Regex Fundamentals

Presented on September 16 2016 at Codemotion Warsaw, Warsaw, Poland.
http://warsaw2016.codemotionworld.com/
---------------------------------------------------------------
No matter whether you develop in PHP, Javascript, Ruby, Python or even HTML5, knowing how to write Regular Expressions is an essential skill for any developer. While a lot of people consider regexes to be black magic, used appropriately they're an awesome power-tool in your tool-belt. This talk will take you on a little walk on the wild side, show you how to build effective regular expressions, introduce you to some of the more advanced features and teach you some useful tips and tricks of the trade.
---------------------------------------------------------------

Links:
http://regexcheatsheets.com/
https://www.pluralsight.com/courses/regular-expressions-fundamentals

Transcript

1. Regular Expression Fundamentals Juliette Reinders Folmer @jrf_nl regexcheatsheets.com
2. pluralsight.com
3. Wildcards on Steriods
4. Pattern Recognition
5. Serial numbers Barcodes Flight numbers CSV files Log files Email headers Twitter handles Facebook username Skype usernames MD5 hash Sentences Good passwords Isbn numbers HTML code Html tags Html attributes CSS code Urls Email addresses File names File extensions Directory paths Postal codes Telephone numbers Number plates Credit card numbers Bank account numbers Mathematical formulas Elements from the periodical table Patterns in text strings
6. Whitelisting Blacklisting Input string Input string ? ?
7. Typical Uses for Regular Expressions Search (and replace) String parsing Data mapping Syntax highlighting Data scraping Input validation
8. (Sys-)Admins File system Server directives Data Professionals Query data Developers Working with strings Users of Regular Expressions
9. How It Works
10. Subject String Subject
11. How It Works Pattern Regex Subject Function Engine Result
12. What are the matches ? How many matches have been found ? Does it match ? Result Types
13. Regex Engines POSIX PCRE ECMAscript Oniguruma Boost DEELX RE2 TRE Pattwo GRETA GLib/ GRegex FREJ RGX QT CL-PPCRE Jakarta Henry Spencer’s regex
14. Syntax Overlap
15. Still with me ?
16. Terminology /[a-z0-9]+/im Regular Expression /[a-z0-9]+/im Delimiters /[a-z0-9]+/im Modifiers
17. A a 1 . ? * + {#} [...] ( ... | ... ) ^ ... $ \w \d \s g m s i  Literals  Wildcard  Quantifiers  Character ranges  Grouping and alternation  Anchors  Shorthand character codes  Modifiers Basic Syntax
19. The Pattern # AB 12 34
21. Visualization of the Pattern
22. Tips & Tricks
23. Photo by Scott Liddell 1. If you need a screwdriver, why use a hammer ?
24. Jamie Zawinski, August 1997 alt.religion.emacs Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems.
25. 2. Not all matches are made in heaven... Photo by Petr Kratochvil
26. 3. Only Elephants Remember Everything © Photo by Juliette Reinders Folmer
27. (?:<expr>)
28. 4. Being negative isn't always a bad thing © Photo by Juliette Reinders Folmer
29. [^<chars>]
30. Less is the new more 5
31. / / o on one one. one.* one.*s one.*s. one.*s.? one.*s.?t one.*s.?t [a-z] one.*s.?t[a-z]+ one.*s.?t[a-z]+p = space one.*s.?t[a-z]+p one.*s.?t[a-z]+p . one.*s.?t[a-z]+p . {2,} one.*s.?t[a-z]+p .{2,}, one.*s.?t[a-z]+p .{2,}, We take one step forward, two steps back ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
32. / / We take one step back, two steps forward
33. <unit>{,m}? <unit>{n,}? <unit>{n,m}? <unit>*? <unit>+? <unit>?? Reluctant Quantifiers
34. 6. Explore Your Boundaries Photo by Miguel A.C. Domingo
35. Beginning of string Beginning of line Word boundaries End of string End of line
36. 7. The first love is the deepest...
37. /#?([A-F0-9]{6}|[A-F0-9]{3})/i
38. 8. What's this global village people keep talking about ???
39. Character classes PCRE POSIX [0-9] [^0-9] \d \D [[:digit:]] [^[:digit:]] [A-Za-z0-9_] [^A-Za-z0-9_] \w \W [[:word:]] [^[:word:]] [\t\f\r\n \v] [^\t\f\r\n \v] \s \S [[:space:]] [^[:space:]] [\t\f ] [^\t\f ] \h \H [[:blank:]] [^[:blank:]] [\r\n] [^\r\n] \v \V - -
40. déjà vu [\w ]+ French (fr) déjà vu [\w ]+ English (en)
41. 9. Escape and escape again
42. \[ \] \( \) \| \. \? \* \+ \{ \} \^ \$ \\ \/ Literals [ ] ( ) | . ? * + { } ^ $ \ / (delimiter) Special Meaning Escaping Meta Characters
43. [(] [)] [|] [.] [?][*][+][{][}] [$] [/] Literals [ ] ( ) | . ? * + { } ^ $ \ / (delimiter) Special Meaning Escaping Meta Characters
44. Java String.quote() quoteReplacement() PHP preg_quote() Matlab regexptranslate() Python re.escape() Objective-C escapedTemplateForString() escapedPatternForString() Ruby Regexp.escape() Regexp.quote() Escaping Arbitrary Strings // Javascript: function escapeInputString( str ) { return str.replace(/[[\]\/\\{}()|?+^$*.-]/g, "\\$&"); }
45. Matching a Literal Backslash \\\\ The actual backslash \\\\ Escaping for use in regex \\\\ String escape
46. Modify your behaviour 10
48. Setting: Unsetting: Combined: Apply to subpattern (non-capturing): Inline Modifiers (?i) (?-i) (?im-sx) (?i:subp)
50. Advanced Features Look around Named sub-matches Conditional sub-patterns Recursion Inline comments
51. Thanks! Any questions ? Slides: https://speakerdeck.com/jrf Course: https://www.pluralsight.com/courses/ regular-expressions-fundamentals