I’m feeling totally comfortable with the Rails and Ruby part of this course. What I’m having trouble with is Father Time himself. I’ve spent the last couple of day getting three finals together for my CCSF course. What made it more time-consuming (yet more rewarding) was that I got a wild idea to write an automated testing suite to evaluate the functionality of the insanely complex HTML forms I’m having my students create (and validate) as part of the Final. The test suite is done with SimpleTest, the rather fabulous PHP Unit Testing library.

Check out the SaaS course here — Software Engineering for SaaS | Coursera. Maybe you can catch it the next time it comes around.

I’m enrolled in this UC Berkeley SaaS course. The cool thing is that some of my Ruby and PHP students will be in the course too. The course starts May 18, so you’d better get with it if you want to hang with us.

I’ll post about my experiences as I go along. This will be all new to me, and I’m looking forward learning the cool stuff that the cool kids are doing.

The prototype for the singleton class, in PHP, goes like this:

Singleton Pattern

class ClassName {
    static $instance = NULL;
    private function __construct() {}
    private function __clone() {}
    static function getInstance() {
        if(self::$instance === NULL) self::$instance = new ClassName();
        return self::$instance;
    }
}

$obj = ClassName::getInstance();

It’s All About Scope

PHP variables have scope restrictions that prevent them from being visible in all parts of your program. We often need these variables inside classes and functions. One way to provide globally accessible variables is to pass them into classes or functions as parameters. This method makes it clear that the function of class method is dependent on an external variable or object. Here’s an example:

Option #1: Pass the Variable As A Parameter

Here’s an example of passing a database handle into a hypothetical function and into a class.

function logger($info, $dbhandle);

class Logger {
    static $handle = NULL;
    static function logIt($info, $dbhandle) {
        self::$handle = $dbhandle;
    }
}

When you have only a few parameters this tactic works fine, but if your functions have many parameters the result is unwieldy code. It is not uncommon to find programmers creating functions or methods that have parameteritis, with dozens of confusing parameters.

Fortunately, a singleton class provides a cleaner solution: it provides global availability of a single object—with the side-effect that the sole object cannot be modified. If we want to ensure that this class cannot be cloned or sub-classed, we will mark it as final and the construct() and clone() methods as protected.

Option #2: Use a Singleton Class

Here’s an example a properly formed singleton class that cannot be cloned or sub-classed, ensuring that there will only be one instance of this class.

final class DbConnection {

    private static $handle = null;
    private static $instance = NULL;
    private static $db = 'default.db';

    // Deny new DbConnection();
    private function __construct($db = NULL) {} 

    // We deny cloning, as with:
    //
    $instance = DbConnection::connect();
    //
    $clone = $instance;
    private function __clone() {} 

    function connect() {
        if(is_null(self::$handle)) {
            if(defined('DEFAULT_DB') {
                 self::$db = DEFAULT_DB;
            }
            // Create the only possible instance of this class
            self::$handle = new SqliteDatabase(self::$db);
        }
        return self::$handle;
    }

    static function getInstance() {
        if(self::$instance === NULL) {
            self::$instance = new DbConnection();
        }
        return self::$instance;
    }
}

This class encapsulates the entire process of creating the single instance and the database handle, and checks to see if a default database constant exists. We can use it this way:

class Logger {
    // Notice that this, too, is a singleton pattern class.
    static private $logger = NULL;

    static function logIt($it) {
        $dbc = DbConnection::getInstance()->connect();
        if(self::$instance == NULL) {
            self::$instance = new Logger);
        }
    }
    private function __construct() {}
}

Refactoring

Since the sole function of the DbConnection class is to provide a database connection, we can simplify the code considerably by eliminating the getInstance() method:

final class DbConnection {

    private static $handle = null;
    private static $db = 'default.db';

    // Deny new DbConnection();
    private function __construct($db = NULL) {} 

    // We deny cloning
    private function __clone() {} 

    function connect() {
        if(is_null(self::$handle)) {
            if(defined('DEFAULT_DB') {
                self::$db = DEFAULT_DB;
            }
            // Create the only possible instance of this class
            self::$handle = new SqliteDatabase(self::$db);
        }
        return self::$handle;
    }
}

class Logger {

    static private $logger = NULL;

    static function logIt($it) {
        $dbc = DbConnection::connect();
        if(self::$instance == NULL) {
            self::$instance = new Logger);
        }
    }

    // Your other methods go here

    private function __construct() {}
}

Happy hacking…

In a world of curated blogs, where every life is golden and reeking of the sweet smell of success, Average Magazine is a winner. It’s an annual magazine, so get your copy now. 2013 is a long way away.

A shiny magazine without the shine, Average celebrates ordinary moments & the minutia our lives are based on, without pretension & full of honesty. Articles include:

• Softpants: characteristics, occasions & litmus tests
• Sheet Cake: the building block of group celebration
• Law & Order: a one-week analysis of the franchise
• The Wire Coat Hanger: one man’s quest to have his coat remained unwrinkled
• The Word Count: one thousand, one hundred & eighty words
• Oblong Sandwiches: and the cities that claimed to have coined them
• The Green Book: profoundly calm & unhurried
• Snails: the life of a pair of clip on earrings
• People: and how they like their toast among other things
• Trees That Look Like Giant Vegetables
• Reflections on Regression Towards the Mean
• Your Grandmother Taught You To Steal To Survive A Depression
• You Are What You Eat: a photo essay examining the interior of refrigerators in homes across Texas
• Sky Chart: paintings & analysis of the sky over a three month period
• On Swimming: a short story
• Someone Named Joe: the first in a series of portraits
• + a crossword puzzle

The plan is that face-to-face courses will be restored once the economy rebounds, but the reality is that online courses draw more enrollment, and F2F courses will become second class citizens.

The upside of all these changes is I’ve decided to make my college courses available on this web site beginning in June, 2012. As I edit this semester’s course work, I am simultaneously moving content to this web stie.. The first course will be Beginning PHP. Later I’ll add a beginning Python and Ruby courses.

My courses are designed for motivated students who want a beginner-friendly introduction to web development. Click here to subscribe to updates.

Keep hacking…

Here are my results, as generated by my four-year old PC. My math tells me that localhost can handle about 406 million hits a day. Too bad it’s so difficult to monetize the computers stacked under my desk.

Linux Mint LMDE, 2.66GHz Core 2 Duo, Nginx, Varnish, PHP5-FPM, etc.

% /usr/bin/ab -t 60  -c 100 http://localhost/2012/03/02/setting-up-two-portrait-monitors-with-linux/
This is ApacheBench, Version 2.3
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient)
Completed 5000 requests
Completed 10000 requests
Completed 15000 requests
Completed 20000 requests
Completed 25000 requests
Completed 30000 requests
Completed 35000 requests
Completed 40000 requests
Completed 45000 requests
Completed 50000 requests
Finished 50000 requests

Server Software:        nginx/1.1.0
Server Hostname:        localhost
Server Port:            80

Document Path:          /2012/03/02/setting-up-two-portrait-monitors-with-linux/
Document Length:        14171 bytes

Concurrency Level:      100
Time taken for tests:   10.606 seconds
Complete requests:      50000
Failed requests:        0
Write errors:           0
Total transferred:      728605005 bytes
HTML transferred:       708550000 bytes
Requests per second:    4714.15 [#/sec] (mean)
Time per request:       21.213 [ms] (mean)
Time per request:       0.212 [ms] (mean, across all concurrent requests)
Transfer rate:          67085.01 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.4      0      16
Processing:     0   21   9.4     19     134
Waiting:        0   20   8.8     19     133
Total:          0   21   9.5     19     136

Percentage of the requests served within a certain time (ms)
  50%     19
  66%     22
  75%     24
  80%     25
  90%     31
  95%     38
  98%     45
  99%     53
 100%    136 (longest request)

I had always imagined that flying would be fun, but this just looks like a lot of work, or a nicely produced hoax.

UPDATE: Wired has changed “Successfully” to “Claimed”.

Jerry Brown is playing hardball now.

You’ll have to read the article to see why these ideas are so frightening — or you can just cast a cold eye on this list.

1. Build a better search engine — replace the current ego-oriented Google with a hacker-type search engine that give real results, not “social” results. Make it like the old Google.
2. Replace email with a new protocol that does not allow anyone to push their junk into your mindspace.
3. Replace universities with something better, then move on to community colleges, then to high schools.
4. Replace TV (cable) with Internet Delivery.
5. Be the next Steve Jobs — it could be you, since the next Steve Jobs will definitely not be working at Apple.
6. Bring back Moore’s Law. Forget about creating faster — and “better” — software, which is pretty much impossible, and get back to making better, faster hardware.
7. Create a way to do ongoing medical diagnosis.  (This is totally Star Trekky, Paul.)

Paul, I’m with you on #4. I, too, use my iMac as my TV.

This guy is, after all, all about numbers.

Jason Fried misses a chance to explain what you have to do when that hothead jerk/creep/troll is trying to stomp the life out of your fragile idea: you have to push back until they buzz off — or, like Jason Fried, see the light.

HD Monitors Suck, Portrait Monitors Rock

My solution to the monitor problem is to buy wide monitors that can operate in portrait mode. This setup works effortlessly with Windows 7 and OS X. You plug them in, go to the control panel, rotate both monitors, and click Apply, and it just works. You can have two portrait monitors with Linux, too, but the path to success is paved with unpleasantness and frustration — if you don’t know what you’re doing, and I didn’t know, until today.

The Hardware

My funky HP box (got it for cheap at Costco) has an older NVidia card (8400GS) with both DVI and HDMI outputs, and I thought, naively, that it would work out of the box with Linux Mint, as it does in Windows and with my iMac. Wrong!

The Software — NVidia Proprietary Drivers

Since I like to use Compiz (I’m a sucker for drop shadows and and 3-D effects), I installed the proprietary NVidia drivers. Getting that done took some serious searching, but I found the clues I needed on the Linux Mint forum. Check it out here.

The Fabulous Shinobu’s Secrets

After digging around I found a tutorial on Shinobu’s Secrets that showed how to set up dual monitors. You might also want to check out Shinobu’s eclectic collection of Linux/Emacs/Vim/programming tutorials.

By following the NVidia tutorial I was able to get the two monitors working side by side. The next step was to rotate them into portrait mode.

The NVidia Gui Settings App

nvidia Settings

Unfortunately, the Linux version of nvidia-settings is missing the rotation settings! So, back to foraging I went, and I found the xorg.conf documentation where I saw the options for rotation: “normal”, “left”, “right”, and “inverted”.

After a little experimentation, I added this line to the xorg.conf Monitor section.

Option "Rotate" "Left"

Dual Monitors in Portrait Mode using Linx Mint Debian Edition, with Happy Hacking Professional 2 Keyboard.

The final xorg.conf

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 280.13  (buildd@biber)  Sat Aug  6 10:45:52 UTC 2011

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection

Section "Files"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Mouse0"
    Driver         "mouse"
    Option         "Protocol" "auto"
    Option         "Device" "/dev/psaux"
    Option         "Emulate3Buttons" "no"
    Option         "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
    # generated from default
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "DELL U2412M"
    HorizSync       30.0 - 83.0
    VertRefresh     50.0 - 61.0
    Option         "DPMS"
    Option         "Rotate" "Left"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 8400 GS"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "1"
    Option         "TwinViewXineramaInfoOrder" "DFP-1"
    Option         "metamodes" "DFP-0: nvidia-auto-select +0+0, DFP-1: nvidia-auto-select +0+1200"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

I’m catching up on four years of Breaking Bad. Since the fourth season hasn’t been released on DVD, I’m watching it using Amazon’s Digital (works fine). The iMac has a decent-sized screen, though it is too glossy to do a great job. At least it’s connected to the Internet. So, I moved it into the living room where I can kick back in my Ikea Klackbo and watch Walter and Jesse’s adventures in the meth trade.

Linux Mint

To do my hacking, I pulled out my 5-year old PC and installed Linux Mint on it. This is one sweet Linux distro.

Successes

• The desktop looks good. Guys, it really doesn’t suck, like these Linux desktops.
• It’s Debian.
• There’s no crappy Unity desktop (Ubuntu, big dumb mistake going with that!)
• No crappy Gnome 3 (tried it, hated it!).
• Apt-get works like a dream, as always.
• The wifi works with my hardware. This can be a hassle with some distros (SuSE, I mean you).
• The sound works. I can listen to my Balearic Trance just fine.
• Installing all my work tools went off without a hitch: LAMP, Ruby, Python, Vim, etc all installed easily.

Inconveniences

There are a couple tweaks I had to make.

• The default Debian kernel recognizes only one core of my super spiffy Core 2 Duo processor, so I had to install the PAE kernel. By the way, I had to look at the Debian documentation to get this one working.
• I wanted the proprietary NVidia drivers, so I had to dig around to figure that out. This involves installing a kernel module. It worked just fine, though the portrait mode wasn’t working. I had to tweak the xorg.conf to handle the rotation. See below.

The Big Advantages

The real advantage of Linux is that it’s a cinch to install the software I need. I need Ruby, PHP, Python, and all that other good GNU software. For editors I use Vim and… well, I use Vim.

Frankly, Linux running on a humble, and homely, HP box, with an awesome Happy Hacking Professional 2 keyboard (worth its weight in gold), and a 24″ Dell monitor in portrait mode (can’t do that with any Apple monitor), is the low-friction OS for web development.

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
    Option         "Rotate" "Left"
EndSection

Courses
My introductory PHP and Ruby courses will be available June 1, 2012. Eventually my Python and HTML5 courses will make it over. My college courses run for 18-weeks, but I will be rewriting my WiseBison courses to be self-paced, modular, month-long classes.

Besides putting my the courses here, I’ll have my blog, code tips, PDFs, free stuff, and reviews. If you’re  interested in updates while I’m getting set up, sign on to the RSS feed.

Keep hacking…

This will also be my blog, replacing my HackingtheValley.com blog. Check back now and then to see what’s going on, or sign up for the RSS feed to stay up to date.

Keep hacking…

Sometimes you create Ruby or Python code looks perfect, yet it will not run when you upload it to the server. You will get mysterious error messages like this:

Server error!

The server encountered an internal error and was unable to complete your request.

Error message:

Premature end of script headers: lab1.2.py

So, you look at your script, and all you can see is absolute perfection, but it still won’t work, so you run it on the command line, like this:

python3 lab1.2.py

./lab1.2.py

… it goes down in flames:

unable to exec joesmith88/public_html/lab1.2.py: No such file or directory

What’s Going On?

What’s going on is that you really do have a fatal error in your code, and it’s an error that you can’t see. In fact, it’s invisible. The error is that you have uploaded a file that you created on a Windows machine.

There’s nothing intrinsically wrong with Windows, but Windows editors often, by default, do something that breaks — fatally breaks — CGI scripts that run on a Unix server: they add Windows line endings to the end of every line.

What Are Windows Line Endings?

Unix Line Endings

Why Do WIndows Line Endings Break CGI Scripts?

#!/usr/local/bin/python3\r\n
print(’Content-type:text/html\n’)\r\n
print(’Hello, world’)\r\n

#!/usr/local/bin/python3\r\n

Here’s how Linux sees that line. First, Linux doesn’t know about Windows line endings; the “\r” character is just another character, like an “a”, “b”, or “c”. The shell sees the shebang and looks for a program named /usr/local/bin/python3\r.

Since Linux the “\r” as just another character in the program’s name, it looks on the files system for a file named /usr/local/bin/python3\r. Of course, that file doesn’t exist, so you get a mysterious fatal error, the error caused by the invisible “\r” character.

od (octal dump)

Your can see all of the characters in your scripts by using the od

program to dump all of the characters in your script.

Here’s an example that shows how to use it. This example dump comes from a script a student uploaded from a Windows machine. The “cr” and “nl” characters in the output represent the “\r\n” Windows line endings, and they appear at the end of every line of code. As we’ve already discussed, the “cr” will cause fatal errors when they are at the end of the shebang line. In a Unix CGI script, there should not be ANY cr characters unless you put them there intentionally.

% od -a joesmith88/public_html/lab1.2.py
0000000   #   !   /   u   s   r   /   l   o   c   a   l   /   b   i   n
0000020   /   p   y   t   h   o   n   3  cr  nl   #  sp   N   a   m   e
0000040   :  sp   J   o   s   e   p   h  sp  sp   S   m   i   t   h  cr
0000060  nl   #  sp   F   i   l   e  sp   n   a   m   e   :  sp   l   a
0000100   b   1   .   2   .   p   y  cr  nl   #  sp   D   a   t   e   :
0000120  sp   J   u   n   e  sp   2   1   ,  sp   2   0   1   1  cr  nl
0000140  cr  nl   #  sp   *   *   *   *   *   *   *   *   *   *  sp   L
0000160   a   b  sp   1  sp   E   x   e   r   c   i   s   e  sp   1   .
0000200   2  sp   *   *   *   *   *   *   *   *   *   *  cr  nl  cr  nl
0000220   p   r   i   n   t   (   ’   C   o   n   t   e   n   t   -   t
0000240   y   p   e   :  sp   t   e   x   t   /   h   t   m   l   \   n
0000260   ’   )  cr  nl   p   r   i   n   t   (   ’   \   n   ’   )  cr
0000300  nl   p   r   i   n   t   (  sp   ’   *   ’  sp   *  sp   1   0
0000320  sp   +  sp   ’  sp   L   a   b  sp   E   x   e   r   c   i   s
0000340   e  sp   1   .   2  sp   ’  sp   +  sp   ’   *   ’  sp   *  sp
0000360   1   0  sp   )  cr  nl   p   r   i   n   t   (   ’   H   e   l
0000400   l   o   ,  sp   w   o   r   l   d   !   ’   )  cr  nl  cr  nl

The Solution

The solution, fortunately, is really simple: tell your Windows or Mac editor (yes, even Mac editors misbehave), to stop using Windows-style line endings. Fix it right now. Dig into your editor’s configuration file and tell it to ALWAYS use Unix-style line endings. End of headache…

FTP Causes Problems, Too

Some FTP clients add a “\r\n” line ending by default. If you upload scripts that you know have Unix-style line endings, and they still fail, check them with od to see whether FTP has added Windows line endings. If so, configure your FTP client to behave properly.

Keep hacking…