
We can avoid the repetition of d by using curly braces as shown below. d{5} means repeat d 5 times.
bd{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.
Expresso is one of the free tools available. Here is the link to download.
Regular Expression Library
