Miscellanea » OpenAlfa Blog

How to compare visually two versions of a file in git

Apr 272015

One of the most common operations in the development of a project that makes use of a version control system, is that of reviewing the differences between the local copy of a given file in the working area, and the last version of the same file stored in the repository.

Using a graphical comparison tool for this operation may help greatly to perform this task. A tool of this kind will show both versions of the file side-by-side, highlighting the lines that have been added, deleted of modified.

This post explains how to do this and other similar operations in a project that uses git as version control system.

HTTP/2 Protocol Specification Characteristics

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Mar 102015

The HTTP Working Group of the IETF (Internet Engineering Task Force) has approved on 17-Feb-2015 version 2 of the HTTP protocol (Hypertext Transfer Protocol 2 specification). This new version will gradually replace the older HTTP/1.0 and HTTP/1.1 versions, that for many years have been one of the basic building blocks of the web (HTTP/1.1 was approved on 1999).

Together with HTTP/2, the Working Group has approved the HPACK specification for the compression of HTTP/2 headers.

This new version of the HTTP protocol is intended to solve the shortcomings of the previous versions, by implementing several improvements, as explained in this post.

Working in vim with lines that do not match a given pattern

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Mar 062015

vim (vi improved) is probably the most popular text editor in Linux systems. The main strengh of vim lies in the ability to use regular expressions to select and edit with a single command all lines that match a given text pattern.

But sometimes, the inverse is required: editing all lines that DO NOT match a text pattern. This is also possible in vim, as explained in this post.

How to do FTP transfers from a bash script

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Feb 222015

This post is a fast recipe to include a file transfer using the FTP protocol inside a bash script.

How to edit non-printing and unicode characters in vim editor

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Feb 212015

Sometimes, while editing a text file in vim, you might need to insert, rearch or replace characters that are not in your keyboard, such as æ, å, ě, … or non-printing characters such as the control characters^A, ^B, … or characters with hexadecimal codes in the range 0x7F to 0xFF.

This post explains some of the possible ways that vim offers to handle those characters.

How to list the files modified in a revision of a subversion repo

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Feb 142015

The easiest way to find out which files were modified, added or deleted in a given revision of a subversion repository is using the “svn log” command with the “verbose” switch:

How to redirect HTTP traffic to HTTPS using .htaccess in apache

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Feb 142015

There are good reasons that might lead a website administrator to take the decision to implement the HTTPS security layer. Once the certificate is installed and the web server has been configured to accept HTTPS requests, the pages in the site will be accessible using https encrypted connections. But, by that time, surely many of the pages will have already been indexed as using the http protocol by major search engines such as Google, Yahoo or Bing. There will also be backlinks to the site from pages in other domains, using “http://”

This post explains how to setup a redirect from the old “http://” to the new “https://” urls.

Working in the vim editor with non-graphical and unicode characters

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Jan 182015

Sometimes, while editing a text file with the vim editor, we might need to enter, search and/or replace characters not available in our keyboard, such as æ, å, ě, … or non-printable characters such as controls characters ^A, ^B, … or characters with hexadecimal codes between 0x7F and 0xFF.

This post goes through some of the possibilities in vim to work with those characters.

Using CSS media queries to create a responsive design for a web site

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Jan 062015

Nowadays, the webmasters of most websites must take into account the growing number of users browsing the web from mobile devices, smartphones and tablets.

The screen size and resolution of these devices is generally much smaller than that in the desktop and laptop devices that were taken as reference at the time the design of most websites was created.

Ideally, the design of a web site should be responsive, detecting the characteristics (screen size, resolution) of the device and adapting the layout consequently. The first step in this direction was the specification of the viewport meta tag, thas has already been explained in other articles in this blog. Currently, a more precise control on the responsive layout can be achieved using CSS media queries. This technique allows the designer to setup sets of CSS rules specific for different screen resolutions, device orientations, etc. In this way, the design can be made to adapt to different devices using the same HTML code for the page.

This post gives an overview of the usage of CSS media queries in the design of a web site.

Introduction to Twitter Bootstrap

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Sep 302014

Designing a web site has always been more of an art than a science. A web page is made of multiple areas: header, footer, sidebars, main content, etc. Inside of each of those areas, the designer places elements of many different types: blocks of text, menus, buttons, forms, images,… The result must be aesthetically pleasing, without compromising the usability.

To make things more difficult, the appearance of mobile devices with all types of screen sizes and resolutions poses a new challenge, as the design should ideally be “responsive”, adapting to the characteristics of the device where the pages are being rendered.

To ease this task, Twitter has released to the community of web developers and designers a free, open source design framework known as “Bootstrap”. This framework enforces a set of style guidelines, and includes a javascript library that implements the functionalities required to achieve an homogeneous, appealing and user-friendly design.

This post examines the possibilities offered by Bootstrap, and gives a brief introduction on how to make use of it.

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