How to downgrade Firefox Version on ubuntu

In  this tutorial I will show you how to downgrade your firefox version in this case from firefox 47.0 to 45.

First run this command:


apt-cache show firefox | grep Version

then you will see a list of available Firefox versions:

• Version: 47.0+build3-0ubuntu0.16.04.1
• Version: 45.0.2+build1-0ubuntu1

Now, run the next command to install the desired firefox version

sudo apt-get install firefox=28.0+build2-0ubuntu2

Finally, you have to avoid upgrading to the newer version.


sudo apt-mark hold firefox

And that's all.



If for any reason you do not see the version that you want, that means that version is very old.
To install a very old version of Firefox, you need to do the following:



1. First you must uninstall your current Firefox version.

  

$ sudo apt-get purge firefox

2. Then run the following command to download firefox 47.0 source code, which comes as .tar file.

 
$ wget http://ftp.mozilla.org/pub/firefox/releases/47.0/firefox-47.0.linux-i686.sdk.tar.bz2

3. Extract the package.

 $ tar -xjf firefox-47.0.linux-i686.sdk.tar.bz2

4. Move firefox to /opt directory.

 $ sudo mv firefox /opt/

5. Create symlink in order to set the new Firefox as default.

$ sudo mv /usr/bin/firefox /usr/bin/firefox_old

$ sudo mv /usr/bin/firefox /usr/bin/firefox_old

6.  Avoid upgrading to the newer version.

$ sudo apt-mark hold firefox

Note: This is the original source [here]

How to install GIT on Ubuntu from command line

To install GIT on Ubuntu what you have to do is following these steps:

1.  Type this command on your terminal:

sudo apt install git



      2. Add your configuration:


git config --global user.email "your_email@example.com"
git config --global user.name "Your Name"

How to install Mysql on Ubuntu from command line

To install Mysql on Ubuntu what you have to  do is type  the following command:

sudo apt-get install mysql-client mysql-server

and then you will see something like this:

What you have to do there is type the  password for the root user.

and that's all.

Good luck!!!!!

Ruby on Rails Remove Blank elements from array

Sometimes, when you are working with arrays it is possible to have  empty elements,therefore you will need to clean it. In this section I will show you how to remove blank elements from a array using either Ruby on Rails or just Ruby.

Given the array called test
=> ["test", "", 1, 2, ""]

so, to remove the blank elements this is the syntax:

for Ruby on Rails:

test.reject &:blank? 

For Ruby:
  test.reject &:empty?