Let me help you geeks

Chrome for Android APK available

2012-02-08T01:01:00.000+05:30

Google just released Chrome for Android Beta! Awesomeness!

But it is not available for all countries (at least not in India) yet. For those not willing to wait, just like me,
Here is the Chrome apk file.

(Thanks to JerleMinara at XDA. )

Speeding up ftp transfer in linux command line

2012-01-25T15:00:00.001+05:30

Use the following command to download a single file in multiple segments in ftp
lftp -c pget ftp://<filepath>

For example,
lftp -c pget ftp://example.com/example.zip

Encoding a binary file(image/video/audio) using Base64 encoding

2011-06-06T20:00:00.002+05:30

Firefox supports a url schema called data:, which allows binary files to be embedded in a html/js file. This can be quite handy when you want to say send a simple html file with images, but don't want to deal with the complexities of folder structure and stuff. But for embedding a binary file using the data feature, you need the binary file to be encoded in Base64 format. The following java code helps in encoding a binary file in Base64 format. The following code reads a .gif file and outputs an img tag that can be used directly in a html/js file

    public static void main(String[] args) throws IOException {

        File file=new File("C:\temp\temp.gif");
        InputStream is = new FileInputStream(file);
        int length = (int)file.length();
        byte[] bytes = new byte[length];
        int offset = 0;
        int numRead = 0;
        while (offset < bytes.length
               && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
            offset += numRead;
        }
        is.close();

        BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File("C:\\temp\temp.txt"))));
        bw.write("<img src="\"data:image/gif;base64,"+new" string(org.apache.commons.codec.binary.base64.encodebase64(bytes))+"\"="" />");
        bw.close();
    }

You can download the apache commons library from http://commons.apache.org/

Transform a org.w3c.dom.Node to String

2011-06-04T13:47:00.000+05:30

While I expected getting the data as a string from a Node object would be as straight forward as doing something like a .toString(), it turns out, it is much harder than that. I suspect the reason being that the datasource for the Document object can also be a data stream.

Coming to the point, the following code does the job of transforming a node object to a String object..

    public static String nodeToString(Node node) {
       StringWriter sw = new StringWriter();
       try {
           Transformer t = TransformerFactory.newInstance().newTransformer();
           t.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
           t.transform(new DOMSource(node), new StreamResult(sw));
       } catch (TransformerException te) {
           System.err.println("nodeToString Transformer Exception");
           te.printStackTrace();
       }
       return sw.toString();
   }

Play Framework - The Holy Grail for Web Developer

2011-06-04T00:13:00.000+05:30

Developing web applications in java involves a lot of work. You need to create servlets, worry about the backend datastore, etc.. If you are worried about all these, the Play Framework is just for you! Play Framework automatically takes care of quite a lot of routine, yet time consuming stuff.

The Play Framework has been created with developers in mind (That's strange, isn't it? :) )

Go ahead and try it out at http://www.playframework.org/

It is distributed under Apache 2 license.

Reading a file in Java with only \r\n (0D0A) as line separator

2010-04-01T18:09:00.000+05:30

One of the features of BufferedReader.readLine() is that it considers any of \r,\r\n,\n as line separator. One possible problem due to this is that, if you wanted to consider only say \r\n as separator and was any other character(\r or \n) to be considered as part of the line, it makes it impossible to use BufferedReader.readLine(). This is because there is no way find what the new line character that readLine() used as the line delimiter for the currently returned line.

If you had wanted to use only say \r\n as line separator, we can use the Scanner to do the job for us..

public void testScanner()
    {
        Scanner scanner=new Scanner(getClass().getResourceAsStream("parseText.txt"),"UTF-8");
        scanner.useDelimiter("\\x0D\\x0A"); //Hex values for \r\n
        while(scanner.hasNext())
        {
            String line=scanner.next();
            System.out.println("Line: " + line);
        }
    }

Get hostname of the machine in java

2010-03-13T18:56:00.001+05:30

InetAddress.getLocalHost().getHostName() returns the hostname of the local machine.

Communicating within a circle

2010-03-11T00:47:00.002+05:30

Ever since I came to know about bluetooth I had wanted to create an application that would allow people to communicate with people nearby. My idea was.. People would create profiles on their phones that would give more details about themselves, like photos, interests, etc. Whenever somebody wants to start a conversation, they can start by searching for people nearby, and ping them after knowing more about them from their profile. Other people in the zone can view this conversation and join the conversation if they like. Ofcourse this has lot of privacy concerns and there is a need for a good privacy policy.
I was using google buzz in google maps sometime back and it provides most of the functionality explained above in a different and interesting way. Since google buzz in google maps allows people to tag locations to their buzz, it allows for people to find what other people are talking about/in that particular area of interest. It also allows for people to join an ongoing public conversation. This will get even more interesting if google merges the google chat, google latitude functionality too. Such an application will take social networking to truly another level (of privacy issues??). And will also help people like Rajesh koothrappali(Big Bang Theory) to socialize and get connected.

Firefox Offline Mode

2010-03-10T23:45:00.002+05:30

Ever wondered how to view the cached pages in firefox?
The offline mode is the answer. This option can be found in the file menu of firefox. When the offline mode is enabled, firefox always uses the cached page instead of trying to get the latest page. This can come in quite handy when you know that you have visited a particular page and you don't have internet connection now.
The awesome bar will as ever help you get to the url and the offline mode will help you browse the cached page. Though you can see the entire cache using either about:cache or some other applications noting gives a seamless experience as offline mode.

Get the list of databases in DB2 using DB2 command Prompt

2010-03-10T14:44:00.002+05:30

1. Open db2 command prompt(db2cmd).
2. Issue "db2 list database directory"
3. All the databases in the machine should get listed.

Send Ctrl+Alt+Delete in a remote desktop session

2010-03-08T15:47:00.000+05:30

Typing Ctrl+Alt+End in a remote session has the same effect as Ctrl+Alt+Delete.

Flirting with SQL Injection

2010-02-28T15:18:00.001+05:30

So what to do on a boring Saturday, BREAK INTO WEBSITES! Believe me, it is much much easier than presumed. I played around with 3 websites today and was successfully able to hack into 2 of them. I used the simple technique of SQL injection.

First encounter[Failure]
http://www.********.edu/research/result.html
If you look at the page, it is a very simple webpage. The webpage is supposed to be used to enquire about the results of the Phd thesis.
Firstly the website has a client side check which you can quite easily deduce by just entering an incorrect register number. So I copied the webpage, and edited the function checkregno() to return true even if the regex check fails. This allowed me to send incorrect values/sql statements to the server. But the site seems to have some server side check[before encountering with the database, which you can guess from the response time.] too for the registry number validity, so I could not find any way to progress beyond this point.
checkregno()
{
if (window.RegExp)
{
strval=document.forms["result"]["regno"].value;
reExp=new RegExp("^\\d{9}$");
if (reExp.test(strval))
    return(true);
else
    {
//    alert("Regno is not correct");
//       document.forms["result"]["regno"].value=""
    return(true);
    }
}
}

Second Encounter[Partial Success]
http://www.******.in/Admissions/ApplStatus.asp
This website did not really have any client side check other than a limit for the text box field. So I used firebug to change the limit of the textbox field and inserted some junk characters into the text box to figure out whether the call ends up to the database or is there any middle level check. To my surprise, I got back the following

Microsoft OLE DB Provider for ODBC Drivers error '80040e14'

[Microsoft][ODBC driver for Oracle][Oracle]ORA-00911: invalid character

/Admissions/Applstatus_submit.asp, line 71

The above error message explained a lot about their database configuration. They are using some Microsoft Windows Server and they are using Oracle for the database. This emboldened me and I used the value 12 OR 1=1 as the input string. That gave me the following error message.

Application No: 12 OR 1=1

Microsoft VBScript runtime error '800a000d'

Type mismatch: '[string: "12 OR 1=1"]'

/Admissions/Applstatus_submit.asp, line 87

That proved two things. The query execution has actually passed. So some query of the sort "SELECT * FROM STUDENT WHERE APPNO=12 OR 1=1" has got executed. But to their luck, somebody has tried to cast the Application No in the return result which has resulted in a Type Mismatch error. But the bright spot is the query has actually got executed. So if suppose I had wanted to change the value or deleted some records in the database I could have very well accomplished it, provided the user they are using the query the records has the rights to modify records too.

Third Encounter[Success]:
http://www.***********.com/exam_results.asp
This one was the easiest to break into. I gave 234' in the input box and it gave me back almost all the information I need about that website to hack into.

Microsoft OLE DB Provider for ODBC Drivers error '80040e14'

[Microsoft][ODBC Microsoft Access Driver] Syntax error in string in query expression 'fdRegNo='234'' AND (tblResult.fdHead=1)'.

/show_Result.asp, line 29

The website uses Microsoft Windows operating system and Microsoft Access Database. The column name that is used to store the register number is fdRegNo and the type of the column is a string. Now all I have to do is to extract more information from the website, which is quite simple as making the fdRegNo condition to always return true. So I used 12' OR '1'='1 as the input literal. Now the resultant query that will get executed in the database is something of the form SELECT fdRegNo,COL1 FROM result WHERE fdRegNo='12' OR '1'='1' AND (tblResult.fdHead=1)'. This would have resulted in all the columns from the results table from being fetched. So after some delay(hope I have not overloaded the server :( ) I got back all the records in the table :). Here I could have very well fudged with the table by just giving in a input which would have thrown me a error message with the name of the table, and using that table name to delete or modify the records in the table.

Mission Accomplished!! Learned a great deal about how secure the production websites are and how easy it is to fudge with the websites.

Wow! I never thought production websites are this easy to compromise. It did not even necessitate me to learn anything otherthan just the meaning of the word SQL Injection and I am now a hacker.. Hope these websites fix these security holes, or else students will determine their grades and not the teachers :P

P.S: The intention of all the above experiments was just to learn more about how sql injection works and to find out in real world how many of the production websites are vulnerable. I have not changed/deleted any data in any of these websites, though it seems like it would be easy to mess around with these sites.

Changing @author name in eclipse

2010-01-31T19:25:00.000+05:30

1. Open eclipse.ini file in the eclipse base directory.
2. Add "-Duser.name={New Name}" after -vmargs
3. Restart eclipse.

SETLOCAL in a windows batch file

2010-01-25T20:54:00.001+05:30

SETLOCAL

Set options to control the visibility of environment variables in a batch file.

Syntax
      SETLOCAL

      SETLOCAL EnableDelayedExpansion

      SETLOCAL EnableExtensions | DisableExtensions

SETLOCAL on it's own, usually at the start of a batch file, will begin localisation of Environment Variables.

If a batch script does not use SETLOCAL and ENDLOCAL then all variables will be Global - visible and modifiable by other scripts.

Although global variables are easy to work with they are not good practice - for example if you have several batch scripts dealing with filenames (and these scripts may be CALLing one another), the first script may have a variable called _filename, the second script a different variable called file-name (you choose a different name to avoid conflicting with the other script) a third script now needs something like file_name it quickly becomes very difficult to manage things like this.

With local variables you are free to standardise and use the same name in multiple batch scripts - it doesn't matter because they are not visible to any other script.
Local Variables can be passed from one batch routine to another with the ENDLOCAL command.

Issuing a SETLOCAL command, the batch script will inherit all current variables from the master environment/session.

Issuing an ENDLOCAL command will restore any environment variables present before the SETLOCAL was issued.

EnableDelayedExpansion

Normally batch files will expand environment variables once for each command/line. Also escaped characters (^) are evaluated just once. This can have undesirable side-effects when using commands which span multiple lines, like FOR and IF. Setting EnableDelayedExpansion will reverse this behaviour.

Examples

Escaping control characters:

@echo off
setlocal
Set _html=Hello^>World
Echo %_html%

In the above, the Echo command will create a text file called 'world' - not quite what we wanted! This is because the '^' caret works once for the SET command, but then vanishes.
If we now try the same thing with EnableDelayedExpansion, the caret works all the way through the script:

SETLOCAL EnableDelayedExpansion
Set _html=^<title^>Hello world ^</title^>
Echo !_html!
<title>Hello world </title>

With delayed expansion the caret ^ escapes each special character all the time, not just for one command.
This makes it possible to work with HTML and XML formatted strings in a variable.

Delayed variable expansion has a slightly different effect when working with Loops.
This is the default behaviour of a FOR loop:

@echo off
setlocal
:: count to 5 storing the results in a variable
set _tst=0
FOR /l %%G in (1,1,5) Do (echo [%_tst%] & set /a _tst+=1)
echo Total = %_tst%

C:\>demo_batch.cmd
[0]
[0]
  [0]
[0]
[0]
Total = 5

Notice that when the FOR loop finishes we get the correct total, so the variable correctly increments, but during each iteration of the loop
the variable is stuck at it's initial value of 0

The same script with EnableDelayedExpansion, gives the same final result but also displays the intermediate values:

@echo off
setlocal EnableDelayedExpansion 
:: count to 5 storing the results in a variable
set _tst=0
FOR /l %%G in (1,1,5) Do (echo [!_tst!] & set /a _tst+=1)
echo Total = !_tst!
C:\>demo_batch.cmd
  [0]
[1]
[2]
[3]
[4]
Total = 5

Notice that instead of %variable% we use !variable!

Example of replacing one variable with values from another:

@echo off
setlocal EnableDelayedExpansion
Set var1=Hello ABC how are you
Set var2=ABC
Set result=!var1:%var2%=Beautiful!
Echo [!result!]

An alternative method for achieving the above is CALL SET

EnableDelayedExpansion is Disabled by default.
EnableDelayedExpansion may also be enabled by starting CMD with the /v switch.

EnableDelayedExpansion can also be set in the registry:

[HKEY_LOCAL_MACHINE\Software\Microsoft\Command Processor]
"DelayedExpansion"= (REG_DWORD)
1=enabled 0=disabled (default)

Overloading a variable

SETLOCAL can be used more than once in the same batch file so that multiple values can be stored in one Environment Variable.

@echo off
SETLOCAL
::Standard commission
SET _Commission=20
echo %_Commission%

::Premium commission
SETLOCAL
set _Commission=30
echo %_Commission%

::back to Standard commission
ENDLOCAL
echo %_Commission%

DISABLEEXTENSIONS

Command Extensions are enabled by default, DisableExtensions will attempt to disable Command extensions. (ENABLEEXTENSIONS - will attempt to re-enable)

SETLOCAL will set an ERRORLEVEL if given an argument. It will be zero if one of the two valid arguments is given and one otherwise.

You can use this in a batch file to determine if command extensions are available, using the following technique:

   VERIFY errors 2>nul
   SETLOCAL ENABLEEXTENSIONS
   IF ERRORLEVEL 1 echo Unable to enable extensions

This works because "VERIFY errors" sets ERRORLEVEL to 1 and then the SETLOCAL will fail to reset the ERRORLEVEL value if extensions are not available (e.g. if the script is running under command.com)

If Command Extensions are permanently disabled then SETLOCAL ENABLEEXTENSIONS will not restore them.

Source : http://ss64.com/nt/setlocal.html

Pick colors for your UI

2009-12-15T14:21:00.001+05:30

http://www.tayloredmktg.com/rgb/

Finding the number of days of each weekday in a duration

2009-12-05T12:19:00.000+05:30

import java.util.Date;

public class DaysOfWeek {

public static void main(String[] args) {

Date startDate=new Date(2009,12,4);

Date endDate=new Date(2009,12,13);

long[] dayArray=getWeekDays(startDate, endDate);

for (int i = 0; i < dayArray.length; i++) {

System.out.println(dayArray[i]);

}

private static long[] getWeekDays(Date startDate, Date endDate) {

long[] dayArray=new long[7];

long numberOfDays=diffInDays(startDate,endDate);

System.out.println("Number Of Days ="+numberOfDays);

long numberOfWeeks=numberOfDays/7;

System.out.println("Number Of Weeks ="+numberOfWeeks);

for (int i = 0; i < dayArray.length; i++) {

dayArray[i]=numberOfWeeks;

}

int startDay=startDate.getDay();

int endDay=endDate.getDay();

for(int i=startDay;i!=(endDay+1)%7;i=(i+1)%7)

{

dayArray[i]=dayArray[i]+1;

}

return dayArray;

}

private static long diffInDays(Date startDate,Date endDate) {

return (endDate.getTime()-startDate.getTime()+(1000*24*60*60))/(1000*24*60*60);

}

2009-12-02T15:45:00.002+05:30

Two ways to build a list/array in javascript

1. object literals

var obj = new Object();

obj["id4"] = {name:”deepak”, id:”123-456-789″};

In this case it’s not easy to figure out how many objects are within the current list.

2. array literals

var arr = new Array();

arr[0] = {name:”deepak”, id:”123-456-789″};

arr[1] = {name:”Ashok”, id:”987-654-321″};

//arr.length will be 2.
It’s easy traverse the array list by index number and to figure out how many objects are really inside the list

Bypass/Delete browser Cache

2009-11-21T23:32:00.000+05:30

Mozilla family

This includes Firefox, Netscape Navigator (versions 6.x and 7.x) and SeaMonkey.

To reload a page and bypass the cache:
- either: Hold down both the Ctrl and Shift keys and then press R. (Alternatively, hold down the Ctrl key and then press F5.) On a Mac, use the Command key instead of Ctrl.
- or: Hold down the Shift key and click the Reload button on the navigation toolbar.
To completely clear the cache (see note above):
- From the 'Edit' or 'Tools' menu, choose 'Preferences' or 'Options'. Expand the 'Advanced' options and choose 'Cache' or 'Privacy'. Click the button called 'Clear Cache'.
- In newer versions of Mozilla Firefox, you can easily clear the cache, history and cookies: Hold down the Ctrl and Shift keys, and press Delete (or Del), then choose what you want to remove. Or from the 'Tools' menu, select 'Clear Recent History'.
- For older versions of Mozilla Firefox, go to 'Tools' → 'Options' and click on 'Privacy' (picture of a key) in the sidebar of the window that pops up. Click the 'Clear' button that is next to the word 'Cache'.
To disable caching (only do this if you are reasonably confident in what you are doing):
- For Firefox
  - Choose Tools | Options... (or Edit | Preferences in the Linux version)
  - Choose Advanced at the top
  - Choose the Network tab
  - Change the cache size to 0 (zero).
- For SeaMonkey
  - Choose Edit | Preferences...
  - Expand the Advanced item near the left bottom
  - Choose Cache item
  - Change the Size value to 0 (zero).

FireFox has memory caching, which might also need to be considered when troubleshooting cache-related issues.

In the address bar, enter 'about:config'
Filter the configurations options by entering 'cache' in the filter at the top
Change browser.cache.memory.enable to FALSE

Source: http://en.wikipedia.org/wiki/Bypass_your_cache

Internet Explorer

To reload a page and bypass the cache:
- either: Hold the Ctrl key, and press F5.
- or: Hold the Ctrl key, and click the Refresh button on the Start bar.
To completely clear the cache (see note above):
- Internet Explorer 8
  - Click "Safety" and select "Delete Browsing History", make sure "Temporary Internet Files" and "History" is checked, then click "Delete". If you want, you can also opt to delete cookies.
- Internet Explorer 7
  - Click "Tools" and select "Internet Options", choose the "General" tab and click "Delete Files" under the Temporary Internet Files section. If you want, you can also opt to delete cookies and browsing history.
- Older versions
  - Click on 'Tools' and then 'Internet Options' and choose the 'General' tab. Then click on "Delete..." under "Browsing history". In the 'Temporary Internet files' section, click 'Delete Files...'. You will then get a dialogue box asking if you want to delete just the temporary files, or all offline content. Choose the latter and click 'OK'.
To change cache settings (only do this if you are reasonably confident of what you are doing):
- Selecting 'Tools' → 'Internet Options' → 'Temporary Internet files' → 'Settings...' allows you to make advanced configuration changes to the cache.
  - There is an option labeled "Check for a new version of stored pages:" This does not bypass the cache, it merely determines how often the browser asks if there is a newer version available.

Google Chrome

To clear the cache:
- Go to the Tools menu (the wrench on the upper right of the browser) Click on Options and click on Clear browsing data...
- Select the types of data you want to clear
- On the Clear data from this period: drop-down list, select one of the following:

Everything to clear all the data you selected;

Last day to clear the data only from the last day;

Last week to clear the data only from the last week; or

Last 4 weeks to clear the data only from the last 4 weeks.

Java performance analysis

2009-11-13T18:22:00.002+05:30

Java Performance Blog

JVM Memory Structure plus other bunch on docs on yourkit.com

Memory usage of Java objects

Memory usage of Java Strings and string-related objects

How to save memory occupied by Java strings

Getting VNC working with GUI in Linux

2009-11-12T03:01:00.000+05:30

Note: You will have to have root credentials

1. First login to the Linux machine using some command line client say putty(SSH)
2. Start the VNC Server as a service
     service vncserver start
3. Issue the command
     vncserver

Having done the above steps you will see a command line interface, no GNOME/KDE..

To get that started as soon as you login using vnc

1. Goto root using
             cd /root
2. Go to VNC Settings folder .vnc
           cd .vnc
3. Open the xstartup file for editing
           vi xstartup
4. Now add the line "startx &" to the end of the file if you want to start GNOME or "startkde &" if you want to use KDE environment at startup.

Now when you login using a VNC client you will see GNOME/KDE getting launched automatically.

Is Firefox sluggish?

2009-11-05T00:23:00.001+05:30

If you have ever felt that firefox is being sluggish, then do the following...

Disabling unwanted plugins & Addons:
1. Goto Tools->Addons
2. Go to Plugins tab.
3. You will find a quite a few plugins that you are never/rarely going to use. Most of the plugins get installed as part of some software installs and they are totally unnecessary. Disable the plugins that you don't use.
4. Go to Extensions tab
5. Disable the extensions you don't generally use.

Alternative to commenting out code

2009-09-25T13:24:00.002+05:30

if (0 == 1) {...}

and

boolean enable = 0 == 1;
if (enable) {...}

The advantage of "0 == 1" instead of commenting out the code is that you don't have to fix the imports, local variables etc plus it's only a single character change.

Cognos Knowledge base

2009-09-05T16:24:00.001+05:30

Cognos knowledge base, documentation etc

http://www-01.ibm.com/software/data/cognos/customercenter/

Many to Many relationships in Data warehouse

2009-09-01T22:55:00.001+05:30

For dealing with Many to Many relationships in Data warehouse, see Complete guide to dimensional modeling by Ralph Kimball - 2nd edition pg 262 (Multivalued Diagnosis Dimension)

Multi level multi parent hierarchy in data warehouse

2009-09-01T15:57:00.002+05:30

For multi level multi parent hierarchies, see Complete guide to dimensional modeling by Ralph Kimball - 2nd edition pg 162