vi Editor Commands

The VI editor is a screen-based editor used by many Unix users. The VI editor has powerful features to aid programmers, but many beginning users avoid using VI because the different features overwhelm them.

General startup
        To use vi: vi
        To exit vi and save changes: ZZ or :wq
        To exit vi without saving changes: :q!
        To enter vi command mode: [esc]
        Read the original file back in so that you can start over.: :e!


Counts
        A number preceding any vi command tells vi to repeat that command that many times.

Deleting
        x       delete character under cursor
        X       delete character before cursor
        dd      delete line under cursor
        dw      delete word under cursor
        db      delete word before cursor
        D       delete to the end of line from the current cursor position
        d^      delete from current cursor position to the beginning of the line
        d$      delete from current cursor position to the end of the line

Copy/Paste Text
        yy     copies line
        P      paste copied data before cursor
        p      paste copied data after cursor

Find Commands
        ?       finds a word going backwards
        /       finds a word going forwards
        f       finds a character on the line under the cursor going forward
        F       finds a character on the line under the cursor going backwards
        t       find a character on the current line going forward and stop one character before it
        T       find a character on the current line going backward and stop one character before it
        ;       repeat last f, F, t, T
        ,       repeat last f, F, t, T going backwards
        n       repeat last search given by ‘/’ or ‘?’
        N       repeat last search given by ‘/’ or ‘?’ going backwards

Miscellaneous Commands
        .       repeat last command
        u       undoes last command issued
        U       undoes all commands on one line
        xp      deletes first character and inserts after second (swap)
        J       join current line with the next line
        ^G      display current line number
        %       if at one parenthesis, will jump to its mate
        mx      mark current line with character x
        'x      find line marked with character x
        ^^      Go back to last file 

READING/WRITING FILES
        :r filename    Copies filename after cursor in file currently editing
        :n      Start editing next file in list
        :rew    rewind file list, start editing 1st file on argument list
        :w      Saves the current file without quitting

MOVING
        :#      Move to line #
        :$      Move to last line of file


Character/Line Formatting
        ~      Switch the case of the character under cursor
        <      Shifts the line upto where to the left by one shiftwidth
        <<     Shifts the current line to the left, and can be specified with a count
        >      Shifts the line upto where to the right by one shiftwidth
        >>     Shifts the current line to the right, and can be specified with a count
        J      Join the current line with the next one.

SHELL ESCAPE
        :!'CMD'      Executes CMD as a shell command
        :!sh         Fork shell in vi; hit ctrl-d to go back to vi

INSERTING
        r      replace character under cursor with next character typed
        R      keep replacing character until [esc] is hit
        i      insert before cursor
        I      insert from the beginning of line
        a      append after cursor
        A      append at end of line
        o      open line below cursor and enter append mode
        O      open line above cursor and enter append mode
        c      change until . "cc" changes the current line
        C      change to the end of line from the current cursor position
        s      substitute one character under the cursor and go into insert mode
        S      change an entire line


Screen Movement
        G      move to the last line in the file
        xG     move to line x
        z+     move current line to top of screen
        z      move current line to the middle of screen
        z-     move current line to the bottom of screen
        ^F     move forward one screen
        ^B     move backward one line
        ^D     move forward one half screen
        ^U     move backward one half screen
        ^R     redraw screen (does not work with vt100 type terminals)
        ^L     redraw screen (does not work with Televideo terminals)

Cursor Movement
        h      move left
        j      move down
        k      move up
        l      move right
        [return]    move to the beginning of next line
        $      last column on the current line
        0      move cursor to the first column on the current line
        ^      move cursor to the first nonblank column on the current line
        w      move to the beginning of the previous word or punctuation
        W      move past the next space
        b      move to the beginning of the previous word or punctuation mark
        B      move to the beginning of the previous word, ignores punctuation
        e      end of next word or punctuation mark
        E      end of next word, ignoring punctuation
        H      move cursor to the top of the screen
        M      move cursor to the middle of the screen
        L      move cursor to the bottom of the screen
        ^H     move cursor one space to the left
        ^J     move cursor down one line in same column
        ^M     move to the first character on the next line
        ^N     move cursor down one line in same column
        ^P     move cursor up one line in same column
        %      move cursor to the matching parenthesis or brace
        (      move cursor to the beginning of a sentence
        )      move cursor to the beginning of the next sentence
        {      move cursor to the preceding paragraph
        }      move cursor to the next paragraph
        |      move cursor to the column specified by the count
        +      move cursor to the first non-whitespace character in the next line
        -      move cursor to the first non-whitespace character in the previous line
        _      move cursor to the first non-whitespace character in the current line

Finding bugs in the application

A QA engineer always thinks of a bug in the application and always try to find them. Finding bugs in any application is really a challenging work and if you find bugs, it gives you the satisfaction of your job. Below are few tips by which you can find bugs in the application:


1. Understand the application/module in depth before starting the testing
2. Prepare good functional test cases before starting the testing.
3. Create all possible type of test data before testing.
4. Test the system in different environments.
5. When you tired or bored by testing same module or application, do MONKEY TESTING, really it works. I tried it many times and got good bugs :)
6. Try some standard test cases for which you found the bugs in some different application.
7. Test the application with dedication and passion.
8. Think alike of different users while testing the application.


Doing QA is like being a goalkeeper. You can make a hundred brilliant saves but the only shot that people remember is the one that gets past you.

Read properties from ant build file using perl

I want to read some properties from my ant build file in my perl script. I wrote a sample perl script for it. below is the script:

Check all arguments of a running process

Many Java processes have long command lines, and as as a regular user, I may wish to determine that my java processes are running with the correct arguments or not.
unfortunately with the ps (/usr/bin/ps) command, users can only see the first 80 characters of command line, rest are ignored. So the user can not see the all command line arguments.

Solution:
1. Use pargs argument (ex. ps -eaf | pargs -a <pid>)
or
2. Use /usr/ucb/ps command ( /usr/ucb/ps -awwx | grep <pid>)

What version of Flash do you have?

Visit following link to display the currently installed version of the Flash player.

www.adobe.com/products/flash/about

http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_15507

Kill java processes from perl script

Requirement:- If multiple java processes are running on your system and you want to kill only few specific from them.
If we do it manually then we have to perform below two steps:

1. jps (it will return all the java processes running on the system) in below format:
<pid>     <process name>
<pid>     <process name>
<pid>     <process name>
<pid>     <process name>
...

in my case i got the below output from above command:

1234 Server1
1334 Server2
1454 Server3
1264 Server4
1238 Server5
1244 Server6

2. now i have the process id of all the java processes so i can kill them using kill command, (let say if i have to kill only Server1, Server5 , then)

kill -9 1234
kill -9 1238

By using perl script, i can write below simple script which will do my above task:

foreach $_ (`jps`) {
my($pid,$pname) = /(\S+)\s+(.*)/;
if($pname eq "Server1" | $pname eq "Server5" ) {
print("Killing Process : $pname ($pid) \n");
system("kill -9 $pid");
}
}

Searching tips in Google

1. Explicit Phrase: Lets say you are looking for content about internet marketing. Instead of just typing internet marketing into the Google search box, you will likely be better off searching explicitly for the phrase. To do this, simply enclose the search phrase within double quotes.

Example: “internet marketing”

2. Exclude Words: Lets say you want to search for content about internet marketing, but you want to exclude any results that contain the term advertising. To do this, simply use the “-“ sign in front of the word you want to exclude.

Example Search: internet marketing -advertising

3. Site Specific Search: Often, you want to search a specific website for content that matches a certain phrase. Even if the site doesn’t support a built-in search feature, you can use Google to search the site for your term. Simply use the “site:somesite.com” modifier.

Example: “internet marketing” site:www.smallbusinesshub.com

4. Similar Words and Synonyms: Let’s say you want to include a word in your search, but want to include results that contain similar words or synonyms. To do this, use the “~” in front of the word.

Example: “internet marketing” ~professional

5. Specific Document Types: If you’re looking to find results that are of a specific type, you can use the modifier “filetype:”. For example, you might want to find only PowerPoint presentations related to internet marketing.

Example: “internet marketing” filetype:ppt

6. This OR That: By default, when you do a search, Google will include all the terms specified in the search. If you are looking for any one of one or more terms to match, then you can use the OR operator. (Note: The OR has to be capitalized).

Example: internet marketing OR advertising

7. Phone Listing: Let’s say someone calls you on your mobile number and you don’t know how it is. If all you have is a phone number, you can look it up on Google using the phonebook feature.

Example: phonebook:617-555-1212 (note: the provided number does not work – you’ll have to use a real number to get any results).

8. Area Code Lookup: If all you need to do is to look-up the area code for a phone number, just enter the 3-digit area code and Google will tell you where it’s from.

Example: 617

9. Numeric Ranges: This is a rarely used, but highly useful tip. Let’s say you want to find results that contain any of a range of numbers. You can do this by using the X..Y modifier (in case this is hard to read, what’s between the X and Y are two periods. This type of search is useful for years (as shown below), prices or anywhere where you want to provide a series of numbers.

Example: president 1940..1950

10. Stock (Ticker Symbol): Just enter a valid ticker symbol as your search term and Google will give you the current financials and a quick thumb-nail chart for the stock.

Example: GOOG

11. Calculator: The next time you need to do a quick calculation, instead of bringing up the Calculator applet, you can just type your expression in to Google.

Example: 48512 * 1.02

12. Conversion: The next time you need to do a quick calculation on the temperature, you can just type your expression in to Google.

Example: 72F in C

The conversion feature works for a whole host of things: "100cm in inches", "100us gallons in uk gallons", "100bar in psi", "100 GBP in USD", etc.

13. Word Definitions: If you need to quickly look up the definition of a word or phrase, simply use the “define:” command.

Example: define:plethora

14. Searching for URLs containing certain words. Use the "inurl:word" modifier.

Example site:i-hack.org inurl:psp

Find Nth Max salary of employee

I have following table in the DB

Create table Employee
(
Eid int,
Name varchar(10),
Salary money
)

insert few values in the table:

Insert into Employee values (1,\'harry\',3500)
Insert into Employee values (2,\'jack\',2500)
Insert into Employee values (3,\'john\',2500)
Insert into Employee values (4,\'xavier\',5500)
Insert into Employee values (5,\'steven\',7500)
Insert into Employee values (6,\'susana\',2400)


A simple query that can find the employee with the maximum salary, would be:

Select * from Employee where salary = (Select max(Salary) from Employee)

[The SQL Engine evaluates the inner most query and then moves to the next level (outer query). So, in the above example inner query i.e. Select max(Salary) from Employee is evaluated first. This query will return a value of 7500 (based on the sample data shown as above). This value is substituted in the outer query and it is evaluated as: ]

Select * from Employee where salary = (7500)
Returns:

Eid Name Salary
5 steven 7500

If the same syntax is applied to find out the 2nd or 3rd or 4th level of salary, the query would become bit complex to understand. See the example below:

Select * from Employee where salary =
(Select max(Salary) from Employee where salary
< (Select max(Salary) from Employee where
Salary < (Select max(Salary) from Employee where
Salary < …………………………………………… N

The above query would go on and on, depending on the level of salary that is to be determined. As mentioned earlier, the SQL Engine evaluates the inner most query first and moves the next outer level. One wouldn’t want to write such a big query just to find out this simple information.

The same result can be achieved with a simple syntax and easily understandable logic, by using a CORRELATED SUBQUERY. Correlated sub-query is a performance overhead to the database server and so, you have to use it only if it is required. Avoid using Correlated subquery on large tables, as the inner query is evaluated for each row of the outer query

Following is the query that captures the Nth maximum value:

Select * From Employee E1 Where
(N-1) = (Select Count(Distinct(E2.Salary)) From Employee E2 Where
E2.Salary > E1.Salary)
(Where N is the level of Salary to be determined)

In the above example, the inner query uses a value of the outer query in its filter condition meaning; the inner query cannot be evaluated before evaluating the outer query. So each row in the outer query is evaluated first and the inner query is run for that row. Let’s look into the background process of this query, by substituting a value for N i.e. 4,(Idea is to find the 4th maximum salary):

Select * From Employee E1 Where
(4-1) = (Select Count(Distinct(E2.Salary)) From Employee E2 Where
E2.Salary > E1.Salary)

Since the outer query’s value is referred in the inner query, the operation is done row-by-row. Based on the sample data as shown above, the process starts with the following record:

Employee E1
----------------------------------
Eid Name Salary
1 harry 3500
The salary of this record is substituted in the inner query and evaluated as:

Select Count(Distinct(E2.Salary)) From Employee E2
Where E2.Salary > 3500
Above query returns 2 (as there are only 2 salaries greater than 3500). This value is substituted in the outer query and will be evaluated as:

Select * From Employee E1 Where (4-1) = (2)
condition evaluates to FALSE and so, this record is NOT fetched in the result.

Next the SQL Engine processes the 2nd record which is:

Employee E1
----------------------------------
Eid Name Salary
2 jack 2500
Now the inner query is evaluated as:

Select Count(Distinct(E2.Salary)) From Employee E2
Where E2.Salary > 2500
This query returns a value of 3 (as there are 3 salaries greater than 2500). The value is substituted in the outer query and evaluated as:

Select * From Employee E1 Where (4-1) = (3)
condition evaluates to TRUE and so, this record is fetched in the result. This operation continues for all the remaining records. Finally the result shows these 2 records:

Eid Name Salary
2 jack 2500
3 john 2500

Exponential(TM) Identifies Top Online Advertising Trends For 2008

Exponential(TM) Interactive, Inc., the technology-driven media services company that delivers innovative products and services to meet the demands of advertisers and publishers, today announced online advertising trends for 2008. The parent company of Tribal Fusion, one of the industry's leading online ad networks, Exponential has identified top trends emerging from technology and business innovation, creativity and brand measurement. Trends to watch include: one-to-one marketing, online video advertising, new local advertising platforms, innovation in ad effectiveness measures, marketing opportunities from the semantic web, and virtual worlds.

Read Full Article here

GNU Screen utility

Screen, this command might not be well known to many people 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 it and use 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 -S vishnu) Create a screen session with the name vishnu
(screen -r vishnu) reconnect to the session with the name vishnu
(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
(Ctrl+a :escape ^Ww) Change key binding to w character
(Ctrl-a * ) List all currently attached displays. (displays)
(Ctrl-a Ctrl\) Kill all windows and terminate screen. (quit)
(Ctrl-a w ) List all windows. (windows)
(Ctrl-a h ) Write contents of the current window to the file hardcopy.n. (hardcopy)
(Ctrl-a H ) Begin/end logging of the current window to the file screenlog.n. (log)
(Ctrl-a ' ) Prompt for window name or number to switch to. (select)