Snippet IT

Unix Shell Script: How to Receive Input Right After Echoing A Line

szehau — Mon, 16 Aug 2010 13:21:23 +0000

For example, say I echo a line of text in shell script and I want to receive user input just right after the text (not in the next line). The are several ways to do it:

Method 1

echo "Enter a value: \c" read value

Method 2

echo -n "Enter a value: " read value

Method 3

read -p "Enter a value: " value

Database: CHAR and VARCHAR – What are the differences?

szehau — Sun, 30 May 2010 15:28:01 +0000

Most programmers may already know the main different between CHAR and VARCHAR - The first one supports fixed-length data and the second one supports variable-lengths of data.

Some people may think, since VARCHAR can do what CHAR does, then why we still need CHAR in our database design. I even have heard one of the very experienced Oracle database administrator say "Nowadays nobody is using CHAR anymore, you can forget about putting CHAR column in your database design".

The statement is not totally right. Even though VARCHAR can do what CHAR does, CHAR does has certain level of advantages over VARCHAR in terms of performance, efficiency and space.

I think it is good for a database designer to know how a database is being design. In other words, to think how a database programmer will design the database management system (DBMS) for the best performance and efficiency.

1. When a table column size is quite small, for instance 1 to 4 bytes, using CHAR helps save more space then VARCHAR. This is because DBMS will need additional few bytes (depends on database limitation for VARCHAR) to keep track the length of the data (all the rows) for the VARCHAR column.

2. Since VARCHAR can keep variable size of data, therefore it needs to keep track the length of the data for all the records. Therefore it adds little overhead to the DBMS's performance if compared to CHAR.

3. DBMS (I would say most systems) keeps fixed-length data and index more efficiently. Retrieving and updating data from and to a fixed-length row table is faster then a variable-length row table.

Therefore, I think CHAR is still very useful. We should always use CHAR if the column size is small enough or the data input is always going to be the size of the column (e.g. most of the data is in 10-12 bytes size and the column size is 12 bytes), so that we can get better performance for our application.

Java: Use ByteBuffer As InputStream

szehau — Mon, 11 Jan 2010 17:05:38 +0000

Sometime, your program may need to read data from a ByteBuffer buffer into a InputStream object. There is no class in Java library that provide the facility to do the conversion.

Anyway, to use a ByteBuffer object as an InputStream is pretty simple. What you need to do is to write a class wrapper that inherit InputStream and override the read() function in InputStream.

Here is the example:


public class ByteBufferInputStream extends InputStream {

  private int bbisInitPos;
  private int bbisLimit;
  private ByteBuffer bbisBuffer;

  public ByteBufferInputStream(ByteBuffer buffer) {
    this(buffer, buffer.limit() - buffer.position());
  }

  public ByteBufferInputStream(ByteBuffer buffer, int limit) {
    bbisBuffer = buffer;
    bbisLimit = limit;
    bbisInitPos = bbisBuffer.position();
  }

  @Override
  public int read() throws IOException {
    if (bbisBuffer.position() - bbisInitPos > bbisLimit)
      return -1;
    return bbisBuffer.get();
  }
}

In this class, ByteBufferInputStream, you can specify the limit to read from the ByteBuffer so that you can use the data in ByteBuffer later for other purposes. The read behavior is same as other InputStream class, where when there is no more data to read (or reached the preset limit), the read() function returns negative one.

100th Posts For Snippet IT

szehau — Mon, 11 Jan 2010 16:53:55 +0000

Finally, this blog has reached 100 posts! Yeah!

It really takes a long time for me to do this because I'm not blogging this site full timely. Second, sometime I'm just out of idea what to blog.

I will try work harder to share more information on programming and anything related to information technology in this new year. Thanks for reading!

Java: Format Integer Into Fixed Width String

szehau — Mon, 04 Jan 2010 17:36:47 +0000

Sometime, you may want to format an integer or a long value into a fixed width String. You need to display the value in fixed width especially in reports where you want to keep the numbers in aligned (e.g. 3456 as 0003456 and 1234 as 0001234).

Other than that, you may also want to format the integer value for a better visibility. For example, to display integer value as a document number (e.g. 12345678 as 00-01234-5678), for example an account number.

The Java.format() is not flexible enough to solve my problem. At least it cannot be used to format a fixed length document number in the format I want: XX-XXXX-XXXX. Therefore I decide write my own format function.

The following function format a integer value into a fixed length String.


public class IntegerUtil {
    public static String formatFixedWidth(int value, int width) {
        char[] chars;
        int i;
        int c;

        chars = new char[width];
        for (i = 0; i < width; i++) {
            c = value % 10;
            chars[width-i-1] = (char)('0' + c);
            value = value / 10;
        }
        return new String(chars);
    }
}

To format the document number like the one I said above, you simply modify the source code above to add one or two lines code to append a "-" to the String when the loop iterate to the place where you want to put the "-". Remember to increase the characters buffer as well.

The following function shows a sample implementation of my document number format.


public class IntegerUtil {
  public static String formatDocumentNumber(int value) {
    char[] chars;
    int i;
    int c;
    int size;

    size = 10+2;
    chars = new char[size];
    for (i = 0; i < size; i++) {
      if (i == 4 || i == 9) {
        chars[width-i-1] = '-';
        continue;
      }
      c = value % 10;
      chars[width-i-1] = (char)('0' + c);
      value = value / 10;
    }
    return new String(chars);
  }
}

Happy Holidays from your Google team!

szehau — Mon, 21 Dec 2009 14:40:20 +0000

I just got a greeting card from Google Team. Do you have one?

The email entitles "Happy Holidays from your Google team!". Opps... when do I have a Google Team that works for me? Ha ha.

Anyway thank you Google! Happy Holiday too.

Google Wave Invitation Giveaway

szehau — Sun, 20 Dec 2009 12:20:12 +0000

I got my free Google Wave invitation from LiewCf, thanks for the invitation! Ok, now is my turn to give you guys, my blog readers, the free invitations.

First impression to Google Wave

To me, Google Wave is like a chatting program (e.g. MSN) where a few people can have collaboration in a channel (the Wave). Everything can be happened in real time (e.g. the message you type) and everyone in the Wave can see the chances in real time (almost). And it is also like a social website (e.g. Facebook) too where you can put in applications (Gadgets) and use it within a group of people.

How to Get a Free Google Wave Invitation?

It's very simple. All you need to do is to leave a comment in this post (with your email address) and state that you want to have a free Google Wave Invitation.

You will not need to do anything else in order to get the invitation but it would be appreciated, if you could subscribe to my blog feed. Thanks.

Be hurry, I only have 8 invitations in total. First come first served.

Invitations left: 1

Note: It may take some time to get the invitation arrive to you inbox (as according to Google Wave).

WordPress: Version 2.9

szehau — Sat, 19 Dec 2009 11:58:35 +0000

The latest WordPress version 2.9 is now available for download. The new WordPress has a new codename - Carmen - which is named in honor of magical jazz vocalist Carmen McRae (whom were added to the Last.fm WP release station).

Here are the cool stuffs from user point of view and feature highlights:

Global undo/”trash” feature - trash is added to the blogging system where you can temporary put the unwanted things (e.g. post and comment) in the trash. You can undo the action by restoring the deleted item from the trash too.
Built-in image editor - This is pretty cool when you want to have control over you images. You can edit, rotate and etc like how you do it in an image editing software.
Batch plugin update and compatibility checking - Update all you plugins at once without having clicks for each one. It is also now support compatibility checking to see if the plugin compatible with your current version of WordPress.
Easier video embeds - Inserting videos to post is now much easier. Instead of copying codes and paste it to your post under HTML mode. You can now simply copy the URL of the video to WordPress and it will do the rest for you. The following websites are supported: YouTube, Daily Motion, Blip.tv, Flickr, Hulu, Viddler, Qik, Revision3, Scribd, Google Video, Photobucket, PollDaddy, and WordPress.tv

There are a lot more features have been added to the new version of WordPress such as to support better SEO, new TinyMCE and etc. Visit WordPress Blog for WordPress Version 2.9 to read more about it.

To start upgrade, simply click on the upgrade link on top of the admin page after you have logged in as an administrator. If you don't see the link, you can kick start the upgrade by clicking the "Tools -> Upgrade on your left side bar of admin page to check for unpgrade.

If you are new to WordPress, you can download the latest WordPress here.

Adobe Acrobat Reader: Possible Security Vulnerability When Acrobat JavaScript Is Enabled

szehau — Thu, 17 Dec 2009 16:16:43 +0000

It is possible to have security vulnerability in Adobe's Acrobat Reader if the Acrobat Javascript option is enable.

When the option is enabled and you open a crafted PDF file with Adobe Reader that allows JavaScript execution, your computer will be exposed to security risk - hacker may able to access your valuable data from your hard disk.

JavaScript is a scripting language that is tend to be safe to be used in web browsers due to its limitation to access to client computer. Since it is safe, your antivirus software may not able to detect a pdf file with Javascript is actually contain an virus.

To prevent the security vulnerability, you should now check whether your Adobe Acrobat's Javascript option is enabled. If it is enabled, disable it as soon as possible. The default setting for Acrobat Javascript is set to enabled for most of the Acrobat Reader version.

To disable the option, open your Acrobat Reader application, click on Edit -> Preferences and a window will pop up. Select the "JavaScript" option from your left and make sure the "Enable Acrobat JavaScript" option is un-ticked.

Thanks for Walker for heading up the Acrobat JavaScript issue.

Java: Continuously Read Data From FileChannel Without MappedByteBuffer

szehau — Thu, 17 Dec 2009 11:46:01 +0000

When programmer writes a program to read data from a file continuously and sequentially with a fixed data type reading sequence (e.g. to read three integers then 2 doubles repeatedly), he or she may find the MappedByteBuffer from Java library is useful.

MappedByteBuffer is pretty useful because its content is a memory-mapped region of a file. Program can access to the position of the file it wants directly. It also does some optimization on loading data from file, where part of the content are loaded into memory before the read action is actually performed. But when the data will be load? It remains unknown and it is operating system dependent. This is the first problem when using MappedByteBuffer - are the data buffered?

The second problem arises when programmer uses MappedByteBuffer to read a big file. MappedByteBuffer only allows data reading up to the maximum value of an integer (2,147,483,648 bytes). If the program needs to read further from that, it will need to re-map the file by calling the FileChannle.map function by parsing in the correct file position. The programmer will need to be very careful in passing the correct file position because some time it can be very confusing.

To overcome these two problems, we can introduce, design and write a new class that ensures the data reading action is buffered for the best performance and also allows continuous of reading without the need of re-mapping the FileChannle. First, let's write out the pseudo code for the read file action:


get data (e.g. get integer)
  ensure the memory buffer has enough data for the requested data type
    if not enough, read data from file
read the data from buffer and return them in the requested data type

Below is the example of implementation:


public class FileChannelReader {

  private final static int BUFFER_SIZE = 64 * 1024; // 64k

  private ByteBuffer readerBuffer;
  private FileChannel readerFileChannel;

  public FileChannelReader(FileChannel fileChannel) {
    readerBuffer = ByteBuffer.allocate(PAGE_SIZE);
    readerFileChannel = fileChannel;
    readerBuffer.clear();
    readerBuffer.flip();
  }

  // Ensure the buffer has enough data
  private void ensureData(int size) throws IOException  {
    if (readerBuffer.remaining() < size) {
      readerBuffer.compact();
      if (readerFileChannel.read(readerBuffer) <= 0)
        throw new IOException("Unexpected end-of-stream");
      readerBuffer.flip();
    }
  }

  // Get current position
  public long position() throws IOException {
    return readerFileChannel.position() - readerBuffer.remaining();
  }

  // Set current position
  public void position(long position) throws IOException {
    readerFileChannel.position(position);
    readerBuffer.clear();
    readerBuffer.flip();
  }

  // Get integer
  public int getInt() throws IOException {
    ensureData(Integer.SIZE/8);
    return readerBuffer.getInt();
  }

  // Get long
  public long getLong() throws IOException {
    ensureData(Long.SIZE/8);
    return readerBuffer.getLong();
  }

  // And so on ...
}

I'm using this technique in my programming projects and it performs pretty well. The data to be read is always ensured to be buffered and it also reduces complexity in writing a program to read data sequentially.

WordPress: Catch A Spam Comment With Statcounter

szehau — Fri, 11 Dec 2009 17:21:59 +0000

Sometime your WordPress' anti spam software (e.g. Akismet) may not able to stop all the comment spam because the comment looks too real to it and to human too. In this case, you will need to identify the comment whether it is actually a real comment or it is automatically submitted by software.

Someone who made a comment must have visited your site. That's it, if he or she has not visited your site but his or her comment is posted on one of your post. Then it is very high possibility that the comment is a spam comment.

How do you ensure someone who left a comment on your blog actually visited your site? The best way to do it is by looking at the IP address where the computer submitted the comment.

In WordPress, when someone has made a comment, his computer's IP address is recorded. With the IP address, you can check the IP address against the IP address recorded in your website's stats counter.

One of the stats counter software that allows you to look up an IP address is Statcounter. After you have logged in into Statcounter, select your blog website's statistic and then click on the "Look Up IP address" link on the left.

Key in the IP address where your WordPress comment entry came from and click "Search!". If an entry is matched, that means he or she who submitted the comment has actually visited your website before.

Short URL: Top 5 Websites That Provide Free Short URL Service

szehau — Wed, 09 Dec 2009 17:56:55 +0000

What is a "short URL"? Short URL or tiny URL is an URL used to represent a long URL For example, http://tinyurl.com/45lk7x can be used to represent and will be used to redirect to http://www.snippetit.com/2008/10/implement-your-own-short-url.

Why people use short URL? First, because it is easy to remember. Imagine when you read an article on a magazine or newspaper that shows you a site with 100 characters and complicated URL. How can you remember the long URL, put down the magazine or newspaper, sit in front of your computer and type out the URL at web browser correctly? When the URL is short, for example tinyurl.com/45lk7x, you can do it easily.

Second, short URL is more portable. For instance, when you want to send your friend a SMS that contains some message and an URL, with short URL you can save a lot of space and give you more space to type your message.

Most short URL services are free and easy to use. You just need to provide the long URL and it will generate a new short URL for you. Here are the list of most popular short URL websites sorted by its traffic rank (by Alexa):

bit.ly (Alexa traffic rank: 220)
tinyurl.com (Alexa traffic rank: 660)
is.gd (Alexa traffic rank: 10,833)
ff.im (Alexa traffic rank: 45,395)
twurl.nl (Alexa traffic rank: 120,846)

If you are good in computer programming language, you interested in implementing your own short URL.

SherWeb: Hosted Exchange, Web Hosting, SharePoint Hosting, Hosted CRM

szehau — Sun, 06 Dec 2009 05:54:36 +0000

SherWeb is a hosting provider that delivers high quality service at the reasonable price. SherWeb guarantees 99.9% uptime at both application level and network level. That means you will have less downtime on using both software and hardware.

SherWeb provides a wide range of hosting service including web hosting, exchange server hosting, SharePoint hosting and hosted CRM. You can sign up their packages with risk free because all Web Hosting and Hosted Exchange packages include a 30 day money back guarantee.

Web Hosting
There are various tiers of web hosting to accommodate customer with different needs. Web hosting packages' price start from $7.25/month only, run on Linux servers, in addition to supporting PHP, ASP, RoR, Python and MySQL database applications.

Hosted Exchange
Hosted exchange price is $8.95/month per mailbox. No minimum number of users required. You will have 3Gb of storage per mailbox and free setup (mobile synchronization, antivirus, copy of Outlook 2007 and SharePoint) when you signed up the package. Take a look at their exchange demo to see what it can do for you.

SharePoint Hosting
SharePoint provides you or your business an environment for collaboration, document sharing and also mobile access. The plans' affordable price start from $8.95/month. All SharePoint plans include unlimited users, unlimited subsites, free webparts and exchange link.

Hosted CRM
CRM or client relationship management system is one of the essential tools to a business. With start from only $29.95 per month from SherWeb, you can get a quality hosted CRM for your business. SherWeb hosted CRM plans range from entry level online CRM or a comprehensive system fully customizable to your complex business needs. Contact Sherweb to design a perfect package for you!

WordPress: How To Add Table Into A Post

szehau — Wed, 25 Nov 2009 16:23:41 +0000

WordPress' WYSIWYG post editor does not come with the functionality that allows user to create table when editing a post (like what you can do in Microsoft word).

However, putting a table into a post in WordPress editor is not as hard as writing a software codes. What you need to know is to familiar yourself with some HTML tags.

To create a table in post, you will need to switch your editor to HTML mode. Simply click on the HTML tab on the top-right of your WordPress editor and then insert the table codes into the position where you want the table appear.

Here is a simple table:





Column 1
Column 2


Data 1
Data 2

And it looks like this:

Column 1	Column 2
Data 1	Data 2

You can change the table width by changing the width parameter to a certain value, either in pixels (without unit) or percentage (with %). You can also change the border size (border), cell's padding (cellpadding) and cell's spacing (cellspacing). Border size, cell's padding and cell's spacing are in unit pixels.

After you have put the code, change back to visual mode to preview your table. At that time, you can apply format (e.g. color, bold, link and etc) to your text in the table.

Another table with 2 columns in a row are merged:





2 Columns merged


Data 1
Data 2

And it looks like this:

2 Columns merged
Data 1	Data 2

Another table with 2 rows in a column are merged:





Column 1
Column 2


Data 2

And it looks like this:

Column 1	Column 2
	Data 2

It is easy and fun, right? You always have to trial and error to create the table you want. Once you have understood the basic, you can easily create tables with the design you want.

Have fun!;

Google Chromium OS

szehau — Mon, 23 Nov 2009 13:29:16 +0000

Google Chromium OS or Chrome OS is an open source project created by Google that aims to build an operating system that provide fast, simple and more secure computing experience. The new OS is target for people who spend most of their time on the web.

The following videos explain in detailed what Chrome OS is:

What is Google Chrome OS?

Chrome OS Security

Chromium OS & Open Source

Chromium OS Fast Boot

The basic architecture of Google Chromium OS is pretty simple. Instead of loading all the stuffs by ordinary operating systems (like drivers, detecting hardware, kernel and etc.), the computer that runs Chromium OS directly load the necessary softwares (in this case, the Chrome browser and other multimedia stuffs) and does not need to load other inessential stuffs.

It is pretty interesting to go through how why Google builds up the Chromium OS. Although the project is still in very early stage, you can get involve in the project or to download the source code to have a test run. You can join them at the Chromium Projects website for Chromium OS.

Chrome OS will be available for consumers around end of next year. If you can't wait for the final release of Chrome OS, you can download Chrome OS VMWare/VirtualBox image and run it as virtual machine on top of your current operating system (Windows, Mac, Linux).

Download it at your own risk because it is still in early development stage. However it should not have much risk since everything will be running in a virtual enviroment.

Stay updated with Google Chromium by visiting The Google Official Blog and The Chromium Projects website.

Snippet IT

Unix Shell Script: How to Receive Input Right After Echoing A Line

Most Commented Posts

Database: CHAR and VARCHAR – What are the differences?

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Java: Use ByteBuffer As InputStream

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Java: Format Integer Into Fixed Width String

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