Ruby Tips

Shuffle a word

The same technique to shuffle an array of numbers can be used to shuffle words. This is great if you want to scramble words, as in creating anagram puzzles.

'anagram'.split(//).shuffle.join
=> "gnaarma"

Shuffle a list of numbers

<geshi lang="ruby"> (1..14).to_a.sort {rand <=> 0.5} => [14, 8, 1, 9, 3, 10, 5, 11, 7, 12, 4, 13, 2, 6]

1. or

(1..14).to_a.shuffle => [2, 5, 8, 12, 4, 3, 6, 13, 7, 11, 10, 1, 9, 14] </geshi>

Rename files

<geshi lang="bash"> for f in `ls`; do mv -u $f $(ruby -e "puts '$f'.gsub('14','13')"); done </geshi>

Check CLASSPATH

<geshi lang="ruby">

1. !/bin/env ruby
3. Checks to make sure all the entries on the classpath are valid

1. We only want to emit color codes if we're outputting to a terminal. If this is getting piped into grep or less, we'll ignore these

red=STDOUT.isatty ? "\e[1;31m" :"" normal=STDOUT.isatty ? "\e[0;0m" : ""

cp = ENV['CLASSPATH']

if cp == nil then

 STDERR.puts "No CLASSPATH set"
 exit 1

else

 # We'll assume a Windows CP.  We could do something ticky, but we have to be very tricky, because we're probably in Cygwin
 cp.split(';').each do |file|
   if !File.readable?(file) then
     STDERR.puts "Warning: Classpath file #{red}#{file}#{normal} can't be read"
   end
 end

end </geshi>

nextPrime

Short script to return the next prime number. <geshi lang="ruby">

1. !/bin/env ruby

def isPrime(n)

 prime = true
 3.step(Math::sqrt(n), 2) do |i|
   if (n % i == 0) then
     prime = false
     break
   end
 end
 if (( n%2 !=0 && prime && n > 2) || n == 2) then
   return true
 else
   return false
 end

end

i = ARGV[0].to_i

while !isPrime(i)

 i += 1

end

puts i </geshi>

Tab Completion in IRb

Add this to your .irbrc.

<geshi lang="ruby">

require 'irb/completion'
ARGV.concat [ "--readline", "--prompt-mode", "simple" ]

</geshi>

Thanks [why].

Ruby Patch to Zip

A script to take an Eclipse generated patch file, and zip every file which is referenced in the patch.

Ruby gems on Cygwin

aka how to fix ruby: no such file to load -- ubygem (LoadError) or /usr/bin/ruby: no such file to load -- ubygems (LoadError) <geshi lang="bash"> $ unset RUBYOPT $ cd /tmp/ $ wget http://rubyforge.org/frs/download.php/20989/rubygems-0.9.4.tgz $ tar -zxf rubygems-0.9.4.tgz $ cd rubygems-0.9.4 $ ruby setup.rb </geshi>

Ruby detab

A script for removing tabs from source files

Error Messages

• uninitialized constant PStore
• nonexistent sybase adapter

irb

Setup tab completion and history here: http://wiki.rubygarden.org/Ruby/page/show/Irb/TipsAndTricks

Escape invalid XML characters.

This is useful for running stuff through before posting it to the wiki.

echo "<a href=\"foo\">" | ruby -pe 'gsub!(/\&/, "&"); gsub!(/"/, """); gsub!(/</, "<"); gsub!(/>/, ">"); '
&lt;a href=&quot;foo&quot;&gt;