Tech 1.0 Blog

Cygwin: rebaseall utility

2012-02-09T10:08:00.000-08:00

You may sometimes see cygwin error like this.

bash 4944 exception::handle: Exception: STATUS_ACCESS_VIOLATION

emap to same address as parent

Short answer

To fix these errors, run these commands from your MS-DOS command prompt.

cd \cygwin\bin
ash
PATH=. rebaseall -v

More Details

Rebaseall utility
Rebaseall utility should be available under /cygwin/bin/ directory.
To check if rebaseall is available or not. If it is available it will print something like this.

priyank@~:>which rebaseall
/usr/bin/rebaseall

Only ash process is allowed to run rebaseall. Means you cannot run rebaseall directly from cygwin.
Open MS-DOS command prompt and follow these steps to to run rebaseall.

cd \cygwin\bin
ash
PATH=. rebaseall -v

JAVA: SAXParseException - entiry must end with ';' delimiter

2011-12-29T13:34:00.000-08:00

Exception: org.xml.sax.SAXParseException: The reference to entity “T” must end with the ';' delimiter

The problem is with an XML which you are trying to parse.Your xml contains special character "&". It should be replaced with "&"

2011-09-22T11:35:00.000-07:00

How to generate ssh public/private key (using command)
Use following command:

ssh-keygen -t rsa

where
-t: specifies type of key to create
rsa: is a type to createYou can to check more options by using man command.

man ssh-keygen

Some advice

2011-08-19T10:51:00.000-07:00

I stumbled upon this while reading a blog.

- An hour of sleep before midnight is worth two, and an hour of work before noon is worth two.

- Always pick your kids up from school. That’s when they want to talk.

- Never let your skill exceed your virtue.

- Never take less than two weeks off when you have a child or for your honeymoon. Don’t let them talk you down.

- When you mess up, admit it frankly and quickly, and move on.

- Always do your very best in your job, but if you don’t like what you’re doing enough that you would do it for free, quit.

MYSQL: Change mysql db schema name

2011-07-15T14:07:00.001-07:00

How to change mysql database schema name?

Here s what you need to do:
1. Use mysqldump to dump old mysql database.
2. Create new database using mysqladmin.
3. And run the sql generated via mysqldump.

e.g. if you want to change database named "school_old" to "school_new"
Here are the commands.

mysqldump -u username -p -v school_old > old_db_dump.sql
mysqladmin -u username -p create school_new
mysql -u username -p school_new < old_db_dump.sql

Updated twitter bookmarklet

2011-06-15T13:00:00.000-07:00

Recently twitter updated the way you post tweets. So the previous version of bookmarklet stopped working.

So here is the updated version. Just drag this bookmarklet to your bookmarks bar.

Twitter Bookmarklet

Check out his link if you want to know what this bookmarklet does.
Click here

Here is the code:

javascript: var longUrl=document.location; var url = 'http://api.bit.ly/shorten?version=2.0.1&login=tweetthees&apiKey=R_e1266a2cb3177ea0a9e1114cc49d8ad9&longUrl='+longUrl; loadScript(url+'&callback=tweetme'); function loadScript(scriptURL){ var scriptElem = document.createElement('SCRIPT'); scriptElem.setAttribute('language','JavaScript'); scriptElem.setAttribute('src', scriptURL); document.body.appendChild(scriptElem); } function tweetme(json){ var shortLink=json.results[longUrl].shortUrl; window.location='http://twitter.com/intent/tweet?text=Reading: '+document.title+' '+shortLink }

JAVA: LinkedList implementation in java

2011-04-12T12:44:00.001-07:00

Will be updated soon

JAVA: Convert String to InputStream

2010-07-06T18:34:00.000-07:00

You can use ByteArrayInputStream to convert String to InputStream.
ByteArrayInputStream extends InputStream.

Example:

String content = "Convert string to inputstream";
ByteArrayInputStream stream = new ByteArrayInputStream(content.getBytes());

Reference:
1. http://forums.sun.com/thread.jspa?threadID=670188

2. http://java.sun.com/j2se/1.4.2/docs/api/java/io/ByteArrayInputStream.html

JSTL: Find length of a collection

2010-05-12T13:19:00.001-07:00

To get a length of a collection:
${fn:length(tvPackageGroup.addonOptions)}

Include <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %> namespace.
http://stackoverflow.com/questions/851880/check-a-collection-size-with-jstl

Sorting a collection in JSTL

javadoc: http://java.sun.com/products/jsp/jstl/1.1/docs/tlddocs/fn/tld-summary.html

JAVA: reverse string interview question

2010-02-02T15:52:00.000-08:00

When you go for an interview, lot of companies ask String manipulation questions.

Some of the most common questions are:

Reverse words in a string (words are separated by spaces) - Most Common
Reverse String
Revers the order of words

I have written a code that performs all these functions. Hope this will help you.

/**
 * Created by IntelliJ IDEA.
 * User: priyank
 * Date: Feb 2, 2010
 */
public class StringTest {

    public static void main(String[] args) {
        String str = "My name is khan";
//        String result = reverseString(str);
//        String result = reverseWords(str);
//        String result = reverseSequence(str);
        String result = iReverseSequence(str);

        System.out.println(result);
    }

    static String reverseString(String str) {
        char[] ch = str.toCharArray();
        StringBuilder sb = new StringBuilder();
        for (int i=(ch.length-1);i>=0;i--) {
            sb.append(ch[i]);
        }
        return sb.toString();
    }

    static String reverseWords(String str) {
        String[] st = str.split("\\s");
        StringBuilder sb = new StringBuilder();
        for(int i=0; i < st.length;i++) {
            sb.append(reverseString(st[i])+" ");
        }
        return sb.toString();
    }

    static String reverseSequence(String str) {
        String[] st = str.split("\\s");
        StringBuilder sb = new StringBuilder();
        for(int i=(st.length-1);i>=0;i--) {
            sb.append(st[i]+" ");
        }
        return sb.toString();
    }


    // Without using inbuilt java functions (for ex without using split())
    // I still used substr() though
    static String iReverseSequence(String str) {
        String word = "";
        int lastIndex = str.length();
        for(int i=(str.length()-1);i>=0;i--) {
            if(str.charAt(i) == ' ') {
                word += str.substring(i+1,lastIndex)+" ";
                lastIndex = i;
            }
        }
        word += str.substring(0,lastIndex);
        return word;
    }
}

My regex Notes

2009-10-13T20:02:00.000-07:00

These are notes I have created for regex. It is not formatted right now but I will update this post soon.

[] = use square brackets [] as OR operator. You can also call it a character class.
[^xyz] = ^ in the beginning of [] means "(not x) or y or z"
^abc means start char must be a
abc$ means end characted must be c
example:
^\s+ = beginning with whitespace-charater one or more times
\s+$ matches trailing white space
in perl trim function can be $input =~ s/^\s+|\s+$//g

Word boundaries:
[a-zA-A0-9_] are word characters. [a-zA-A0-9] = \w
\b is used to define boundary
\bis => "my name is priyank" and "I like Hawai islands" will match. But "this was a book" won't.
\bis\b => Only "my name is priyank" will match.
is\b => "my name is priyank" and "this was a book" will match "I like Hawai islands" won't.

Regex is Eager
ref: http://www.regular-expressions.info/alternation.html

You use "?" for optional items. ? means 1 or 0 times
B4?U matched both BU and B4U.
(Jan)?uary mathces Jan and January
* means 0 or more times.
+ means 1 or more times.

You use "?" to make regex non-greedy.
So in "tennis is a nice sport. ", if your regex is (.*is)will match the string "tennis is" but if your regex is "(.*?is).*" will find only "this".
SO "?" makes the regex lazy or ungreedy.

Round brackets are used for grouping.
Round bracket also create a 'backreference'.
What is a "back reference" in regex?
Ans: A backreference stores the part of the string matched by the of the regex inside the parantheses.
Backreference slows down the regex engine as it has to some more work.
You use "?:" to tell regex engine not to create any back reference.
How to use a backreference ?
Backreference allows you to re-use matched part of a regex. You can re-use it inside the regex itself.
A very good example ofr backreference is find starting and closing html tag ans contetnt inside that tag.
<([A-Z][A-Z0-9]*)\b[^>]*>.*?

Download regex cheatsheet

How to show line number in VI editor

2009-10-11T01:35:00.000-07:00

Use following command to view line numbers

:set number

To remove line numbers, use following command.

:set nonumber

Twitter bookmarklet

2009-08-26T17:38:00.000-07:00

Updated version of this bookmarklet is here Twitter bookmarklet

What does this bookmarklet do?

You are reading a great article on the web or you found a great website. Now you want to share it with everyone on twitter. Just click on "TweetThis" bookmark in your bookmarks tab and it will take you to twitter with url already shortened with bit.ly.

Drag this Twitter Bookmarklet to your favorite browser's Bookmarks Toolbar.

Old: TweetThis Check out the latest one below.

UPDATED bookmarklet - includes page title in a your tweet.

New: TweetThis

1. You found a great article on yahoo and you want to share it on twitter. To do this- Click on TweetThis bookmarklet.

2. Once you click on the bookmarklet, it will create bitly url for the webpage and take you to twitter.com to post.

If you want to view what it is doing, check this.

Source code:
javascript:function loadScript(scriptURL) { var scriptElem = document.createElement('SCRIPT'); scriptElem.setAttribute('language', 'JavaScript'); scriptElem.setAttribute('src', scriptURL); document.body.appendChild(scriptElem);}var url = 'http://api.bit.ly/shorten?version=2.0.1&login=bitlyapidemo&apiKey=R_0da49e0a9118ff35f52f629d2d71bf07&longUrl='+document.location;var longUrl=document.location;loadScript(url+'&callback=tweetme');function tweetme(json){var shortLink = json.results[longUrl].shortUrl;document.location='http://twitter.com/home?status=I+found+this+great+thing+'+shortLink}

Syntax highlighting in vi/vim editor on ubuntu

2009-08-14T10:51:00.000-07:00

To turn on syntax highlighting, use this command. :syntax on
When you open any file in vi editor, press escape and enter :syntax on.
Ubuntu by deafult has vim-tiny installed. So syntax command may not work. You may get this message: "E319: Sorry, the command is not available in this version"

To install full version of vim, use following command.

$ sudo apt-get install vim

$ sudo apt-get install vim-full

You can also check which package is ubuntu using by entering following command.

$ dpkg -l vim*

priyank@priyank-laptop:~$ dpkg -l vim*
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name Version Description
+++-=======================-=======================-============================================
ii vim 2:7.2.079-1ubuntu5 Vi IMproved - enhanced vi editor
ii vim-common 2:7.2.079-1ubuntu5 Vi IMproved - Common files
un vim-doc (no description available)
un vim-gnome (no description available)
un vim-gtk (no description available)
un vim-lesstif (no description available)
un vim-nox (no description available)
ii vim-runtime 2:7.2.079-1ubuntu5 Vi IMproved - Runtime files
un vim-scripts (no description available)
ii vim-tiny 2:7.2.079-1ubuntu5 Vi IMproved - enhanced vi editor - compact version

Once you install vim, and open any file using vi/vim editor turn on syntax highlighting by using the commnad given above. You should be able to see your code like this.

Voyij.com travel deals widget

2009-08-13T14:58:00.000-07:00

Latest Travel Deals powered by Voyij

UNIX: useful applications list (opensource)

2009-08-04T18:11:00.000-07:00

I came across this website - thanks to Bing.
It contains list of applications every UNIX/Ubuntu user should have.
The list includes following categories.
- Audio Applications
- Graphic Design Applications (2D)
- Graphic Design Applications (3D)
- Video Applications
- System Applications:
- Developer Applications
- Productivity Applications
- Web Development Applications

Some the applications that I am using or I have installed are:
GNOME Do
Basket Note Pads
Pidgin
jEdit
Audocity
GIMPshop
Wine
OpenSSH
OpenOffice
Putty
bugzilla
Eclipse
Geany
TrueCrypt

Installing and configuring mysql on ubuntu

2009-07-29T12:33:00.000-07:00

Open terminal.

Enter following commands.

$ sudo apt-get install mysql-server mysql-client
$ mysql_secure_installation

First command will install mysql server and client both.
Second command is not required butif you want to make your database more secure, it is helpful.
Default port for mysql is 3306. If you wish to change this, you can do so by editing mysql configuration (my.cnf) file which is located under /etc/mysql.

$ sudo vi /etc/mysql/my.cnf

Look for string port=3306
Update it to your desired port number.
Once you save my.cnf file, you will have to restart mysql server to effect your changes.
You can use following command (remove curly brackets) to start,stop or restart mysql server.

$ service mysql {start|stop|restart}

JAVA: PatternSyntaxException: Dangling meta character '*' near index

2009-06-03T17:09:00.000-07:00

Pattern Syntax Exception is thrown when you have "*" in any String and you want to replace "*" with something else.
This exception is likely when you use method java.lang.String.replaceAll().

There are two solutions to this problem.
Solution 1: escape all metacharacters and use replaceAll().

Solution 2: I prefer this solution over solution 1. This method reduces most of the work as you don't need to escape any metacharacters.
Just use org.apache.commons.lang.StringUtils

Information about Internet Explorer and CSS issues

2009-05-20T19:00:00.000-07:00

I found out this website when I was fixing IE and Iframe issues for a website.
This website contains lot of good and important information about different CSS issues you will face in Internet Explorer.

The article talks about following issues.

Narrower page elements in IE
Text spilling out of container in Non-IE browsers
Disappearing background images
Widths only working on IE
Unstyled version of web page appearing in IE
Fixed width webpage center alignment issue

Click Here

Pidgin + Twitter integration

2009-05-05T18:04:00.000-07:00

Interested in twittering from your IM???
You can also "chat" with your twitter contacts.
There is an interesting plugin microblog-purple for pidgin which enables twitter in conversion windows.
This works on both Windows and Unix.
Follow link: microblog-purple

For Windows, download this file.

UNIX: File permissions

2009-04-30T15:04:00.000-07:00

How to modify file permissions

There are three types of permissions: Read, Write and Execute
And there are three groups you have to consider while changin permissions for a file. user, group (which user belongs to), others (Other users outside of the group)

Use command:

$ chmod 777 file.txt

777 = 7-> user, 7-> group, 7->others
Binary value of 7 is 111 = Read->1, Write->1, Execute->1
So 111 for all three groups.

755 = 7-> user, 5-> group, 5->others
Binary value 7 is 111.
Binary value of 5 is 101 = Read->1, Write->0, Execute->1
So only you have the permission to read, write and execute a file.
Other users can read or execute the file but cannot write.

Still editing this post. Will update soon.

JAVA: IOException - LocalRMIServerSocketFactory

2009-04-13T18:41:00.000-07:00

"The server sockets created using the LocalRMIServerSocketFactory only accept connections from clients running on the host where the RMI remote objects have been exported"

If you r using ubuntu and while running jconsole you are getting this message, then you should comment 127.0.1.1 ~domain from /etc/hosts file.

$ sudo vi /etc/hosts
127.0.0.1 localhost
#127.0.1.1 ubuntu

This is Ubuntu specific bug.

For more information visit:
This link

JAVA: illegal group reference

2009-04-09T18:43:00.000-07:00

How:
You have a string "I like dollar symbol".
and you want to replace the string with "I like $ symbol".
Code:

String a = "I like dollar symbol"
String replacement = "$"
a = a.replaceAll("dollar", replacement);

This will throw an exception "Illegal group reference."

java.lang.IllegalArgumentException: Illegal group reference
at java.util.regex.Matcher.appendReplacement(Matcher.java:713)
at java.util.regex.Matcher.replaceAll(Matcher.java:813)
at java.lang.String.replaceAll(String.java:2190)

Solution:
Here the problem is "$" is a Metacharacter which should be escaped.

replacement = Matcher.quoteReplacement(replacement);
a = a.replaceAll("dollar", replacement);

About quoteReplacement method in Matcher class
Ref. link: Click here
Returns a literal replacement String for the specified String. This method produces a String that will work use as a literal replacement s in the appendReplacement method of the Matcher class. The String produced will match the sequence of characters in s treated as a literal sequence. Slashes ('\') and dollar signs ('$') will be given no special meaning.

put two backslashes before "$".
String replacement = "\\$"

UNIX: 'export' vs 'setenv', what is the difference

2009-03-31T20:50:00.000-07:00

Both of them have same purpose but which one to use depends on what shell you are using.

If you are using sh and ksh shells, you use 'export'

If you are using csh, you use 'setenv'

Image in div container in IE6

2008-05-30T16:32:00.000-07:00

When you have image in a div container(w/o borders), it adds 2px gap between bottom edge of the image and bottom border of the div.
This problem occurs in IE6 only.(I haven't tested below IE6 browsers).

Solution:
Apply this css to image element. This will solve the problem.
img {vertical-align:bottom;}

Source: Click here

Firefox, Images and Myterious Gaps

2008-05-30T13:09:00.000-07:00

Scenario:

You are using tables

You are using firefox

You are using <img> element to inside table

And firefox is setting extra white space below the image in table cell

Example:

This happens when you have Strict doc type declaration.

Quick Fix:
Apply style to that image. display: block
Ex: td img {
display: block;
}
or
.image {
display: block;
}

Reference: mozilla developer center

Chart of Support for CSS Filters/Hacks

2008-05-23T13:02:00.000-07:00

http://www.dynamicsitesolutions.com/css/filters/support-chart/

Hack for IE 7 under strict mode

2008-05-23T12:30:00.001-07:00

If you have given doctype declaration as STRICT mode and you want to apply hack specifically for IE 7:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

You can use *:first-child+html CSS Hack that works only with IE 7.

Example:
#test {
background-color: #FFFFFF;
}

*:first-child+html #test {
background-color: #000000;
}

SOURCE:
http://www.dynamicsitesolutions.com/css/filters/first-child-plus-html/

Tired of cross browser css problems???

2008-03-25T14:16:00.000-07:00

Are you looking for CSS hacks to solve cross browser issues?
This site contains very good documentation for css hacks.

http://www.webdevout.net/css-hacks

In nutshell use following tags for separate styles for different browsers.

IE 6 and below
* html {}
IE 7 and below
*:first-child+html {} * html {}
IE 7 only
*:first-child+html {}
IE 7 and modern browsers only
html>body {}
Modern browsers only (not IE 7)
html>/**/body {}
Recent Opera versions 9 and below
html:first-child {}

Verify your blogspot site to google webmaster tools

2008-03-12T22:02:00.000-07:00

Hi everyone,

Please follow this great link which has a tutorial for adding your blog in google webmaster tools and verify it.

Title fof the following blog is "Google webmaster Tools and HOWTO verify your Blogger/blogspot.com site"

http://linuxlore.blogspot.com/2006/10/google-webmaster-tools-and-howto.html

Nice tool for converting html code to text format so that you can disply HTML code inside HTML document

2008-03-07T13:38:00.000-08:00

http://centricle.com/tools/html-entities/

Onclick( ) event inside anchor element changes the mouse pointer

2008-03-07T13:12:00.000-08:00

While using show/hide div tag I came across one problem where I was using onclick() event inside anchor tag.
Though it was working fine, it changes the mouse shape (Shows cursor symbol instead of hand).

Solution:
Add href="#" inside anchor tab. This will also allow you to use onClick() event.
You can also try style="cursor: hand;".
Example:
<a onclick="Effect.toggle('player','BLIND'); return false;" href="#">

Handling Select/option in html with javascript

2008-02-29T15:00:00.000-08:00

I came across one situation where I have to show/hide text according to the option selected by user.

As shown in the image below, I have a drop down box. Here when user selects any option except first option ("Individua Team- No registration"), I want to display a some text.

Example: See image below.

Solution

HTML Code:
<select name="Team" id="Team" onchange="showDiv(this.value)">
<option value="noteam" selected>Individual-No Team</option>
<option value='Ben&Jerry' >Ben & Jerry</option>
<option value='Giants'>Giants</option>
<option value='Gladiators'>Gladiators</option>
<option value='greatestteam' >greatest team</option>
<option value='MyTeam'>My Team</option>
<option value='starone'>star one</option>
</select>
</form>

CSS:
.hiddenDiv {
display: none;
}
.visibleDiv {
display: block;
}

Javascript:
function showDiv(divName) {
// hide div
if (divName == 'Individual-no team') {
document.getElementById("teaminfo").className = "hiddenDiv";
}
else {
document.getElementById("teaminfo").className = "visibleDiv";
}
}

2008-02-25T14:03:00.000-08:00

Check box and text alignment in Firefox.

I have a check box and a text next to it.
In Firefox, they are not aligned properly.
here is the screen shot

Solution
To fix this problem just apply CSS "vertical-align: middle" to input element.

2008-02-22T15:07:00.000-08:00

Few interesting websites for web designing

http://www.alistapart.com
http://www.webdesignerwall.com/
http://www.cssplay.co.uk/

Start

2008-02-22T13:05:00.000-08:00

Since long I was thinking to create a blog but I never found out any interesting stuff to put in the blog. But right now while browsing different web dev/design forums to find the solution of different design issues I decided t create a blog where I can put the problem I am facing and also the solution I found from different forums.

Hopefully this will help other web designers also. :)