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Testing Articles

vishnuagrawal — Sun, 14 Oct 2007 15:27:51 +0000

Screen command

vishnuagrawal — Sun, 14 Oct 2007 15:17:17 +0000

Screen, this command might not be well known to many people but but its one of those programs that you just can’t stop using once you’ve started. Previously I used VNC to connect the remote servers, but now i have stopped using VNC. Now I am using SCREEN on a regular daily basis and it’s really easy to use.

Screen program provides the following functionality:

Remote terminal session management (detaching or sharing terminal sessions)
Unlimited windows (unlike the hardcoded number of Linux virtual consoles)
Scrollback buffer (not limited to video memory like Linux virtual consoles)
Copy/paste between windows
Split terminal (horizontally) into multiple regions
Locking other users out of terminal
Screen is an easy way to allow processes to continue running after the session is terminated, if you lose connection screen will save your spot

Following is the content of my ~/.screenrc file
************************************************************
startup_message off
vbell off
caption always “%{= bb}%{+b w}%n %h %=%t %c”
hardstatus alwayslastline “%-Lw%{= BW}%50>%n%f* %t%{-}%+Lw%<”
activity “Activity in %t(%n)”
shell -/bin/bash
************************************************************
Screen Commands

screen Start screen

screen -x Connect to an existing screen session

screen -d detaching a screen session

screen -r reattaching the screen session

Ctrl+a c New window

Ctrl+a n Next Window

Ctrl+a p Previous Window

Ctrl+a ” Select window from list

Ctrl+a Ctrl+a Previous window viewed

Ctrl+a <0-9> Select the numbered window

Ctrl+a A Set window title

Ctrl+a K Kill window

Ctrl+a d Detach screen from terminal

Ctrl+a x Lock Session

Ctrl+a : Goto screen command prompt

Ctrl+a ? Show key binding/command names

Ctrl+s Pause the output on screen

Ctrl+q Resume the output on screen

Is it the Chak De India effect?

vishnuagrawal — Sun, 30 Sep 2007 17:03:29 +0000

First Indian football team won Nehru Cup, then Indian Hockey Team won the Asia cup and then it was the turn of Indian cricket team, They won the 20-20 World cup and then Vishwanathan Anand became the World Chess champion. All these 4 big events happened in just in a span of almost one month. Isn’t it the CHAK DE INDIA effect?

August 29, 2007 – Football Nehru Cup, India never reached finals of Nehru cup before, and this time they won this title be defeating Syria by 1-0.

September 9, 2007 – Hockey Asia Cup, India started this tournament with a win of 1-0 on China. Later, India played at its best while thrashing Sri Lanka with 20-0, Thailand with 16-0. In final, they performed superbly and won the title by defeating Korea with 7-2. India ended the tournament with 57 goals and just 5 goals against them without a single defeat. Isn’t it unbelievable?

September 24, 2007 – Cricket 20-20 World Cup, I am a big fan of cricket but due to poor performance of India since last year, i lost interest in cricket and when India was out from ODI world cup 2007 in the first round, i just stopped the watching Indian cricket matches, i thought its very hard for Indian cricket team to come back. But the Indian cricket team proved me (and of course others also) wrong very soon. In 20-20 world cup, they were playing like champions, Sometimes luck also favored them and they WON the 20-20 world cup. They won this title by defeating Pakistan, South Africa, England and our world champion Australia.

September 30, 2007 – Vishwanathan Anand became the World Chess champion, after winning the global tournament in Mexico.

All this happened just after CHAK DE INDIA was released, I think that all the teams must have followed what SRK told in the movie.
“Play for India first, then for the team, if anything is still left then play for yourself”

I hope India will continue this Chak De India effect.

CHAK DE INDIA!………

Linux Cut command

vishnuagrawal — Sun, 09 Sep 2007 17:19:00 +0000

Cut Command
————

Divide a file into several parts (columns)

syntax:
cut [-b] [-c] [-f] list [-n] [-d delim] [-s] [file]

Examples:
——–

1. Let say you have a file test.txt which has colon(:) seperated data

406378:Sales:Itorre:Jan
031762:Marketing:Nasium:Jim
636496:Research:Ancholie:Mel
396082:Sales:Jucacion:Ed

If you want to print first set of data from each row, you can use cut command as follow:

cut -d”:” -f1 test.txt

If you want to print just columns 1 to 6 of each line (the employee serial numbers), use the -c1-6 flag, as in this command

cut -c1-6 test.txt

Linux Tips

vishnuagrawal — Sun, 09 Sep 2007 17:12:00 +0000

Display the top most process utilizing most CPU (top -b 1)
Show the working directory of a process ? (pwdx pid )
Display the parent/child tree of a process ? (ptree pid )
Display the no.of active established connections to localhost ? (netstat -a | grep EST)
How to create null file ? (cat /dev/null > filename1)
Display top ten largest files/directories ? (du -sk * | sort -nr | head)
Display disk usage (du -h)
How to save man pages to a file ? (man | col -b > filename )
Display the files in the directory by file size ? (ls -ltr | sort -nr -k 5)
Display the processes, which are running under yourusername ( ps -aef | grep username)
Display the all files recursively with path under current directory ? ( find . -depth -print)
Display the Disk Usage of file sizes under each directory in currentDirectory ? (du -k . | sort -nr)
List the files in current directory sorted by size ? (ls -l | grep ^- | sort -nr)

Soalris: Kill a process which is using a particular port number

vishnuagrawal — Wed, 05 Sep 2007 11:30:00 +0000

Today i came across a problem in solaris. The problem was that while starting my application server, it was throwing an error “Address already in use”.

My app server is a java process and there are many other java process which are running on my zone. But the issue is, how may i know that which java process is using that particular port?

I followed following steps:
1. List all the java process running on my zone ( ps -eaf |grep vagrawal| grep java )
2. Go through each java process and check if it using that particular port ( pfiles $pid|grep 1182 )
(here $pid is the process id of the java process and 1182 is the port number of which i am looking for)

Above method works fine but it is bit a long process, as i have to run step 2 for all java processes, so i ran a folowing command on my console:

for pid in `ps -eaf|grep vagrawal|grep java|grep -v grep|awk -F” ” ‘{print $2}’`; do echo ================= $pid >>myfile; pfiles $pid|grep 1182 >>myfile; done

above loop goes through all the java process and write there process IDs in the file ‘myfile’, and i am also checking usage of my port for that particular process (using pfiles) and prints its output in same file.

Finally there would be a single process which would be using that particular port. Now I can find easily that process in ‘myfile’

Now i have process ID of the process which is occupying my port, and i can kill that by kill -9 pid

Puzzle links

vishnuagrawal — Wed, 02 May 2007 12:51:00 +0000

http://puzzles-tricks.blogspot.com/

http://www.brainvista.com/bv/index.php

http://www.allinterview.com/Interview-Questions/Puzzles.html

http://www.techinterview.org/index.html

Limitation of Junit

vishnuagrawal — Mon, 30 Apr 2007 10:30:00 +0000

Tests that verify the integrity of a small unit are useful but limited. Experience has taught us that most bugs are found in the integration phase. These problems range from two modules that fail to work together, all the way to two separate applications that are acting up. Whether it is two application servers, a client/server environment, or even a peer-to-peer scenario, it is highly important to test these complex scenarios because of the tricky bugs that can be found in them. But it is nearly impossible to do so with JUnit.

Although Java is platform-independent, it is wise to check an application on more than one operating system. Your application may work very well on all operating systems, but it may not function exactly the way you expect it to work on some of them. Running the same set of tests over and over again for every OS is time-consuming, and with JUnit you cannot perform distributed tests, so you don’t have a way to run the same series of tests simultaneously on several JVMs each running on different OSes.

Some units of code can only be tested in a multiple-JVM scenario. For example, testing the opening of a connection (TCP socket or HTTP connection) and the integrity of the information retrieved from it is not possible (or very hard) to test with only one JVM, which is the only option that exists with JUnit.

JUnit was designed to have all tests run within a single process within a single class. It is also designed with the constraint that all tests are atomic and independent of any other code outside the test being run and that the lifecycle for these tests are independent for each test. This is all great for testing low level units of code, but not for client/server scenario tests.

Special Shell Script Variables

vishnuagrawal — Mon, 30 Apr 2007 09:05:00 +0000

There are some variables which are set internally by the shell and which are available to the user:

$1 - $9   These variables are the positional parameters.

$0        The name of the command currently being executed.

$#        The number of positional arguments given to this invocation of the shell.

$?        The exit status of the last command executed is given as a decimal string.        When a command completes successfully, it returns the exit status of 0        (zero), otherwise it returns a non-zero exit status.

$$        The process number of this shell - useful for including in filenames, to        make them unique.

$!        The process id of the last command run in the background.

$-        The current options supplied to this invocation of the shell.

$*        A string containing all the arguments to the shell, starting at $1.

$@@       Same as above, except when quoted.

Web Server Vs Application Server

vishnuagrawal — Fri, 27 Apr 2007 13:10:00 +0000

A Web server exclusively handles HTTP requests, whereas an application server serves business logic to application programs through any number of protocols.The Web server
A Web server handles the HTTP protocol. When the Web server receives an HTTP request, it responds with an HTTP response, such as sending back an HTML page. To process a request, a Web server may respond with a static HTML page or image, send a redirect, or delegate the dynamic response generation to some other program such as CGI scripts, JSPs (JavaServer Pages), servlets, ASPs (Active Server Pages), server-side JavaScripts, or some other server-side technology. Whatever their purpose, such server-side programs generate a response, most often in HTML, for viewing in a Web browser.

When a request comes into the Web server, the Web server simply passes the request to the program best able to handle it. The Web server doesn’t provide any functionality beyond simply providing an environment in which the server-side program can execute and pass back the generated responses. The server-side program usually provides for itself such functions as transaction processing, database connectivity, and messaging.

The application server
As for the application server, according to our definition, an application server exposes business logic to client applications through various protocols, possibly including HTTP. While a Web server mainly deals with sending HTML for display in a Web browser, an application server provides access to business logic for use by client application programs. The application program can use this logic just as it would call a method on an object (or a function in the procedural world).

Such application server clients can include GUIs (graphical user interface) running on a PC, a Web server, or even other application servers. The information traveling back and forth between an application server and its client is not restricted to simple display markup. Instead, the information is program logic. Since the logic takes the form of data and method calls and not static HTML, the client can employ the exposed business logic however it wants.

In most cases, the server exposes this business logic through a component API, such as the EJB (Enterprise JavaBean) component model found on J2EE (Java 2 Platform, Enterprise Edition) application servers. Moreover, the application server manages its own resources. Such gate-keeping duties include security, transaction processing, resource pooling, and messaging. Like a Web server, an application server may also employ various scalability and fault-tolerance techniques.

An example
As an example, consider an online store that provides real-time pricing and availability information. Most likely, the site will provide a form with which you can choose a product. When you submit your query, the site performs a lookup and returns the results embedded within an HTML page. The site may implement this functionality in numerous ways. I’ll show you one scenario that doesn’t use an application server and another that does. Seeing how these scenarios differ will help you to see the application server’s function.

Scenario 1: Web server without an application server
In the first scenario, a Web server alone provides the online store’s functionality. The Web server takes your request, then passes it to a server-side program able to handle the request. The server-side program looks up the pricing information from a database or a flat file. Once retrieved, the server-side program uses the information to formulate the HTML response, then the Web server sends it back to your Web browser.

To summarize, a Web server simply processes HTTP requests by responding with HTML pages.

Scenario 2: Web server with an application server
Scenario 2 resembles Scenario 1 in that the Web server still delegates the response generation to a script. However, you can now put the business logic for the pricing lookup onto an application server. With that change, instead of the script knowing how to look up the data and formulate a response, the script can simply call the application server’s lookup service. The script can then use the service’s result when the script generates its HTML response.

In this scenario, the application server serves the business logic for looking up a product’s pricing information. That functionality doesn’t say anything about display or how the client must use the information. Instead, the client and application server send data back and forth. When a client calls the application server’s lookup service, the service simply looks up the information and returns it to the client.

By separating the pricing logic from the HTML response-generating code, the pricing logic becomes far more reusable between applications. A second client, such as a cash register, could also call the same service as a clerk checks out a customer. In contrast, in Scenario 1 the pricing lookup service is not reusable because the information is embedded within the HTML page. To summarize, in Scenario 2′s model, the Web server handles HTTP requests by replying with an HTML page while the application server serves application logic by processing pricing and availability requests.

Caveats
Recently, XML Web services have blurred the line between application servers and Web servers. By passing an XML payload to a Web server, the Web server can now process the data and respond much as application servers have in the past.

Additionally, most application servers also contain a Web server, meaning you can consider a Web server a subset of an application server. While application servers contain Web server functionality, developers rarely deploy application servers in that capacity. Instead, when needed, they often deploy standalone Web servers in tandem with application servers. Such a separation of functionality aids performance (simple Web requests won’t impact application server performance), deployment configuration (dedicated Web servers, clustering, and so on), and allows for best-of-breed product selection.