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Regular ExpressionsRegular Expressions

ashishFA@cseashishFA@cse

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Where can I useWhere can I use

Powerful in- Search , search and replace, text processing

ext Editors ! "i, editplus Progra##ing languages - perl, $a"a

%rep,aw&

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'efore RegEx'efore RegEx

Wildcard! ()txt

! *+report()doc

ere the ( indicates an+ nu#.er of an+characters)

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//

Regular expressions (RegEx) end o

!e easier o "rie #an #ey are oread

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What is RegExWhat is RegEx

a regular expression-- a pattern that descri.es or#atches a set of strings

*atched text! chun& of text which #atches theregular expression)

ca0trn1! *atches car, can, cat

Editplus is used throughout this presentation as tool to de#onstrate theregular expressions

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StructureStructure of RegExof RegEx

*ade up of nor#al charactersand#etacharacters)

*etacharacters ! special function

23 ) 4 01 45 46 7 8

2#eans end of line

3start of line

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9iteral #atch9iteral #atch

RegEx: cat will #atch the word cat

It will also #atch words li&econcatenation , delicate, located,#odification

It is not desired so#eti#es 8

! solution

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*atching*atching

*atch the space .efore and after;caton? )) So searching RegEx : 0io1n will #atch in

and on .oth

0 1 : used to specif+ a set of character toselect fro#)! 0a-h1: indicates set of all characters fro# a to

h

! 0-A-1

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=haracter class=haracter class

It can also contain indi"idualcharacters as : 0acBC+D1! 0D-1: 8

! 0D-10D-1:8! 0D-10D-1:8

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Exa#pleExa#ple

set of "owels! 0aeiou1

set of consonents! 0.cdfghG&l#npHrst"wx+1

=onsider #atching words which start with J"owels and end with consonant! 0aeiou10aeiou10.cdfghG&l#npHrst"wx+1 8

! ;0aeiou10aeiou10.cdfghG&l#npHrst"wx+1