Having a private snmp number for ones organization ..... No fee invovled

http://pen.iana.org/pen/PenApplication.page

How does one sort the files based on size in Unix ???

Again elementary but not used much

ls does not give an option to sort the files based on file sizes. (some os have -S option not sure which)

Here is a way to do it in a very generic way


bash-2.05# ls -hl /tmp/a.out /tmp/test.c |sort -k 4 -n
-rw-r--r-- 1 root other 0 Mar 30 21:41 /tmp/a.out
-rw-r--r-- 1 root other 108 Mar 29 11:49 /tmp/test.c

sort -k does the trick. So position can be any column in the output.
For more details man sort

Debugging tomcat applications using IDE's

Problem:
You have deployed your war file into tomcat. You have the source code, but you cannot innitate a DEBUG from the IDE(Eclipse or Netbeans). How does one debug?

Solution:
Run tomcat in DEBUG mode

WINDOWS
EDIT %CATALINA_HOME%/bin/catalina.bat
set JAVA_OPTS=-Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=3091,suspend=n

UNIX

EDIT $CATALINA_HOME/bin/catalina.sh
JAVA_OPTS=-Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=3091,suspend=n

Restarting tomcat will render it in debug mode listening on port 3091.

Now in your favourite IDE have the REMOTE DEBUGGING listening on port 3091.
Then the course is normal, place breakpoints in your code and trace for possible bugs.

Partitioning in postgres

Partioning is useful to drop group of data in a table in bulk. In most cases year old data is purged on a regular basis by an application. Partitions are a useful design design to manage the data.

create table master (i int);

create table slave1 ( CHECK ( i > 0 AND i <> 10 AND i <> 20 AND i < postgres="#"> 0 AND i <> 10 AND i <> 20 AND i < 30) ) inherits (master);

postgres=# insert into master values(5);
INSERT 0 1
postgres=# insert into master values(15);
INSERT 0 1
postgres=# insert into master values(25);
INSERT 0 1
postgres=# select * from master;
i
----
15
25
5
(3 rows)
postgres=# select * from slave1;
i
---
5
(1 row)
postgres=# select * from slave2;
i
---
15
(1 rows)
postgres=# select * from slave3;
i
---
25
(1 rows)

Note: Copy command of postres does not copy the rules associated with the table. So to make sure the rules are reflected, create partitions as a trigger.

Also here is an interesting thing

postgres=# update master set i=15 where i=5;
ERROR: new row for relation "slave1" violates check constraint "slave1_i_check"

This says it all

Effective JDBC

JDBC supports connection pooling, which essentially involves keeping open a cache of database connection objects and making them available for immediate use for any application that requests a connection. Instead of performing expensive network roundtrips to the database server, a connection attempt results in the re-assignment of a connection from the local cache to the application. When the application disconnects, the physical tie to the database server is not severed, but instead, the connection is placed back into the cache for immediate re-use, substantially improving data access performance.

To get more of it checkout these links
http://java.sun.com/developer/onlineTraining/Programming/JDCBook/conpool.html
http://dev.mysql.com/tech-resources/articles/connection_pooling_with_connectorj.html

From my limited research, I understand tomcat implements connection pool by default.
Here is the link taking at length about it http://www.javapractices.com/Topic75.cjp


Also during the research came up with this nice article by the Martin Fowler talking about the design decisions of allowing certain business logic in the database rather than handling them exclusively in the application software (esp things like orderby, filtering tools (WHERE,LIKE etc))
Here's the link
http://www.martinfowler.com/articles/dblogic.html

This was typically the point made by the oracle database legend Tom Kyte in the article JDBC : SQL vs PL/SQL, Which performs better



Simple anology(not entrirely a perfect analogy) ,
when we know we need to grep for say automountd process to just know the pid of the process
instead of ps -aef|grep auto
a simple ps -a -o comm,pid|grep auto
will be more effective.

This design problem is tackled at across various layers. A simple typical case is the OS, where we typically end up getting huge data( say in truss or ps output), there after prunning the processed(cpu) data using grep,awk like utilities. A tool which stops from generating the unwanted data from being generated always scores over the basic tools we use.

How to know the current process state

This one feature though trivial will be thoughly learnt on a need basis.

When we need to find out what is the current state of a process is (aka Running(R), Sleeping(S), Stopped(T),Zombie(Z) etc), we can use the ps command effectively.

Here is the basic setup
test@shantanu>more simple1.c
#include
int main()
{
int i=0;
printf("Waiting for a console output\n");
scanf("%d",&i);
return(0);
}
test@shantanu>gcc simple1.c -o simple1
test@shantanu>./simple1
Waiting for a console output
........///No input is yet given

In another terminal run
test@shantanu>ps -a -o comm -o s|grep simple1
./simple1 S

So the process is currently sleeping for my input.
All the state changes hereafter can be observed independently.

core file generation

Got to know this interesting bit today

By default in solaris core dump occurs when an application misbehaves(say segmentation fault).
But in linux the default core dumping is disabled.

Using ulimit command one can turn on this feature.

Just enable the application to core dump by
$>ulimit -c unlimited

For more on this refer to
http://www.novell.com/coolsolutions/feature/16257.html

Amazon turks now in Indian rupees

Amazon turk now renders Indian rupee transaction. Check it out
http://www.mturk.com/mturk/welcome

Sun Tech days in Hyderabad

Sun tech days from Feb 21st to 23rd. Though most of the technical community is aware of this event , please check this link to get the details. The list of talks,hands on labs, codecamps are here

Continuations in java

Continuation is an object that represents the execution state of a program at a certain point. We can use continuation to restart the execution from the point stored in it.
One area that has seen practical use of continuations is in web programming

Check out an enumeration here

Krugle - Code Search for Developers

This is a nice site for code stealing

Read more at www.krugle.com/

Crystal clear Bangalore on google map

Check this out

Now the map is much more detailed and expressive than the satellite based imagery.

How to list only directories in Unix

Well this may seem a very simple problem, but its not. So it deserves a thread for sure

Traditional method

ls -l|grep ^d

But u get the other unwanted details, incase u are automating

Slightly Sophisticated

find . -type d

But on execution u will dicern that find is recursive, so "just the" folders of the current directory are not displayed

If its getting slightly complicated try this simpler solution.

ls -l|grep ^d|awk '{print $9}'

Pretty neat.
This command works almost fine. But just in case the folder has a "space", the command fails to get the exact name of the folder.

Here is a solution which "WORKS" and is very simple

ls -p |grep /

Just an indicator of the power of the raw tools invented ages ago. KISS(Keep it Simple S......)

Google does it again

Check this out. Its out and open for people to use.

Now here are the interesting issues with it.
1) Be prepared for spams. Just try this, you will know.
2) Emotions the poor developers go through :-X . Just pick your slang, google does the rest.I just hope openSolaris is clean!!!!!!!!!!!!!!
3) Some programmers put the default password in sourcecode and Most lazy users never change the default password.This makes it easy to get the default password which can be exploited. Try this

Actually this is not a great innovation in itself. Krugle, Koders, and Codease are into this. But a gaint entering will have its own advatages.

"Good programmers write good code. Great programmers find it on Google!"

PHP sucks big time

I was trying to integrate Apache--PHP--mysql for a HR project at janagraha.

The problem is that the php documentation is very old...or I should say it works for lower versions of php and apache.

So here is a small TO-DO on how to go about integrating
1) Download Apache here. Apply your user friendly GUI knowledge of windows and get it installed.
2)Download php here.
3)Unzip in d:\php5.
4)Rename php.ini-recommended to php.ini
5)Add these lines to the top of httpd.conf
# PHP 5 Support
LoadModule php5_module "d:/php5/php5apache2_2_filter.dll"
LoadFile "d:/php5/php5ts.dll"
AddOutputFilter PHP php
PHPIniDir "d:/php5"
***Please note the locations used.
6) Finally process is over. Create a test.php.
Having say

copy to htdocs folder of apache.

7)RESTART APACHE. (hopefully no errors).
Run http://localhost/test.php

Worth a try though

Google Releases Tesseract as Open Source

Google recently released Tesseract as open source. Originally developed at the HP Labs from 1985-1995, it has been vouched as one of the most accurate Optical Character Recognition (OCR) programs available. You can download Tesseract here.

Checkout one possible use of this technology here

Leaving the rest to imagination....

Does machine have JAVA

My friend can up with a curious problem.

To run an applet a prerequiste is to actually check whether JRE(or JVM) is actually present on the machine. Although applet inherits the intelligence to actually point the browser to the web location.

However if the application has to be in total control then how??????

In short for Non-IE browsers then navigator.mimeTypes gets the registry values for the installed runtimes.
But alas IE does not implement mimetypes. So an activeX document to implement the same.


Here is a small snippet of the code written in javascript.


if(navigator.mimeTypes) {
//For non-IE browsers
for (i=0; i < navigator.mimeTypes.length; i++) {
if( (navigator.mimeTypes[ i].type != null)
&& (navigator.mimeTypes[ i].type.indexOf(
"application/x-java-applet;jpi-version=1.5") != -1) ) {
pluginDetected = true;
break;
}

}
}
} else if (is_ie5up) {
var javaVersion;
var shell;
try {
// Create WSH(WindowsScriptHost) shell, available on Windows only
shell = new ActiveXObject("WScript.Shell");

if (shell != null) {
// Read JRE version from Window Registry
try {
javaVersion = shell.regRead("HKEY_LOCAL_MACHINE\\Software\\JavaSoft\\Java Runtime Environment\\CurrentVersion");
} catch(e) {
// handle exceptions raised by 'shell.regRead(...)' here
// so that the outer try-catch block would receive only
// exceptions raised by 'shell = new ActiveXObject(...)'
}
}
} catch(e) {
}

My friend can up with a curious problem.

To run an applet a prerequiste is to actually check whether JRE(or JVM) is actually present on the machine. Although applet inherits the intelligence to actually point the browser to the web location.

However if the application has to be in total control then how??????

In short for Non-IE browsers then navigator.mimeTypes gets the registry values for the installed runtimes.
But alas IE does not implement mimetypes. So an activeX document to implement the same.


Here is a small snippet of the code written in javascript.


if(navigator.mimeTypes) {
//For non-IE browsers
for (i=0; i < navigator.mimeTypes.length; i++) {
if( (navigator.mimeTypes[ i].type != null)
&& (navigator.mimeTypes[ i].type.indexOf(
"application/x-java-applet;jpi-version=1.5") != -1) ) {
pluginDetected = true;
break;
}

}
}
} else if (is_ie5up) {
var javaVersion;
var shell;
try {
// Create WSH(WindowsScriptHost) shell, available on Windows only
shell = new ActiveXObject("WScript.Shell");

if (shell != null) {
// Read JRE version from Window Registry
try {
javaVersion = shell.regRead("HKEY_LOCAL_MACHINE\\Software\\JavaSoft\\Java Runtime Environment\\CurrentVersion");
} catch(e) {
// handle exceptions raised by 'shell.regRead(...)' here
// so that the outer try-catch block would receive only
// exceptions raised by 'shell = new ActiveXObject(...)'
}
}
} catch(e) {
}

Richard Stallman @IISc

Title: Free Software: current status and challenges

Time: 19 Aug (Sat) 11am
Place: Faculty Hall

Speaker: Richard Stallman,
Founder of GNU project and FSF (Free Software Foundation)

Abstract:
Richard Stallman will give a talk on free software and current status on
aspects such as GPLv3, DRM (digital rights mgmt), DMCA, etc.

Bio:
Richard Stallman is the founder of the GNU Project, launched in 1984 to
develop the free software operating system GNU. The name ``GNU'' is a
recursive acronym for ``GNU's Not Unix''.

Stallman graduated from Harvard in 1974 with a BA in physics. During his
college years, he also worked as a staff hacker at the MIT Artificial
Intelligence Lab, learning operating system development by doing it. He
wrote the first extensible Emacs text editor there in 1975. He also
developed the AI technique of dependency-directed backtracking, also
known as truth maintenance. In January 1984 he resigned from MIT to
start the GNU project.

Stallman received the Grace Hopper award for 1991 from the Association
for Computing Machinery, for his development of the first Emacs editor.
In 1990 he was awarded a Macarthur foundation fellowship, and in 1996 an
honorary doctorate from the Royal Institute of Technology in Sweden. In
1998 he received the Electronic Frontier Foundation's pioneer award
along with Linus Torvalds. In 1999 he received the Yuri Rubinski award.
In 2001 he received a second honorary doctorate, from the University of
Glasgow, and shared the Takeda award for social/economic betterment with
Torvalds and Ken Sakamura. In 2002 he was elected to the US National
Academy of Engineering, and in 2003 to the American Academy of Arts and
Sciences. In 2003 he was named an honorary professor of the Universidad
Nacional de Ingenieria in Peru, and received an honorary doctorate from
the Free University of Brussels. In 2004 he received an honorary
doctorate from the Universidad Nacional de Salta, in Argentina.

About GNU:

GNU is free software: everyone is free to copy it and redistribute it,
as well as to make changes either large or small. Non-free software
keeps users divided and helpless, forbidden to share it and unable to
change it. A free operating system is essential for people to be able to
use computers in freedom.

Today, Linux-based variants of the GNU system, based on the kernel Linux
developed by Linus Torvalds, are in widespread use. There are estimated
to be some 20 million users of GNU/Linux systems today.

Richard Stallman is the principal author of the GNU Compiler Collection,
a portable optimizing compiler which was designed to support diverse
architectures and multiple languages. The compiler now supports over 30
different architectures and 7 programming languages.

Stallman also wrote the GNU symbolic debugger (gdb), GNU Emacs, and
various other programs for the GNU operating system.

Is this methods fool proof?

Does this method make a valid check for even numbers?

public static boolean isEven(int i) {
return i % 2 == 1;
}