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Using Git for Source Control |
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| GIT is the source control tool, a distributed version control system (dvcs) which is written in C. This provides a history of the files that are maintained by it. In distributed version control each user has a complete copy of the code so there is no central code repository. In this scenario an administrator makes changes, adds them to the index (called staging) and then adds them to the repository (called commit). Git will take this information and maintain a version history that users can track. This is all performed locally but could be synchronized with a remote repository. read more... |
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| | mail this link | permapage | score:9911 | -aweber, May 5, 2012 |
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Tutorial: Android app development environment on Debian 6 |
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| This tutorial describes how you can set up an development environment for building Android apps on a Debian Squeeze desktop using Eclipse, the Android SDK, and PhoneGap. I will describe how to build Android apps from the command line with PhoneGap and from the GUI with Eclipse and PhoneGap and how to test them in an Android emulator and on a real Android device. PhoneGap allows you to develop your Android applications using web technologies such as HTML, CSS, and JavaScript (e.g. with JavaScript libraries such as jQuery/jQTouch), and it will turn these web apps into native Android apps (in fact, PhoneGap supports multiple platforms such as Android, iPhone, Palm, Windows Mobile, Symbian, so you can use the same sources to create apps for multiple platforms). read more... |
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| | mail this link | permapage | score:9740 | -falko, March 15, 2011 |
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E-book: Perl One-Liners Explained |
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I'm happy to announce my 3rd e-book called "Perl One-Liners Explained."
Perl one-liners are small and awesome Perl programs that fit in a single line of code and they do one thing really well. These things include changing line spacing, numbering lines, doing calculations, converting and substituting text, deleting and printing certain lines, parsing logs, editing files in-place, doing statistics, carrying out system administration tasks, updating a bunch of files at once, and many more.
Here is an example. Suppose you quickly need to generate a random, 8 character password. You can do it quickly with this Perl one-liner:
perl -le 'print map { ("a".."z")[rand 26] } 1..8'
Overall, the e-book has 111 pages and it explains 130 unique one-liners. Many of one-liners are presented in several different ways so the total number of one-liners in the book is over 200. read more... |
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| | mail this link | permapage | score:9720 | -pkrumins, February 4, 2012 |
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perl1line.txt: A handy Perl script collection |
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The ultimate goal of the Perl One-Liners Explained article series was to release the perl1line.txt file. Last week I finished the series and now I am happy to announce perl1line.txt - a collection of handy Perl one-liner scripts.
The perl1line.txt file contains over a hundred short Perl one-line scripts for various text processing tasks. The file processing tasks include: changing file spacing, numbering lines, doing calculations, creating strings and arrays, converting and substituting text, selective printing and deleting of certain lines and text filtering and modifications through regular expressions.
The latest version of perl1line.txt is always at:http://www.catonmat.net/download/perl1line.txt Enjoy! It took me over 3 years to write all the one-liners down. read more... |
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| | mail this link | permapage | score:9674 | -pkrumins, November 21, 2011 |
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Tutorial: Android app build environment with Eclipse, PhoneGap (Ubuntu 11.04) |
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| This tutorial describes how you can set up an development environment for building Android apps on an Ubuntu 11.04 desktop using Eclipse, the Android SDK, and PhoneGap. I will describe how to build Android apps from the command line with PhoneGap and from the GUI with Eclipse and PhoneGap and how to test them in an Android emulator and on a real Android device. PhoneGap allows you to develop your Android applications using web technologies such as HTML, CSS, and JavaScript (e.g. with JavaScript libraries such as jQuery/jQTouch), and it will turn these web apps into native Android apps (in fact, PhoneGap supports multiple platforms such as Android, iPhone, Palm, Windows Mobile, Symbian, so you can use the same sources to create apps for multiple platforms). read more... |
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| | mail this link | permapage | score:9607 | -falko, June 28, 2011 |
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Python Client/Server Tutorial |
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A tiny Python tutorial...
This application can easily be coded in Python with performance levels of thousands of transactions per second on a desktop PC. Simple sample programs for the server and client sides are listed below, with discussions following read more... |
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| | permapage | score:9559 | -Ray, June 22, 2009 |
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Expect Script Examples |
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Expressions, if statements, for loops, and while loops examples are covered in this mini-tutorial:
This article explains the following in the expect scripting language.- Expressions – arithmetic operation
- if construct in expect
- looping constructs
read more... |
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| | permapage | score:9553 | -Ray, January 21, 2011 |
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Add Video Streaming to C/C++ apps with Nex Gen Media Server API |
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| Recently I took a closer look at Nex Gen Media Server and their API framework. NGMS is a multi-purpose streaming server which supports some of the popular streaming protocols such as RTSP, RTMP, Apple's HTTP Live, and MPEG-2 Transport Stream. NGMS comes with transcoding support and is able to capture and reformat live video streams and adapt them to be received by another type of device, such as capturing an HD video feed and converting it to be received by an iPhone over 3g. My focus was to integrate the NGMS API to control the streaming features directly from my own C application. In this example I am using Ubuntu Linux 10.04. read more... |
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| | mail this link | permapage | score:9540 | -falko, November 17, 2011 |
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Build Apps with Android SDK, Eclipse, PhoneGap (Ubuntu 10.10) |
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| This tutorial describes how you can set up a development environment for building Android apps on an Ubuntu 10.10 desktop using Eclipse, the Android SDK, and PhoneGap. I will describe how to build Android apps from the command line with PhoneGap and from the GUI with Eclipse and PhoneGap and how to test them in an Android emulator and on a real Android device. PhoneGap allows you to develop your Android applications using web technologies such as HTML, CSS, and JavaScript (e.g. with JavaScript libraries such as jQuery/jQTouch), and it will turn these web apps into native Android apps (in fact, PhoneGap supports multiple platforms such as Android, iPhone, Palm, Windows Mobile, Symbian, so you can use the same sources to create apps for multiple platforms). read more... |
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| | mail this link | permapage | score:9523 | -falko, January 27, 2011 |
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Tutorial: Install SVN, Configure multi-protocol access (Ubuntu 11.10) |
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| Subversion (svn) is an open-source version control system (VCS), used in the development of many software projects. This tutorial shows how to install Subversion on Ubuntu 11.10 and how to configure it to allow access to a repository through different protocols: file://, http://, https://, svn://, and svn+ssh://. read more... |
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| | permapage | score:9520 | -falko, February 28, 2012 |
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bash scripting: Looping through a list |
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| This is an example of a Bash shell script used to loop through a list to compare to text strings found in logs. The script is used to detect and block attacks on a web site. read more... |
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| | permapage | score:9485 | -aweber, December 26, 2011 |
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Perl One-Liners Explained: Handy Regular Expressions |
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This is the seventh part of a nine-part article on Perl one-liners.
Perl one-liners are short programs that do one and only one task well and they fit on a single line in the shell.
Perl is not Perl without regular expressions, therefore in this part I come up with and explain various Perl regular expressions. Please see part one for the introduction of the series.
This part explains the following regular expressions:- Match something that looks like an IP address.
- Test if a number is in range 0-255
- Match an IP address
- Check if the string looks like an email address
- Check if the string is a decimal number
- Check if a word appears twice in the string
- Increase all numbers by one in the string
- Extract HTTP User-Agent string from the HTTP headers
- Match printable ASCII characters
- Match text between two HTML tags
- Replace all bold tags with strong tag
- Extract all matches from a regular expression
read more... |
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| | mail this link | permapage | score:9478 | -pkrumins, November 11, 2011 |
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HTML5: Drag and Drop to a webpage |
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Here's a cool, simple but useful demonstration that exercises HTML5 in a novel way. Get the key methods needed to implement the File APIs to use Drag and Drop to select an image file off your local file system.
For my example, I have provided a palette from which to drag & drop into, or alternatively use the File chooser, to select image files off your local file system. For this example, please select image files only, as I have not built in any filtering or error detection for non-graphical files. read more... |
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| | mail this link | permapage | score:9476 | -solrac, February 1, 2011 |
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Space Tyrant: A multiplayer network game for Linux |
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Since the last release of Space Tyrant, it has gained some actual game-like functionality. The new code can be downloaded from st2.c. Download it as well as the shell script you’ll need to compile it: makeit2.sh.
It’s now possible to connect to the game via telnet and to create an account, log in, and be issued a ship. Once you’re logged in, there is a universe to explore filled with ports for buying and selling goods and planets for scooping free goods. From those trading activities you can earn money, called microbots. Other than trading to earn more money, you only use your microbots to buy fighters -- which you can use to attack other players or the neutral fighters that guard some sectors.
The neutral fighters are only good for parking under while you’re not playing. They afford a little bit of free protection for your ship since no one can attack you until they first destroy the neutral fighters. Note that you can attack other players whether they are logged in or not and any fighters with their ship will automatically try to defend them.
Each player starts out with a specific supply of fuel, called antimatter. Each minute a small amount of additional antimatter is issued by a function called updatefuel(). If you’re not logged in, fuel just accumulates in your ship. This continuous allocation of fuel makes Space Tyrant a type of turn-based game. Unlike traditional turn-based games, however, you can play your fuel all at once or a little at a time and completely independently of how and when other players play.
You can also talk to other players on the radio. There is only one channel so everyone who is logged in hears everything that is said on the radio.
The game isn’t yet playable in any reliable sense, however, because it doesn’t yet back up and reload the data from disk files. The software creates an instance of the game when you run it and it remains running until you stop it or the system goes down. There is also no way to establish a time limit on a game.
That’s pretty much the extent of the functionality changes. Now, on to the code.
First, there is a login function. That function looks in the player database struct and, if the player name doesn’t already exist, it creates an account there. If the name does exist, it prompts for a password, matches it against the stored password, and logs you in if the two match. There is not yet a way to change your password.
Once a player is logged in, he is faced with a sector description and a ‘choice:’ prompt. Any character that the player types at this prompt is immediately acted on as if it were a command. There is a string called ‘commlist’, short for command list, containing the letters and characters that are used as commands. A function pointer array, ‘fp[]()’, is used to store the locations of the command functions. Another function called ‘commscan()’ looks up the command letter typed and returns an index into the fp[]() function pointer array. This combination of the commlist string, the commscan function, and the fp function pointer array constitute the command processing loop of the game, as shown below:
userndx=commscan(
tolower(
threc[th].inbuf
[threc[th].inptr][0]
),commlist
);
result=fp[userndx](th);
These lines are embedded in a loop where each user’s input thread, represented by the variable ‘th’, is examined for new input. The new input arrives in string called inbuf. Since each thread has several buffers, an index called inptr is used to keep track of which one is currently being processed.
And, as described above, commscan is used to extract the appropriate function index and place it in a variable called ‘userndx’. Then, userndx is used to index into the fp function pointer array and the thread index (th) is passed to the appropriate command-processing function.
There’s a small amount of misdirection in that first line but, once understood, it becomes trivial to add additional commands. Basically, you just need to replace the placeholder function, ‘nullrtn’, with your new function name adjacent to the command letter you select in the fp[]() definition list.
The new functions are discussed below.
makemap()
In keeping with the evolving game nature of this project, several actual game functions have been added. The first new function, makemap(), builds a 20,000-sector single-galaxy universe and populates it with objects. By changing the GAMESIZE constant, you can build a universe of arbitrary size, but make sure you don’t try to build a universe so big as to consume too much of your system’s memory. I’ve tested universes of up to 1,000,000 sectors, which seem to work just fine. The makemap() function randomly puts ports, planets, fleets of neutral fighters, and nebulas in various sectors throughout the universe, and interconnects the sectors with randomly-generated one-way ‘warps’. Note that planets and ports are randomly given varying productivity's and random initial inventories of our three commodities: Iron, Alcohol, and Hardware.
Note that makemap() builds each sectors array of six warps, sorts them into ascending order, and then looks for duplicate warps. If any duplicates are found, it decrements the loop-controlling variable and simply rebuilds that entire sector from scratch. The sorted warps are a convention that we will maintain throughout the project. Each new galaxy type that we add in the future will adhere to that convention and other functions (and users) will be allowed to assume that warps are in ascending order.
command()
We have added a function to simply list the implemented commands and a short line of description. For now, the function is attached to the command letters ‘?’ and ‘H’ via the function pointer array and the commlist array. This function is mostly useful to illustrate a design limitation. The output of any single sprintf buffer-building function cannot exceed the MAXLINE buffer size constant. This function produces a single buffer out output very near the current 511-byte limit and will soon have to be split to produce two buffers of output. Assuming, of course, that we don’t increase the MAXLINE buffer size.
jettison()
The ‘J’ command activates the jettison() function. It’s only purpose is to dump any cargo out of your cargo holds. It illustrates the method we use to let a function that requires multiple characters of input -- or simple confirmation -- to temporarily turn off command processing and send the next character of input back to it. Jettison requires confirmation so that you don’t accidentally dump your cargo just by hitting the J key. (Since all commands operate as ‘hot’ keys you do not have to hit the [Enter] key to activate a command -- each command immediately executes as soon as you press a key.)
Each command function has the ability to set the thread’s control variable to it’s own command letter. That way, the command processing loop can simply check ‘control’ pass the next buffer of input directly to whichever function is indicated.
warprtn()
jumprtn()
The warprtn and jumprtn functions process requests to move to another sector. warprtn() processes the commands 1, 2, 3, 4, 5, and 6, which represent a user’s request to move to the first through the sixth sector number in the warp list, respectively. jumprtn() processes requests to move to a randomly selected sector in the warp list via the ‘-’ (or ‘=’) key. jumprtn() also implements commands to move to the next larger sector, the next smaller sector, as well as the largest and smallest sector number via the ‘.’, ‘,’, ‘>’, and ‘game design and the programming model. The second article discusses the IO handling code and more of the details of the programming model.]
[Update, June 25, 2005: A Space Tyrant home page has been created as a central index to the various ST articles, links, and files.]
[Update, March 21, 2007: Space Tyrant now has a website of its own!. This site is new but growing and will be the quickest way to find new information and code on the Space Tyrant project.] |
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| | mail this link | permapage | score:9475 | -Ray, May 30, 2005 (Updated: March 21, 2007) |
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Install FB4Linux in Eclipse |
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| Flash development in Linux is often left to a generic text editor used with the free Flex SDK. It is certainly possible to code this way, but you do lose out on a lot of the functionality of a more specific IDE. The FB4Linux project provides a plugin for Eclipse that provides a similar environment to FlashBuilder 4. The only downside is that the installation instructions gloss over a few of the details required to get the plugin installed in Eclipse 3.5.2, which is the version of Eclipse that is available in the Ubuntu software repositories at the time of writing. This article shows you how to get FB4Linux up and running from start to finish. read more... |
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| | mail this link | permapage | score:9471 | -mcasperson, July 27, 2010 |
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Create native looking Firefox web apps |
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HTML5 and Flash have been used to great effect in recreating traditional desktop apps that can be run through your web browser. Google is so confident that web apps can replace your desktop apps that it has released the ChromeOS, which is not much more than the Chrome web browser presented as a desktop operating system.
Firefox has long supported running web apps in a kind of desktop mode through projects like Prism, WebRunner and Chromeless. But a lot of these projects are either dead, in their early stages, or require a lot of mucking around to get running.
The good news is that it is quite easy to launch your favourite web apps in a chromeless Firefox 4/5 window with just a few simple steps. read more... |
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| | mail this link | permapage | score:9468 | -mcasperson, August 5, 2011 |
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Tutorial: Build a C/C++ memory manager |
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| As a developer, one of the most powerful tools that C/C++ arms you with to improve processing time and prevent memory corruption is the control over how memory is allocated or deallocated in your code. This tutorial demystifies memory management concepts by telling you how to create your very own memory manager for specific situations. read more... |
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| | permapage | score:9451 | -BlueVoodoo, February 23, 2008 |
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e-book: Sed One-Liners Explained |
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I love writing about programming and I am happy to announce my second e-book called "Sed One-Liners Explained".
Sed one-liners are short sed scripts for everyday situations in the shell, such as changing line spacing, numbering lines, and converting and deleting text.
For example, the following sed one-liner numbers the lines of a file:
sed = file | sed 'N; s/n/: /'
Here is how it works - it's made out of two sed commands. The first one uses the = command that inserts a line containing the line number before every original line in the file. Then this output gets piped to the second sed command that joins two adjacent lines with the N command. When joining lines with the N command, a newline character n is placed between them. Therefore it uses the s command to replace this newline n with a colon followed by a space ": ".
The e-book is 98 pages long and it explains exactly 100 one-liners. It's divided into the following chapters:
Preface.
1. Introduction to sed.
2. Line Spacing.
3. Line Numbering.
4. Text Conversion and Substitution.
5. Selective Printing of Certain Lines.
6. Selective Deletion of Certain Lines.
7. Special sed Applications.
Appendix A. Summary of All sed Commands.
Appendix B. Addresses and Ranges.
Appendix C. Debugging sed Scripts with sed-sed.
Index.
Did you know that sed was as powerful as any other programming language? Someone even wrote Tetris in it.
After you read the e-book, you'll be able to write your own Tetris if you wanted to. read more... |
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| | mail this link | permapage | score:9445 | -pkrumins, September 19, 2011 |
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Online Ruby Interpreter |
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Try Ruby online with this online tutorial / interpreter. It runs in your browser.
Ruby is a programming language from Japan (available at ruby-lang.org) which is revolutionizing the web. The beauty of Ruby is found in its balance between simplicity and power.
Try out Ruby code at the prompt above. In addition to Ruby's builtin methods, the following commands are available: read more... |
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| | permapage | score:9434 | -Ray, November 30, 2005 |
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Debugging Shell Scripts |
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| Learning how to find the errors in your shell scripts is an important skill for successful shell scripting. The debug options in the Bash shell can help with that. read more... |
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| | permapage | score:9431 | -aweber, February 2, 2012 |
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