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‎README.md‎

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# learn_ruby_oneliners
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Example based guide for text processing with ruby from the command line
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# Ruby one-liners cookbook
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Example based guide for text processing with `ruby` from the command line.
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<p align="center">
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<img src="./images/ruby_oneliners.png" width="320px" height="400px" />
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</p>
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The book also includes exercises to test your understanding, which is presented together as a single file in this repo - [Exercises.md](./exercises/Exercises.md)
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For solutions to the exercises, see [Exercise_solutions.md](./exercises/Exercise_solutions.md).
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See [Version_changes.md](./Version_changes.md) to keep track of changes made to the book.
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<br>
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# E-book
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TODO
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<br>
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# Feedback
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Please open an issue if you spot any typo/errors.
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I'd also highly appreciate your feedback about the book.
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Twitter: https://twitter.com/learn_byexample
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<br>
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# Table of Contents
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1) Preface
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2) One-liner introduction
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3) Line processing
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4) Field separators
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5) Record separators
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6) Multiple file input
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7) Processing multiple records
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8) Two file processing
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9) Dealing with duplicates
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10) Processing structured data
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<br>
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# Acknowledgements
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* [ruby-lang documentation](https://www.ruby-lang.org/en/documentation/) — manuals and tutorials
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* [/r/ruby/](https://www.reddit.com/r/ruby/) — helpful forum for beginners and experienced programmers alike
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* [stackoverflow](https://stackoverflow.com/) — for getting answers to pertinent questions on Ruby, one-liners, etc
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* [tex.stackexchange](https://tex.stackexchange.com/) — for help on `pandoc` and `tex` related questions
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* [LibreOffice Draw](https://www.libreoffice.org/discover/draw/) — cover image
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* [Warning](https://commons.wikimedia.org/wiki/File:Warning_icon.svg) and [Info](https://commons.wikimedia.org/wiki/File:Info_icon_002.svg) icons by [Amada44](https://commons.wikimedia.org/wiki/User:Amada44) under public domain
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* [softwareengineering.stackexchange](https://softwareengineering.stackexchange.com/questions/39/whats-your-favourite-quote-about-programming) and [skolakoda](https://skolakoda.org/programming-quotes) for programming quotes
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A heartfelt thanks to all my readers. Your valuable support has significantly eased my financial concerns and allows me to continue writing books.
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<br>
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# License
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The book is licensed under a [Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License](https://creativecommons.org/licenses/by-nc-sa/4.0/)
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The code snippets are licensed under MIT, see [LICENSE](./LICENSE) file
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‎Version_changes.md‎

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<br>
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### 1.0
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* First version

‎code_snippets/Dealing_with_duplicates.sh‎

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## Whole line duplicates
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cat purchases.txt
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ruby -e 'puts readlines.uniq' purchases.txt
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ruby -rset -ne 'BEGIN{s=Set.new}; print if s.add?($_)' purchases.txt
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## Column wise duplicates
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cat duplicates.txt
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ruby -rset -F, -ane 'BEGIN{s=Set.new}; print if s.add?($F[-1])' duplicates.txt
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ruby -rset -F, -ane 'BEGIN{s=Set.new};
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print if s.add?($F.values_at(0,2))' duplicates.txt
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## Duplicate count
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ruby -F, -ane 'BEGIN{h=Hash.new(0)};
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print if (h[$F[1]]+=1)==2' duplicates.txt
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ruby -F, -ane 'BEGIN{h=Hash.new(0)};
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print if (h[$F[-1]]+=1)==3' duplicates.txt
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tac duplicates.txt | ruby -rset -F, -ane 'BEGIN{s=Set.new};
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print if s.add?($F[-1])' | tac
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ruby -F, -ane 'BEGIN{h=Hash.new(0)}; ARGV.size==1 ? h[$F[-1]]+=1 :
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h[$F[-1]]>1 && print' duplicates.txt duplicates.txt
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ruby -F, -ane 'BEGIN{h=Hash.new(0)}; ARGV.size==1 ? h[$F[-1]]+=1 :
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h[$F[-1]]>2 && print' duplicates.txt duplicates.txt
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ruby -F, -ane 'BEGIN{h=Hash.new(0)}; ARGV.size==1 ? h[$F[2]]+=1 :
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h[$F[2]]==1 && print' duplicates.txt duplicates.txt
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‎code_snippets/Field_separators.sh‎

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## Default field separation
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echo ' a b c ' | ruby -ane 'puts $F.size'
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echo ' a b c ' | ruby -ane 'puts $F[0]'
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echo ' a b c ' | ruby -ane 'puts $F[-1] + "."'
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printf ' one \t\f\v two\t\r\tthree ' | ruby -ane 'puts $F.size'
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printf ' one \t\f\v two\t\r\tthree ' | ruby -ane 'puts $F[1] + "."'
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## Input field separator
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echo 'goal:amazing:whistle:kwality' | ruby -F: -ane 'puts $F[0], $F[-1]'
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echo 'one;two;three;four' | ruby -F';' -ane 'puts $F[2]'
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echo 'load;err_msg--\ant,r2..not' | ruby -F'\W+' -ane 'puts $F[2]'
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echo 'hi.bye.hello' | ruby -F'\.' -ane 'puts $F[1]'
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printf 'COOL\nnice car\n' | ruby -F'(?i)[aeiou]' -ane 'puts $F.size - 1'
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echo 'apple' | ruby -ne 'puts $_[0]'
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ruby -e 'puts Encoding.default_external'
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LC_ALL=C ruby -e 'puts Encoding.default_external'
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echo 'fox:αλεπού' | ruby -ne 'puts $_[4..5]'
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echo 'fox:αλεπού' | ruby -E UTF-8:UTF-8 -ne 'puts $_[4..5]'
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echo 'cat dog' | ruby -ane 'puts "[#{$F[-1]}]"'
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echo 'cat:dog' | ruby -F: -ane 'puts "[#{$F[-1]}]"'
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printf 'cat:dog' | ruby -F: -ane 'puts "[#{$F[-1]}]"'
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echo ' a b c ' | ruby -ane 'puts $F.size'
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echo ':a:b:c:' | ruby -F: -ane 'puts $F.size'
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echo 'cat:dog' | ruby -F: -lane 'puts "[#{$F[-1]}]"'
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echo 'cat:dog' | ruby -F: -lane 'print "[#{$F[-1]}]"'
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echo ':a:b:c:' | ruby -F: -lane 'puts $F.size'
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echo ':a:b:c:' | ruby -lane 'puts $_.split(/:/, -1).size'
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## Output field separator
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ruby -lane 'BEGIN{$, = " "}; print $F[0], $F[2]' table.txt
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ruby -W:no-deprecated -lane 'BEGIN{$, = " "}; print $F[0], $F[2]' table.txt
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ruby -lane 'puts "#{$F[0]} #{$F[2]}"' table.txt
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echo 'Sample123string42with777numbers' | ruby -F'\d+' -lane 'puts $F.join(",")'
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s='goal:amazing:whistle:kwality'
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echo "$s" | ruby -F: -lane 'puts $F.values_at(-1, 1, 0).join("-")'
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echo "$s" | ruby -F: -lane '$F.append(42); puts $F * "::"'
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## scan method
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s='Sample123string42with777numbers'
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echo "$s" | ruby -lne 'puts $_.scan(/\d+/)[1]'
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echo "$s" | ruby -lne 'puts $_.scan(/[a-z]+/i) * ","'
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s='eagle,"fox,42",bee,frog'
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echo "$s" | ruby -F, -lane 'puts $F[1]'
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echo "$s" | ruby -lne 'puts $_.scan(/"[^"]*"|[^,]+/)[1]'
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## Fixed width processing
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cat items.txt
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ruby -ne 'puts $_.unpack("a8a4a6") * ","' items.txt
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ruby -ne 'puts $_.unpack("a8a4a6")[1]' items.txt
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ruby -ne 'puts $_.unpack("a5x3a3xa6") * ","' items.txt
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printf 'banana\x0050\x00' | ruby -ne 'puts $_.unpack("Z*Z*") * ":"'
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ruby -ne 'puts $_.unpack("a5x3a*") * ","' items.txt
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echo 'b 123 good' | ruby -ne 'puts $_[2,3]'
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echo 'b 123 good' | ruby -ne 'puts $_[6,4]'
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echo 'b 123 good' | ruby -lpe '$_[2,3] = "gleam"'
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## Assorted field processing methods
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s='goal:amazing:42:whistle:kwality:3.14'
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echo "$s" | ruby -F: -lane 'puts $F.grep(/i[nts]/) * ":"'
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echo "$s" | ruby -F: -lane 'puts $F.grep_v(/\d/) * ":"'
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s='goal:amazing:42:whistle:kwality:3.14'
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echo "$s" | ruby -F: -lane 'puts $F.map(&:upcase) * ":"'
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echo '23 756 -983 5' | ruby -ane 'puts $F.map {|n| n.to_i ** 2} * " "'
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echo 'AaBbCc' | ruby -lne 'puts $_.chars.map(&:ord) * " "'
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echo '3.14,17,6' | ruby -F, -ane 'puts $F.map(&:to_f).sum'
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s='hour hand band mat heated pineapple'
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echo "$s" | ruby -ane 'puts $F.filter {|w| w[0]!="h" && w.size<6}'
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echo "$s" | ruby -ane 'puts $F.filter_map {|w|
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w.gsub(/[ae]/, "X") if w[0]=="h"}'
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echo '3.14,17,6' | ruby -F, -lane 'puts $F.map(&:to_f).reduce(100, :+)'
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echo '3.14,17,6' | ruby -F, -lane 'puts $F.map(&:to_f).reduce(:*)'
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echo '3.14,17,6' | ruby -F, -lane 'puts $F.reduce(1) {|op,n| op*n.to_f}'
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s='floor bat to dubious four'
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echo "$s" | ruby -ane 'puts $F.sort * ":"'
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echo "$s" | ruby -ane 'puts $F.sort_by(&:size) * ":"'
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echo 'foobar' | ruby -lne 'puts $_.chars.sort.reverse * ""'
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s='try a bad to good i teal by nice how'
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echo "$s" | ruby -ane 'puts $F.sort { |a, b|
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[b.size, a] <=> [a.size, b] } * ":"'
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s='3,b,a,3,c,d,1,d,c,2,2,2,3,1,b'
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echo "$s" | ruby -F, -lane 'puts $F.uniq * ","'
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cat marks.txt
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ruby -ane 'idx = $F.each_index.sort {|i,j| $F[j] <=> $F[i]} if $.==1;
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puts $F.values_at(*idx) * "\t"' marks.txt
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s='floor bat to dubious four'
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echo "$s" | ruby -ane 'puts $F.shuffle * ":"'
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echo 'foobar' | ruby -lne 'print $_.chars.shuffle * ""'
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s='hour hand band mat heated pineapple'
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echo "$s" | ruby -ane 'puts $F.sample'
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echo "$s" | ruby -ane 'puts $F.sample(2)'
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