Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
The Language of Regular Expressions. So You Thi...
Search
Riga Dev Day
March 13, 2016
0
68
The Language of Regular Expressions. So You Think You Can Speak It? by Rustam Mehmandarov
Riga Dev Day
March 13, 2016
Tweet
Share
More Decks by Riga Dev Day
See All by Riga Dev Day
Faster Java by Adding Structs (Sort Of)
rigadevday
0
160
Prepare for JDK 9! by Dalibor Topic
rigadevday
0
110
Little Important Things in Distributed Architectures by Andres Jaan Tack
rigadevday
0
120
Oracle 12c for Developers by Alex Nuijten
rigadevday
1
120
Modern Java Component Design with Spring 4.3 by Juergen Hoeller
rigadevday
0
230
Open Source and OpenJDK: Do They Deliver? by Simon Ritter
rigadevday
0
60
Google Apps Integration in Oracle Apex by Richard Martens
rigadevday
0
280
Integration Testing from the Trenches by Nicolas Fränkel
rigadevday
0
230
Distributed Systems at ok.ru by Oleg Anastasyev
rigadevday
0
76
Featured
See All Featured
No one is an island. Learnings from fostering a developers community.
thoeni
21
3.5k
Being A Developer After 40
akosma
91
590k
The Psychology of Web Performance [Beyond Tellerrand 2023]
tammyeverts
49
3.1k
Why You Should Never Use an ORM
jnunemaker
PRO
59
9.6k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
37
2.6k
The Art of Delivering Value - GDevCon NA Keynote
reverentgeek
16
1.7k
Gamification - CAS2011
davidbonilla
81
5.5k
Imperfection Machines: The Place of Print at Facebook
scottboms
269
13k
jQuery: Nuts, Bolts and Bling
dougneiner
65
7.9k
How to train your dragon (web standard)
notwaldorf
97
6.3k
Fantastic passwords and where to find them - at NoRuKo
philnash
52
3.5k
CoffeeScript is Beautiful & I Never Want to Write Plain JavaScript Again
sstephenson
162
15k
Transcript
The Language of Regular Expressions. So You Think You Can
Speak It? Rustam Mehmandarov Riga Dev Day
The Vision http://xkcd.com/208/
…but regex ain’t one! Oh, wait! http://xkcd.com/1171/
The Reality
None
(([0-9]{4})-([0-9]{2})-([0-9]{2})).*\sINFO\s(.*)
Log4j Log File
.*(INFO|WARN).*
.*(INFO|WARN).*
(([0-9]{4})-([0-9]{2})-([0-9]{2})).*ERROR(.*)
(([0-9]{4})-([0-9]{2})-([0-9]{2})).*ERROR(.*)
^.*192\.168\.0\.6[^9](.*)$
^.*192.168.0.6[^9](.*)
^.*192\.168\.0\.6[^9](.*)$
^.*192\.168\.0\.6[0-9]+[^9](.*)$
flavou?r
Recap: Quantifiers * + ? {num} {num, num}
Recap: Grouping .*(INFO|WARN)(.*) .*(INFO|WARN)(?:.*)
(WA) 2014-09-09 WAR FILE WARN [com.example.logging.MyLog]
(?=WARN)WA 2014-09-09 WAR FILE WARN [com.example.logging.MyLog]
(?=WARN)WA
Recap: Lookaround (?=foo) -> Lookahead (?<=foo) -> Lookbehind (?!foo) ->
Negative Lookahead (?<!foo) -> Negative Lookbehind
Lookahead: Example
The list
Backreferences
Backreferences (contd.)
Text: OSDC is awesome! HTML: OSDC is <em>awesome</em>! Regex: <.+>
Result:
Text: OSDC is awesome! HTML: OSDC is <em>awesome</em>! Regex: <.+?>
Result:
None
http://stackoverflow.com/questions/1732348/ regex-match-open-tags-except-xhtml-self- contained-tags
Quantifiers Revisited Greedy: *, +, ?, {num, num} Non-greedy: *?,
+?, ??, {num, num}?
Final Recap • Know your data! – Think what you
should match – Think what you should not match • Know your flavor • Know your engine (DFA, NFA) – Backtracking • Greediness • Non-capturing parenthesis • Anchors
MOAR! EXAMPLES!
Matching an IP - 1 Idea 1: ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ Result:
Matching an IP - 2 Idea 2: ^\d\d\d\.\d\d\d\.\d\d\d\.\d\d\d$ Result:
Matching an IP - 3 Idea 3: ^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$ Result:
Matching an IP - 4 Idea 4: ^ ([01]?\d\d?|2[0-4]\d|25[0-5])\. ([01]?\d\d?|2[0-4]\d|25[0-5])\.
([01]?\d\d?|2[0-4]\d|25[0-5])\. ([01]?\d\d?|2[0-4]\d|25[0-5]) $ Result:
Your New Reality! http://xkcd.com/208/
Thank you! rmehmandarov
[email protected]
None