Genlinux

Nil objects in Ruby

gen@blogger.com (Gen.lostwarrior) — Thu, 29 Oct 2009 07:18:37 PDT

If everything is an object, what happens when you do not really have an object? For exactly those occasions, Ruby supplies us with a special object that represents the idea of not having an object, of being utterly object-less, sans object. This special value is nil. Everything in Ruby is an object, and so it is: nil.we can get the class of nil: irb(main):011:0> nil.class => NilClass This turns out to be something very predictable,There is only one instance of NilClass (called nil) and you cannot make any new instances of NilClass.

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Binding objects in ruby

gen@blogger.com (Gen.lostwarrior) — Thu, 29 Oct 2009 03:53:36 PDT

The RDOC(standard Ruby documentation format)page for ERB states that the result method of an ERB instance takes a Binding object. Binding doesn't support any methods beyond those provided by Object.Binding objects are used to represent the visible scope from some location or we can say encapsulate the execution context at some particular place in the code and retain this context for future use.They have no methods because they are intended to be opaque.We can capture the current bindings at any time with the binding kernel method. mybinding=binding() This binding can be passed to a very few other methods, one which is eval. def binding_with_ex ex = 21 return binding end ge=binding_with_ex eval("ex") will return the error NameError: undefined local variable or method `b' for main:Object eval("ex",ge) =>21 class Genbinder def initialize(n) @val=n ** 2 end def fetchbind return...

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Ruby on Rails interview questions

gen@blogger.com (Gen.lostwarrior) — Wed, 28 Oct 2009 07:52:03 PDT

1.Difference between html.erb & rhtml It's just a change of philosophy between Rails 1 and Rails 2.Before Rails 2, we had file.rhtml, file.rxml and file.rjs.In Rails 2.0, that changed to file.content_type.template_engine. So with file.html.erb,the content type is html and the template engine is ERB. rxml is now xml.builder and rjs should now (mostly) be js.rjs.2.What is dynamic database 3.Difference between dynamic hasfinder and hasfinder Most common operations in many applications is to simply query based on one or two columns, Rails has an easy and effective way to do these queries without having to resort to the conditions parameter of find.Dynamic finder methods begin with find_by_name or find_all_by_name, indicating whether you want a single value or array of results returned. The semantics are simi- lar to calling find with the :first versus the :all option. >> City.find_by_name("Hackensack") => # "Hackensack", "latitude" =>"40.8858330000", "id" => "15942",...

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How to add a favicon in Blogger

gen@blogger.com (Gen.lostwarrior) — Tue, 20 Oct 2009 06:37:05 PDT

Adding favicon in blogger is very easier, by default blogger will have the default favico.If you know how to use Gimp or Photoshop, then you can use your own creativity to create favico.Or there plenty of sites out there that generates a favicon for you when you upload an image.Do a Google Search for "free favicon Generator" and plenty of sites would come up I used to create my images in png format, earlier i used to upload my images in Google page creator.Currently Google page creator is getting deprecated, so i have start uploading my images in code.google.com Now in your blogger go to Layout -> Edit HTML Now click 'Expand Widget Templates' Now place <link href='you url' rel='shortcut icon' type='image/x-icon'/> after <title><data:blog.pageTitle/></title> *Note : Please be sure you should place your link href after <title><data:blog.pageTitle/></title>, otherwise you will get the default blogger favico

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Ruby on Rails - Short Summary

gen@blogger.com (Gen.lostwarrior) — Sat, 10 Oct 2009 04:06:52 PDT

This article is for my own reference, my honourable thanks to the author Alanbradburne Models: ActiveRecord ActiveRecord is what is known as an Object/Relationship Mapping (ORM) library. An ORM library maps the data stored in a database to a class in your application. This allows you to access your data without having to worry about the SQL queries or even exactly how the data is accessed. The rows in each database table become instances of an object. Although this sounds complex, in practice, it makes working with a database incredibly simple and easy. In a Rails application, all of the interaction with the database is performed through ActiveRecord, so learning how to get the most from it is important. Views and Controllers: ActionPack ActionPack is simply a collection of libraries and tools to help you build web applications.These provide the “view” and “controller” of the MVC stack. The view part of ActionPack is used to create the web pages themselves. Since...

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Equal height columns with prototype

gen@blogger.com (Gen.lostwarrior) — Wed, 30 Sep 2009 07:47:57 PDT

As i am beginner to learn jquery, i surfed in web and got newbie's Equal height columns with jquery.Its seems to be simple and cool.Then i started doing this technique using prototype.I have checked in firebox browsers, it seems to be working fine. Thanks to the author Rob Glazebrook from Newbie Server side script from Newbie(Jquery) <script language="javascript" type="text/javascript" src="jquery-1.3.2.js"></script> <script> function equalHeight(group) { tallest = 0; group.each(function() { thisHeight = $(this).height(); if(thisHeight > tallest) { tallest = thisHeight; } }); group.height(tallest); } $(document).ready(function() { equalHeight($(".column")); }); </script> Server side script from me(Prototype) <script language="javascript" type="text/javascript" src="prototype-1.6.0.3.js"></script> <script language='javascript'> function equalHeight(group) { tallest = 0; group.each(function(c) { thisHeight =...

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Restore original(default) VLC skin and config on Ubuntu

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:28:45 PDT

If you already have a new skin for your vlc player, but you want to change to its default skin, since many user handy options are not feasible or you mess up the options, then we can start restoring the player to its default one by typing the command in your terminal vlc --reset-config

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Removing white spaces with squish method

gen@blogger.com (Gen.lostwarrior) — Fri, 23 Oct 2009 01:33:16 PDT

Two new methods added to the String object, squish and squish!. These methods do the same as strip method. It removes white spaces from the beginning and the end of the text. It also removes unused white-spaces (multiple white-spaces) from the middle of the text Look the example: “ A text full of spaces “.strip #=> “A text full of spaces” “ A text full of spaces #=> “A text full of spaces”

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Transfer folders from server to server in linux

gen@blogger.com (Gen.lostwarrior) — Fri, 18 Sep 2009 01:00:50 PDT

If you want to transfer files or folders from one linux system to another, then scp would be enough. To get help on the usage of a linux command, just type man scp Now i want to get the files from Linux A to Linux B First Login into Linux A and enter into the directory you want to transfer to Linux B cd /home/Linux A/Music scp -r foldername linuxb@genlinux.org:/home/Linux B/Music/ For all folders scp -r * linuxb@genlinux.org:/home/Linux B/Music/ Related posts Mount remote folders into Linux Machine using sshfs Moving, renaming, and copying files in linux

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Enabling BITS Service in windows operating system

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:39:23 PDT

BITS Service BITS service must be enabled before you start the installation process.Enable the BITS service and run the setup again Click Start> Run> Services.msc, double click BITS and set it to Automatic, then Start, then Apply.

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proxy: No protocol handler was valid for the URL

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:40:09 PDT

While trying to configure mod_proxy_balancer.Although i configured everything correctly and enabled all required modules(mod_proxy, mod_proxy_http).But after restarting the apache server i used to get internal server in my browser.Then i verified the apache error log [warn] proxy: No protocol handler was valid for the URL /login.html. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule After searching a lot in google i got tips from Serendipitous In my terminal i created some soft links for proxy_http.load like this ln -s /etc/apache2/mods-available/proxy_http.load \ /etc/apache2/mods-enabled/proxy_http.load Now i restarted my server and it was working fine.For the same problem i have referred another usefull blog Kai`s Blog in that they have tried by adding a trailing slash to the url of the balancer like this <Proxy balancer://mycluster/> BalancerMember http://foobar.de:8080/...

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Balancermember Can't find 'byrequests' lb method

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:40:22 PDT

I am using apache 2.2.8 for my debian ubuntu, while configuring apacehe with proxy balancer.I faced the problem "BalancerMember Can't find 'byrequest lb method'". sudo /etc/init.d/apache2 restart * Forcing reload of web server (apache2)... Syntax error on line 673 of /etc/apache2/apache2.conf: BalancerMember Can't find 'byrequests' lb method ...fail! ## Apache file (from error line) BalancerMember http://127.0.0.1:8000 BalancerMember http://127.0.0.1:8001 ServerName data_seed DocumentRoot /var/www/ruby/public Options FollowSymLinks AllowOverride None Order allow,deny Allow from all RewriteEngine On RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f RewriteCond %{SCRIPT_FILENAME} !maintenance.html RewriteRule ^.*$ /system/maintenance.html [L] RewriteRule ^/$ /index.html [QSA] Rewrite to check for Rails cached page RewriteRule ^([^.]+)$ $1.html [QSA] RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f RewriteRule ^/(.*)$ balancer://mongrel_cluster%{REQUEST_URI}...

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Ruby array transpose

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:40:33 PDT

Ruby Arrays are ordered, integer-indexed collections of any objects.In Array transpose assumes the self is an array of arrays and transposes the rows and columns. a = [[1,2], [3,4], [5,6]] Now to create array of array its easy to do rails helper in_groups_of %w(1 2 3 4 5 6 ).in_groups_of(2,false) [["1", "2"], ["3", "4"], ["5", "6"]] Note if the array length is odd then try to pass the array with in_groups_of(number,string) instead of false Then with ruby we can use some tricky methods.such as shifting the array position. array=[["1", "2"], ["3", "4"], ["5", "6"]] array.transpose [["1", "3", "5"], ["2", "4", "6"]]

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linux last modified file | last created file

gen@blogger.com (Gen.lostwarrior) — Mon, 28 Sep 2009 00:40:40 PDT

So how do you find Linux / UNIX system last created file or edited file?.The ls utility will list all the files,by doing some combinations from the ls command we can find the results 1.ls -t | awk '{print $1}' | head -1 2.ls -ct1 | head -1 3.ls -rt| tail -1

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Tips and Tricks

gen@blogger.com (Gen.lostwarrior) — Thu, 18 Jun 2009 22:25:26 PDT

Start irb with tab completion enabledirb --readline -r irb/completion Executing shel commands in ruby system "curl http://www.google.com" Combination of in_groups_of and cycle helper <table> <% articles.in_groups_of(2, false) do |row_tasks| %> <tr> <%row_tasks.each do |task| %> <td style="background-color:<%=cycle("red","white","blue") %>"> <%= task.title %> </td> <% end %> </tr> <% end %> </table>

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Strip html tags

gen@blogger.com (Gen.lostwarrior) — Sat, 23 May 2009 04:50:41 PDT

This article deals with how to strip the html tags and fetch the tags we needed, after referring some of the articles (dzone.snippets) and with the help of my friend Jon Here we have used regex with grep method.Pattern for matching the tags /<p>(.+?)</p>/ For example i have used for p tag text="<p>He's the man who helped make \"Slumdog Millionaire\" an international hit, scoring the soundtrack of the Oscar winning film. Despite his performance at the Oscars ceremony and being caught up in all the glitz and adulation, Rahman is a reluctant star.</p>\r\n<p>He's worked on films since he was a teenager, taking over the role of family breadwinner after his father died and followed in his footsteps as a composer.</p>\r\n<p>While he had stints writing advertising jingles in India, composing for films as been his life's work so far, yet from his studio in Chennai he admitted to CNN he didn't want to score...

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Customized truncate helper in rails

gen@blogger.com (Gen.lostwarrior) — Tue, 19 May 2009 01:43:40 PDT

In Rails truncate helper will truncates a given text after a given :length if text is longer than :length (defaults to 30).The problem is that when we truncate the string by character or word, it will cutoff the text mid-word and creating open tag problems. So i started referring some of the articles Pretty truncate helper and customized my own helper like this def truncate_words(text, length = 30, string = "...") return if text.nil? l = text.index(/\s/,length) text.chars.length > length ? text[0,l] + string : text + string end Example >> text => "In unprecedented market conditions, Murex retained its top position in Risk's 2008 technology rankings. However, Thomson Reuters and Algorithmics are close behind, demonstrating that, despite the financial crisis, competition among software vendors remains as fierce as ever. By Clive Davidson, with research by Xiao-Long Chen" >> helper.truncate(text,130) => "In unprecedented market conditions, Murex retained its top...

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Working with Hashes

gen@blogger.com (Gen.lostwarrior) — Fri, 15 May 2009 14:16:42 PDT

A Hash is a collection of key-value pairs. It is similar to an Array, except that indexing is done via arbitrary keys of any object type, not an integer index. The order in which you traverse a hash by either key or value may seem arbitrary, and will generally not be in the insertion order. Deleting Key/Value Pairs Key/value pairs of a Hash object can be deleted using clear, delete, delete_if, reject, reject!, and shift. Use clear to remove all key/value pairs. This is essentially the same as assigning a new empty hash, but it's marginally faster. Use shift to remove an unspecified key/value pair. This method returns the pair as a two-element array (or nil if no keys are left):irb(main):004:0> a={5=>6,7=>8} => {5=>6, 7=>8} irb(main):005:0> b=a.shift => [5, 6] irb(main):006:0> a => {7=>8} irb(main):007:0> Use delete to remove a specific key/value pair. It accepts a key and returns the value associated with the key removed (if found). If the key is not found, the default value is...

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Randomizing an Array

gen@blogger.com (Gen.lostwarrior) — Tue, 12 May 2009 03:09:41 PDT

This article deals about ruby array randomize.Some of the piece of code available are taken from web.If we want to scramble an array into a random order, then we want to use the rand in the kernel module Ruby array randomize By slice & rand class Array def random a=self.dup result=[] self.length.times do result [1, 2, 3, 4, 5] irb(main):107:0> x.random => [1, 4, 5, 2, 3] irb(main):108:0> x.random => [1, 4, 3, 5, 2] irb(main):109:0> x.random => [4, 2, 3, 1, 5]By Sort_by & randrandomize=(1..10).to_a.sort_by{rand}=> [1, 4, 6, 2, 5, 3] irb(main):262:0> x.sort_by{rand} => [4, 5, 3, 1, 6, 2] irb(main):263:0> x.sort_by{rand} => [3, 1, 6, 2, 4, 5] irb(main):264:0> x.sort_by{rand} => [2, 1, 6, 3, 5, 4]

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Vertical navigation menus

gen@blogger.com (Gen.lostwarrior) — Fri, 08 May 2009 08:11:58 PDT

Navigation is the most significant element in webdesign.This article presents the implementation of vertical sliding navigation menus In this we have used the slidetoggle effects for sliding the menus in onlcik event. For live demo Click here Code <html> <head> <script type="text/javascript" src="jquery.min.js"> </script> <style type='text/css'> body { font-family: Arial, Helvetica, sans-serif; font-size: 12px; background: #3A362F; } ul, li { margin: 0; padding: 0; list-style: none; } .menu_body li { background: #fff; } .menu_body li a { color: #333; text-decoration: none; padding: 10px; display: block; } .menu_body { display: none; ...

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SHUTDOWN/REBOOT in linux

gen@blogger.com (Gen.lostwarrior) — Mon, 04 May 2009 01:50:35 PDT

Basic command to shutdown/reboot the system in terminal modeTo shutdown your system shutdown -h now "message"This command will shutdown the system.The message can be any message you want send when shutdown/reboot.If you want to shutdown the system for a specific time,then useshutdown -h hh:mm "message"Here hh is hours and mm is minutes.To rebootshutdown -r now "message"To reboot the system for automated specific time then,shutdown -r hh:mm "message"

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Free Blogger Template -001

gen@blogger.com (Gen.lostwarrior) — Sat, 02 May 2009 00:51:42 PDT

This was our first blogger templates design, here we have customized the templates so that you can used 300x250 ad slots for more than 2 times,After the header we have created a block so that you can create your welcome text.In down footer part also you can add your text.If you want to customize our template,then go to edit html section.If you want to place share script, then get the code from sharethis.com.Then you can add your own menus in the navigation area. Live Demo Download Template

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Remote Diff in linux

gen@blogger.com (Gen.lostwarrior) — Tue, 28 Apr 2009 10:13:54 PDT

Basically we will be using the diff command to compare between the files, but if we want to compare between two remote servers.Then we have use the diff command in a different format like this ssh <remote-host> "cat /path/to/remotefile" | diff - /path/to/localfile For example gen@lostwarrior:~/Mypace/base/layout$ ssh gen@genlinux.org "cat /home/genlinux/base/layout/base.txt" | diff - /home/gen/base/layout/base.txt Here gen@genlinux.org is the remote server/home/genlinux/base/layout/base.txt is the remote file/home/gen/base/layout/base.txt is the local file

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Apache configuration for single application serving requests from mulitple domains

gen@blogger.com (Gen.lostwarrior) — Wed, 22 Apr 2009 09:30:52 PDT

# # Proxy Server directives. Uncomment the following lines to # enable the proxy server: # <IfModule mod_proxy.c> ProxyRequests Off <Proxy *> Order deny,allow Deny from all Allow from all </Proxy> #ProxyPass / http://127.0.0.1:8000/dl #ProxyPassReverse / http://127.0.0.1:8000/dl #ProxyPreserveHost On </IfModule> # End of proxy directives. Listen 8080 <VirtualHost *:8080> <Location /> SetHandler balancer-manager Deny from all Allow from localhost </Location> </VirtualHost> <Proxy balancer://mongrel_cluster> BalancerMember http://127.0.0.1:7000 BalancerMember http://127.0.0.1:7001 BalancerMember http://127.0.0.1:7002 </Proxy> <VirtualHost *:80> Include /etc/apache2/sites-enabled/1.conf ServerName example1.com LogFormat "%h %l %u %t \"%r\" %>s %b" common ErrorLog /home/logs/error_log CustomLog /home/logs/access_log...

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Date time format with suffix in ruby on rails

gen@blogger.com (Gen.lostwarrior) — Tue, 21 Apr 2009 12:20:18 PDT

For formatting the date time with suffixes like (st,th,rd,nd) rails provides ordinalize helper which will truns a number into an ordinal string used to denote the position in an ordered sequence such as 1st, 2nd, 3rd, 4th. >> time = Time.new => Tue Apr 21 19:11:13 +0000 2009 >> time.strftime("%a %b #{time.ordinalize}") => "Tue Apr 21st" Note that this is inside a Rails console so if you did this in plain Ruby, you'd have to require 'rubygems' and require 'activesupport' to get Fixnum#ordinalize

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