Índice para Issue 8 em Linux Coding & Programming The Complete Manual

Linux is everywhere. It powers the Internet as the main operating system behind the Web’s servers, it powers spacecraft, it’s the operating system for the fastest supercomputers in the world and it’s used in smart TVs and mobile devices. Why? Because it’s ultra stable, lightning fast and completely free of charge. However, there’s more to Linux than simply being a free to use operating system. Its unique configuration allows the user to customise and personalise the OS into any form they wish. A Linux user can change their OS look and feel from one day to the next, install thousands of freely available apps and programs and take back control of their computer. With this book, you too can become a part of the open community of Linux users. The…

GOING LINUX The installation process for most distributions is similar. You download a disk image from the website and burn it to an optical disk or create a USB Flash Drive installer. Just be careful to get the right distribution for your hardware and read the instructions carefully. LINUX MINT By far the most popular Linux distro (distribution) is Linux Mint. Mint began life back in 2006, as an alternative to the then most popular distro, Ubuntu. Although based on Ubuntu’s Long Term Support build, Linux Mint took a different direction and offered the user a better overall experience. Linux Mint has three main desktop versions available with each new version of the core OS it releases. This may sound confusing at first but it’s quite simple. Currently, Linux Mint…

DISTRO HOPPING Distro hopping is a term used by the community for people who never stick to a single distribution. Instead, they hop from one to the other and back again, testing each, using them, then moving on to another or a newly released distro. There’s nothing wrong with distro hopping, as it’s a good way to get to grips with what’s out there and discover the elements of one distro over another that may or may not appeal to your tastes. The problem of course is which one do you use overall? While distro hopping is a good thing, it’s not exactly a stable way to enjoy Linux and get the most from it. We’re not saying you should stick to one distro and never look elsewhere, as you…

UEFI BIOS The Unified Extensible Firmware Interface (UEFI) is used to identify hardware and protect a PC during its boot-up process. It replaces the traditional BIOS but can cause issues when installing Linux. STEP 1 Insert your DVD or USB flash drive into your PC and, if you haven’t already, shutdown Windows. In this instance we’re using the USB boot media but the process is virtually identical. Start the PC and when prompted press the appropriate keys to enter the BIOS or SETUP, which could for example be: F2, Del or even F12. STEP 2 There are different versions of a UEFI BIOS, so covering them all would be impossible. What you’re looking for is a section that details the Boot Sequence or Boot Mode. Here you have the option…

We’ve used Linux Mint as a guideline here, as it’s an easy to use distro and perfect for former Windows users. It’s also one of the most developed and well documented Linux distros as well as having some fantastic configuration options. In this section, we introduce the Linux Mint Cinnamon Menu and Desktop Environment, how it works and what you can do to customise it. Want to create another user or even discover how to become anonymous online? Then read on. “Anyone can build a fast processor. The trick is to build a fast system.”– Seymour Cray (Electrical Engineer, and designer/founder of Cray Supercomputers)…

LINUX TWEAKS Some of these post-installation actions are highly recommended, while others are just handy additions and simply tweak the system or add a customisation. STEP 1 The first, and most important, post-installation action is to update the system. Click on the shield icon in the Panel, found at the bottom right of the desktop next to the time and date. This launches the Update Manager. STEP 2 Linux Mint offers the user a three level policy approach to updates: Don’t Break My Computer, Optimise Stability and Security and Always Update Everything. The recommended option is the Optimise Stability and Security, which only updates safe, essential patches that won’t impact critical elements of the core OS. Read through the descriptions but choose the middle, and recommended option. STEP 3 Click…

YOUR DESKTOP Linux is probably one of the customisable operating systems there is. With just a few tweaks, one or two extras installed and some imagination, you can create something incredible. STEP 1 The first aspect of desktop customisation is to change the wallpaper. Right-click the desktop and choose Change Desktop Background. This opens the Backgrounds app in Linux Mint; remember, other distros may present their background, wallpaper selection tools differently. STEP 2 More recent versions of Linux Mint display available backgrounds depending on the version the user is running. You normally get three categories followed by a fourth, Pictures, which is separated from the others. The Pictures option is different because it reads the image content from the Pictures folder in your Home area. STEP 3 You just need…

TAKING COMMAND The command line, or Terminal, is an extremely powerful interface. Everything you can do on the desktop can be done within the Terminal. Let’s start by seeing how it works. STEP 1 The Terminal can be accessed by either clicking on the Terminal icon on the Panel, located between the Firefox and files icons or launched by opening the Menu and selecting it from the left-hand quick launch strip. STEP 2 The Terminal gives you access to the Linux Mint Shell, called Bash, which gives you access to the underlying operating system. Everything in Mint, including the desktop and GUI, is a module running from the command line. STEP 3 What you currently see in the Terminal is your login name followed by the name of the computer;…

FROM THE SOURCE The commands you’ll need to become familiar with here are Configure, Make and Install. You’ll find a lot of apps use installing from source, so it’s certainly a skill worth investing time in. STEP 1 Source code files for Linux usually come in the form of. TAR.GZ or. TAR.BZ2. Both are compressed files holding all the core files needed to ‘make’ the app. Start off this tutorial by creating a new folder in Home: mkdir Vim. STEP 2 Vim, by the way, is an advanced text editor which we’ll use as an example to install. Enter the new folder, cd Vim, then from within the new Vim folder, enter the following command into the Terminal: wget ftp://ftp.vim.org/pub/vim/unix/vim-7.4.tar.bz2. STEP 3 The wget command retrieves content from the internet,…

TERMINAL FUN You’ll be working exclusively in the Terminal for these next two sections, so start warming up your fingers. After all, all work and no play… as the saying goes. STEP 1 The first command we’re going to use is sl, it’s not installed by default so enter: sudo apt-get install sl. The command can be run with sl and when executed will display a Steam Locomotive travelling across the screen (hence ‘sl’). Entering LS, note the upper case, also works. STEP 2 Fans of Star Wars even get a fix when it comes to the Terminal. By linking to a remote server via the telnet command, you can watch Episode IV: A New Hope being played out, albeit in ASCII. To view this spectacle, enter: telnet towel.blinkenlights.nl. STEP…

DID YOU KNOW… that Linux is at the heart of the science behind the Large Hadron Collider? Using a combination of Red Hat Linux and CentOS (an ultra-stable distro built from the Red Hat core) as the base distributions of choice, scientists, developers and engineers have created SL – Scientific Linux. Using SL as the base, the clever people at CERN have developed several different versions of their own custom Linux distro to help with all aspects of the LHC. Most notable is SLC, or Scientific Linux CERN, also known as CERN6. According to reports, there are over 36,000 systems running SL, and over 15,000 running SLC.…

IF, THEN, ELSE With most programming structures there will come a time where you need to loop through the commands you’ve entered to create better functionality, and ultimately a better program. STEP 1 Let’s look at the If, Then and Else statements now, which when executed correctly, compare a set of instructions and simply work out that IF something is present, THEN do something, ELSE do something different. Create a new script called greeting2.sh and enter the text in the screenshot below into it. STEP 2 Greeting2.sh is a copy of greeting.sh but with a slight difference. Here we’ve added a loop starting at the if statement. This means, IF the variable entered is equal to David the next line, THEN, is the reaction to what happens, in this case…

When the Raspberry Pi was in its developmental stages its designers needed to ensure that they were creating a piece of hardware that could offer much more than simply being a cheap, but small, computer. The Pi needed to be flexible with what it could do, it needed to have room to grow into more ambitious project concepts and ideas, and it needed to do so in as easy to use fashion as possible. The goal was to create a universal learning platform, that students of any age could expand on and tinker with, while learning new concepts such as programming, electronics, and computing. Naturally, once the hardware was developed, the only real choice of operating system was of course, Linux. The versatility of Linux is legendary. This incredible core…

DID YOU KNOW… that NASA’s state-of-the-art supercomputing cluster, Pleiades, is powered by Linux? Pleiades consists of 160 racks (11,440 nodes), 245,536 CPU cores, a total memory count of 935TB, 184,320 NVIDIA CUDA cores, and over six miles of fibre optic cabling. At the heart of it lies a complex setup of SUSE Linux Enterprise Server, along with many custom development packages and other software unique to NASA’s projects. The projects NASA’s Advanced Supercomputing Division uses Pleiades for are: The Kepler Mission – searching for extra-solar Earth-like planets; CFD (Computational Fluid Dynamics) modelling to help create more efficient space launch systems; Dark Matter research and simulation; and visualisation of Earth’s ocean currents, building data for the ECCO (Estimating the Circulation and Climate of the Ocean) Project.…

Why Linux? What is it? Where do I get it? Why are there so many different versions of it? Most beginners ask these, and many more, questions when starting out. It’s true that Linux is an incredibly versatile and powerful operating system but where do you start? Thankfully, you can find the answers in this section. There is so much you can do with Linux but you need to know where to start; we’re here to help you out. In this section you can learn what Linux is, what a distro is and what a desktop environment is. You can also begin to explore how Linux works and how it can work for you. “How did you know so much about computers?” “I didn’t, it was the first one.”– Admiral…

MINTY INGREDIENTS Before we start working our way through this book, here’s what you need to install and run Linux Mint. You have several choices available, so take your time and see which works best for you. SYSTEM REQUIREMENTS The minimum system requirements for Linux Mint are as follows: CPU – 700MHz RAM/Memory – 512MB Hard Drive space – 9GB (20GB recommended) Display – 1024 x 768 resolution Obviously the better the system you have, the better the experience will be and quicker too. USB INSTALLATION You can install Linux Mint onto your computer via USB or DVD. We look into each a little later on but if you’re already familiar with the process, or thinking of USB and just gathering the hardware you need, then you’re going to need…

“In real open source, you have the right to control your own destiny.”– Linus Torvalds (developer of the Linux kernel) It’s all fine and well talking about how good Linux is but how do you get it on your computer? Installing Linux is remarkably simple but there are several options available to you. This section looks into how you can download the Linux ISO, install it on a PC as your main operating system and even how to install a virtual environment. With a virtual environment you can run Linux while still using your main operating system, be that Windows or macOS. Intrigued? Read on and find out more.…

GOING VIRTUAL Using a Virtual Machine (VM) takes resources from your computer: memory, hard drive space, processor usage and so on. Make sure you have enough of each before commencing. STEP 1 We’re using VirtualBox in this instance, as it’s one of the easiest virtual environments to get to grips with. Enter www.virtualbox.org and click on ‘Download VirtualBox’. This takes you to the main download page. Locate the correct host for your system: Windows or Mac, the Host being the current installed operating system, and click the link to begin the download. STEP 2 Next, while still at the VirtualBox download page, locate the VirtualBox Extension Pack link. The Extension Pack supports USB devices as well as numerous other extras that can help make the VM environment a more accurate…

CINNAMON VIRTUALBOX FIX You’ve already looked at some list functions, using. insert,. remove, and. pop but there are also functions that can be applied to strings. STEP 1 Before we begin, we’re assuming you’re having this issue within Virtualbox. The Software Rendering message appears in the top right of the desktop. To fix this, click on Devices in the Virtualbox window, followed by Insert Guest Additions CD Image. STEP 2 The Guest Additions CD contains drivers for Virtualbox, including the virtual video hardware. When it’s loaded in, you get a ‘software needs running’ notification box with two options, Cancel and Run. Click the Run button and enter your Linux user password. STEP 3 After a moment or two you’re automatically dropped into a command line view, called the Terminal in…

DID YOU KNOW… July 20th 1969 is remembered as a turning point in human history, when mankind first stepped on the moon. The software that helped the crew make that pivotal voyage didn’t even exist at the time and had to be developed from scratch. Using a new method of storing programs called Rope Memory, the engineers at MIT Instrumentation Laboratory populated the memory with a special version of assembly. Incredibly, that code is freely available to view on GitHub. Uploaded by a researcher in 2003, you can view the code by visiting www.github.com/chrislgarry/Apollo-11/. Look out for code snippets, such as Burn_Baby_Burn, in particular line 925 with the comment “Goodbye. Come again soon.” Have a look through, and see what else you can find. One giant leap for mankind, and…

ANONYMITY WITH MINT While it’s virtually impossible to become totally anonymous online, you can take measures to ensure our privacy is at its best. STEP 1 Starting with the basics, use HTTPS instead of the standard HTTP when browsing. This means that anything that’s transmitted over HTTPS is secure (hence the S part at the end) and encrypted. STEP 2 When you’re browsing, consider using the Incognito or Private browsing modes available in a browser. This disables your web history and web cache, allowing you to browse without the details being stored for later scrutiny by someone else. However, it doesn’t stop any data or search tracking. STEP 3 Although using Google may seem like the obvious choice for a modern Internet search, the company does track all searches made…

USING APT-GET To update and upgrade via the Terminal you use the APT (Advanced Packaging Tool) command. It’s a powerful command and combines different elements depending on its use. STEP 1 Start by opening a new Terminal or if you already have one opened clear its contents with the clear command. This starts you off with a clean slate on which to work. STEP 2 Enter: apt-get into the Terminal. This brings up a list of the most used apt-get commands, along with a brief description of what the command does. It’s worth having a look at, even if it doesn’t make a huge amount of sense at this time. STEP 3 Apt-get is used to update and upgrade the software in Mint, as well as Ubuntu and other Debian-based…

MORE TERMINAL WORK Creating content using the Terminal isn’t quite as strenuous as it may first appear. Yes, the Terminal can look a daunting place for the newcomer, but once mastered it’s really quite intuitive. STEP 1 Open up the Terminal, and make sure you’re in the Home folder. If not use the cd ~ command to return you to the Home folder from wherever you’re currently located. STEP 2 Let’s start by creating a new folder within Home, and call it Test. The command you’ll need is mkdir Test. Press Enter to create the folder when you’ve typed in the command, then cd Test and press Enter. This will Change Directory (hence CD) to the newly created Test folder. STEP 3 Your command line should change to the Test…

MORE FUN, YAY Since the Terminal session is already open, and your keyboard digits are nicely warmed up, here are another two pages of Terminal nonsense. STEP 1 Remember the old ZX Spectrum days of computing, when you could type in 10 print “Hello”, 20 goto 10 and Hello would list down the screen? Well, in Linux Mint you can do the same. Simply enter yes followed by some text, i.e. yes Linux is ace. It’ll keep going until you press Ctrl+C. STEP 2 The Matrix was one of the most graphically copied films ever released; there’s even a version of the Matrix code available for Linux Mint. Install it with: sudo apt-get install cmatrix. When it’s done enter: cmatrix and follow the white rabbit, Neo. Unlike the real Matrix…

GET SCRIPTING A Bash script is simply a series of commands that Mint will run through to complete a certain task. They can be simple or remarkably complex, it all depends on the situation. STEP 1 You’ll be working within the Terminal and with a text editor throughout the coming pages. There are alternatives to the text editor, which we’ll look at in a moment but for the sake of ease, we’ll be doing our examples in Xed. Before you begin, however, run through the customary update check: sudo apt-get update && sudo apt-get upgrade. STEP 2 There are several text editors we can use to create a Bash script: Xed, Vi, Nano, Vim, GNU Emacs and so on. In the end it all comes down to personal preference. Our…

CHOICES AND LOOPS Let’s bring in another command, CHOICE, along with some nested IF and ELSE statements. Start by creating a new script called mychoice.sh. STEP 1 The mychoice.sh script is beginning to look a lot more complex. What we have here is a list of four choices, with three possible options. The options: Mint, Is, and Awesome will be displayed if the user presses the correct option key. If not, then the menu will reappear, the fourth choice. STEP 2 If you follow the script through you soon get the hang of what’s going on, based on what we’ve already covered. WHILE, IF, and ELSE, with the FI closing loop statement will run through the options and bring you back to the start if you pick the wrong option.…

TOP 10 COMMANDS These may not be the most common commands used by everyone but they will certainly feature frequently for many users of Linux and the command line. cd The cd command is one of the commands you will use the most at the command line in Linux. It allows you to change your working directory. You use it to move around within the hierarchy of your file system. You can also use chdir. ls The ls command shows you the files in your current directory. Used with certain options, it lets you see file sizes, when files where created and file permissions. For example, ls ~ shows you the files that are in your home directory. cp The cp command is used to make copies of files and…

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FREE AND OPEN Linux is a fantastic fit for those who want something different. The efficiency of the system, the availability of applications and stability are just a few good reasons. The first thing you need to know is that there is no such operating system called Linux. Linux is in fact the operating system kernel, the core component of an OS. When talking about Linux what we, and others, are referring to are one of the many distributions, or distros, that use the Linux kernel. No doubt you’ve heard of at least one of the current popular distros: Ubuntu, Linux Mint, Fedora, openSUSE, Debian, Raspbian, the list goes on. Each one of these distros offer something a little different for the user. While each has the Linux kernel at…

WHICH MINT? A Desktop Environment is the graphical interface which you use to interact with the core Linux system. Just as the graphical desktop for Windows 10 is also called Fluent Design. Linux Mint offers the user a choice of versions of the distro: Cinnamon, MATE and Xfce. While that may sound a little confusing for the newcomer, essentially each of the versions available contains the same core Linux structure and kernel, the kernel is the core of the operating system, that handles all the instructions between the software and hardware. Each version is simply a different desktop environment, the Graphical User Interface (GUI) that you use to interact with the operating system. Each of the desktop environments uses different apps to access or use the system, such as the…

DVD BOOTABLE MEDIA We’re using a Windows 10 PC here to transfer the ISO to a DVD. If you’re using a version of Windows from 7 onward the process is extremely easy. STEP 1 First locate the ISO image of Linux you’ve already downloaded. You can usually find it in the Downloads folder in Windows 7, 8.1 and 10 computers, unless you specified a different location when saving it. STEP 2 Next insert a recordable DVD disc into your computer’s optical drive. After a few seconds, while the disc is read, Windows displays a pop-up message asking you what to do with the newly inserted disc. Ignore this, as we’re going to use the built-in image burning function. STEP 3 Right-click the Linux ISO and from the menu select Burn…

CREATING THE VM There are plenty of options to choose from when creating a VM. For now though, let’s set up a VM adequate to run Mint Cinnamon and perform well. STEP 1 With VirtualBox open, click on the New icon in the top right of the app. This opens the new VM Wizard. STEP 2 In the box next to Name, type Linux Mint and VirtualBox should automatically choose Linux as the Type and Ubuntu (64-bit) as the Version; if not then use the drop-down boxes to select the correct settings (remember Mint mainstream is based on Ubuntu). Click Next when you’re ready to proceed. STEP 3 The next section defines the amount of system memory, or RAM, the VM has allocated. Remember this amount is taken from the…

A TOUCH OF SPICE The Cinnamon desktop environment is a great blend of style and performance. There’s lots to like about it, which is why it’s such a popular DE. STEP 1 Begin exploring the Cinnamon desktop by double-clicking the Computer icon. This brings up Nemo, the file manager used in Cinnamon. The Computer icon opens up the root level file system, with access and views to the optical drive (if you have one installed), hard drive and core Linux file system. STEP 2 The Linux file system can appear confusing to a former Windows user, so until you’re a little more knowledgeable on how it all works, we’d recommend you concentrate on the Home icon on the desktop instead. In here is everything relating to your user account: where…

NEW USERS Having different users means each user has access to his or hers own areas on the system. Documents, pictures, videos and so on are separate, as with multiple users on other operating systems. STEP 1 Click on the Linux Mint Menu and type ‘users’ to begin searching for the relevant console. From the search results, choose Users and Groups and enter your password. The Users and Groups console is quite basic looking, and thankfully easy to use. At first, you can just see your own username from when you installed Linux Mint. STEP 2 To add a new user, click the Add button at the bottom of the console. There are two types of user you can create, Standard and Administrator. Unless the new user has need to…

“Linux: the operating system with a CLUE… Command Line User Environment.”– Anonymous (Posted on comp. software.testing) The Linux command line, the Terminal, is an incredibly powerful environment. From it, you can bring the OS to its knees, or update it to something spectacular. You can hack into remote computers, look at an animated ASCII camp fire, install new apps and programs, watch Star Wars played out from a server in the Netherlands, and code intricate automated scripts. In this section you will explore the intricacies of the Terminal, and how it works with Linux. You will learn how to manipulate the Linux file system from the Terminal, and you will discover some odd, but fun things you can do in the Terminal. The Terminal rules supreme in the world of…

COMMAND LINE INSTALLS Installing an app with the Terminal may require some nifty keyboard work but you get a better sense of what’s being installed and where. STEP 1 Installing apps form the Terminal is often relatively simple. First though, you need to make sure that the system is up to date. To do this open up the Terminal and enter: sudo apt-get update && sudo apt-get upgrade. Enter your password and accept any necessary updates. STEP 2 Just as you’ve seen, sudo apt-get update/upgrade and so on are designed to upgrade the software that’s already installed on the system. How do you install more apps though? It just so happens that it’s extraordinarily simple. First you need an app to install, so let’s use Stella again. Enter: sudo apt-get…

MANAGING FOLDERS Learning how to create and delete folders in the Terminal is an important Mint, and indeed Linux overall, skill to master. Here’s the basics for you to try out. STEP 1 With the Terminal open enter cd ~ to make sure you’re in your own Home directory. Now enter ls to view the current folders you have housed in the Home directory. You’ll notice that folders are labelled in Mint in cyan (light blue). Let’s start by creating a new directory. Enter: mkdir testdir. STEP 2 If you now enter ls again, you’ll see that the new directory, testdir, has been created alongside the other directories in the Home area. Obviously the command mkdir is what creates the directory, and no doubt you’ve already guessed it stands for…

TAKING COMMAND There are countless Linux tips, secrets, hacks and tricks out there. Some are very old, originating from Linux’s Unix heritage, while others are recent additions to Linux lore. Here’s our favourite ten tips and tricks. EASTER EGGS Emacs, the text editor, is a great piece of software, however, did you know it also contains a hidden Easter Egg? With Emacs installed (sudo apt-get install emacs25), drop to a Terminal session and enter: Dunnet is a text adventure written by Ron Schnell in 1982, and hidden in Emacs since 1994. MOON BUGGY Based on the classic 1982 arcade game, Moon Patrol, Moon Buggy appeared on the home computers of 1985 amid much praise. It’s a cracking Atari game, and it’s available in the Linux Terminal by entering: Then: Enjoy.…

VARIABLES Just as in every other programming language a Bash script can store and call certain variables from the system, either generic or user created. STEP 1 Let’s start by creating a new script called hello.sh; xed hello.sh. In it enter: #!/bin/bash, then, echo Hello $1. Save the file and exit Xed. Back in the Terminal make the script executable with: chmod +x hello.sh. STEP 2 As the script is now executable, run it with. /hello.sh. Now, as you probably expected a simple ‘Hello’ is displayed in the Terminal. However, if you then issue the command with a variable, it begins to get interesting. For example, try. /hello.sh David. STEP 3 The output now will be Hello David. This is because Bash automatically assigns variables for the user, which are…

EASY AUTOMATION AND HANDY SCRIPTS Entering line after line of commands to retrieve system information, find a file or rename a batch of files? A script is a better answer. STEP 1 Let’s start by creating a script to help display the Mint system information; always a handy thing to have. Create a new script called sysinfo.sh and enter the following into Xed, or the text editor of your choice. STEP 2 We’ve included a couple of extra commands in this script. The first is the -e extension for echo, this means it’ll enable echo interpretation of additional instances of a new line, as well as other special characters. The proceeding ‘31;43m’ element enables colour for foreground and background. STEP 3 Each of the sections runs a different Terminal command,…

A adduser Add a new user arch Print machine architecture awk Find and replace text within file(s) B bc An arbitrary precision calculator language C cat Concatenate files and print on the standard output chdir Change working directory chgrp Change the group ownership of files chroot Change root directory cksum Print CRC checksum and byte counts cmp Compare two files comm Compare two sorted files line by line cp Copy one or more files to another location crontab Schedule a command to run at a later time csplit Split a file into context determined pieces cut Divide a file into several parts D date Display or change the date & time dc Desk calculator dd Data Dump, convert and copy a file diff Display the differences between two files dirname…