Regex-Fu

Presented on May 8th, 2018 at Codemotion Amsterdam, The Netherlands.
https://amsterdam2018.codemotionworld.com/
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Regular expression, you either hate them or you love them, but do you really know how to harness their power ? Based on the PCRE implementation, this talk will show you how to get the most out of your /^regex(es)?$/, how switches affect your results, how to be less greedy, how to assert your power and let's not forget: when *not* to use regex.
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Links:
http://regexcheatsheets.com/
https://www.pluralsight.com/courses/regular-expressions-fundamentals

Transcript

1. RegEx-Fu Juliette Reinders Folmer @jrf_nl AMSTERDAM | MAY 8-9, 2018
3. Wildcards on Steroids
4. Pattern Recognition
5. Regex Engines POSIX PCRE ECMAscript Oniguruma Boost DEELX RE2 TRE Pattwo GRETA GLib/ GRegex FREJ RGX QT CL-PPCRE Jakarta Henry Spencer’s regex
6. Syntax Overlap
7. PCRE
8. Terminology /[a-z0-9]+/im Regular Expression /[a-z0-9]+/im Delimiters /[a-z0-9]+/im Modifiers
9. Tips & Tricks
10. Photo by Scott Liddell 1. If you need a screwdriver, why use a hammer ?
11. 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.
12. 2. Nothing in life is to be feared. It is only to be understood. Marie Curie
13. Whitelisting Blacklisting Input string Input string ? ?
14. 3. Not all matches are made in heaven... Photo by Petr Kratochvil
15. 4. Only Elephants Remember Everything © Photo by Juliette Reinders Folmer
16. (?:<expr>)
17. Less is the new more 5
18. / / 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 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
19. / / We take one step back, two steps forward
20. <unit>{,m}? <unit>{n,}? <unit>{n,m}? <unit>*? <unit>+? <unit>?? Reluctant Quantifiers
21. 6. Being negative isn't always a bad thing © Photo by Juliette Reinders Folmer
22. [^<chars>]
23. 7. Explore Your Boundaries Photo by Miguel A.C. Domingo
24. Beginning of string Beginning of line Word boundaries End of string End of line
25. 8. The first love is the deepest...
26. /#?([A-F0-9]{6}|[A-F0-9]{3})/i
27. 9. What's this global village people keep talking about ???
28. 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 - -
29. déjà vu [\w ]+ French (fr) déjà vu [\w ]+ English (en)
30. 10. Escape and escape again
31. String delimiter - for prog language Regex delimiter - for regex - for prog language Meta-characters - for regex - for prog language What to Escape ?
32. \[ \] \( \) \| \. \? \* \+ \{ \} \^ \$ \\ \/ Literals [ ] ( ) | . ? * + { } ^ $ \ / (delimiter) Special Meaning Escaping Meta Characters
33. [(] [)] [|] [.] [?][*][+][{][}] [$] [/] Literals [ ] ( ) | . ? * + { } ^ $ \ / (delimiter) Special Meaning Escaping Meta Characters
34. 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(/[[\]\/\\{}()|?+^$*.-]/g, "\\$&"); }
35. Matching a Literal Backslash \\\\ The actual backslash \\\\ Escaping for use in regex \\\\ String escape
36. Modify your behaviour 11
38. Setting: Unsetting: Combined: Apply to subpattern (non-capturing): Inline Modifiers (?i) (?-i) (?im-sx) (?i:subp)
39. Explore
41. /^(( 25[0-5]| # Match 250-255 range 2[0-4][0-9]| # Match 200-249 range [01]?[0-9]{1,2} # Match 0-199 range )\.){3} # Repeat 3 times with period (25[0-5]|2[0-4][0-9]|[01]?[0-9]{1,2}) # and once without $/x
43. [0] – Complete match [1] – Match against sub-pattern 1 [2] – Match against sub-pattern 2 [3] – Match against sub-pattern 3 ... Match Array Photo by Petr Kratochvil
44. (?<name><expr>) (?P>name)
45. [0] – Complete match [firstname] – Match against named sub-pattern firstname [lastname] – Match against named sub-pattern lastname ... Match Array Photo by Petr Kratochvil
46. Image by Gerd Altmann
47. — Richard Feynman Know how to solve every problem that has been solved. What I cannot create, I do not understand. Photo by Gleick, J. Genius. p. 310f
48. Advanced Features Look around Conditional sub-patterns Recursion Inline comments
49. Thanks! Any questions ? Slides: https://speakerdeck.com/jrf Course: https://www.pluralsight.com/courses/ regular-expressions-fundamentals