RegEx is a sequence of characters for a search to match a pattern. Arose in the 1950 by Stephen Kleene, an American Mathematician. Regular expressions are composed of characters, metacharacters and quantifiers.

1. RegEx : Expressions and
Parsing Examples

2. Overview
 What is RegEx
 Purpose of RegEx
 How it Works
 Advantages
 Demonstration
 Q&A
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3. Introduction to RegEx
 RegEx is a sequence of characters for a search to match a
pattern.
 Arose in the 1950 by Stephen Kleene, an American
Mathematician.
 Regular expressions are composed of characters,
metacharacters and quantifiers.
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4. Purpose of RegEx
 To match the pieces of text within a larger document.
 To capture the string.
 RegEx is used in PERL, Java and other programming
languages.
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5. How it Works
 Regular Expressions: Exact Matches
regular expression
cks
rocks.
match
is okay.
no match
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6. How it Works
 Regular Expressions: Multiple Matches
regular expression
a p p l e
Scrapple from the apple.
match 1
match 2
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7. Metacharacters of RegEx
.
- Matches any single character.
 d - Matches a digit character.
 s - Matches any whitespace character including space, tab,
form-feed, etc.
 w - Matches any word character including underscore.
 n
- Matches a newline character.
^
- The beginning of a line
$
- The end of a line
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8. Metacharacters of RegEx
 abc
- Exactly this sequence of three letters
 [abc]
- Any one of the letters a, b, or c
 [^abc]
- Any character except one of the letters a, b, or c
 [a-z]
- Any one character from a through z
 [a-zA-Z0-9]-Any one letter or digit.
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9. Quantifier
Quantifier specify the number of string pattern should
occur in matching string.
*
- Zero or more times.
+
- One or more times.
?
- Zero or one time
 {m,n}
- Matches for atleast m times and atmost n times.
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10. Advantages
 The regular expression syntax is declarative: The pattern
"looks like" what you want to match.
 Easily compatible with different programing languages.
 Easier for non-programmers than code.
 Less error prone than code.
 Use in Compiler Construction.
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