C Manual Pages in Ubuntu

To get a manual over C statements in Ubuntu, you have to run these commands in the terminal :

sudo apt-get install build-essential gcc-3.3-doc c-cpp-reference
apt-cache search gcc|grep doc
sudo apt-get install manpages-posix
sudo apt-get install manpages-posix-dev

Command Line Arguments, C programming

Command Line Arguments

C provides a fairly simple mechanism for retrieving command line parameters entered by the user. It passes an argv parameter to the main function in th

e program. argv structures appear in a fair number of the more advanced library calls, so understanding them is useful to any C programmer.

Enter the following code and compile it:

In this code, the main program accepts two parameters, argv and argc. The argv parameter is an array of pointers to string that contains the parameters entered when the program was invoked at the UNIX command line. The argc integer contains a count of the number of parameters. This particular piece of code types out the command line parameters. To try this, compile the code to an executable file named aaa and type aaa xxx yyy zzz. The code will print the command line parameters xxx, yyy and zzz, one per line.

The char *argv[] line is an array of pointers to string. In other words, each element of the array is a pointer, and each pointer points to a string (technically, to the first character of the string). Thus, argv[0] points to a string that contains the first parameter on the command line (the program's name), argv[1] points to the next parameter, and so on. The argc variable tells you how many of the pointers in the array are valid. You will find that the preceding code does nothing more than print each of the valid strings pointed to by argv.

Because argv exists, you can let your program react to command line parameters entered by the user fairly easily. For example, you might have your program detect the word help as the first parameter following the program name, and dump a help file to stdout. File names can also be passed in and used in your fopen statements.

Source : http://computer.howstuffworks.com/c38.htm

Setting up Persian language in Ubuntu

For viewing Persian alphabet in Ubuntu, you can simply install the package called "msttcorefonts".

Code:

setxkbmap -option grp:switch,grp:shift_toggle,grp_led:scroll us,ir &

Then press both SHIFT keys at the same time (SHIFT+SHIFT) to toggle your keyboard between English and Farsi.

If it works then you just need to have this line executed everytime you login (for example have it in a script that will be run in your profile or in your Autorun)

Source : http://ubuntuforums.org/showthread.php?t=198188

install C/C++ on your Ubuntu, HOWTO

If you are a developer you need C and C++ Compiler for your development work.In ubuntu you can install the build-essential for C and C++ compilers.

Install C and C++ Compilers in Ubuntu

sudo aptitude install build-essential

This will install all the required packages for C and C++ compilers

Testing C and C++ Programs

Compiling Your first C Programs

Now you need to open first.c file

sudo gedit first.c

add the following lines save and exit the file

Firstly compile the code using the following command

cc -c first.c

that would produce an object file you may need to add to the library.

then create an executable using the following command

cc -o first first.c

Now run this executable using the following command

./first

Output should show as follows

Hello, world

Compiling your first C++ program

If you want to run c++ program follow this procedure

g++ is the compiler that you must use.

you should use a .cpp file extension rather than a .c one

You need to create a file

sudo gedit first.cpp

add the following lines save and exit the file

Run your C++ Program using the following command

g++ first.cpp -o test

./test

Output should show as follows

Hello World!

Source : http://www.ubuntugeek.com/how-to-install-c-and-c-compilers-in-ubuntu-and-testing-your-first-c-and-c-program.html

How to install VLC media player on Ubuntu

You need to check that a "universe" mirror is listed in your /etc/apt/sources.list.

   % sudo apt-get update
 % sudo apt-get install vlc vlc-plugin-esd mozilla-plugin-vlc

How to change the root password in Ubuntu

In Linux (and Unix in general), there is a superuser named root. The Windows equivalent of root is Administrator. The superuser can do anything and everything, and thus doing daily work as the superuser can be dangerous. You could type a command incorrectly and destroy the system. Ideally, you run as a user that has only the privileges needed for the task at hand. In some cases, this is necessarily root, but most of the time it is a regular user.

By default, the root account password is locked in Ubuntu. This means that you cannot login as root directly or use the su command to become the root user. However, since the root account physically exists it is still possible to run programs with root-level privileges. This is where sudo comes in - it allows authorized users (normally "Administrative" users; for further information please refer to AddUsersHowto) to run certain programs as root without having to know the root password.

This means that in the terminal you should use sudo for commands that require root privileges; simply prepend sudo to all the commands you would normally run as root. For more extensive usage examples, please see below. Similarly, when you run GUI programs that require root privileges (e.g. the network configuration applet), use graphical sudo and you will also be prompted for a password (more below). Just remember, when sudo asks for a password, it needs YOUR USER password, and not the root account password.

BUT anyway, if you really want to make the root user, you can do as followed :

To manually set a password for the root user, type in the following in the shell:
sudo passwd

After that you are asked to type in the new root password twice. Finally, your root user has its own password.

Logging in as another user

Please don't use this to become root, see further down in the page for more information about that.

sudo -i -u username

For example to become the user amanda for tape management purposes.

sudo -i -u amanda

The password being asked for is your own, not amanda's.