Vi is one of the most powerful text editors available to the programmer today. It comes with a number of features and is highly flexible. This is what makes it such a powerful programming tool. vi comes installed by default on a number of Linux distributions. If you are using a mainstream distribution, you already have it installed. You can always install it by following instructions specific to your Linux distribution.

In vi, you can precede most vi commands with numbers to have the command repeated that number of times. Putting a number in front of the command will run the command those number of times. This comes very handy while dealing with several lines, words, or characters at a time.

Here are some examples that show how to use numbers with commands in the vi editor:

* 3dw — This will delete the next three words.

* 5cl — This will change the next five letters. That is, this will remove the letters and enters input mode.

* 12j — This will move down 12 lines.

Putting a number in front on most commands just repeats those commands the number of times specified.

If you would like further instructions, I suggest you try the VIM Tutor by running the vimtutor command.

Note: When you invoke vi on most Linux distros, you are actually invoking the vim text editor, which runs in vi compatibility mode. vim is an improvised version of vi. In other words, it is vi with a lot of bells and whistles.

Programmers and Linux geeks usually prefer vim over vi  because comes with color coding. vim also comes with other useful features such as the ability to open a document with the cursor at the same place where it was when you last exited that file.

If you are using Windows, you can still use vi editor on your system. There are two ways to do this–you can either install CygWin or use gvim (a Windows port is available).

A constant is a fixed value that the program may not alter. Constants can be any of the basic data types i.e. they can be int, float or char. The way each constant is represented depends on its type. Constants are also known as literals in C i.e. constants and literals are one and the same.

Character constants are enclosed between single quotes. E.g.’a', ‘%’ represent character constants. In C, you can use both multibyte characters and wide characters. Multibyte characters consist of one or more bytes while wide characters are usually 16 bits long. Multibyte characters and wide characters are used to represent languages that have large character sets. To specify a multibyte character, enclose the characters within single quotesm for example, ‘xy’. To specify a wide character constant, precede the character with an L.

For example:

wchar_t wc;
wc=L’A';

Rhythmbox is an application for managing and playing music files in Linux. Rhythmbox allows you to import music files, sort them by album, artist, title or some other variable. You can also play Internet radio using Rhythmbox.

When you launch Rhythmbox, you will see a setup wizard. Using the wizard, you can configure the folder in which to store music files. The location you choose for your music collection may need a lot of space depending on the size of your collection. You could add an entire disk or create a separate partition for your music collection. If you allocate a separate partition, you won’t lose any files if you reinstall Linux.

After you complete the setup wizard, you will see the main music library interface. Rhythmbox makes it easy to organize even large collections of music files.

Here are some ways to use Rhythmbox…

=> Import Music from Audio CDs–Extract tracks from an audio CD by selecting Music -> Import Audio CD. This launches Sound Juicer to rip and compress the music from your CD.

=> Import Location–Identify a folder of music from a Web site (http) or FTP site (ftp) and you can load the artist, album, song and related information from that folder. Note that this doesn’t download the songs to your computer. Select to play a song from that imported location and Rhythmbox gets it and plays it live. Your network connection must be up for this to work. You can also copy the song to your local disk using wget.

=> Create Playlist–To create a playlist, select Music->Playlist. If you have a really large music collection, select New Automatic Playlist. A pop-up window lets you choose search criteria to find songs music, artists, title, or other criteria to load into your playlist. You can also create a new empty playlist or load a stored playlist from a file. Once a playlist is created, you can add songs to the list by importing or dragging and dropping from a Nautilus window. Right-click on a song to copy, cut or delete it.

=> Check Statistics–Rhythmbox stores how many times a song has been played, when it was last played, and how you rate it (one to five stars). Select Edit -> Preferences to select to have columns of that information appear on your Rhythmbox window.

=> Play Music Tracks–With your music available, play that music by double clicking an album, artist, or track. Buttons at the top of Rhythmbox let you play/ pause or go forward or backward a track. Select Shuffle or Repeat boxes on the bottom of Rhythmbox to randomly play the songs in the album or play the same album repeatedly. Use the slider to move ahead or back in a song and select the speaker icon to adjust volume.

=> Play Internet Radio–Rhythmbox can also play Internet radio stations. The easiest way to do this is to find a streaming radio station, save the PLS file, right-click the file in your file browser and then select Open with Music Player. Nautilus comes configured to launch Rhythmbox for playing audio.

Note: In some (in fact many!) Linux distributions, you cannot play mp3 files ‘out-of-the-box’. This is because of patent issues.

You should be able to play mp3 files by installing the required libraries. The procedure will depend on the Linux distribution you are using. Another way to solve this problem is to install VLC Player (www.videolan.org). VLC Player can play a number of audio and video formats ‘out-of-the-box’.

The userdel command takes a single argument, which is the login name of the account to delete. If you supply the optional -r option, it also deletes the user’s home directory and all the files in it. To delete the user account with login name mary, you would type this:

# userdel mary

To wipe out her home directory along with her account, type this:

# userdel -r mary

Files owned by the deletec user but not located in the user’s home directory will not be deleted. The system administrator must search for and delete those files manually. The find command comes in very handy for this type of task.

Using find to locate and change user files:

– find / -user mary : Search the entire file hierarchy (start at /) for all files and directories owned by mary and print the filenames to the screen.

– find /home -user mary -exec rm -i {} \; : Search for all files and subdirectories under /home owned by mary. Run the rm command interactively to delete each file.

– find / -user mary -exec chown jenny {} \; : Search for all files and subdirectories under /home that are owned by user mary and run the chown command to change each file so that it is owned by jenny instead.

– find / -uid 500 -exec chown jenny {} \; : This command is basically the same as the previous example, but it uses the user ID number instead of the user name to identify the matching files. This is useful if you have deleted a user before converting her files.

There are a few common things about each invocation of the find command. The first parameter is always the directory to start the recursive search in. After that come the file attributes to match. You can use the -exec parameter to run a command against each matching file or directory. The {} characters designate where the matching filename should be filled in when find runs the -exec option. The \; at the end simply tells Linux where the command ends. These are only a few of find’s capabilities.

For more information on using find, check the man page. Type man find to view the page.

In Linux, directories storing temporary files used by applications can consume lots of disk space over time. These directories are usually /tmp and /var/tmp. To deal with this problem, most Linux distros come with a tool called tmpwatch. The tmpwatch command runs the cron file /etc/cron.daily/tmpwatch to delete unused temporary files.

Here is what this file contains:

/usr/sbin/tmpwatch 240 /tmp
/usr/sbin/tmpwatch 720 /var/tmp
for d in /var/{cache/man,catman}/{cat?,X11R6/cat?,local/cat?};do
if [ -d "$d" ]; then
/usr/sbin/tmpwatch -f 720 $d
fi
done

Each day, this tmpwatch script runs to delete temporary files that haven’t been used for a while. Files from the /tmp and /var/tmp directories are removed after 240 and 720 hours of not being accessed, respectively. Temporary man page files stored in /var/cache subdirectories are also checked and deleted after 720 hours of disuse.

It is important that you back up your gmail account. Your emails may contain confidential information such as bank statements, money details, etc. and should these land in the hands of some unscruplous hacker, it could prove dangerous. Your email account can also be hijacked by password cracking or some other means. So, it is better to delete confidential emails once you read them or back them up to your hard drive and encrypt them.

There are two ways to backup your gmail account:

- Forward your email to another account:

This will be depending on your other account’s stability. Go to Settings, then Forwarding and POP. Select Forward a copy, and enter an email address. Then Save Changes.

- Download all your email to your computer:

Enable POP for all mail and then follow Google’s guide to configuring your desktop email client such as Thunderbird or Outlook. Download all emails to hard disk and keep them safe.

This seems definitely like a good time for Bing. Microsoft remained quiet for as long as it could, and then eventually announced it would continue operations in China.

Microsoft CEO Steve Ballmer stated the company’s stand again in a post on The Microsoft Blog.

“We have done business in China for more than 20 years and we intend to stay engaged, which means our business must respect the laws of China. That’s true for every company doing business in countries around the world: we are all subject to local laws.”

This is not a surprise at all–if one of Microsoft’s biggest competitors has decided to leave a market, it is time to take advantage. Microsoft maintains that its systems were not hacked in the Chinese cyber-attacks on the 30 or so US companies.

Which free database programs can be used that will accept input from a program written in C?

Answer: It is possible to interface quite a few different databases with the correct libraries in C.

For example, Microsoft’s Visual C++ allows binding to Microsoft’s JET engine (used by Access), SQL and a couple of others.

However for C language, the best bet will probably be MySQL as it has libraries for most OS’s.

To convert a FAT partition to NTFS, perform the following steps.

1) Click Start, click Programs, and then click Command Prompt.

2) In Windows XP, click Start, click Run, type cmd and then click OK.

3) At the command prompt, type CONVERT [driveletter]: /FS:NTFS.

4) Convert.exe will attempt to convert the partition to NTFS.

NOTE: Although the chance of corruption or data loss during the conversion from FAT to NTFS is minimal, it is best to perform a full backup of the data on the drive that it is to be converted prior to executing the convert command. It is also recommended to verify the integrity of the backup before proceeding, as well as to run RDISK and update the emergency repair disk (ERD).

The website of India’s largest software firm, Tata Consultancy Services (TCS) became disrupted for sometime as Network Solutions came under a cyber attack on Sunday. The company’s website was unavailable for over three hours and redirected to a “domain name for sale” page.

www.tcs.com displayed the message ‘this domain name is for sale’ for nearly three hours. Everything was back to normal by Monday morning.

A TCS spokesman stated that the attackers breached at the domain name registrar’s end i.e. Network Solutions. Network Solutions is one of the top five domain name registrars on internet, managing almost 6.4 million domains.

According to a report on techie-buzz.com, a French hacker was involved in the hijacking. This hack appears to be a DNS hijack which is quite similar to the breach that Twitter buckled under last year.

None of the servers were breached and so there would be no data loss. Initial investigation reveals a DNS redirection at the domain name registrar’s end. TCS is busy in further investigations.