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RegEx : Expressions and Parsing Examples
 

RegEx : Expressions and Parsing Examples

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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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RegEx : Expressions and Parsing Examples RegEx : Expressions and Parsing Examples Presentation Transcript

  • RegEx : Expressions and Parsing Examples
  • Overview  What is RegEx  Purpose of RegEx  How it Works  Advantages  Demonstration  Q&A 2
  • 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. 3
  • 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. 4
  • How it Works  Regular Expressions: Exact Matches regular expression cks rocks. match is okay. no match 5
  • How it Works  Regular Expressions: Multiple Matches regular expression a p p l e Scrapple from the apple. match 1 match 2 6
  • 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 7
  • 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. 8
  • 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. 9
  • 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. 10
  • Questions ? Email Us @ support@zeteoconsulting.com 11
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