It should be noted that the following function works best for JSON objects and hasn’t been tested with JSON arrays. The tests worked reliably with properly quoted names and values. I cannot promise that this function would work on non-quoted names and values, but there is code to allow non-quoted value types.

#Gets a single json element value from a json blob.
#For json values (like {"key":{"k2":"val"}}) you need to first get "key"
#then do an additional call with the value as the input to the function and "k2" as the argument
#Example1: cityvar=$(jsonElement "city" "{\"city\":\"Seattle\"}")
#Example2: cityvar=$(jsonElement "city" "{\"city\":{\"name\":\"Seattle\","county":"King"}")
#			countyvar=$(jsonElement "county" "$cityvar")
#			echo $countyvar #outputs "King" (without quotes)
jsonElement(){
	#echo $1
	out=$(echo $2 | awk -F"[,:]" '{for(i=1;i<=NF;i++){if($i~/'$1'\042/){print $(i+1)} } }')
	if [[ $out == \"*\" ]]; #test if the string starts and ends in a quote
	then
		echo "${out:1:${#out}-2}" #removes first and last quotes
	else
		echo $out
	fi
}

void str_replace(std::string& str, const std::string find, const std::string replace){
	size_t index = 0;
	while (true) {
		 /* Locate the substring to replace. */
		 index = str.find(find, index);
		 if (index == std::string::npos) break;

		 /* Make the replacement. */
		 str.replace(index, find.length(), replace);

		 /* Advance index forward one spot so the next iteration doesn't pick it up as well. */
		 ++index;
	}
}

Usage:

std::string str = "Hello Earth!";
str_replace(str,"Earth","World");
//str is "Hello World!" now.

This example will show a login form which is pre-populated with some helper information. When the user clicks on it, the information is modified. An additional feature to this code is that the password textbox is dynamically modified from a “text” type to a “password” type, hiding all of the text that the user enters.

<form action="#" method="post">
	<p>Please sign in.</p>
	<div><label for="email">Email</label><br />
	<input type="text" name="email" id="email" value="" /></div>
	<div>
		<label for="password">Password</label><br />
		<input type="password" name="password" id="password" value="" />
	</div>
	<div><input type="submit" name="submit" value="Login" /></div>
</form>

<script type="text/javascript">
//required: JQuery
//automatically performs the following on page ready
$(document).ready(function(){
	//sets the email text to the following:
	$("#email").val("Email you used to create your account")
		.css({color:"#ccc"}) //changes the color to be hint-like
		.click(function(){
			//changes the text color back to black, 
			//clears the helper text
			$(this).css({color:"#000"}).val("");
		});

	//save the original password box
	var inptPassword = $("#password");

	//replace the password box with a normal text box
	$("#password").replaceWith($('<input type="text" />').attr({
			name:"password",
			id:"password",
			value:"Password"
		}).css({color:"#ccc"})
		.click(
			function(){
				//replace the textbox-style password box
				//with the original
				$(this).replaceWith(inptPassword);
			}
		).keyup(
			function(){
				var val = $(this).val();
				if($(this).attr("type") == "text"){
					$(this).replaceWith(twdc_inptPassword);
					twdc_inptPassword.focus()
				}
			}
		));
});
</script>

Note: Instead of setting a color in Javascript, you should use css classes and the addClass/removeClass methods for when you load and click on a text box.

Click here to benchmark some code.

When you visit the page it’ll show you some sample code that you can run. The number of iterations will default to 1,000,000 for all browsers except IE (100,000 for IE). You can change the code to your own algorithm and run the benchmark.

As soon as you press the button, a cookie will be created to store what you entered. At any time you can come back to the webpage and continue your testing with the code that you entered last.

The page includes jQuery 1.7.1, so you can be confident in using jQuery functions. It also includes setCookie and getCookie functions if you wanted to work with cookies. Instead of using the eval() function, which is considered bad practice in Javascript, the webpage sets your code to a new Function object. This improves the speed considerably at runtime.

The Code

//Pads a number to 2 decimal places
function pad2(number) {
	 return (number < 10 ? '0' : '') + number	   
}

//An output variable that you can use.
var out = "";

//Does the work
function startBenchmark(){
	out = "";
	var SB_iterations;
	var SB_results = document.getElementById("results");
	var SB_code = document.getElementById("code").value;
	setCookie("code",escape(SB_code),365);
		
	//test iterations for incorrect value
	if((SB_iterations = parseInt(document.getElementById("iterations").value,10)) == 'NaN'){
		SB_results.innerHTML = '<span style="color:red;font-weight:bold;">Error: The iterations must be a whole number such as 100000. Do not use commas or words.</span>';
		return false;
	}
	//check for blank code
	if(SB_code == ''){
		SB_results.innerHTML = '<span style="color:red;font-weight:bold;">Error: You must type some code into the text area.</span>';
		return false;
	}
		
	//too slow
	/*var fn = function() {
		window.eval.call(window,SB_code);
	};*/
	
	//better method
	var fn = new Function(SB_code);

	var SB_start = (new Date).getTime();
	/* Run a test. */
	for(var SB_i=0; SB_i < SB_iterations; SB_i++){
		fn();
	}
	var SB_diff = (new Date).getTime() - SB_start;
		
	var seconds = Math.floor((SB_diff/1000)%60);
	var minutes = Math.floor((SB_diff/(1000*60))%60);
	var ms = SB_diff - (minutes*60*1000) - (seconds*1000);
	SB_results.innerHTML = "<p>Runtime: "+SB_diff+"ms<br />"+
		pad2(minutes)+":"+pad2(seconds)+":"+pad2(ms)+" (mm:ss:ms)</p>"+
		(out != ''?'<p><span class="bold">Output Variable:</span> '+out+'</p>':'');
}

The question that people get stuck on is, besides making the code look prettier, which type of statement is better to use? Some people say If is faster, while others say Switch is. Obviously you should make your code look good, which is why Switch is commonly used, but if Switch causes your website or application to run slow then you wouldn’t want to use it.

So to answer this question, I’ve designed some code that tests each version in a very simple manner. The resulting number of milliseconds is written on the webpage after each section is done processing.

var start = (new Date).getTime();
var b = 0;
var a = 1;
for(var i=0; i<100000000; i++){
	if(a == 1){
		b++;
		a = 0;
	}else if(a == 0){
		a = 1;
	}
}
var diff = (new Date).getTime() - start;
	
document.write(diff+"<br />");
	
start = (new Date).getTime();
b = 0;
a = 1;
for(var i=0; i<100000000; i++){
	switch(a){
		case 1:
			b++;
			a = 0;
			break;
		case 0: 
			a = 1;
			break;		
	}
}
diff = (new Date).getTime() - start;
	
document.write(diff+"<br />");

    in = [1,"2",[3,"4"]];
    out = [1,"2",3,"4"]; //this is what he wanted out.

Keywords

Given this task I started to code. However, I had forgotten one glaring issue. His code would fail from the start. He could never use the variable “in” because “in” is a reserved keyword in Javascript.

http://www.quackit.com/javascript/javascript_reserved_words.cfm

Reserved keywords are those special words that you can’t use as variables because they have some significant meaning to the Javascript interpreter. In this case “in” is used for certain for loops.

Maybe this was a trick question or maybe he just happened to use those variable names. I changed the input variable and tried to figure out the problem.

Type Checking Variables

My friend also wanted to make sure that the variable being passed into the function was an array. As I somewhat knew already, this type checking brings all sorts of issues with Javascript. “typeof” is a keyword that allows you to check what data type a variable is, but it has some limitations for Arrays and is best used in checking if something is undefined. Arrays will output a typeof “Object” instead of “Array”.

I found that “instanceof” would work, however it has issues if two different objects have the same prototypical attributes. A Javascript object with the class name of “Object” is the same as “Other” if both objects have the same attributes. Doing a bit more research led me to this website which describes a better way to check arrays (and the possibly incorrect ways that systems like JQuery used to use). Doug Crockford suggested Duck Typing in 2003 to address the issue of typing objects and John Resig points out that “as of 1.3 jQuery no longer uses instanceof or .constructor – for the same reasons that you list here. We were especially hitting problems when dealing with cross-frame pages.”

The Code

Without further adieu, here’s the code.

//can't use "in" as a variable!
inArr = ["1",[2,["3"]],4,[5,[6,7,8,[9,[10]]]]];

out = flatten(inArr);
debug(out);

/**
 * Flattens a multidimensional array into a flat 1D array.
 * @param arr -  a multidimensional array
 * @param arrOut - Optional, an initial array
 * @return a flat array
 */
function flatten(arr, arrOut){
	if(typeof arrOut === "undefined") //optional variable
		var arrOut = []; //new Array or [] work the same
	
	//not so easy to simply check if it's an array
	//http://perfectionkills.com/instanceof-considered-harmful-or-how-to-write-a-robust-isarray/
	if(Object.prototype.toString.call(arr) === '[object Array]'){
		//loop through array values
		for(var i = 0; i < arr.length; i++){
			console.log(i+" - "+arr[i]);
			//check if there's a sub-array
			if(Object.prototype.toString.call(arr[i]) === '[object Array]'){
				//recurse!!
				arrOut = flatten(arr[i],arrOut);
			}else{
				//push the value onto the exising array
				arrOut.push(arr[i]);
			}
		}
	}
	return arrOut; //return the modified array
}

//just a helper function to show the array
function debug(obj){
	out = "";
	for(i in obj){
		out += i+" - "+obj[i]+"\n";
	}
	alert(out);
}

The Raspberry Pi is a computer system the size of a credit card for $25.

Raspberry Pi became such a sensation that the Raspberry Pi foundation asked website owners to devote some space to the first Linux distribution downloads. The Open Code project has become a mirror to the project and you can find the Debian (and other later distributions) here.

When it was released for public purchases on Wednesday, February 29, 2012 so many people hit the foundation’s website that they had to implement a static webpage and take down the forums. Premier Farnell and RS Components, the manufacturers, were set up to take all of the pre-orders. During the morning of the 29th, so many people were interested that all three websites were taken down. At the time of writing they were back up. The Open Code Project mirror, one of hundreds of mirrors all over the world, was hit 76 times, exceeding 60GB of bandwidth usage.

So many people are interested in the Raspberry Pi because it’s the first sub-$100 computer system that can be used for development and education. Its design and OS is open source as well.

One Laptop Per Child

The FXI Cotton Candy

There are other mini-computer systems out there, such as the FXI Cotton Candy. This system is a computer that runs Ubuntu, the size of a USB thumb drive, for about $200. The price is more expensive than the Raspberry Pi but the processing power is also greater. Raspberry Pi doesn’t expect their computer to run Crysis, so they’ve devoted their attention to making a useful educational system for $25 (intended goal price).

Glasir

Glasir is the name of a tree which is “the most beautiful among gods and men”, according to Norse mythology, bearing golden leaves located in the realm of Asgard, outside the doors of Valhalla (source). The folder structure presented in the Glasir music player is supposed to resemble the golden leaves of the Glasir tree.

Glasir – The Music Player Website

The Glasir website was developed as an alternative to systems like Subsonic and Grooveshark_[1], which require a paid license to index your local files_[2].

[1] Grooveshark offers free music and playlists. Subscribers to Grooveshark Anywhere can get commercial free music for phones and mobile devices for $9 per month (at the time of writing).
[2] Subsonic is a free music server which requires a single payment/donation for a premium license. Mentioning it here is not a complaint, but a sign of respect to a wonderful cross-OS music system.

Glasir is open source and completely free, although the development and updates are more limited than a paid system. Its intended purpose is to scan your media folder for mp3 and ogg files, such as music, then it will index those files using their ID3 properties and display the information to you. You can then create a playlist and play your songs in order or shuffle them.

Screenshots

User not logged in.

User logged in. Playlist shown.

Compatibility

Glasir is developed for Google Chrome (or Linux Chromium) and Firefox. While it may work in other browsers, it’s not specifically targeting them at this point in the development process. It also seems to work with Firefox mobile and Opera Mobile, to a limited extent.

Future of Glasir

Future development of Glasir will include various features depending on the availability within the HTML5 specification. The github notes about functionality include these possibilities:

--Volume Buttons--
	Up and down independant of the system volume (mute not necessary)

--Export playlist to zip--
   Playlists are great but, what about taking a copy with you?

--Cover Art--
	If the folder has cover art, then try to use that.
	Check the album name, artist, and song against a website like Amazon to find the cover art.

--Custom playlists/Searches--
	- Songs listened to most
	- Songs listened to least
	- Artist
	- Album
	- Year
	- Song name

#### Low priority ####

--Visualizations--
	Firefox includes a method to obtain visualization information from the audio tags. Include the functionality
	only for Firefox users. Add more visualizations as other browsers adopt the functionality.

--Beats per Minute--
	Process the audio in the database to determine the BPM for each song. This requires background processing.
	Load the BPM into the database to allow custom playlists, like "Fast Songs", "Slow Songs", etc.

--Song Preview--
	If the player is paused and the user hovers over a song in the playlist then play a short sample (10 seconds?)

You can find more information and the source files here if you’re interested in testing it out. The project is open for new developers too, so if you like the idea and think you can add something to the project, then please join.

http://ajbogh.github.com/Glasir/

I determined that the problem must have been a failing hard drive, although there was very little to go by, so I purchased a new one and began the copy process. I started with Clonezilla, which is a very good drive duplication utility, but it kept failing. At first I thought this was because of the bad sectors, but it may have been because the USB drive that I had connected would turn off after a while (perhaps it wasn’t getting enough power from the one USB port). I decided to try something different.

Within Linux there’s a program called ‘dd‘. This program can take a bit-for-bit backup of a drive and copy it to another. Since each bit on the drive is duplicated, it will also copy partition maps and boot sectors. Surprisingly, it also copies potentially bad data from within a bad sector, but this is easily fixed afterward. The problem again with dd is that if the external backup drive keeps disconnecting from the computer then I would always have to restart it. This is where a program called ddrescue saves the day

ddrescue takes the power of dd and gives it a memory. In the simplest configuration you would tell it what drive to copy from, what drive to copy data to, and where a log file can be found. If anything happens during the copy process, such as if a drive suddenly fails or stops responding, then ddrescue can continue where it left off because of the log file.

I was able to use the following command:

ddrescue -B -v /dev/sda /dev/sdb /mnt/log/ddrescue_logfile_AAAA-MM-JJ.log

The “-B” option will display units of 1024 instead of 1000 for the number of bits copied. The “-v” option is for verbose mode. “/dev/sda” is the source drive that has the errors. “/dev/sdb” is the new destination drive, it can be a larger size with Windows Vista or later computers. The “mnt/log” location is a mounted folder that is not located on either drive. This can be a flash drive or, in my case, a network share. The log file is named “ddrescue_logfile_2012-02-19.log”. As long as this same command is used whenever the copy process is interrupted, the process will automatically continue where it left off, as if nothing ever happened.

Once ddrescue was complete (a long time later), I put the new drive in the computer and booted into Windows. Windows booted up and I was able to log in. I told it to do a chkdsk by opening the command prompt and typing “chkdsk C: -F -R -B” and rebooted. Windows found several bad files and fixed them during the reboot. Using Windows’ disk management tool I was able to extend the volume to fill the new, larger drive.

Later on I found out that Microsoft Office was unable to run due to the bad sectors being where an important Office file was located. I was able to use the Programs and Features Control Panel application to repair the Office install. I didn’t even need the Office disk (which you never get with new computers). Now everything works again. I do have to say that LibreOffice was used to supplement MS Office until I could find out the problem with MS Office and figure out a solution.

With this I have to thank the GNU/Linux developers, the creators of Clonezilla, dd, and ddrescue, Ubuntu for their live CDs, and the LibreOffice developers.

If you’re using a VMWare client then you must set a static MAC address, don’t allow your VM software to automatically update the MAC address.

Setup your network

First, set your IP to static IP and configure DNS to point to your domain controllers or any other DNS server you may have. This will allow you to call Windows computers by their short names. You must also fill in the Search Domains with your domain name.

Notice that I used “mydomain.local“. This causes a stupid issue with mDNS that will need to be adjusted. If you use something like “mydomain.com” then you shouldn’t need to do the next step.

Modify nsswitch.conf (fix the .local mDNS issue)

Open the file /etc/nsswitch.conf by starting your terminal (Applications >> Accessories >> Terminal) and type in:

sudo gedit /etc/nsswitch.conf

Modify the line that reads:

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4

Change it to:

hosts:          files dns mdns4_minimal mdns4

This should allow a program called Likewise-open to authenticate with Active Directory and create a computer account.

Install Likewise-open

Now, in the terminal, type in

sudo apt-get install likewise-open5 likewise-open5-gui

You can also use Synaptic and search for “likewise”. You’ll notice a likewise-open and also likewise-open5. They both seem to work. I have installed likewise-open5 and likewise-open5-gui.

Join the domain

Once those are installed you can configure Likewise-open by going to System >> Administration >> Active Directory membership. Likewise-open will ask you for a username and password. This user must have privileges to join a computer to the domain.

You can also use the command line to join the computer to the domain:

sudo domainjoin-cli join mydomain.local Administrator

You will then be asked to restart the computer. When the computer restarts you can use the Other User login option.

Type in “mydomain\username” where “mydomain” is the short name for your domain and “username” is some domain user account. If all of the steps above worked out well then you should be authenticated and logged into Ubuntu. You might get an Authentication Failure notice, which is usually due to one of the network settings from above being messed up or the username being typed in wrong.

When you’ve verified that the account can log in you can log out and return to your normal Ubuntu account. A few more optional steps can be used to complete the process.

Sudoers

Edit your sudoers file by opening up a terminal window and typing

sudo visudo

A vi-style program will show and allow you to edit the sudoers configuration. Under the %admin line you should add the following:

%MYDOMAIN\\Domain^Admins ALL=(ALL) ALL

Make MYDOMAIN whatever your short domain name is (don’t make it MYDOMAIN.LOCAL).

Add users to the login screen

Most domains won’t want this but you might like it for a Kiosk or a sample computer. When using domain logins you will have to type “mydomain\username” using the Other User login option. This can be too many steps for some people so it may be necessary to add a single-click option for their username. The end result will look like the following image.

Log in as your domain user and open up the terminal. Type “id” in the terminal window to view your UID and GID information. It will look something like:

DOMAIN\username@ubuntu-client:~$ id
uid=1234567889(username) ....

We only really care about the uid at this point. Write it down and log out of this user and back into the normal Ubuntu user account.

You will need to edit your /etc/passwd file. Open a terminal window and type the following command:

sudo gedit /etc/passwd

Make a new line at the bottom and duplicate the following information with the numbers that you wrote down:

DOMAIN\username:x:1234567889:0:John Doe,,,:/home/DOMAIN/username:/bin/bash

The group id (0) is admin to help make this person a local admin, but you should be able to use the uid in it’s place if you don’t want to use the admin group. It should look like this in that case:

DOMAIN\username:x:1234567889:1234567889:John Doe,,,:/home/DOMAIN/username:/bin/bash

Now you can log out of the local Ubuntu user’s account and see the updated login screen. The domain user or kiosk user can click on the big button and type in the password for the account.