regular expressions

Regular Expressions 101@!#?@!

KNOW YOUR ENEMY

rubular.com

Part ICharacter Literals and Wildcards

"Now is the time for all good men to come to the aid of their country." was proposed as a typing drill by a teacher named Charles E. Weller aka "Chase" in 1918.

/m/

http://tinyurl.com/rx101-2

http://rubular.com/r/4HG6NFOlT7


/me/




/./




/\./




/.e/




/[aeiou]/




/[a-f]/



/[A-z]/?


/[a-fw-z]/




/[^A-Z]/




/\d/



"Now_is_the_time_for_all_good_men_to_come_to_the_aid_of_their_country."_was_proposed_as_a_typing_drill_by_a_teacher_named_Charles_E._Weller_aka_"Chase"_in_1918.

/\s/



/\w/




"Now_is_the_time_for_all_good_men_to_come_to_the_aid_of_their_country."_was_proposed_as_a_typing_drill_by_a_teacher_named_Charles_E._Weller_aka_"Chase"_in_1918.

/\W/



Activity!Write a regular expression to match the telephone number in this text:

http://tinyurl.com/rx101-a1

For a good time call Stanley: 555-1212 - you will not be disappoint.

http://tinyurl.com/rx101-a

Part IIQuantifiers


/men?/




/".*"/




/".*?"/




/"[^"]*"/“TMTOWTDI”




/t\w+[aeiou]/




/t\w*[aeiou]/




/[aeiou]{2}/



squee squeee squeeee squeeeee squeeeeee!

/sque{3,4}/




/sque{4,}/




/sque{,2}/



/men?/ /men{0,1}/=

“TMTOWTDI”

/.*/ /.{0,}/=

“TMTOWTDI”

/.+/ /.{1,}/=

“TMTOWTDI”

Activity!Rewrite the telephone number regular expression

to use quantifiers.


For a good time call Stanley: 555-1212 - you will not be disappoint.

Extra credit - extract the email address.

For a good time email [email protected] - you will not be disappoint.




Part IIIAnchors


/^[^\s]+/




/[^\s]+$/




/\ba\w*/




/\b\w{3}\b/



Activity!Go back and fix this example to find wholewords that start with ‘t’ and end in a vowel.



Part IVMatch Groups


/"(.*?)"/

1. Now is the time for all good men to come to the aid of their country.2. Chase



str = '"Now is the time for all good men to come to the aid of their country." was proposed as a typing drill by a teacher named Charles E. Weller aka "Chase" in 1918.'puts str.gsub(/"(.*?)"/, '\1')

Now is the time for all good men to come to the aid of their country. was proposed as a typing drill by a teacher named Charles E. Weller aka Chase in 1918.

Replacement


/\b(the|is|of)\b/

1. is2. the3. the4. of




/\b(?:the|is|of)\b/



Walkthrough!



Part VFlags

/cat/giflags

regex

delimiters

Perl / PCRE Style

Pattern.compile(“cat”, CASE_INSENSITIVE | DOTALL);

flagsregex

delimiters

Java Style

Javaglue

i CASE_INSENSITIVE

g

s DOTALL

m MULTILINE

Part VIHow do I use my powers?

grepaka cheat at Letterpress!

Your Text Editor!

$str = 'three cats chased five mice';$str =~ /(cats|mice)/;print $1;$str =~ s/(cats|mice)/fuzzy $1/g;print $str;

catsthree fuzzy cats chased five fuzzy mice

var str = 'three cats chased five mice';var matches = str.match(/(cats|mice)/);console.log( matches[1] );str.replace(/(cats|mice)/g, ‘fuzzy $1’);console.log( str );


Script

str = 'three cats chased five mice'matches = str.match(/(cats|mice)/)puts matches[1]str.gsub!(/(cats|mice)/, ‘fuzzy \1’)puts str


String str = “three cats chased five mice”;Pattern p = Pattern.compile(“(cats|mice)”);Matcher m = p.matcher( str );System.out.println( m.group(1) );String newStr = str.replaceAll(“(cats|mice)”, “fuzzy $1”);System.out.println( str );


String str = “three cats chased five mice”;Pattern p = Pattern.compile(“\b\w{4}\b”);Matcher m = p.matcher( str );System.out.println( m.group(1) );

String str = “three cats chased five mice”;Pattern p = Pattern.compile(“\b\w{4}\b”);Matcher m = p.matcher( str );System.out.println( m.group(1) );

No.

String str = “three cats chased five mice”;Pattern p = Pattern.compile(“\\b\\w{4}\\b”);Matcher m = p.matcher( str );System.out.println( m.group(1) );

http://www.regexplanet.com/advanced/java/index.html

regular expressions

Technology

good men

typing drill

weller aka chase

good time email

aeiou http

tmtowtdi http

s http

w http