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Convert HTML to PDF using WKHTMLTOPDF

2012-07-18T20:23:00.003+05:30

I was looking for solution to generate the PDF from dynamic HTML in last week. I was looking for easy way to generate the PDF without being affected with syntax and design.

While goggling I found the tool: WKHTMLTOPDF

This tool is converting HTML (CSS support) to PDF the same way you save a PDF from browser.

Here are the steps to install and integrate the tool.

First, install the webkit library on your server.

$ wget
http://wkhtmltopdf.googlecode.com/files/wkhtmltopdf-0.8.3-static.tar.bz2

$
tar -jxvf wkhtmltopdf-0.8.3-static.tar.bz2

$
sudo aptitude install ia32-libs

Make symbolic
link to tool in /usr/local/bin

$ sudo ln -s
/full_path/WKHTMLTOPDF /usr/local/bin/WKHTMLTOPDF

Now we are ready to useJ.

Now try the following command to convert the google page into PDF:

$ wkhtmltopdf http://www.google.com example1.pdf

There are many options where you can generate the different size/types of PDF like A4, A2 etc

Here are few examples:

$ wkhtmltopdf http://www.google.com examplea1.pdf -s A4

$ wkhtmltopdf http://www.google.com examplea2.pdf -s A2

Increase size of the file system in AWS

2012-07-11T20:25:00.001+05:30

Assuming that you are using a linux AMI, in your case you have an easy method for increasing the size of the file system:

1) Stop the instance
2) Detach the root volume
3) Snapshot the volume
4) Create a new volume from the snapshot using the new size
5) Attach the new volume to the instance on the same place where the original one was
6) Start the instance, stop all services except ssh and set the root filesystem read only
7) Enlarge the filesystem (using resize2fs command) and/or the partition if needed
8) Reboot

As an alternative you can also launch a new instance and map the instance storage or you can create a new ami combining the two previous steps.

Install GD Library and ImageMagick on Linux server

2012-07-11T19:19:00.001+05:30

Most scripting language is mostly used to manipulate and create image files in various different image formats including GIF, PNG, JPEG, etc. with the help of GD. Also scripting language can output image streams directly to a browser.

ImageMagick is an open source software suite for displaying, converting, and editing raster image files.

Following are the steps to install GD library:

Step 1: $ yum install php-gd
Step 2: $ yum install glib
Step 3: $ yum install glib2
Step 4: $ yum install libpng
Step 5: $ yum install libjpeg
Step 6: $ yum install libtiff
Step 7: $ yum install ghostscript
Step 8: $ yum install freetype

Following are the steps to install ImageMagick:

Note: Download ImageMagick.tar.gz from www.imagemagick.org or a mirrors and verify its message digest.

Step 1: $ tar xvfz ImageMagick.tar.gz
Step 2: $ cd ImageMagick-[VERSION]
Step 3: $./configure
Step 4: $ make
Step 5: $ sudo make install
Step 6: $ sudo ldconfig /usr/local/lib

Great :) Now ImageMagick is installed on your server.

You can verify the installation by following Commands:

$ /usr/local/bin/convert logo: logo.gif
$ make check

LEARNING TO LIVE WITHOUT RECOGNITION IS A SKILL - Horse & Pig Story

2011-08-02T11:50:00.000+05:30

There was a farmer who collected horses; he only needed one more breed to complete his collection. One day, he found out that his neighbor had the particular horse breed he needed. So, he constantly bothered his neighbor until he sold it to him. A month later, the horse became ill and he called the veterinarian, who said: Well, your horse has a virus. He must take this medicine for three days. I'll come back on the 3rd day and if he's not better, we're going to have to put him down. Nearby, the pig listened closely to their conversation. The next day, they gave him the medicine and left. The pig approached the horse and said: Be strong, my friend. Get up or else they're going to put you to sleep!
On the second day, they gave him the medicine and left.
The pig came back and said: Come on buddy, get up or else you're going to die! Come on, I'll help you get up. Let's go! One, two, three...
On the third day, they came to give him the medicine and the vet said: Unfortunately, we're going to have to put him down tomorrow. Otherwise, the virus might spread and infect the other horses. After they left, the pig approached the horse and said: Listen pal, it's now or never! Get up, come on! Have courage! Come on! Get up! Get up! That's it, slowly! Great! Come on, one, two, three... Good, good. Now faster, come on.... Fantastic! Run, run more! Yes! Yay! Yes! You did it,
you're a champion!!!
All of a sudden, the owner came back, saw the horse running in the field and began shouting: It's a miracle! My horse is cured. This deserves a party. Let's kill the pig!

Point for reflection: This often happens in the workplace. Nobody truly knows which employee actually deserves the merit of success, or who's actually contributing the necessary support to make things happen.

LEARNING TO LIVE WITHOUT RECOGNITION IS A SKILL

If anyone ever tells you that your work is unprofessional, remember: amateurs built the Ark and professionals built the Titanic.

Install phpmyadmin to operate MySQL from web

2011-07-27T20:35:00.000+05:30

In my last post, we saw how to setup a LAMP on AWS. Let's have a look into how to install phpmyadmin on your linux server.

To install phpmyadmin to operate MySql from web browser, web server is needed.

Steps to install phpmyadmin:
1. yum -y install phpMyAdmin php-mysql php-mcrypt
2. vi /etc/httpd/conf.d/phpMyAdmin.conf
3. Add IP address you allow on line #14
Allow from 127.0.0.1
4. Close Editor
5. Reload the httpd process
/etc/rc.d/init.d/httpd reload

Once you are successfully run the above 6 steps, phpmyadmin is installed on your server.

Now we will see how we can access phpmyadmin.

Access to 'http://(your hostname or IP address)/(alias name you set)/' with web browser.
Alias name is by default 'phpmyadmin'.

When you enter above url on browser, it will ask you the login credentials for MySql user.
You can enter MySql user login credentials, can able to see phpmyadmin dashboard.

Getting started with Amazon EC2 and PHP – MySql

2011-07-06T16:34:00.000+05:30

Do you know nothing about AWS or linux, but want to run PHP/MySql server set up on AWS? Are you new comer on AWS?
I was like you, relying on webhosting services to manage/configured on servers, so it was tough to work on AWS EC2 but later I feel it’s simpler.
In this tutorial I will show you how to setup PHP and MySql and how to make it web-accessible.

AWS:
Amazon has different products, but we are more interested in Amazon Elastic Compute Cloud (EC2).
Click on link and Sign up for Amazon EC2.
Once you have setup for EC2, go to AWS Console and click on Instance in left hand side panel.
You can see more details on Amazon documentation.
Now you create a Key Pair - this will be the credentials you will use to SSH.
Next is the Security Group - which will be used to specify the firewall used for your instance.
For now use the default Group and add port numbers as you want to open.
Now Elastic IP address — In the AWS Management Console, click on “Elastic IPs”, then “Allocate New Address” under “Addresses”. Once the address is created, click on it, then “Associate Address”. Select the instance and associate it.

You should now be able to SSH into your instance using your .pem file.
Now question is how do I access my instance? Couple of Software.
PuTTY.exe — Secure Shell client
PuTTYgen.exe — SSH public/private key generator
Putty available at your finger tip, For that you need http://www.putty.nl/download.html

Configuring the Linux Server:
We have got server up and running, now lets setup some packages.
I’ll show you how to set up PHP and MySQL on the server.

PHP:
sudo yum install php-mysql php php-xml php-mcrypt php-mbstring php-cli mysql httpd
Press ‘y’ for each of the prompts that show up. Note that you’re logged in as ec2-user, so you need to sudo all of these command (No need on fedora).
You should now be able to create and run a PHP sample file.

MySql:
Install MySql server.
sudo yum install mysql-server
Now start the mysql server
sudo /etc/init.d/mysqld start
Next, set the root password.
mysqladmin -u root password '[PASSWORD]'
Now we set up two users for MySQL: the administrator, which you’ll use to create and modify tables; and the app user, which the app will use to query the DB (with more limited privileges).
Log into MySQL as root (mysql -u root -p) for mysql prompt.
If you want to grant privileges for other server (MySql is not setup on same server)then type following command
GRANT ALL PRIVILEGES ON *.* TO root@'SCRIPTSERVERIPADDRESS' IDENTIFIED BY 'MYSQLUSERNAME' WITH GRANT OPTION;
FLUSH PRIVILEGES;
Now you have PHP and MySql running on server, but cannot accessible though browser.

Make it web accessible:
Now we need to configure the web server.
To set up web server, we need to modify config file which is httpd.conf, located at /etc/httpd/conf/httpd.conf.
You can open this file using editor, I used vi.
Now go to bottom of the file, where there is a small section on the VirtualHost.
Add the following code in it.
NameVirtualHost *:80
<VirtualHost *:80>
ServerAdmin webmaster@dummy-host.example.com
DocumentRoot [your document root]
ServerName [your server name]
ErrorLog logs/dummy-host.example.com-error_log
CustomLog logs/dummy-host.example.com-access_log common
</VirtualHost>

Note: If you are planning to run multiple sites on same server, you can add multiple virtual host section with document root and server name changes according to site.

Now restart the httpd process or server using following command.
sudo /etc/init.d/httpd restart

Using two Instances

It will be better to separate the web/script server and the DB server. For this, you will need to set up two Instances with two Elastic IPs, one of which has the web server httpd running, and the other of which has the mysql server mysqld running.
To make accessible on the web, instead of using “localhost” as the MySQL host, use the IP address of the MySQL instance. On the DB instance, set up your grant permissions (Given the query in MySql section) to allow db from anywhere.

Now you are done with setting up Amazon server and your server is loaded with PHP and MySql.
In upcoming blogs, I will introduce you with FTP server setup and phpmyadmin setup.

Time Management

2011-07-04T20:39:00.000+05:30

Everyone wants to make the most of their time. You recognize that time is a unique and precious resource that you need in order to do your work, accomplish your goals, spend time with your loved ones, and enjoy everything that life has to offer.
Perhaps you have a heavy workload and want to find ways to become more effective so you can get more done in less time.
Maybe you feel overwhelmed or “stressed out” and want to find ways to do less and enjoy more. Or maybe you simply want to feel more focused and in control of your time, instead of feeling like you rush madly from one activity to the next until you fall into bed exhausted every night.
A Thought, “Do you love life? Then do not squander time, for that's the stuff that life is made of.”

What Exactly Is Time Management?

Time management is a set of principles, practices, skills, tools, and systems working together to help you get more value out of your time with the aim of improving the quality of your life.
The important point is that time management is not necessarily about getting lots of stuff done, because much more important than that is making sure that you are working on the right things, the things that truly need to be done.
Smart time managers know that there is much more to do than anyone could possibly accomplish. So instead of trying to do it all, smart time managers are very picky about how they spend their time.
They choose to focus and spend their time doing a few vital projects that will really make a difference, rather than spending all their time doing many trivial things that don't really matter all that much.
If you become a good time manager, you’ll not only get a lot more done in less time, but you’ll feel more relaxed, focused and in control of your life.
You’ll be able to use your time in a much more balanced and effective way and you’ll be able to make time for the people and activities that you love. When you get to the end of a busy day, you’ll feel a strong sense of accomplishment from everything that you actually got done.
Improving your time management skills can even help you get better results by doing less work, because you're focusing on the things that really matter rather than all the low-priority busywork that just keeps you busy.
If you don’t learn how to manage your time well, you’ll be far less productive than you could be and you’ll get a lot less done. You’ll also feel much more stressed and overwhelmed, and you’ll struggle to find time to spend with the people you care about and to do the things you enjoy.

Learning Time Management Skills

In the end, time management comes down to choices. Good choices lead to better results, while poor choices lead to wasted time and energy.
The good news is that time management skills can be learned and mastered by anyone. All it takes is practice and dedication.
Like any other skill, you can teach time management the easy way or you can learn it the hard way.
The hard way usually involves years of trial and error and lots of false starts trying to figure out what works and what doesn't.
If you'd like to save yourself some time, money and effort, I recommend you try the easy way: learn from someone who has already done it.

15 Time Management Tips

Here are 15 practical time management tips to help you get started...

1. Write things down
A common time management mistake is to try to use your memory to keep track of too many details leading to information overload. Using a to-do list to write things down is a great way to take control of your projects and tasks and keep you organized.

2. Prioritize your list
Prioritizing your to-do list helps you focus and spend more of your time on the things that really matter to you. Rate your tasks into categories using the ABCD prioritization system described in the time management course.

3. Plan your week
Spend some time at the beginning of each week to plan your schedule. Taking the extra time to do this will help increase your productivity and balance your important long-term projects with your more urgent tasks. All you need is fifteen to thirty minutes each week for your planning session.

4. Carry a notebook
You never know when you are going to have a great idea or brilliant insight. Carry a small notebook with you wherever you go so you can capture your thoughts. If you wait too long to write them down you could forget. Another option is to use a digital recorder.

5. Learn to say no
Many people become overloaded with too much work because they overcommitted; they say yes when they really should be saying no. Learn to say no to low priority requests and you will free up time to spend on things that are more important.

6. Think before acting
How many times have you said yes to something you later regretted? Before committing to a new task, stop to think about it before you give your answer. This will prevent you from taking on too much work.

7. Continuously improve yourself
Make time in your schedule to learn new things and develop your natural talents and abilities. For example, you could take a class, attend a training program, or read a book. Continuously improving your knowledge and skills increases your marketability, can help boost your career, and is the most reliable path to financial independence.

8. Think about what you are giving up to do your regular activities
It is a good idea to evaluate regularly how you are spending your time. In some cases, the best thing you can do is to stop doing an activity that is no longer serving you so you can spend the time doing something more valuable. Consider what you are giving up in order to maintain your current activities.

9. Use a time management system
Using a time management system can help you keep track of everything that you need to do, organize and prioritize your work, and develop sound plans to complete it.

10. Identify bad habits
Make a list of bad habits that are stealing your time, sabotaging your goals, and blocking your success. After you do, work on them one at a time and systematically eliminate them from your life. Remember that the easiest way to eliminate a bad habit, it to replace it with a better habit. In these days it’s a social networking addiction.

11. Don’t do other people’s work
Are you in the habit of doing other people’s work because of a ‘hero’ mentality? Doing this takes up time that you may not have. Instead, focus on your own projects and goals, learn to delegate effectively, and teach others how to do their own work.

12. Keep a goal journal
Schedule time to set and evaluate your goals. Start a journal and write down your progress for each goal. Go through your goal journal each week to make sure you are on the right track. Keeping a journal on your computer has never been easier!

13. Don’t be a perfectionist
Some tasks don’t require your best effort. Sending a short email to a colleague, for example, shouldn’t take any more than a few minutes. Learn to distinguish between tasks that deserve to be done excellently and tasks that just need to be done.

14. Beware of “filler” tasks
When you have a to-do list filled with important tasks, be careful not to get distracted by “filler” tasks. Things such as organizing your bookcase or filing papers can wait until you tackle the items that have the highest priority.

15. Avoid “efficiency traps”
Being efficient doesn’t necessarily mean that you are being productive. Avoid taking on tasks that you can do with efficiency that don’t need to be done at all. Just because you are busy and getting things done doesn’t mean you are actually accomplishing anything significant.

I have learned this stuff from my managers and from my past experience. Do share your thoughts here to make time more precious.

Trends in Mobile Application Development

2011-02-07T12:10:00.000+05:30

Major software companies, such as Apple and Google, are disturbing the relatively safe and established actors of the mobile application business. These newcomers have caused signi cant structural changes by imposing and enforcing their own rules for the future of mobile application development. The implications of these changes do not only concern the mobile network operators and mobile phone manufacturers. This changed environment also brings additional opportunities and constraints for current mobile application developers. Therefore, developers need to assess what their options are and how they can take advantages of these current trends. In this presentation, we take a developer's perspective in order to explore how the structural changes will in fence the mobile application development markets. Moreover, we discuss what aspects developers need to take into account in order to position themselves within the current trends.

Grab the URL from Site or Page

2010-11-19T22:33:00.001+05:30

If you want to crawel links from all the site or pages, Below is the function:

$arrGetAllLinks = array();

// if you want all links from site, set $isRecuressive = 1

// if you want all links from page, set $isRecuressive = 0

function fnGrabTHeURLFromLink($strLink,$isRecuressive = 0)

{

$parse = parse_url($strLink);

$strMainHost = $parse['host'];

global $arrGetAllLinks;

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL,$strLink);

curl_setopt($ch, CURLOPT_TIMEOUT, 30); //timeout after 30 seconds

curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);

$result=curl_exec ($ch);

curl_close ($ch);

if( $result )

{

preg_match_all( '/href="(http:\/\/www.[^0-9].+?)"/', $result, $output, PREG_SET_ORDER );

foreach( $output as $item )

{

$parse = parse_url($item[1]);

$strHostOfURL = $parse['host'];

// ALL LINKS DISPLAY HERE

//print "

";

//print_r($item);

if(($strMainHost == $strHostOfURL) && !in_array($item[1], $arrGetAllLinks))

{

$arrGetAllLinks[] = $item[1];

if($isRecuressive == 1)

{

$arrTempGetAllLinks = fnGrabTHeURLFromLink($item[1]);

$arrGetAllLinks = array_merge((array)$arrGetAllLinks, (array)$arrTempGetAllLinks);

$arrGetAllLinks = array_unique($arrGetAllLinks);

}

return array_unique($arrGetAllLinks);

}

print_r(fnGrabTHeURLFromLink("MENTION SITE HERE"));

Fragment Id Messaging Concept

2010-11-04T11:07:00.000+05:30

we use a hack called fragment id messaging. This should be cross-browser, provided the page containing your iframe is the top level.

In other words, there are a total of two levels.

Basically, the child sets the fragment of the parent, and the parent watches for this.

Generally fragment id messaging use for cross-domain communication.

Technically, this hack uses window.location.hash (the part of the URL following #) to communicate.

Historically, any window could change the location of any other window. This turned out to be a problem because, among other things, it meant embedding a login iframe in a window was unsafe (because then a malicious site could replace the login iframe with a spoofed version). Over time further restrictions have been applied to location changes to browser windows, until now, when HTML5 and most browsers have reached common agreement on the ancestor policy. In a nutshell, paraphrasing the HTML5 specification, a window A can change the location of another window B if:

* the locations of A and B have the same origin, which is to say they have the same scheme, host, and port (http, stackoverflow.com, 80 for example), or

* B is a top-level window, and A is a window in a frame nested at some depth within B (direct child, child of a child, etc.), or

* B is a window opened using window.open and A can change the location of the window that opened B (so B is a popup opened by A, by a popup window opened by A, or at greater depth), or

* B isn't a top-level window, but its parent window, or its parent's parent window, or at some similar amount of parentage the locations of that window and A are same-origin

(Same origin is more complicated than this, but the embedded description above catches its essence and covers the most common cases.)

Under this policy, C may change the location of A, and A may change the location of B or C, but C may not change the location of B. If you need to work around this, then you should change your page A's location to something that changes B as appropriate; alternately, you could ask your page B to change its own location.

Configuring SSL (Godaddy) for Apache 2.X

2010-11-04T11:04:00.000+05:30

While configuring SSL you will need to provide Certificate Signing Request (CSR).

Steps to generate CSR can be found on below url:
http://help.godaddy.com/topic/746/article/5269

Steps are also described below:

Creating a CSR (required while registering ssl certificate)

Create a directory /usr/bin/ssl/ where your csr files will be stored.

Type below command from the shell:

1 . cd /usr/bin/ (/your path to openssl/)
which will change your directory to the one which is going to store the CSR files.
Then type below command on shell
2. openssl genrsa -des3 -out .key 2048
Replace with the name which you want.
3. openssl req -new -key .key -out .csr
Replace with the name which you want.
The above two commands will create a .key and .csr file at the location which you have specified above.

Note – while creation of a CSR you will be asked the details about organization.
Once the certificate is registered you will get two files with .crt extension. Place these two files in the same directory as the one which you have created while CSR.

Now for apache server configuration:
Go to /etc/httpd/conf.d folder where you will find a ssl.conf file.

In ssl.conf file you will find below lines
SSLCertificateFile – replace the path of your SSL certificate file (from above e.g. /usr/bin/ssl/yourcertificate.crt)

SSLCertificateKeyFile - replace the path of your SSL key file (from above e.g. /usr/bin/ssl/key.crt)

SSLCertificateChainFile – replace with the path of 2nd .crt file which you got after registering the certificate. (its generally named as gd_bundle.crt) (from above e.g. /usr/bin/ssl/gd_bundle.crt)

How to Get the Base Url with Javascript for a Domain or Localhost

2010-07-06T10:42:00.000+05:30

In the code below, you will be able to find the baseUrl of your website using javascript. The following javascript code will work when used on your localhost or when it's used in a live site (finds the root url of the domain address).

function fnGetBaseURL() {
var strUrl = location.href;
// entire url including querystring - also: window.location.href;
var strBaseURL = strUrl.substring(0, strUrl.indexOf('/', 14));

if (strBaseURL.indexOf('http://localhost') != -1) {
// Base Url for localhost
var strUrl = location.href; // window.location.href;
var strPathName = location.pathname; // window.location.pathname;
var intIndex1 = strUrl.indexOf(strPathName);
var intIndex2 = strUrl.indexOf("/",intIndex1 + 1);
var strBaseLocalUrl = strUrl.substr(0, intIndex2);

return strBaseLocalUrl + "/";
}
else {
// Root Url for domain name
return strBaseURL + "/";
}

}

If you'd like to test the fnGetBaseURL function in an html page and view the result, simply add the following after the closing tag of the fnGetBaseURL () function:
document.write(fnGetBaseURL());

linkedin API.... Exploring Frustration Discovering Satisfaction

2010-02-13T17:34:00.000+05:30

Hi All,

last month Me and My team from CueLogic implemented LinkedIn connect with Oauth for Justmeans.... Its really frustrated.......... at last we Succeed....

True Said:

linkedin API.... Exploring Frustration Discovering Satisfaction

Stay tuned... API's coming soon.............................

Web Scalability and Performance

2009-09-09T19:43:00.000+05:30

Web Scalability and Performance – Real Life Lessons

Last Saturday, we had TechWeekend #3 in Pune, on the theme of Website Scalability and Performance. Mukul Kumar, co-founder, and VP of Engineering at Pubmatic, talked about the hard lessons inscalability they learnt on their way to building a web service that serves billions of ad impressions per month.

Here are the slides used by Mukul. If you cannot see the slides, click here.
Web Scalability & Performance

The talk was live-tweeted by @punetechlive and @d7ylive. Here are a few highlights from the talk:

Keep it simple: If you cannot explain your application to your sales staff, you probably won’t be able to scale it!
Use JMeter to monitor performance, to a good job of scaling your site
Performance testing idea: Take 15/20 Amazon EC2 servers, run JMeter with 200threads on each for 10 hours. Bang on your website! (a few days later, @d7y pointed out that using openSTA instead of JMeter can give you upto 500 threads per server even on old machines.)
Scaling your application: have a loosely coupled, shared nothing, stateless, distributed architecture
Mysql scalability tip: Be careful before using new features, or new versions. Or don’t use them at all!
Website scalability: think global. Some servers in California, some servers in London, etc. Similarly, think global when designing your app. Having servers across the world will drive architecture decisions. When half your data-center is 3000 miles from the other half, interesting, non-trivial problems start cropping up. Also, think carefully about horizontal scaling (lots of cheap servers) vs vertical scaling (few big fat servers)
memcache tip: pre-populate memcache with most common objects
Scalability tip: Get a hardware load balancer (if you can afford one). Amazon AWS has some load-balancers, but they don’t perform so well
Remember the YouTube algo for scaling:
while(1){ identify_and_fix_bottlenecks(); eat_drink(); sleep(); notice_new_bottleneck(); }
there’s no alternative to this.
Scalability tip: You can’t be sure of your performance unless you test with real load, real env, real hardware, real software!
Scalability tip – keep the various replicated copies of data loosely consistent. Speeds up your updates. But, figure out which parts of your database must be consistent at all times, and which ones can have “eventual consisteny”
Hard lessons: keep spare servers at all times. Keep servers independent – on failure shouldn’t affect other servers
Hard lessons: Keep all commands in a script. You will have to run them at 2am. Then 3am. Then 7am.
Hard lessons: Have a well defined process for fault identification, communication and resolution (because figuring these things out at 2am, with a site that is down, is terrible.)
Hard lessons: Monitor your web service from 12 cities around the world!
Hard lesson, Be Paranoid – At any time: servers can go down, DDOS can happen, NICs can become slow or fail!

2009-06-05T11:31:00.001+05:30

When the going gets tough, upgrade.

canonical URL

2009-05-27T12:45:00.000+05:30

Canonical URL:

Some websites differentiates some.com and www.some.com as two different websites, but actually it is not.

Example:

Justmeans.com
&
www.justmeans.com

Those are just the “same” ones.

Solution:
replace non www URL with www url and redirect it.

$strNewRedirection = preg_replace('/(^http:\/\/www\.|^www\.|^http:\/\/)/', '', $strServerName);
$strNewRedirection = "http://www.".$strNewRedirection.$_SERVER['REQUEST_URI'];
header("Location: ".$strNewRedirection);
exit();

Really a class analogy...

2009-05-09T17:53:00.000+05:30

Really a class analogy...

An Old Story:

The Ant works hard in the withering heat all summer building its house and

laying up supplies for the winter.

The Grasshopper thinks the Ant is a fool and laughs & dances & plays the

summer away.

Come winter, the Ant is warm and well fed. The Grasshopper has no food or

shelter so he dies out in the cold.

Indian Version:

The Ant works hard in the withering heat all summer building its house and

laying up supplies for the winter.

The Grasshopper thinks the Ant's a fool and laughs & dances & plays the

summer away.

Come winter, the shivering Grasshopper calls a press conference and

demands to know why the Ant should be allowed to be warm and well fed

while others are cold and starving.

NDTV, BBC, CNN show up to provide pictures of the shivering Grasshopper

next to a video of the Ant in his comfortable home with a table filled

with food.

The World is stunned by the sharp contrast. How can this be that this poor

Grasshopper is allowed to suffer so?

Arundhati Roy stages a demonstration in front of the Ant's house.

Medha Patkar goes on a fast along with other Grasshoppers demanding that

Grasshoppers be relocated to warmer climates during winter .

Mayawati states this as `injustice' done on Minorities.

Amnesty International and Koffi Annan criticize the Indian Government for

not upholding the fundamental rights of the Grasshopper.

The Internet is flooded with online petitions seeking support to the

Grasshopper (many promising Heaven and Everlasting Peace for prompt

support as against the wrath of God for non-compliance) .

Opposition MPs stage a walkout. Left parties call for 'Bengal Bandh' in

West Bengal and Kerala demanding a Judicial Enquiry.

CPM in Kerala immediately passes a law preventing Ants from working hard

in the heat so as to bring about equality of poverty among Ants and

Grasshoppers.

Lalu Prasad allocates one free coach to Grasshoppers on all Indian Railway

Trains, aptly named as the 'Grasshopper Rath'.

Finally, the Judicial Committee drafts the ' Prevention of Terrorism

Against Grasshoppers Act' [POTAGA], with effect from the beginning of the

winter.

Arjun Singh makes 'Special Reservation ' for Grasshoppers in Educational

Institutions & in Government Services.

The Ant is fined for failing to comply with POTAGA and having nothing left

to pay his retroactive taxes,it's home is confiscated by the Government

and handed over to the Grasshopper in a ceremony covered by NDTV.

Arundhati Roy calls it ' A Triumph of Justice'.

Lalu calls it 'Socialistic Justice '.

CPM calls it the ' Revolutionary Resurgence of the Downtrodden '

Koffi Annan invites the Grasshopper to address the UN General Assembly.

Many years later....

The Ant has since migrated to the US and set up a multi-billion dollar

company in Silicon Valley,

100s of Grasshoppers still die of starvation despite reservation somewhere

in India,

......AND

As a result of loosing lot of hard working Ants and feeding the

grasshoppers,

Useful Linux Commands

2009-04-16T21:34:00.000+05:30

Shorthand at the Command Prompt

Some of these are specific to the bash shell. I have not experimented enough with other shells to know which are common to all shells. See also the ``Bash Reference Card'', SSC (2000), available online.

/ - root directory
./ - current directory
./command_name - run a command in the current directory when the current directory is not on the path
../ - parent directory
~ - home directory
$ - typical prompt when logged in as ordinary user
# - typical prompt when logged in as root or superuser
! - repeat specified command
!! - repeat previous command
^^ - repeat previous command with substitution
& - run a program in background mode
[Tab][Tab] - prints a list of all available commands. This is just an example of autocomplete with no restriction on the first letter.
x[Tab][Tab] - prints a list of all available completions for a command, where the beginning is ``x''
[Alt][Ctrl][F1] - switch to the first virtual text console
[Alt][Ctrl][Fn] - switch to the n^th virtual text console. Typically, there are six on a Linux PC system.
[Alt][Ctrl][F7] - switch to the first GUI console, if there is one running. If the graphical console freezes, one can switch to a nongraphical console, kill the process that is giving problems, and switch back to the graphical console using this shortcut.
[ArrowUp] - scroll through the command history (in bash)
[Shift][PageUp] - scroll terminal output up. This also works at the login prompt, so you can scroll through your boot messages.
[Shift][PageDown] - scroll terminal output down
[Ctrl][Alt][+] - switch to next X server resolution (if the server is set up for more than one resolution)
[Ctrl][Alt][-] - change to previous X server resolution
[Ctrl][Alt][BkSpc] - kill the current X server. Used when normal exit is not possible.
[Ctrl][Alt][Del] - shut down the system and reboot
[Ctrl]c - kill the current process
[Ctrl]d - logout from the current terminal
[Ctrl]s - stop transfer to current terminal
[Ctrl]q - resume transfer to current terminal. This should be tried if the terminal stops responding.
[Ctrl]z - send current process to the background
reset - restore a terminal to its default settings
[Leftmousebutton] - Hold down left mouse button and drag to highlight text. Releasing the button copies the region to the text buffer under X and (if gpm is installed) in console mode.
[Middlemousebutton] - Copies text from the text buffer and inserts it at the cursor location. With a two-button mouse, click on both buttons simultaneously. It is necessary for three-button emulation to be enabled, either under gpm or in XF86Config.

Typical Dot Files

There is some redundancy across these programs. For example, the look and behavior of emacs can be customized by usinng the .emacs file, but also by adding the appropriate modifications to the .Xdefaults file. Default versions of these files are often installed in users' home directories when the software packages that use them are installed. If a program doesn't find its configuration file in the user's home directory, it will often fall back on a sytem-wide default configuration file installed in one of the subdirectories that the package lives in.

.bash_logout - file executed by bash shell on logout
.bash_profile - initialization of bash shell run only on login. Bash looks first for a .bash_profile file when started as a login shell or with the -login option. If it does not find .bash_profile, it looks for .bash_login. If it doesn't find that, it looks for .profile. System-wide functions and aliases go in /etc/bashrc and default environment variables go in /etc/profile.
.bashrc - initialization command run when bash shell starts up as a non-login shell
.cshrc - initialization commands that are run automatically (like autoexec.bat) when C shell is initiated
.emacs - configuration file for emacs editor
.fvwmrc - configuration file for fvwm window manager
.fvwm2rc - configuration file for fvwm2 window manager
.jedrc - configuration file for the jed text editor
.lessrc - typically contains key bindings for cursor movement with the less command
.login - initialization file when user logs in
.logout - commands run when user logs out
.wm_style - gives choice of default window manager if one is not specified in startx
.Xdefaults - sets up X resources for individual user. The behavior of many different application programs can be changed by modifying this file.
.xinitrc - initialization file when running startx. Can be used to activate applications, run a given window manager, and modify the appearance of the root window.
.xsession - configuration file for xdm

Useful Files

/boot/vmlinuz - the typical location and name of the Linux kernel. In the Slackware distribution, the kernel is located at /vmlinuz.
/dev/fd0 - first floppy disk drive
/dev/fd0H1440 - driver for the first floppy drive in high density mode. Generally, this is invoked when formatting a floppy drive for a particular density. Slackware comes with drivers that allow for formatting a 3.5" diskette with up to 1.7MB of space. Red Hat and Mandrake do not contain these device driver files by default.
/dev/fd1 - second floppy disk drive
/dev/hda - first IDE hard drive
/dev/hdc - on many machines, the IDE cdrom drive. Most often, there is a symbolic link called /dev/cdrom which is just a link to the true cdrom driver file.
/dev/null - used when you want to send output into oblivion
/etc/aliases - file containing aliases used by sendmail and other MTAs (mail transport agents). After updating this file, it is necessary to run the newaliases utility for the changes to be passed to sendmail.
/etc/bashrc - system-wide default functions and aliases for the bash shell
/etc/conf.modules - aliases and options for configurable modules
/etc/crontab - shell script to run different commands periodically (hourly, daily, weekly, monthly, etc.)
/etc/DIR_COLORS - used to store colors for different file types when using ls command. The dircolors command uses this file when there is not a .dir_colors file in the user's home directory. Used in conjunction with the eval command (see below).
/etc/exports - specifies hosts to which file systems can be exported using NFS. Man exports contains information on how to set up this file for remote users.
/etc/fstab - contains information on partitions and filesystems used by system to mount different partitions and devices on the directory tree
/etc/HOSTNAME - stores the name of the host computer
/etc/hosts - contains a list of host names and absolute IP addresses.
/etc/hosts.allow - hosts allowed (by the tcpd daemon) to access Internet services
/etc/hosts.deny - hosts forbidden (by the tcpd daemon) to access Internet services
/etc/group - similar to /etc/passwd but for groups
/etc/inetd.conf - configures the inetd daemon to tell it what TCP/IP services to provide (which daemons to load at boot time). A good start to securing a Linux box is to turn off these services unless they are necessary.
/etc/inittab - runs different programs and processes on startup. This is typically the program which is responsible for, among other things, setting the default runlevel, running the rc.sysinit script contained in /etc/rc.d, setting up virtual login terminals, bringing down the system in an orderly fashion in response to [Ctrl][Alt][Del], running the rc script in /etc/rc.d, and running xdm for a graphical login prompt (only if the default runlevel is set for a graphical login).
/etc/issue - pre-login message. This is often overwitten by the /etc/rc.d/rc.S script (in Slackware) or by the /etc/rc.d/rc.local script (in Mandrake and Red Hat, and perhaps other rpm-based distributions). The relevant lines should be commented out (or changed) in these scripts if a custom pre-login message is desired.
/etc/lilo.conf - configuration file for lilo boot loader
/etc/motd - message of the day file, printed immediately after login. This is often overwritten by /etc/rc.d/rc.S (Slackware) or /etc/rc.d/rc.local (Mandrake/Red Hat) on startup. See the remarks in connection with /etc/issue.
/etc/mtab - shows currently mounted devices and partitions and their status
/etc/passwd - contains passwords and other information concerning users who are registered to use the system. For obvious security reasons, this is readable only by root. It can be modified by root directly, but it is preferable to use a configuration utility such as passwd to make the changes. A corrupt /etc/passwd file can easily render a Linux box unusable.
/etc/printcap - shows the setup of printers
/etc/profile - sets system-wide defaults for bash shell. It is this file in Slackware that sets up the DIR_COLORS environment variable for the color ls command. Also sets up other system-wide environment variables.
/etc/resolv.conf - contains a list of domain name servers used by the local machine
/etc/securetty - contains a list of terminals on which root can login. For security reasons, this should not include dialup terminals.
/etc/termcap - ASCII database defining the capabilities and characteristics of different consoles, terminals, and printers
/etc/X11/XF86Config - X configuration file. The location in Slackware is /etc/XF86Config.
/proc/cpuinfo - cpu information
/proc/filesystems - prints filesystems currently in use
/proc/interrupts - prints interrupts currently in use
/proc/ioports - contains a list of the i/o addresses used by various devices connected to the computer
/proc/kcore - The command ls -l /proc/kcore will give the amount of RAM on the computer. It's also possible to use the free command to get the same information (and more).
/proc/version - prints Linux version and other info
/var/log/messages - used by syslog daemon to store kernel boot-time messages
/var/log/lastlog - used by system to store information about last boot
/var/log/wtmp - contains binary data indicating login times and duration for each user on system

Important Directories

Different distributions have different directory structures, despite attempts at standardization such as the the Linux Filesystem Hierarchy Standard (FHS) organization.

/bin - essential UNIX commands such as ls, etc. Should contain all binaries needed to boot the system or run it in single-user mode
/boot - files used during booting and possibly the kernel itself are stored here
/dev - contains device files for various devices on system
/etc - files used by subsystems such as networking, NFS, and mail. Includes tables of disks to mount, processes to run on startup, etc.
/etc/profile.d - contains scripts that are run by /etc/profile upon login.
/etc/rc.d - contains a number of shell scripts that are run on bootup at different run levels. There is also typically an rc.inet1 script to set up networking (in Slackwar), an rc.modules script to load modular device drivers, and an rc.local script that can be edited to run commands desired by the administrator, along the lines of autoexec.bat in DOS.
/etc/rc.d/init.d - contains most of the initialization scripts themselves on an rpm-based system.
/etc/rc.d/rc*.d - where ``*'' is a number corresponding to the default run level. Contains files for services to be started and stopped at that run level. On rpm-based systems, these files are symbolic links to the initialization scripts themselves, which are in /etc/rc.d/init.d.
/etc/skel - directory containing several example or skeleton initialization shells. Often contains subdirectories and files used to populate a new user's home directory.
/etc/X11 - configuration files for the X Window system
/home - home directories of individual users
/lib - standard shared library files
/lib/modules - modular device driver files, most with .o extensions
/mnt - typical mount point for many user-mountable devices such as floppy drives, cd-rom readers, etc. Each device is mounted on a subdirectory of /mnt.
/proc - virtual file system that provides a number of system statistics
/root - home directory for root
/sbin - location of binaries used for system administration, configuration, and monitoring
/tmp - directory specifically designed for programs and users to store temporary files.
/usr - directory containing a number of subdirectory with programs, libraries, documentation, etc.
/usr/bin - contains most user commands. Should not contain binaries necessary for booting the system, which go in /bin. The /bin directory is generally located on the same disk partition as /, which is mounted in read-only mode during the boot process. Other filesystems are only mounted at a later stage during startup, so putting binaries essential for boot here is not a good idea.
/usr/bin/X11 - most often a symbolic link to /usr/X11R6/bin, which contains executable binaries related to the X Window system
/usr/doc - location of miscellaneous documentation, and the main location of program documentation files under Slackware
/usr/include - standard location of include files used in C programs such as stdio.h
/usr/info - primary location of the GNU info system files
/usr/lib - standard library files such as libc.a. Searched by the linker when programs are compiled.
/usr/lib/X11 - X Window system distribution
/usr/local/bin - yet another place to look for comon executables
/usr/man - location of manual page files
/usr/sbin - other commands used by superuser for system administration
/usr/share - contains subdirectories where many installed programs have configuration, setup and auxiliary files
/usr/share/doc - location of program documentation files under Mandrake and Red Hat
/usr/src - location of source programs used to build system. Source code for programs of all types are often unpacked in this directory.
/usr/src/linux - often a symbolic link to a subdirectory whose name corresponds to the exact version of the Linux kernel that is running. Contains the kernel sources.
/var - administrative files such as log files, used by various utilities
/var/log/packages - contains files, each of which has detailed information on an installed package in Slackware. The same file can also be found at /var/adm/packages, since the adm subdirectory is a symbolic link to log. Each package file contains a short description plus a list of all installed files.
/var/log/scripts - package installation scripts in Slackware are stored here. You can inspect these scripts to see what special features are included in individual packages.
/var/spool - temporary storage for files being printed, mail that has not yet been picked up, etc.

Important Bash Shell Variables

These variables are most often inherited or declared when a shell is started. A great reference for bash shell variable, bash builtin commands, and bash in general is SSC (2000).

HOME - home directory, abbreviated as ~
MAIL - name of file that mail is stored in (mailbox)
MAILCHECK - sets the frequency at which bash checks for mail
PATH - directory paths to search for executable files. According to A Practical Guide to Linux, p.329, the PATH is set in /etc/profile. On my Linux box, /etc/profile adds /usr/X11R6/bin to the path, which means that the path must be set before by another configuration file. The .bash_profile file in my home directory adds /home/ambler/bin to the path. On my Linux box, the first command to set the path would seem to be in /etc/rc.d/rc.sysinit, which is one of the shell scripts invoked by the init process (inittab). Then, /etc/profile adds /usr/X11R6/bin. Finally, .bash_profile adds /home/ambler/bin.
PS1 - prompt string. Things that can be put in the prompt string include \h (hostname), \u (username), \w (absolute pathname of working directory), \W (name of working directory w/o path), \d (date), \t (time). See p.331 of A Practical Guide to Linux for more details. On my Red Hat boxes, the primary prompt string is set in the /etc/bashrc file. The prompt is also set in /etc/profile, but the setting in bashrc seems to take precedence. I also have a .bashrc file, which in turn runs /etc/bashrc, which sets the prompt. This means that the same prompt is used by xterm and rxvt in X sessions. On my Slackware box, the command line prompt is set in /etc/profile. The xterm and rxvt prompts are different, since I don't have a .bash_profile file which is run when an xterm is started. In fact, I don't know where the prompt is set in X sessions. It is not set by /usr/X11R6/lib/X11/app-defaults/XTerm.
PS2 - secondary prompt string.

Important Daemons and Startup Services

These are programs or processes which are run at boot time. Some remain in memory to execute various tasks when required (daemons). Most are started and stopped with scripts in the /etc/rc.d/init.d directory (see above). The exact contents of this directory will depend on which packages from a particular distribution are installed. For example, installing the Apache package will cause an httpd script to be placed in /etc/rc.d/init.d.

There are man pages on most of these. The Red Hat program tksysv (ntsysv is the non graphical version) allows root to automatically configure which of these are started automatically at boot time. The linuxconf program does the same thing, although I haven't tried it. The utility chkconfig is also designed to query and configure runtime services for different runlevels. The www.mandrakeuser.org site has a good page on common services/daemons, especially those included in recent versions of the Mandrake distribution.

A good source of information on daemons and services is the ``Linux Devices, Daemons, Services'' chapter of the CTDP (2000a) document.

amd - runs the automount daemon for remote filesystem mounting such as nfs
anacron - checks delayed `cron' tasks (see below) at boot time and executes them. Useful if you have cron jobs scheduled but don't run your machine all the time.
apmd - Advanced Power Management BIOS daemon. For use on machines, especially laptops, that support apm. Monitors battery status and can shut down the system if power is too low.
arpwatch - keeps watch for ethernet IP address pairings that are resolved using the ARP protocol.
atd - runs jobs queued by `at'
autofs - control the operation of automount daemons, used to mount and unmount devices on demand
bootparamd - allows computers to boot from a Linux machine using the BOOTP network protocol. A server process that provides information to diskless clients necessary for booting
crond - automatic task scheduler. Manages the execution of tasks that are executed at regular but infrequent intervals, such as rotating log files, cleaning up /tmp directories, etc.
cups - daemon for print services under the Common Unix Printer System, a replacement for lpd
dhcpd - implements the Dynamic Host Configuration Protocol (DHCP) and the Internet Bootstrap Protocol (BOOTP). Used to lease out IP addresses to remote machines.
drakfont - font server in Mandrake
fetchmail - daemon to fetch mail at regular intervals from mail servers
ftpd - ftp server daemon
gated - routing daemon that handles multiple routing protocols and replaces routed and egpup
gpm - useful mouse server for applications running on the Linux console.
httpd - the Apache webserver hypertext transfer protocol daemon
identd - The identd server provides a means to determine the identity of a user of a particular TCP connection. Given a TCP port number pair, it returns a character string which identifies the owner of that connection on the server's system.
inetd - listens for service requests on network connections, particularly dial-in services. This daemon can automatically load and unload other daemons (ftpd, telnetd, etc.), thereby economizing on system resources. In the latest version of Red Hat (7.0 at the time of writing), it has been replaced by xinetd. A partial list of services controlled by inetd is listed below. Under many distributions, inetd will execute scripts in the file /etc/inetd.conf.
innd - Usenet news server daemon
ipchains - daemon for packet forwarding. Used for configuring a gateway/firewall.
isdn provides ISDN network interfacing services
isdn4linux - for users of ISDN cards
kerneld - automatically loads and unloads kernel modules
keytable - loads the appropriate keyboard map from /etc/sysconfig/ keyboard
kheader -
kudzu - detects and configures new or changed hardware during boot
linuxconf - ``startup hook'' needed for the linuxconf system configuration tool
lpd - line printer and print spooler daemon
mcserv - server program for the Midnight Commander networking file system. It provides access to the host file system to clients running the Midnight file system (currently, only the Midnight Commander file manager). If the program is run as root the program will try to get a reserved port otherwise it will use 9876 as the port. If the system has a portmapper running, then the port will be registered with the portmapper and thus clients will automatically connect to the right port. If the system does not have a portmapper, then a port should be manually specified with the -p option (see below).
mysql - database server daemon
named - provides DNS services
netfs - network filesystem mounter. Used for mounting nfs, smb and ncp shares on boot.
network -activates all network interfaces at boot time by calling scripts in /etc/sysconfig/network-scripts
nfsd - used for exporting nfs shares when requested by remote systems
nfslock - starts and stops nfs file locking service
numlock - locks numlock key at init runlevel change
pcmcia - generic services for pcmcia cards in laptops
portmap - needed for Remote Procedure Calls
postfix - mail transport agent which is a replacement for sendmail. Now the default on desktop installations of Mandrake.
postgresql - database server daemon
random - random number generating daemon, related to security and encryption
routed - manages routing tables
rstatd - kernel statistics server. Allows users on a network to get performance statistics for any connected machine.
rusersd - provides services that allow users to find one another over the network
rwalld - allows users to use rwall to write messages on remote terminals
rwhod - server which maintains the database used by the rwho(1) and ruptime(1) programs. Its operation is predicated on the ability to broadcast messages on a network.
sendmail - mail transfer agent. This is the agent that comes with Red Hat. Others, such as smtpd, are not included.
smb - needed for running SAMBA
snmpd - provides Simple Network Management Protocol support
sound - daemon for managing sound
squid - web page proxy server daemon
syslogd - manages system log files
smtpd - Simple Mail Transfer Protocol, designed for the exchange of electronic mail messages. Several daemons that support SMTP are available, including sendmail, smtpd, rsmtpd, qmail, zmail, etc.
tcpd - from the tcp_wrappers package. Intercepts requests normally handled by inetd and filters them through the files hosts.allow and hosts.deny files, which can restrict access to services based on type of service, origin of request, destination, etc. Requests are intercepted because calls to particular services are replaced with calls to tcpd in /etc/inetd.conf.
telnetd - telnet server daemon
usb - daemon for devices on Universal Serial Bus
xfs - X font server
xinetd - more modern replacement for inetd. It apparently allows for similar kinds of access filters to the ones used by tcpd in conjunction with inetd. xinetd replaces inetd as the default network services daemon in Red Hat 7.0.
xntpd - Network Time Protocol daemon. Provides a means to syncronize time over the network.
webmin - daemon for webmin web-based system administration program
ypbind - NIS binder. Needed if computer is part of Network Information Service domain.

Alphabetical List of Principal Commands

In the following command list, the distinction between upper case and lower case letters is important. Most of the commands are utilities that are run by invoking their own executable files. In some cases, they are commands which are internal to a shell such as bash (shell builtins). The shell builtins are indicated. There are now many utilities that are included with either the Gnome or the KDE desktop environments, so many that it would be difficult to include them all here. In many cases, they duplicate the functionality of one or more of the programs listed below. I would suggest consulting the online documentation for these packages.

Another good source of information on commands is the CTDP (2000b) document. There are different chapters which group commands in different categories.

On rpm-based systems, to find out which package owns the command foo (where foo is a standalone executable), use the command rpm -q -f foo.

a2p - translation utility from awk to Perl
a2ps - translation utility from ``any'' to Postscript
ac - print statistics concerning user connect time
access - determine whether a file can be accessed
acroread - Adobe utility for viewing pdf files
adduser - used by root to add user to system

usage: adduser userid

afio - utility to copy or restore files to an archive file. This utility is not part of the basic internal and external programs under Red Hat Linux. It is available as an rpm on the rpmfind.net site.
agetty - enables login on terminals. See getty, mgetty, and uugetty.
ali - list mail aliases
alias - assign name to specified command list. This is actually a shell builtin. On my Red Hat system, I have global alias commands in my /etc/bashrc file and in my /.bashrc file. On my Slackware box, I have made the rm command a little bit safer with

alias rm='rm -i'

so that you can't recursively delete your /dev directory without telling the system you're sure you want to do it.

alien - utility to convert to and from different Linux package formats. Can handle Debian (deb), Stampede (stp), Red Hat (rpm) and Slackware (tgz) packages.
apropos - display command names based on keyword search

usage: apropos keyword

apsfilter - printer filter called by lpd to deal with printing different types of files. This is a fairly sophisticated print filter. It is not set up by default in Slackware. It used to be available on the second cd of a Slackware distribution. Since 4.0, it is available as one of the main packages in the ap set. Read the mail that the installation program sends to the root user. I believe that Red Hat uses its own printer filters.
ar - create, modify and extract from archives
arch - print machine architecture type
as - the portable GNU assembler
asapm - AfterStep laptop advanced power management utility
ash - a shell, a very simple shell program sometimes used on boot diskettes since it takes up much less space than bash, tcsh, zsh, etc.
asload - AfterStep cpu load monitor
asmail - AfterStep mail checking utility
asmodem - AfterStep utility to monitor modem status
aspell - a spell checking program along the lines of ispell
aspostit - X Window postit note utility
at - executes a shell script at specified time. Use atq to show pending jobs, and atrm to remove jobs from the queue.

usage: at time
or: at -f file time

atq - shows pending jobs queued by at. If run by root, shows everybody's pending jobs.
atrm - removes pending jobs queued by at. Use atq to determine the identities of various jobs.

usage: atrm job

awk - searches for and process patterns in a file
banner - print banner to standard output. Syntax is

banner [option] [characters]

bash - Bourne again shell. This is the default shell in the Red Hat installation.
batch - queue, examine, or delete jobs for later execution. See at.
bc - a language (compiler) similar to C, with unlimited precision arithmetic
bg PID - send process with pid ``PID'' to the background. This is the same as executing [Ctrl]z while interacting with the running process. This is a shell builtin.
bh - puts a job in the background. This is a shell builtin.
biff - mail notification utility. Notifies user of mail arrival and sender's name.
bind - displays or redefines key bindings. This is a shell builtin.
bison - parser generator similar to yacc
bru - a powerful backup utility program. Commercial. Demonstration versions are often included with Linux distributions such as Red Hat.
bsh - equivalent to ash
bunzip2 - used to uncompress files compressed with bzip2
byacc - parser generator
bzip2 - compresses with algorithm different from gzip
bzless - view bzipped files
c++ - invokes GNU C and C++ compiler
cal - displays a 12-month calendar for the given year or a one-month calendar of the given month

usage: cal month year

cat - combine, copy standard input to standard output. Used to join or display files.
cd - change working directory. This is a shell builtin in bash, tcsh and zsh.
cdplay - command line utility for playing audio cds
cfdisk - similar to fdisk, but menu-driven
chat - used to interact with a modem via a chat script
chgrp - changes group associated with file. Can be used to change the group associated with subdirectories and files of a directory.

usage: chgrp group files
or: chgrp -R group files

chkconfig - Query or update system services/daemons for different runlevels. Manipulates the various symbolic links in /etc/rc.d. This utility is included with many rpm-based distributions such as RedHat and Mandrake. It is designed to work with System V initialization scripts. Graphical tools for configuring system services include ntsysv, tksysv and ksysv (the latter is a KDE utility).
chmod - set permissions (modes) of files or directories. A value of 4 is used for read permission. A value of 2 is used for write permission. A value of 1 is used for execute permission. See umask for default file permissions upon file creation. Chmod can also be used to change the suid bit on files. The syntax for the symbolic version is

chmod [options] who operation permission file-list

The syntax for the absolute version is

chmod [options] mode file-list

To set the uid to the owner's permissions, use

chmod u +s file-name

To set the uid to the group's permissions, use

chmod g +s file-name

There are lots of security issues related to allowing a program to have root's permissions when run by an ordinary user. I don't pretend to understand all of these issues.

chown - changes ownership of a file. Can be used recursively.

usage: chown userid files
or: chown -R userid files

chsh - change default shell
ci - creates or records changes in an RCS file
clear - clear screen command
cmp - compares two files for differences

usage: cmp file1 file2

co - retrieves an unencoded version of an RCS file
comm - compares sorted files
configure - automatically configures software source code
color-xterm - color xterm program. Under Red Hat, this is just a link to xterm-color.
control-panel - graphical system configuration tool under Red Hat.
cp - copies on or more files. Recursive copying is one simple way of archiving part of a directory structure. Use the command as follows:

cp -r /sourcedirectory /targetdirectory

cpio - direct copy of files to an output device. Allows creation of archive file spanning multiple diskettes. Allows one directory structure to be mirrored elsewhere on the partition or on another partition. In order to back up an entire directory structure on diskettes, cd to the directory and use the following command:

find . -depth -print | cpio -ov > /dev/fd0

To restore from diskettes, use:

cpio -iv < /dev/fd0

The cpio command will prompt the user to insert more diskettes as they are needed. The command for mirroring a directory structure is the following:

find . -depth -print | cpio -pv /destinationdirectory

This copies the working directory and its contents, including subdirectories, into /destinationdirectory. In order to copy an individual file which is larger than a floppy, use:

find . -name nameoffile -print | cpio -iv > /dev/fd0

cpkgtool - Slackware tool to install, uninstall and query packages. Front end to installpkg, removepkg, makepkg. This is the graphical version that uses ncurses.
cpp - GNU C-compatible compiler preprocessor
crontab - schedules command to run at regularly specified time
csh - run C shell
csplit - separate files into sections. See also split.
cvs - manages concurrent acces to files in a hierarchy. Stands for concurrent version system. Is built on RCS. It stores successive revisions of files efficiently and ensures that access to files by multiple developers is done in a controlled manner. Useful when many developers are working on the same project.
cut - selects characters or TAB-separated fields from lines of input and writes them to standard output
date - displays or sets date and time

usage: date
or: date date

dd - direct copy of file from one device to another. Can be used to make copies of boot or root diskettes for installing Linux. It can be used, for example, to make and exact copy of a floppy disk, as follows. First, place the diskette to be copied in the floppy drive. Then,

dd if=/dev/fd0 ibs=512 > floppy.copy
Replace the diskette with a fresh diskette.
dd if=floppy.copy bs=512 of=/dev/fd0

The ibs and bs options specify the block sizes for input and for both input and output. A boot disk image can be directly copied to a floppy using the second of the two dd commands above.

declare - declares attributes for a variable (same as typeset). This is a shell builtin.
df - displays capacity and free capacity on different physical devices such as hard drive partitions and floppy drives that are mounted on the file system. Gives free space in blocks. With the (undocumented) option -h, the program gives free space in Mb or Gb. This is useful for those accustomed to thinking of the capacity of a high-density 3.5 inch diskette as 1440k.
diff - displays differences between two files

usage: diff file1 file2

diff3 - compares three files and reports on differences
dip - used to set up a SLIP or PPP connection. It can be used to set up an outgoing SLIP connection or an incoming connection.
diplogin - used for setting up incoming dip connections. See the man page for dip.
dir - a variation of the GNU ls command that defaults to printing file names in columns
dircolors - set colors for GNU ls command. In Slackware, this command is run by the /etc/profile script. Then, whenever xterm is run with the -ls (login shell) option, ls displays different colors for different types of files. Typical usage is eval `dircolors -b`. In Red Hat and Mandrake, I get color directories by aliasing the ls command (see below).
display - set display for output of programms under X Windows. Can be used to run a program on a remote machine while displaying the output on a local machine. The remote machine must have permission to send output to the local machine. This is actually an environment variable. See the more detailed discussion in connection with the xhost command below.
dmesg - displays messages from /var/log relative to the most recent boot
dos - invoke the DOSEMU DOS emulator
du - displays information on disk usage. The command

du / -bh | less

will display detailed disk usage for each subdirectory starting at root, giving files sizes in bytes.

dumpkeys - print information about the keyboard driver's translation tables to standard output
dvilj - send a dvi file to a Laserjet printer. There are specialized versions for individual models of Laserjet printer.
dvilj2p - specialized version of dvilj for the IIp series of printers. See above.
dvips - send a dvi file to a Postscript printer, to a Postscript capable Laserjet printer, or to a file (with the -o option). There is a switch to print only a subset of the pages, and another switch to print in landscape mode. Use -t landscape, which is one of the arguments to the paper type switch. If you have one page of a document that is a wide table, and you wish to print this in landscape mode, use

dvips filename -pp pagenumber -t landscape

e2fsck - check an ext2 filesystem. The syntax is

e2fsck /dev/devicename

where the filesystem is on /dev/devicename. The device should not be mounted, and this program must be run as root.

echo - write arguments to standard output. One use is to print out information about environment variables, as in

echo $PATH - list paths to search
echo $HOME or echo ~ - list name of home directory

This is a shell builtin.

editres - a dynamic resource editor for X Toolkit applications. Allows the user to change X resources for individual applications.
efax - fax program
efix - convert between fax, text, bit-map and gray-scale formats
egrep - search files for lines that match regular expressions. Runs faster than grep and fgrep.
elm - an interactive mail system
elvis - a version of the vi text editor
emacs - screen oriented text editor
env - desplay the current environment or set a variable equal to a new value
eval - scans and evaluates the command line. See dircolors command. This is a shell builtin.
ex - interactive command-based editor. The man page lists it as being the same as vim, an improved version of vi.
exec - system call which creates a subshell to execute a binary or a script. This is a shell builtin.
execve - a variation of the exec command.
exit - exit a shell. This is a shell builtin.
expand - convert tabs in files to spaces and write to standard output
expect - a program that ``talks'' to other interactive programs according to a script. Following the script, Expect knows what can be expected from a program and what the correct response should be. An interpreted language provides branching and high-level control structures to direct the dialogue. In addition, the user can take control and interact directly when desired, afterward returning control to the script.
export - place the value of a variable in the calling environment (makes it global). This is a shell builtin.
expr - utility evaluates an expression and displays the result
f2c - FORTRAN to C translator
f77 - FORTRAN 77 compiler
false - null command that returns an unsuccessful exit status
fax - simple user interface to efax and efix programs
fc - views, edits, and executes commands for the history list. This is a shell builtin.
fdformat - low level format of a floppy device
fetchmail - retrieve mail from a remote mail server and pass it to local SMTP agents on the local machine
fdisk - used to partition hard drives

usage: fdisk device

fg PID - bring a background or stopped process with pid ``PID'' to the foreground. This is a shell builtin. If only one process is running in background mode, fg with no argument is sufficient to bring it to the foreground
fgrep - search for patterns in files
file - displays classification of a file or files according to the type of data they contain
find - find files according to a large variety of search criteria. The find command that I use the most is

find . -name filename -print

in order to find files matching a particular name on the working directory and all subdirectories. Find can be incredibly powerful, but it is incredibly obscure.

finger - display information about a specified userid or userids
fmt - simple text formatting utility. Tries to make all nonblank lines nearly the same length.
fold - break lines of specified files so they are no wider than a specified lengths
fortune - available in the bsdgames package in Slackware and other distributions. Put a call to fortune in /etc/profile and get something inspirational or amusing every time you fire up an xterm as a login shell.
free - gives used and free memory on system along with other useful information
fromdos - takes a DOS text file from stdin and sends a UNIX file to stdout.
fsck - file system check and repair
ftp - file transfer over network
g++ - C++ compiler
g77 - GNU Fortran 77 compiler
gawk - GNU awk, mostly for processing delimited text files
gcc - invoke C, C++ compiler
getipts - parses arguments to a shell script. This is a shell builtin.
getkeycodes - print kernel's scancode-to-keycode mapping table
ghostscript - set of printing utilities. It seems to be obligatory to have this if a T_EX installation such as teT_EX is installed. How they communicate with one another is somewhat obscure.
ghostview - Aladdin ghostscript interpreter/previewer
gimp - image manipulation and paint program
glint - Red Hat graphical front end for the rpm package installer and manager.
grep - used to find a string within a file. The -i option returns matches without regard to case. The -n option means that each line of output is preceded by file name and line number. The -v option causes non-matched lines to be printed.

usage: grep pattern files
or: grep -i pattern files
or: grep -n pattern files
or: grep -v pattern files

groupadd - create a new group on the system
groups - shows which groups you are in
grub - Gnu grand unified bootloader. Can be used instead of lilo to boot multiple operating systems. I encountered a couple of snafus trying to install grub on my home machine after installing Mandrake 8.0 and choosing the lilo bootloader during the initial install. The Mandrake installation program set up /boot/vmlinuz as a symlink to the actual kernel, vmlinuz-2.4.3-20mdk. It took me a while to figure out that grub doesn't understand symbolic links. The documentation suggests installing grub on a diskette using the ``dd'' command. This refused to work, but

grub-install '(fd0)'

did work. The single quotes are necessary. The files necessary to run grub are normally located in /boot/grub. Once the file menu.lst has been edited and appropriated entries added to boot the different operating systems on one's hard disk(s), the following sequence of commands can be used to install grub in the master boot record (MBR) sector of the hard disk:

root (hd0,x)
setup (hd0)

Here, the x should be replaced by the partition where the /boot/grub directory is located, which is probably the root partition of the Linux system. Note that grub has its own conventions for naming devices and numbering partitions, so that for example a partition which is called hda6 under Linux will be called (hd0,5) by grub.

grub-install - command to install grub on the hard drive (or floppy drive).
gunzip - used to uncompress files compressed with gzip
gv - PostScript and PDF previewer, based on ghostview
gvim - see vi
gzexe - compresses executables
gzip - used to compress or decompress files
halt - shut down system as root, without reboot, immediately
hash - remembers the location of commands in the search path. This is a shell builtin.
head - displays first part of a file
history - command for viewing and manipulating the shell command history list
host - look up host names using domain server
hostname - used to get or set hostname. Typically, the host name is stored in the file /etc/HOSTNAME.
hwclock - used to query and set the hardware clock
hylafax - commercial fax program
id - display userid and groupid
inetd - daemon which starts up other daemons on demand. Configured in /etc/inetd.conf.
ifconfig - display (as root) information on network interfaces that are currently active. First ethernet interface should be listed as eth0, second as eth1, etc. First modem ppp connection should be listed as ppp0, etc. The ``lo'' connection is ``loopback'' only.
ifdown - shut down the network interface
ifup [interface_name] - start up the interface
info - display system information. This is the GNU hypertext reader.
init - the mother of all processes, run at bootup, executes commands in /etc/inittab. Can be used (with root privileges) to change the system run level.

usage: init run_level

insmod - used (by root) to install modular device drivers
installpkg - Slackware command to install one of the packages from the program sets
intr - interrupt key, usually [Ctrl-C]
ispell - checks files for spelling errors

usage: ispell files

jed - programmer's file editor. Behaves like emacs. Has modes for T_EX, FORTRAN, C, etc.
jobs - displays list of current jobs in the background. This is a shell builtin.
joe - simple WordStar-like text editor. It can be invoked in emacs emulation mode with jemacs and in WordStar emulation mode with jstar.
jove - Joseph's Own Version of Emacs. A simple emacs clone.
kbd_mode - print current keyboard mode
kernelcfg - GUI to add/remove kernel modules (as root in X terminal).
kerneld - kernel daemon, a process that stays in memory and does all sorts of useful stuff, like automatic loading of device driver modules
kikbd - a utility program that comes with KDE that allows users to switch on the fly among different international keyboards. It can be used under different window managers than kfm.
kill - sends a signal to (especially to terminate) a job or process. This is a shell builtin in bash, tcsh and zsh.
killall - kill processes by name. Kill all processes which are instances of the speciffied program. Also used to send signals to processes or restart them.
killall5 - kill all processes except the ones on which it depends
last - generate a listing of user logins
lastlog - prints the last login times of all users
latex - compile a L^AT_EX file
ldconfig - creates the necessary links and cache (for use by the run-time linker, ld.so) to the most recent shared libraries found in the directories specified on the command line, in the file /etc/ld.so.conf, and in the trusted directories (/usr/lib and /lib). Ldconfig checks the header and file names of the libraries it encounters when determining which versions should have their links updated. Ldconfig ignores symbolic links when scanning for libraries.
ldd - list the shared libraries on which a given executable depends, and where they are located
leave - display reminder at specified time
less - Linux alternative to ``more'' command. Displays text files, one screenful at a time. When less pauses, there is a large number of available commands to tell it what to do next. One can scroll both forwards and backwards.
let - evaluates a numeric expression. This is a shell builtin.
lilo - installs boot loader on the boot sector of a hard drive, of a diskette, or in another location. My 486 has a hard drive that is too large for the machine's BIOS, so I have to boot from a floppy. To create a boot diskette, I do the following (as root):

/sbin/fdformat /dev/fd0H1440
/sbin/mkfs.ext2 /dev/fd0
mount -t ext2 /dev/fd0 /mnt/floppy
cp -dp /boot/* /mnt/floppy
/sbin/lilo -C /etc/lilo.flop

The -C option to lilo has lilo use the lilo.flop file instead of the default lilo.conf.

linuxconf - interactive tool for configuring Linux system. Uses X if loaded. This is a Gnome tool. It comes with my Red Hat distribution, and is not included with Slackware. It would seem to be the easiest way to configure Linux under Slackware. Version 1.15 is available for Slackware. There is a pretty good introduction to the use of linuxconf in the Red Hat 5.2 installation manual, which is available online at their web site.
ln - creates a link to a file. Used to create hard links and, with the -s option, symbolic links which can link files on different disk partitions. The syntax is

ln [options] source [dest]

locate filename - find the file name which contains the string ``filename''. The syntax is easier than the find command.
lock - temporarily lock terminal
lockfile - create semaphore file(s), used to limit access to a file
- log in to system
logname - consult /etc/utmp for user's login name
logout - execute logout as individual user and bring up login: prompt
look - look for strings in files
lpq - show print jobs that are waiting
lpr - send file to be printed
lprm - cancel a job from print queue
ls - list directory contents. To get colored directory listings under Red Hat, Mandrake, etc., use

ls -color

To get this all the time, add

alias ls='ls -color=auto'

to .bashrc. The following command

alias ls='ls -Fskb -color=auto'

will give directory listings in color, with file sizes in kilobytes, and append a character to the file to indicate its type.

lsattr - list attributes of files in ext2 file system
lsmod - used (by root) to show kernel modules currently loaded
lspci - utility to display information on pci buses and hardware devices attached to them. Part of the pciutils package that comes with many Linux distributions.
lspnp - utility to display information about pnp devices. Part of the pcmcia or kernel-pcmcia package, depending on the distribution.
m4 - an implementation of the traditional UNIX macro processor. It can be used with the sendmail configuration package in Red Hat (and Slackware) to generate a sendmail.conf configuration file without having to edit the configuration file directly.
magicfilter - general purpose printer filter. See apsfilter above. apsfilter is the printer filter that comes with the Red Hat and Slackware distributions.
mail - sends or reads electronic mail
make - keeps a set of programs current. This is a utility that helps when developing a set of programs. It works by executing a script called makefile, Makefile or GNUmakefile in the working directory. It is very often used in combination with configure when compiling and installing noncompiled software packages.
makebootdisk - command in Slackware to do just what the name says
MAKEDEV - executable script to make device files on /dev
makeswap - configures swap space
man - displays information from online Unix reference manual
manpath - attempt to determine path to manual pages
mc - Midnight Commander file manager and visual shell
mesg - enables/disables reception of messages
minicom - terminal program
mkdir - create a directory
mkfs - create a file system (format) on a device or partition. Should be invoked after lowlevel formatting of the disk using fdformat. It has several versions which are all links to the basic program, such as mkfs.ext2 and mkfs.msdos.
mkswap - creates a Linux swap space on the specified hard disk parition (root privileges neede)

usage: mkswap device

more - list file contents, stopping after each full screen
mount -t [fstype] [device] [mountpoint] - mount device using filesystem of type [fstype] with device name [device] at the location [mountpoint] in the filesystem directory tree
mount -a - mount all filesystems according to the specifications in /etc/fstab
mouseconfig - mouse configuration utility under Red Hat. Located in /usr/sbin.
mpage - print multiple pages per sheet on a Postscript printer. Can also be used to print a page in landscape mode.
Mtools - package of MS-DOS utilities. Includes the following commands.

mcd - changes working directory on DOS disk
mcopy - copies DOS files from one directory to another
mdel - deletes DOS files
mdir - lists contents of DOS directories
mformat - adds DOS formatting information to a disk
mtype - displays contents of a DOS file

The default device for execution of these commands is /dev/fd0 and can be referred to as ``a:''.

mv - moves (renames) files
netconf - used (as root) to set up network
newaliases - rebuilds the /etc/aliases database used by sendmail. Must be rerun every time /etc/aliases is modified for the changes to take effect.
newgrp - similar to login. Changes user's identification
nice program_name - sets the priority of the program ``program_name''.
nm - lists the symbols from object files objfile. If no object files are given as arguments, nm assumes `a.out'.
nohup - runs a command that keeps running after logout. The command is in principle immune to hangups, and must have output to a non tty. According to Linux in a Nutshell, this is necessary only in the Bourne shell, since modern shells preserve background processes by default.
ntsysv - run level editor under Red Hat. This is the equivalent of tksysv, but does not require a graphical interface.
nxterm - color xterm program. The man page for nxterm under Red Hat brings up the same page as xterm.
od - dumps contents of a file
passwd - change login password
paste - joins corresponding lines from files
patch - updates source code. Attempts to update a file from a file of change information, or pathces, created by diff.
pathchk - determine validity and portability of filenames
pdflatex - part of the pdftex program suite. Produces pdf output from a L^AT_EX file.
pdftex - produces pdf output from a TeX file. See also pdflatex. This program is part of the tetex 0.9 distribution that is included with Red Hat 5.2 and above, and with Slackware 4.0 and above. It is also available as a separate program.
perl - practical extraction and report language
pg - display data one screenful at a time
pico - simple screen oriented text editor. It is included as part of the Pine program.
ping - check if Internet computer is responding. Can also measure the time it takes the queried computer to respond.
pkgtool - Slackware tool to install, uninstall and query packages. Front end to installpkg, removepkg, makepkg. The cpkgtool is the ncurses graphical version of this program.
popclient - retrieve mail via the Post Office Protocol. Supports POP2 and POP3.
popd - pops the top directory of the directory stack and uses cd to change to that directory. This is a shell builtin.
pr - paginates files for printing
printenv - display list of environment variables
printtool - run (as root) in an X terminal to configure your printer(s)
ps - displays status of processes. Use the -a option for processes for all users. Use the -x option to include processes not attached to a terminal.
pstree - display processes in the form of a tree structure. Killing a parent process will also kill all the children and their descendants.
pushd - pushes the argument onto the top of the directory stack and uses cd to change to that directory. This is a shell builtin.
pwd - print absolute path of working directory. This is a shell builtin.
pwchk - checks the integrity of password and shadow files
pwconv - converts passwords to the shadow password format
pwunconv - unconverts passwords from the shadow password format. Generates a standard Unix password file.
python - interpreted, interactive, object-oriented programming language
rcp - copy one or more files to or from remote computer. The syntax is poorly explained in the documentation that I have, including the man pages. Usage is:

rcp filename username@remotehost:path

The user's home directory on the remote system must contain the file .rhosts with a list of users (preceded by the full domain name or exact IP address of their machine) with access privileges.

localhostname username

rcs - creates or changes the attributes of an RCS file. Stands for Revision Control System.
rdev - query/set image root device, swap device, RAM disk size, or video mode in kernel
read - reads line from standard input. This is a shell builtin.
readonly - declares a variable to be read only. This is a shell builtin.
reboot - in Slackware, reboots the system. Seems to be equivalent to shutdown -r now in generic Linux.
renice program_name - resets the priority of process ``program_name''.
reset - used to reset the screen characteristics. This is useful if the screen gets messed up from, for example, trying to display a binary file in an xterm.
return - exits from a function. This is a shell builtin.
rlog - prints a summary of the history of an RCS file
rlogin - log in to remote computer. The general syntax is as follows, using the UQAM Nobel machine as an example:

rlogin -l userid nobel.si.uqam.ca

The remote computer must recognize the local user and the local machine. See the rcp command for how to set up the .rhosts file on the remote machine.

rm - remove files or directories. With the -r (recursive) option (very dangerous!), can be used to remove the contents of a specified directory including all subdirectories.
rmail - interpret and handle remote mail received via uucp
rmdir - remove empty directories
rmmod - used to remove modular device drivers
route -n - show routing table. The n option returns numerical addresses rather than names.
rpm - invokes the Red Hat package manager in command line mode. I often use this command in query mode to query packages about what files they contain and to find out which package owns a particular file. Examples are

rpm -qil foo. Gives package information and a file list for the package foo.
rpm -qfil foo. Gives package information and a file list for the package that owns the file foo. Foo must be in the working directory, or the full path to foo must be specified.

We need to find out about installing the rpm package on a Slackware box. It's probably better to use a package converter such as alien.

rpm2tgz - an extremely useful utility on Slackware systems that converts rpm packages to tgz format. They can then be installed using the installpkg command (or pkgtool).
rsh - execute shell command on a remote computer. See rcp and rlogin.
rstat - summarize host's status: uptime, load averages, and current time
ruptime - show host status of local machines
rusers - list who is logged on local machines
rwall - write to all users over a network
rwho - show who is logged in on a LAN. The rwho service must be enabled for this command to run. If it isn't, run ``setup'' as root. I don't understand this last remark, which comes from ``Linux Newbie Administrator Guide''.
rxvt - a terminal program similar to xterm, but which has less features and uses less memory
sed - edits a file (not interactively). Also a tool for processing text files.
set - set or display value of shell variables. This is a shell builtin. The command

set | less

prints the current user environment, giving the values of currently defined variables.

setenv - set or display value of environment variables
setserial - used by root to configure a serial port
setterm - set terminal attributes for a virtual console
setuid - set the id of a program when it is run. Used, for example, to give root privileges to a program run by an ordinary user. This is actually done by running the chmod program as root. See the chmod command for the syntax.
setup - Slackware program to set up program sets and configure system. Setup devices and file systems, mount root file system
sh - standard UNIX shell. On Linux, just another name for bash.
shift - promotes each command-line argument. This is a shell builtin.
showmount - show information about an nfs server
shutdown - reboot or shut down system as root, after specified amount of time. With the -r option, reboot. With the -h option, halt the system.

usage: shutdown -r minutes

sleep - creates process that sleeps for specified interval
sliplogin - attaches a SLIP interface to standard input. Used to allow dialin SLIP connections.
sort - sorts and/or merge files
split - split file into specified number of segments
ssh - secure shell. Apparently has many of the same functionalities as rlogin, telnet, ftp, rsh, etc., with better security and encryption features. We may want to learn how to set this up and use it.
startx - front end to xinit in Linux. This is a script which starts up X clients and shuts down the X server on exit from the window manager.
startx -- :1 - start the next X window session on the display 1 (the default is opened on display 0). One can switch between different graphical displays using [Ctrl][Alt][F7], [Ctrl][Alt][F8], etc.
stty - sets or displays operating options for terminal
su - log in as another user, including root
sudo - allows individual users to have root permission to perform specified tasks
swapoff - disables swap disk
swapon - enables swap disk
symlinks - provide list of and information about symbolic links
sync - writes memory buffers to physical devices
systat - query host for system information
tac - print file in reverse
tail - displays the last part of a file
talk - visual communication program that copies lines from one terminal to that of another user
tar - file compression and archiving utility. I find the syntax of this command to be frustratingly opaque. The following works for me. To use this command to unzip gzipped tarballs in verbose mode, use

tar -xvzf filename.tgz

To create a tarball from files in a given directory and its subdirectories, use

tar -cvzf filename.tgz sourcename

Sourcename can be the name of a single file, a wildcard such as *, or the name of a subdirectory. There seem to be two different conventions concerning gzipped tarballs. One often encounters .tar.gz. The other popular choice is .tgz. Slackware packages use the latter convention. The command can also be used to archive a file, a group of files, or a directory (with its subdirectories) on tape or onto floppies. If the material to be archived exceeds the capacity of the backup medium, the program will prompt the user to insert a new tape or diskette. Use the following command to back up to floppies:

tar -cvf /dev/fd0 filename(s) or directoryname(s)

The backup can be restored with

tar -xvf /dev/fd0

Tar can be used for other things. To mirror all the files and subdirectories in from-stuff to to-stuff, use the commands

cd from-stuff
tar cf - . | (cd ../to-stuff; tar xvf -)

No tar file is ever written to disk. The data is sent by pipe from one tar process to another. This example is taken from Running Linux, p.177. To list the table of contents of a tar archive, use

tar tvf tarfile

To extract individual files from a tar archive, use

tar xvf tarfile files

where files is the list of files to extract. When extracting files, tar creates missing subdirectories underneath the current directory in which the cammand is invoked.

tcl - scripting language
tcsh - extended version of the C shell
tee - copy standard input to standard output and one or more files
telinit - used to change run level. Exact run level that corresponds to single-user, multi-user, and X levels depends on distribution.
telnet - remote login over network
test - evaluates an expression or compares arguments. This is a shell builtin in bash, tcsh and zsh.
tftp - user interface to TFTP protocol
time - displays times for the current shell and its children. This is a shell builtin. Strange, because there is also a /usr/bin/time program on my Red Hat system.
tin - Netnews reader
tkdesk - graphical desktop file manager for X
tksysv - graphical runlevel editor under Red Hat. Allows root to configure the services that are started at each run level.
tload - display system load average in graph format
top - dynamically displays process status
touch - update access and modification times of a file. If the file does not exist on disk, an empty file is created.
tr - translation utility that can be used, for example, to replace specified characters in a text file
trap - traps a signal. This is a shell builtin.
true - null command that returns a successful exit status
tset - initializes terminal
tty - shows special file that represents your terminal. Displays the terminal pathname.
type - displays how each argument would be interpreted as a command. This is a shell builtin.
typeset - declares attributes for a variaable (same as declare). This is a shell builtin.
ul - translate underscores to underlining
umask - establishes the file-creation permissions mask. Usage is

umask xyz

The system subtracts x, y and z from the owner, group and other file permissions that it would otherwise assign to new files. This is a shell builtin.

umount [device] - finish writing to the device and remove it from the active filesystem. The command umount -a will (re)mount all file systems listed in /etc/fstab.
unalias - remove name previously defined by alias. This is a shell builtin.
uname - displays information about the system. With no arguments, it displays the name of the operating system. With the -a option, it displays information about the operating system, the host name, and hardware.
uniq - displays lines of a file that are unique
unset - removes a variable or function. This is a shell builtin.
unzip - uncompress files compressed with the zip utility, compatible with DOS PKzip
updatedb - update file database used by locate command
uptime - shows the time, how long the system has been up, the number of users, and average load.
useradd - same as adduser
userdel - remove an account (as root). The user's home directory and undelivered mail must be dealt with separately.
users - prints list of users on the system
vdir - variant of the GNU version of the ls command. Defaults to printing out the long version of directory entries.
vi - standard screen oriented Unix editor
view - vi in read-only mode
vim - improved vi editor
vrfy - query remote host to verify the accuracy of an email address
w - display info about userids and active processes
wait - waits for a background process to terminate. This is a shell builtin.
wc - displays number of lines, characters and words in a file
Wharf - the AfterStep application dock module
whatis - display one-line summary of specified command
whereis - use to find utilities in standard locations
which - used to find utilities in search path. Will return the absolute directory path of the named utility program.
who - display information about currently logged in userids
whoami - display information about userid that is currently logged in
wish - front end to tk, an X window extension of tcl
workbone - console based cd player
workman - graphical cd player program
write - send messages to another local user
X - starts up the X server. Can be invoked with

X -quiet -query remotemachineaddress

in order to get a graphical login screen on the remote machine. See the discussion in connection with xdm below.

xadm - display advanced power management BIOS information
xargs - converts standard output of one command into arguments for another. This is one of those powerful but obscure commands. Xargs reads arguments from the standard input, delimited by blanks (which can be protected with double or single quotes or a backslash) or newlines, and executes the command (default is /bin/echo) one or more times with any initial-arguments followed by arguments read from standard input. Blank lines on the standard input are ignored.
xbiff - graphical mail delivery notification utility
xcalc - simple calculator program
xclipboard - name says it all
Xconfigurator - Red Hat utility for configuring settings for X
xdm - used to start an X login session. This can be used to start a login session on a remote system. See the discussion on the following site:

http://www.menet.umn.edu/~kaszeta/unix/xterminal/index.html

See the man pages for X, xdm, and Xserver. As usual, the man pages are pretty obscure. The best single source seems to be the Xserver man pages. After X is configured, X needs to be started at bootup with the command (in /etc/rc.d/init.d/xterm):

X -quiet -query remotemachineaddress

If the address of a nameserver is not configured, then the numeric address of the remote machine rather than its name should be entered. If the machines are connected through ethernet cards and the net, then obviously basic networking has to be set up. Gnome and KDE come with their own versions of X display/login managers, called respectively gdm and kdm.

xdvi - view a dvi file compiled under L^AT_EX
xedit - a simple text editor for X
xf86config - graphical configuration tool for X
XF86Setup - graphical configuration tool for X
xfd - display an available font in X. Creates a grid in an x-term with one character per rectangle.
xfig - utility for interactive generation of figures
xfm - graphical file manager for X
xhost - tell X server that remote computer has access to your machine and that you will use the remote computer. This can be used to set up remote X sessions. To set up a remote X session on the UQAM Nobel machine, run the following command on the local machine (one doesn't have to be root to do this)

xhost +nobel.si.uqam.ca

Then, log onto the remote machine using rlogin (see above) or telnet. Once logged in, use the following command to get the remote X server to open an X terminal on the local machine:

setenv DISPLAY localhostname:0 ; xterm &

This is valid for csh, which is the default login shell on Nobel. For ksh, (and I think bash) replace with

DISPLAY=localhostname:0
export DISPLAY ; xterm

Other X-based programs such as Netscape or Gauss (graphical version) can also be run on a remote machine with display on the local machine with little trouble. The local X server is the program that has all of the information concerning the properties of the graphics card and terminal, so it must be necessary to have X running on the local machine. The following should also work. After using xhost to give permission to the remote machine to display on the local machine, use

netscape -display localhostname:0.0

Question: can one start the X session on the local machine and then run a remote copy of a window manager?

xinit - start X Window. The command startx is a front end to xinit in Linux, including Slackware.
xload - displays a graphic of the system load
xlpq - graphical interface to print manager. This is included on one of the XFCE menus, but does not seem to be a part of the base Red Hat distribution.
xlsfonts - list fonts available under the X Window system.
xman - browsable command reference. Displays manual pages under X.
xmh - graphical front end under X to the nmh mail handling system. This program is part of the XFree86 package in Red Hat.
xmodmap - utility for modifying keymaps and pointer button mappings in X. Can be used to install a French Canadian keyboard. Download the Xmodmap.cf file from www.linux-quebec.org, and insert the command

xmodmap /etc/X11/Xmodmap.cf &

into the .xession (with xdm) or the .xinitrc (with startx) file.

xosview - displays bar graphs of system load, load average, memory usage, and swap usage
xpaint - simple paint program for X
xpdf - GPL'd utility for previewing dvi files. Doesn't seem to work too well on texts with a lot of math.
xplaycd - X Window audio cd player utility
xsetroot - utility to configure root window of an X terminal
xsysinfo - graphical display of load and memory usage
xterm - start an X Window terminal session
xterm-color - color version of xterm
xv - utility for viewing and manipulating many types of image files. This is a shareware program.
xvidtune - utility for fine tuning of monitor settings under X
yacc - parser generator
ytalk - multi-user program similar to talk
zcat - read one or more files that have been compressed with gzip or compress and write to standard output
zcmp - read compressed files and pass them to cmp
zdiff - read compressed files and pass them to diff
zgrep - read compressed files and pass them to grep
Zharf - AfterStep button panel module
zip - zip utility compatible with DOS PKzip
zless - view zipped files
zmore - print contents of compressed files one screen at a time
znew - uncompress Z files and recompress in .gz format

Eventually, we want to be able to distinguish between commands that are an intrinsic part of the kernel, commands that are executable binaries that come with every distribution of Linux, executable binaries that are not provided with all distributiions of Linux, and executable shell scripts. We also want to point out the typical location of these commands on different Linux distributions. Finally, we want to distinguish between shell commands and Linux commands.

New developer features in Firefox 3.5

2009-04-15T16:03:00.000+05:30

For web site and application developers

HTML 5 support

Using audio and video in Firefox: Firefox 3.5 adds support for the HTML 5 audio and video elements.
Offline resources in Firefox: Firefox 3.5 now fully supports the HTML 5 offline resource specification.
Drag and drop: The HTML 5 drag and drop API allows support for dragging and dropping items within and between web sites. This also provides a simpler API for use by extensions and Mozilla-based applications.

Newly-supported CSS features

Downloadable fonts support: The new @font-face @rule lets web pages provide downloadable fonts, so that sites can be rendered exactly as the page author expects.
CSS media queries: Firefox 3.5 now supports CSS media queries, which enhance support for media-dependent style sheets.
::before and ::after updated to CSS 2.1: The ::before and ::after pseudo-elements have been updated to full CSS 2.1 support, adding support for the position, float, list-style-*, and some display properties.
opacity: The -moz-opacity Mozilla extension to CSS has been removed in favor of the standard opacity property.
text-shadow: The text-shadow property, which allows web content to specify shadow effects to apply to text and text decorations, is now supported.
word-wrap: This newly-supported property lets content specify whether or not lines may be broken within words in order to prevent overflow when an otherwise unbreakable string is too long to fit on one line.
-moz-box-shadow
-moz-border-image
-moz-column-rule
-moz-column-rule-width
-moz-column-rule-style
-moz-column-rule-color
-moz-column-gap: Firefox 3.5 adds support for these Mozilla extensions to CSS.
The -moz-nativehyperlinktext color value: This new color value represents the user's system's default hyperlink color.
The new -moz-window-shadow and -moz-system-metric(mac-graphite-theme) properties: These new CSS properties were added to facilitate theming.
New values for -moz-appearance: The -moz-win-glass and -moz-mac-unified-toolbar values have been added to -moz-appearance.
Using CSS transforms: Firefox 3.5 supports CSS transforms. See -moz-transform and -moz-transform-origin for details.
:nth-child
:nth-last-child
:nth-of-type
:nth-last-of-type
:first-of-type
:last-of-type
:only-of-type: These selectors are all newly-supported in Firefox 3.5.

New DOM features

Using DOM workers: Firefox 3.5 supports DOM workers to allow easy multi-threading support in web applications.
Using geolocation: Firefox 3.5 supports the Geolocation API, which allows web applications to obtain information about the user's current location if a provider for that information is installed and enabled.
Using JSON in Firefox: Support for JSON is now integrated into the DOM.
Locating DOM elements using selectors: The selectors API allows querying a document to locate the elements that match a given selection rule.
The NodeIterator object: The NodeIterator object provides support for iterating over the list of the nodes in a DOM subtree.
The MozAfterPaint event: This new DOM event is sent after painting updates in windows.
The MozMousePixelScroll event: This new DOM event allows detection of pixel-based mouse scroll wheel events instead of line-based scroll events.

New JavaScript features

Object.getPrototypeOf(): This new method returns the prototype of a specified object.
New trim methods on the String object: The String object now has trim(), trimLeft(), and trimRight() methods.

Networking

Cross-site access controls for HTTP: In Firefox 3.5, it's now possible for HTTP requests, including those made by XMLHttpRequest, to work across domains if the server supports it.
Progress events for XMLHttpRequest: Progress events are now offered to enable extensions to monitor the progress of requests.
Improved Synchronous XMLHttpRequest support: DOM Timeout and Input Events are now suppressed during a synchronous XMLHttpRequest.
Controlling DNS prefetching: Firefox 3.5 provides DNS prefetching, whereby it performs domain name resolution ahead of time for links included in the current page, in order to save time when links are actually clicked. This article describes how you can tune your web site to disable prefetching, or to adjust how prefetching operates.

New Canvas features

HTML 5 text API for canvas elements: Canvas elements now support the HTML 5 text API.
Shadow effects in a canvas: Canvas shadow effects are now supported.
moz-opaque attribute: Added the moz-opaque DOM attribute, which lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized.

New SVG features

Applying SVG effects to HTML content: You can now apply SVG effects to HTML and XHTML content; this article describes how.

Miscellaneous new features

ICC color correction in Firefox: Firefox 3.5 now supports ICC color correction for tagged images.
The defer attribute is now supported on script elements: This attribute indicates to the browser that it may choose to continue to parse and render the page without waiting for the script to finish executing.

Other improvements

The ch unit can now be used anywhere that accepts a unit of length; "1 ch" is the width of the "0" character.
The white-space property now accepts the pre-line value.
The Text node's wholeText property and replaceWholeText() method have been implemented.
The property element.children has been added. It returns a collection of child elements of the given element.
The Element Traversal API is now supported by the DOM Element object.
HTML nodes may now be cloned using cloneNode().
Dispatched DOM events can now be re-dispatched. This makes Firefox 3.5 pass Acid 3 test 30.
Improvements have been made to DOM 2 Range handling.
In non-chrome scope, caught objects in exceptions are now the actual thrown object instead of an XPConnect wrapper containing the thrown object.
SVG ID references are now live.
SVG filters now work for foreignObject.
The GetSVGDocument() method has been added to object and iframe elements for compatibility.

For XUL and add-on developers

If you're an extension developer, you should start by reading Updating extensions for Firefox 3.5, which offers a helpful overview of what changes may affect your extension.

New components and functionality

Supporting private browsing mode: Firefox 3.5 offers Private Browsing mode, which doesn't record the user's activities. Extensions may support private browsing following the guidelines offered by this article.
Security changes in Firefox 3.5: This article covers security-related changes in Firefox 3.5.
Theme changes in Firefox 3.5: This article covers theme-related changes in Firefox 3.5.

PHP Warning: Cannot modify header information - headers already sent by (output ...)

2009-04-06T12:18:00.000+05:30

Error Message from your Apache while browsing PHP page.
PHP Warning: Cannot modify header information - headers already sent by (output ...)

There can be only one reason for this kind of error.

Possibly you are trying to change the header of the page. But, you might have printed something before changing the header. For example the below code will give the error to you.


//See you output to browser before printing header
echo "hello... php...";
// printing your header
header("Location: index.php");

There are lots of hosting where you'll not see this kinds of error. Cause probably they have some configuration to handle this issue. But still its a good practice to not follow dirty coding like above.

Not only the Location header, it can be anything. What you can do, if you are sure, then just print all the headers at the top of the php script. This will help you to avoid the error. For example


// printing your header
header("Location: index.php");
//See you output to browser is after printing header
echo "hello... php...";

But the problem is, there can be lots of if and else conditions inside your php script. Depending upon the if else blocks, you need to change the http headers. That case above solution won't work. What you can do is, just use the output buffering technique.

Put the below code at the top of your PHP script to start the output buffering.

ob_start();

And but the below code at the bottom of the php script to flush the buffer.

ob_end_flush();

This way, whatever you are doing inside your php script, won't see this kind of weird error again.

Refer : http://in.php.net/ob_start & http://in.php.net/ob_flush

More security for your form

2009-04-01T16:43:00.000+05:30

Do you want a little more security in your form? Well, there is a tag that you can use to turn off the autocomplete feature in browsers, which keeps users from being able to store private information such as passwords or credit card numbers. This is useful if you are a web developer trying to create a more secure site, or a business trying to keep your users from saving their password on a public computer.

[input type="text" name="password" autocomplete="off"]

PHP and cURL

2009-03-30T11:05:00.000+05:30

cURL or Client URL Library is a very powerful tool, and its something that i recently had to use.

PHP supports libcurl, a library created by Daniel Stenberg, that allows you to connect and communicate to many different types of servers with many different types of protocols. libcurl currently supports the http, https, ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with PHP’s ftp extension), HTTP form based upload, proxies, cookies, and user+password authentication.

These functions have been added in PHP 4.0.2.

You can interact with most APIs using cURL, at first it seams intimidating but once you start to use it you become comfortable with the set up.

Lets get started by parsing an RSS feed.

$ch = curl_init();

	$ch = curl_init();

curl_init() initializes a new session and return a cURL handle for use with the curl_setopt(), curl_exec(), and curl_close() functions. We set $ch with the curl_init() function to get things rolling.

curl_setopt($ch, CURLOPT_URL, $feed);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt ($ch, CURLOPT_USERAGENT, $useragent);

	curl_setopt($ch, CURLOPT_URL, $feed); 	curl_setopt($ch, CURLOPT_HEADER, 0); 	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 	curl_setopt ($ch, CURLOPT_USERAGENT, $useragent);

Just like the name says, curl_setopt() will set an option on the given cURL session handle. There are far to many to list so you are better off reading the manual found here. In our example we are going to need to access a URL and bring back the data.

CURLOPT_URL - This will be the location of the RSS file.
CURLOPT_HEADER - We set this to 0 or false as we do not want to see the header information.
CURLOPT_RETURNTRANSFER - This will transfer the data back as a string instead of outputting directly to the browser.
CURLOPT_USERAGENT - While this is not needed, The contents of the “User-Agent: ” header to be used in a HTTP request.

$rss = curl_exec($ch);
curl_close($ch);

	$rss = curl_exec($ch); 	curl_close($ch);

Once we have our options set the next step is to execute them using curl_exec(), we will asign $rss to curl_exec() thus giving the variable the contents of our look up.

For good measure we close the connection using the curl_close() function.

Since we know RSS feeds are made of XML we can goa head and do some simple parsing of my XML.

// Manipulate string into object
$rss = simplexml_load_string($rss);

	// Manipulate string into object 	$rss = simplexml_load_string($rss);

simplexml_load_string() is available in PHP 5.1.0 and on and will take a well-formed XML string and returns it as an object. This makes it easy for us to work with.

Since my goal was to introduce you to cURL i’m not going to go into much detail with the XML parsing. we have set an array on the variable $rss, i usually use Print_r($rss) to see the structure of the array before i work with it, this makes it easy to work with.

$cnt = count($rss->channel->item);
for($i=0; $i<$cnt; $i++)
{
$url = $rss->channel->item[$i]->link;
$title = $rss->channel->item[$i]->title;
$desc = $rss->channel->item[$i]->description;
echo '
.$url.'">'.$title.'
'.$desc.'';
}

	$cnt = count($rss->channel->item);  	for($i=0; $i<$cnt; $i++) 	{ 		$url = $rss->channel->item[$i]->link; 		$title = $rss->channel->item[$i]->title; 		$desc = $rss->channel->item[$i]->description; 		echo ''.$title.'
'.$desc.''; 	}

The above code is counting the number of items and looping through them one at a time printing the data to the screen, not real magic here.

Below is the complete source code for your coding pleasure.

Function feedMe($feed) {
// Use cURL to fetch text
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $feed);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt ($ch, CURLOPT_USERAGENT, $useragent);
$rss = curl_exec($ch);
curl_close($ch);
// Manipulate string into object
$rss = simplexml_load_string($rss);
$siteTitle = $rss->channel->title;
echo "
".$siteTitle."
";
echo "";
$cnt = count($rss->channel->item);
for($i=0; $i<$cnt; $i++)
{
$url = $rss->channel->item[$i]->link;
$title = $rss->channel->item[$i]->title;
$desc = $rss->channel->item[$i]->description;
echo '
.$url.'">'.$title.'
'.$desc.'';
}
}
feedMe("Yourfeed link here");

Function feedMe($feed) { 	// Use cURL to fetch text 	$ch = curl_init(); 	curl_setopt($ch, CURLOPT_URL, $feed); 	curl_setopt($ch, CURLOPT_HEADER, 0); 	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 	curl_setopt ($ch, CURLOPT_USERAGENT, $useragent); 	$rss = curl_exec($ch); 	curl_close($ch);  	// Manipulate string into object 	$rss = simplexml_load_string($rss);  	$siteTitle = $rss->channel->title; 	echo "".$siteTitle."
"; 	echo "
";  	$cnt = count($rss->channel->item);  	for($i=0; $i<$cnt; $i++) 	{ 		$url = $rss->channel->item[$i]->link; 		$title = $rss->channel->item[$i]->title; 		$desc = $rss->channel->item[$i]->description; 		echo ''.$title.'
'.$desc.''; 	} }  feedMe("http://www.studiolounge.net/feed/rss/");

cURL is a powerful tool, you can interact with APIs as well as sites or services that don’t have an AIL like Google Analytics. So play with it, make a twitter feed parser :)

How to check weather mod_rewrite module is enabled or not?

2009-03-30T10:52:00.000+05:30

Well there are lots of technique to check this but I’ll show you a very simple technique to check weather mod_rewrite module is enabled or not in you web server.

1) Type in a php file and save it and run that file in the server.
2) And now you can the list of information, just search the word “mod_rewrite” from the browser’s search menu
3) If it is found under the “Loaded Modules” section then this module is already loaded as you see in the picture, otherwise you need to go to the next step for enabling mod_rewrite module.

How to enable mod_rewrite module in apache in xampp, wamp?

Now, I’ll show you how to enable how to mod_rewrite module in apache installed under windows environment.
1) Find the “httpd.conf” file under the “conf” folder inside the Apache’s installation folder.
2) Find the following line “#LoadModule rewrite_module modules/mod_rewrite.so” in the “httpd.conf” file.You can do this easily by searching the keyword “mod_rewrite” from find menu.
3) Remove the “#” at the starting of the line, “#” represents that line is commented.
4) Now restart the apache server.
5) You can see now “mod_rewrite” in the Loaded Module section while doing “phpinfo()”.

function : recognize the url and email in text and replace with url link and mailto

2008-12-01T14:20:00.000+05:30

function fnTransformUrl($strText)

{

// convert onkar.tibe@gmail.com into

// onkar.tibe@gmail.com

$strText = ereg_replace('[-a-z0-9!#$%&\'*+/=?^_`{|}~.]+@([.]?[a-zA-Z0-9_/-])*','\\0',$strText);

// convert http://www.justmeans.com into

// www.justmeans.com

$strText = ereg_replace('[a-zA-Z]+://(([.]?[a-zA-Z0-9?=&%_/-?&%])*)','\\1',$strText);

// convert http://www.justmeans.com into

//http://www.justmeans.com

$strText = ereg_replace('(^| )(www([-]*[.]?[a-zA-Z0-9?=&%_/-])*)',' \\2',$strText);

return $strText;

}

Union vs Union All

2008-11-27T16:36:00.000+05:30

Union is used to select distinct values from two tables
where as

Union All is used to select all values including
duplicates from the tables

both UNION ALL and UNION distinct use temporary table for result generation.

The difference in execution speed comes from the fact UNION requires internal temporary table with index (to skip duplicate rows) while UNION ALL will create table without such index.

Interesting enough the fact UNION and UNION ALL require temporary table can only be seen in SHOW STATUS - EXPLAIN does not want to tell you this shameful fact.

In fact EXPLAIN output is the same for UNION and UNION ALL

Q: is UNION ALL indeed faster than UNION DISTINCT (the UNION is shortcut for UNION DISTINCT) ?

A: yes it is.

Union vs. Union All

In simple we can say that
1. union is used to select distinct values from two
tables,where as union all is used to select all values
including duplicates from the tables.

2. The UNION operator allows you to combine the results of
two or more SELECT statements into a single result set. The
result sets combined using UNION must all have the same
structure. They must have the same number of columns, and
the corresponding result set columns must have compatible
data types.By default, the UNION operator removes duplicate
rows from the result set. If you use UNION ALL, all rows
are included in the results and duplicates are not removed.

__Onkar

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linkedin API.... Exploring Frustration Discovering Satisfaction

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Web Scalability and Performance

canonical URL

Really a class analogy...

Useful Linux Commands

New developer features in Firefox 3.5

For web site and application developers

HTML 5 support

Newly-supported CSS features

New DOM features

New JavaScript features

Networking

New Canvas features

New SVG features

Miscellaneous new features

Other improvements

For XUL and add-on developers

New components and functionality

PHP Warning: Cannot modify header information - headers already sent by (output ...)

More security for your form

PHP and cURL

.$url.'">'.$title.'

'.$title.'

".$siteTitle."

.$url.'">'.$title.'

".$siteTitle."

'.$title.'

How to check weather mod_rewrite module is enabled or not?

function : recognize the url and email in text and replace with url link and mailto

Union vs Union All