RE: AWK

Transcript

1. RE: AWK @wtnabe Kanazawa.rb meetup #18 2014-02-15 (Sat) at IT

   Plaza MUSASHI

2. Abstract

3. Regular Expression Basics AWK Basics

4. Regular Expression Basics

5. Difficulties of RE Many different implementations Complex Character Sequences

6. Rough Classification POSIX ( Basic / Extended ) PCRE (Perl

   Compatible Regular Expression) PHP, Apache, GNU Grep, ... GNU ( Basic / Extended ) and more

7. Ignore Minor tool's original expressions What does grep in your

   tools mean ?

8. Basic Syntax Literal Character Meta Character / Escape Sequence Character

   List / Character Class Grouping and Back reference

9. Elementary Operators . * + ? | () grouping and

   back reference

10. Elementary Operators ^ $ ( \A \z ) \r \n

    \s \xXX escape sequence [] [^] character list

11. RE Literal and Language Syntax Such as escape sequence CONFLICT

    with parent language Some Languages have RE Literal AWK, Perl, Ruby, JavaScript, ...

12. Examples /^[0-9]+(-[0-9]+)+$/ /\s[Kk]anazawa\.rb\s/ %r{\bhttps?://.*\b}

13. Keep away Too Match /[0-9-]+/ Complex one-shot match q{[^"'<>]*(? :"[^"]*"[^"'<>]*|'[^']*'[^"'<>]*)*(?

    :>|(?=<)|$(?!\n))}; #'}}}} cf. Perlメモ

14. AWK

15. Name from famous Human Names Aho Weinberger Kernighan

16. Filter-oriented Programming Language $ awk 'script' srcfile $ cat srcfile

    | awk 'script' > destfile $ awk -f script srcfile

17. Basic Syntax C-like / Shell-like ( semicolon less ) Patterns

    and Actions No need to write about stdin and split

18. Patterns and Actions pattern { action } pattern { action

    }

19. BEGIN and END rule BEGIN { ... } END {

    ... }

20. Example Count a number of gems depending on from Gemfile.lock

21. Gemfile.lock GEM remote: https://rubygems.org/ specs: blankslate (2.1.2.4) ... PLATFORMS ruby

    DEPENDENCIES ...

22. BEGIN { counting = 0 } /^$/ { counting =

    0 } counting == 1 && !/:/ { print $1 } /^GEM$/ { counting = 1 }

23. $ awk -f script.awk Gemfile.lock | \ sort | uniq

    | wc -l

24. Same as NF == 2 && $2 ~ /\(.*\)/ {print

    $1}

25. Notes http://www.regular-expressions.info/ 正規表現メモ The GNU Awk User's Guide The GAWK

    Manual - Table of Contents