I&#39;m not really sure, but maybe this can help:
    
    update-alternatives --config ruby

... and here&#39;s the non-interactive, scriptable, way:

    update-alternatives --set ruby /usr/bin/ruby1.9.1

You may find out about available alternatives and respective `/usr/bin/...` paths by doing:

    update-alternatives --query ruby


Martin - Take a look at the following link: http://ryanbigg.com/2010/12/ubuntu-ruby-rvm-rails-and-you/

This is where installation of ruby is heading for ubuntu servers. This should allow you to not only switch to a ruby version when needed, but also keep gems separated based on ruby versions, etc.

You can completely remove Ruby 1.8 too with:

    sudo apt-get remove libruby1.8 ruby1.8 ruby1.8-dev rubygems1.8

After that, you will only have Ruby 1.9 installed. 


    sudo \curl -L https://get.rvm.io | bash -s stable --ruby --rails
will install an up-to-date version of ruby (and rails), and allow you to avoid brokenness of Ubuntu&#39;s RVM, see https://stackoverflow.com/a/9056395/497756.

If you go this route, get rid of Ubuntu-installed versions and associated packages like `bundle`.

Details here: https://rvm.io/rvm/install/

(Note: this is the TL;DR version of the post by henry74.)

Try this:

    sudo apt-get install ruby1.9.1 rubygems1.9.1

or try building from source. this worked for me on ubuntu 9.04 and after a restart 1.9 was the standard ruby



I have this test code:

    import java.util.*;
    
    class MapEQ {
    
      public static void main(String[] args) {
       Map&lt;ToDos, String&gt; m = new HashMap&lt;ToDos, String&gt;();
       ToDos t1 = new ToDos(&quot;Monday&quot;);
       ToDos t2 = new ToDos(&quot;Monday&quot;);
       ToDos t3 = new ToDos(&quot;Tuesday&quot;);
       m.put(t1, &quot;doLaundry&quot;);
       m.put(t2, &quot;payBills&quot;);
       m.put(t3, &quot;cleanAttic&quot;);
       System.out.println(m.size());
    } }
    
    class ToDos{
    
      String day;
    
      ToDos(String d) { day = d; }
    
      public boolean equals(Object o) {
          return ((ToDos)o).day == this.day;
     }

    // public int hashCode() { return 9; }
    }


When `// public int hashCode() { return 9; }` is uncommented  `m.size()` returns 2, when it&#39;s left commented it returns three. Why?



Understanding the workings of equals and hashCode in a HashMap

In Java VisualVM, is there any way to display total method time, rather than &quot;self time&quot;? (The latter is not particularly useful, since it doesn&#39;t tell you anything about how much time methods actually take to run.)

If not, is there any standalone free Java profiler that does calculate total method time?

Total method time in Java VisualVM

Is there any way, on Ubuntu 9.04, to install Ruby 1.8 as `ruby1.8` (or get rid of it altogether) and have Ruby 1.9 be the default `ruby`?

How do I make Ruby 1.9 the default Ruby on Ubuntu?

<p>Is there any way, on Ubuntu 9.04, to install Ruby 1.8 as <code>ruby1.8</code> (or get rid of it altogether) and have Ruby 1.9 be the default <code>ruby</code>?</p>


Been playing with Ruby on Rails for awhile and decided to take a look through the actual source. Grabbed the repo from GitHub and started looking around. Came across some code that I am not sure what it does or what it references. 

I saw this code in actionmailer/test/abstract_unit.rb

    root = File.expand_path(&#39;../../..&#39;, __FILE__)
     begin
     require &quot;#{root}/vendor/gems/environment&quot;
     rescue LoadError
     $:.unshift(&quot;#{root}/activesupport/lib&quot;)
     $:.unshift(&quot;#{root}/actionpack/lib&quot;)
    end

    lib = File.expand_path(&quot;#{File.dirname(__FILE__)}/../lib&quot;)
    $:.unshift(lib) unless $:.include?(&#39;lib&#39;) || $:.include?(lib)

    require &#39;rubygems&#39;
    require &#39;test/unit&#39;

    require &#39;action_mailer&#39;
    require &#39;action_mailer/test_case&#39;

Can someone tell me what the $: (a.k.a. &quot;the bling&quot;) is referencing?



What does the &quot;$&quot; character mean in Ruby?

How do I get a list of the folders that exist in a certain directory with ruby?

`Dir.entries()` looks close but I don&#39;t know how to limit to folders only.


Getting a list of folders in a directory

So matz made the decision to keep `upcase` and `downcase` limited to `/[A-Z]/i` in ruby 1.9.1.

`ActiveSupport::Multibyte` has long had great i18n case jiggering in ruby 1.8.x via `String#mb_chars`.

However, when tried under ruby 1.9.1, it doesn&#39;t seem to work. Here&#39;s a simple test script I wrote, along with the output I&#39;m getting:

    $ cat test.rb
    # encoding: UTF-8

    puts(&quot;@ #{RUBY_VERSION} &quot; + (__ENCODING__ rescue $KCODE).to_s)
    sd, su = &quot;I&#241;t&#235;rn&#226;ti&#244;n&#224;liz&#230;ti&#248;n&quot;, &quot;I&#209;T&#203;RN&#194;TI&#212;N&#192;LIZ&#198;TI&#216;N&quot;
    def ps(u, d, k); puts &quot;%-30s:  %24s / %-24s&quot; % [k, u, d] end
    ps sd.upcase, su.downcase, &quot;Plain ruby&quot;

    require &#39;rubygems&#39;; require &#39;active_support&#39;
    ps sd.upcase, su.downcase, &quot;With active_support&quot;
    ps sd.mb_chars.upcase.to_s, su.mb_chars.downcase.to_s, &quot;With active_support mb_chars&quot;

    $ ruby -KU test.rb
    @ 1.8.7 UTF8
    Plain ruby                    :  I&#241;T&#235;RN&#226;TI&#244;N&#224;LIZ&#230;TI&#248;N / i&#209;t&#203;rn&#194;ti&#212;n&#192;liz&#198;ti&#216;n
    With active_support           :  I&#241;T&#235;RN&#226;TI&#244;N&#224;LIZ&#230;TI&#248;N / i&#209;t&#203;rn&#194;ti&#212;n&#192;liz&#198;ti&#216;n
    With active_support mb_chars  :  I&#209;T&#203;RN&#194;TI&#212;N&#192;LIZ&#198;TI&#216;N / i&#241;t&#235;rn&#226;ti&#244;n&#224;liz&#230;ti&#248;n

    $ ruby1.9 test.rb
    @ 1.9.1 UTF-8
    Plain ruby                    :      I&#241;T&#235;RN&#226;TI&#244;N&#224;LIZ&#230;TI&#248;N / i&#209;t&#203;rn&#194;ti&#212;n&#192;liz&#198;ti&#216;n
    With active_support           :      I&#241;T&#235;RN&#226;TI&#244;N&#224;LIZ&#230;TI&#248;N / i&#209;t&#203;rn&#194;ti&#212;n&#192;liz&#198;ti&#216;n
    With active_support mb_chars  :      I&#241;T&#235;RN&#226;TI&#244;N&#224;LIZ&#230;TI&#248;N / i&#209;t&#203;rn&#194;ti&#212;n&#192;liz&#198;ti&#216;n


So, how do I get internationalized `upcase` and `downcase` with ruby 1.9.1?


### update

I should add that I also tested with ActiveSupport from the current `master`, `2-3-*` and `3-0-unstable` rails branches at GitHub. Same results.

Ruby 1.9: how can I properly upcase &amp; downcase multibyte strings?

I see that in Ruby (and dynamically typed languages, in general) a very common practice is to pass a hash, instead of declaring concrete method parameters. For example, instead of declaring a method with parameters and calling it like this:

    def my_method(width, height, show_border)
    my_method(400, 50, false)

you can do it this way:

    def my_method(options)
    my_method({&quot;width&quot; =&gt; 400, &quot;height&quot; =&gt; 50, &quot;show_border&quot; =&gt; false})

I&#39;d like to know your opinion about it. Is it a good or a bad practice, should we do it or not? In what situation using this practice is valid, and it what situation can it be dangerous?

Passing hashes instead of method parameters

For a simple struct-like class:

    class Tiger
      attr_accessor :name, :num_stripes
    end

what is the correct way to implement equality correctly, to ensure that `==`, `===`, `eql?`, etc work, and so that instances of the class play nicely in sets, hashes, etc.


**EDIT**

Also, what&#39;s a nice way to implement equality when you want to compare based on state that&#39;s not exposed outside the class? For example:

    class Lady
      attr_accessor :name
    
      def initialize(age)
        @age = age
      end
    end

here I&#39;d like my equality method to take @age into account, but the Lady doesn&#39;t expose her age to clients. Would I have to use instance_variable_get in this situation?

What&#39;s the right way to implement equality in ruby

I use the pylons and sqlalchemy. I constantly update the schema files and delete and recreate the database so that new schema can be made. 

Every time I do this by opening the MySql Query Browser and login and delete the database/schema.

**How do I delete the MySQL db/schema thorough linux shell commands in Ubuntu Linux?**

How to delete mysql database through shell command

I am new to shell scripting and can&#39;t figure this out. If you are unfamiliar, the command git branch returns something like

    * develop
      master
, where the asterisk marks the currently checked out branch. When I run the following in the terminal:

    git branch | grep &quot;*&quot;

I get:

    * develop
as expected.

However, when I run 

    test=$(git branch | grep &quot;*&quot;)
or

    test=`git branch | grep &quot;*&quot;`
And then

    echo $test
, the result is just a list of files in the directory. How do we make the value of test=&quot;* develop&quot;?

Then the next step (once we get &quot;* develop&quot; into a variable called test), is to get the substring. Would that just be the following?

    currentBranch=${test:2} 
I was playing around with that substring function and I got &quot;bad substitution&quot; errors a lot and don&#39;t know why.

How to get the name of the current git branch into a variable in a shell script?

I just installed matplotlib in Ubuntu 9.10 using the synaptic package system. 
However, when I try the following simple example

    &gt;&gt;&gt; from pylab import plot;
    &gt;&gt;&gt; plot([1,2,3],[1,2,3])
    [&lt;matplotlib.lines.Line2D object at 0x9aa78ec&gt;]

I get no plot window. Any ideas on how to get the plot window to show?


No plot window in matplotlib

I&#39;m trying to use a shell script to start a command. I don&#39;t care if/when/how/why it finishes. I want the process to start and run, but I want to be able to get back to my shell immediately...

Asynchronous shell commands

I am pretty new to Ubuntu, but I can&#39;t seem to get this to work.  It works fine on my school computers and I don&#39;t know what I am not doing.  I have checked **usr/include** and time.h is there just fine.  Here is the code:

    #include &lt;iostream&gt;
    #include &lt;time.h&gt;
    using namespace std;
    
    int main()
    {
    	timespec time1, time2;
    	int temp;
    	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &amp;time1);
    	//do stuff here
    	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &amp;time2);
    	return 0;
    }

I am using CodeBlocks as my IDE to build and run as well. Any help would be great, thank you.

C++ error: undefined reference to &#39;clock_gettime&#39; and &#39;clock_settime&#39;

In ruby 1.9 is there a way to define this hash with the new syntax?


    irb&gt; { a:  2 }
    =&gt; {:a=&gt;2}

    irb&gt; { a-b:  2 }
    SyntaxError: (irb):5: syntax error, unexpected tLABEL
    { a-b:  2 }
          ^

with the old one, it&#39;s working:

    irb&gt; { :&quot;a-b&quot; =&gt;  2 }
    =&gt; {:&quot;a-b&quot;=&gt;2}

 

Ruby 1.9 hash with a dash in a key

What is the best practice if I want to `require` a relative file in Ruby *and* I want it to work in both 1.8.x and &gt;=1.9.2?

I see a few options:

  * just do `$LOAD_PATH &lt;&lt; &#39;.&#39;` and forget everything
  * do `$LOAD_PATH &lt;&lt; File.dirname(__FILE__)`
  * `require &#39;./path/to/file&#39;`
  * check if `RUBY_VERSION` &lt; 1.9.2, then define `require_relative` as `require`, use `require_relative` everywhere where it&#39;s needed afterwards
  * check if `require_relative` already exists, if it does, try to proceed as in previous case
  * use weird constructions such as &lt;code&gt;&lt;pre&gt;`require File.join(File.dirname(__FILE__), &#39;path/to/file&#39;)`&lt;/pre&gt;&lt;/code&gt; - alas they don&#39;t seem to work in Ruby 1.9 throughly, because, for example: &lt;pre&gt;&lt;code&gt;`$ cat caller.rb
require File.join(File.dirname(__FILE__), &#39;path/to/file&#39;)
$ cat path/to/file.rb
puts &#39;Some testing&#39;
$ ruby caller
Some testing
$ pwd
/tmp
$ ruby /tmp/caller
Some testing
$ ruby tmp/caller
tmp/caller.rb:1:in &#39;require&#39;: no such file to load -- tmp/path/to/file (LoadError)
        from tmp/caller.rb:1:in &#39;&lt;main&gt;&#39;`&lt;/code&gt;&lt;/pre&gt;
  * Even weirder construction: &lt;code&gt;&lt;pre&gt;`require File.join(File.expand_path(File.dirname(__FILE__)), &#39;path/to/file&#39;)`&lt;/pre&gt;&lt;/code&gt; seems to work, but it&#39;s weird and not quite good looking.
  * Use [backports][1] gem - it&#39;s kind of heavy, it requires rubygems infrastructure and includes tons of other workarounds, while I just want `require` to work with relative files.

There&#39;s a [closely related question at StackOverflow][2] that gives some more examples, but it doesn&#39;t give a clear answer - which is a best practice.

Is there are any decent, accepted-by-everyone universal solution to make my application run on both Ruby &lt;1.9.2 and &gt;=1.9.2?

&lt;h2&gt;UPDATE&lt;/h2&gt;

Clarification: I don&#39;t want just answers like &quot;you can do X&quot; - in fact, I&#39;ve already mentioned most of choices in question. I want *rationale*, i.e. *why* it is a best practice, what are its pros and cons and why it should be chosen among the others.

[1]: http://rubygems.org/gems/backports
[2]: https://stackoverflow.com/questions/4325759/is-require-file-expand-path-file-the-best-practice

Ruby: require vs require_relative - best practice to workaround running in both Ruby &lt;1.9.2 and &gt;=1.9.2

When I include a gem that I made, thanks to Bundler (version 1.0.12), in a Gemfile and then I try to bundle or to rake just like that:

  `$ rake`

I&#39;ve got this error message:

    Invalid gemspec in [/Users/zagzag/.rvm/gems/ruby-1.9.2-p180@foobar/specifications/myplugin-1.0.0.gemspec]: invalid date format in specification: &quot;2011-04-21 00:00:00.000000000Z&quot;

I&#39;m on the last Mac OS X (10.6.4), with:

    $ ruby -v
    ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.4.0]

and:

    $ gem -v
    Invalid gemspec in [/Users/zagzag/.rvm/gems/ruby-1.9.2-p180@foobar/specifications/myplugin-1.0.0.gemspec]: invalid date format in specification: &quot;2011-04-21 00:00:00.000000000Z&quot;
    1.7.2

I really don&#39;t see how to solve this issue.  Thanks for any ideas.

Invalid gemspec because of the date format in specification

Is there any difference between `:key =&gt; &quot;value&quot;` (hashrocket) and `key: &quot;value&quot;` (Ruby 1.9) notations?

If not, then I would like to use `key: &quot;value&quot;` notation. Is there a gem that helps me to convert from `:x =&gt;` to `x:` notations?

Is there any difference between the `:key =&gt; &quot;value&quot;` and `key: &quot;value&quot;` hash notations?

The well-cited [RIP Hash rocket post][1] would seem to imply the Hash Rocket syntax (`:foo =&gt; &quot;bar&quot;`) is deprecated in favor of the new-to-Ruby JSON-style hash (`foo: &quot;bar&quot;`), but I can&#39;t find any definitive reference stating the Hash Rocket form is actually deprecated/unadvised as of Ruby 1.9.

  [1]: http://web.archive.org/web/20130909062027/http://peepcode.com/blog/2011/rip-ruby-hash-rocket-syntax

Content Type	Original Author	Original Content on Stackoverflow
Question	Martin DeMello	View Question on Stackoverflow
Solution 1 - Ruby	just_a_dude	View Answer on Stackoverflow
Solution 2 - Ruby	henry74	View Answer on Stackoverflow
Solution 3 - Ruby	Travis Reeder	View Answer on Stackoverflow
Solution 4 - Ruby	Joe Corneli	View Answer on Stackoverflow
Solution 5 - Ruby	user214028	View Answer on Stackoverflow

How do I make Ruby 1.9 the default Ruby on Ubuntu?

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

Solution 3 - Ruby

Solution 4 - Ruby

Solution 5 - Ruby

Total method time in Java VisualVM

Understanding the workings of equals and hashCode in a HashMap

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