Basics of Unix/Linux

What is Unix ?

The UNIX operating system is a set of programs that act as a link between the computer and the user.

The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel.

Users communicate with the kernel through a program known as the shell. The shell is a

command line interpreter; it translates commands entered by the user and converts them into a

language that is understood by the kernel.

# Unix was originally developed  in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna.

# There are various Unix variants available in the market. Solaris Unix, IBM-AIX, HP-UX unix.

# UNIX is called multitasking a user can run multiple programs at the same time.

# UNIX is called a multiuser system because several users can access at the same time.

What is Linux ?

Linux is an operating system that was first created at the University of Helsinki in Finland by a

young student named Linus Torvalds. At this time the student was working on a UNIX system that

was running on an expensive platform. Because of his low budget, and his need to work at home,

he decided to create a copy of the UNIX system in order to run it on a less expensive platform,

such as an IBM PC.

The Linux operating system is developed under the GNU General Public License (also known as

GNU GPL) and its source code is freely available to everyone who downloads it via the Internet.

The CD-ROM version of Linux is also available in many stores, and companies that provide it will

charge you for the cost of the media and support. Linux may be used for a wide variety of

purposes including networking, software development, and as an end-user platform. Linux is

often considered an excellent, low-cost alternative to other more expensive operating systems

because you can install it on multiple computers without paying more.

Advantages of Linux

# There are no royalty or licensing fees for using Linux, and the source code can be modified to fit

your needs. The results can be sold for profit, but original authors retain copyright and you must

provide the source to your modifications.

# Because it comes with source code to the kernel, it is quite portable. Linux runs on more CPUs

and platforms than any other computer operating system.

#The recent direction of the software and hardware industry is to push consumers to purchase

faster computers with more system memory and hard drive storage. Linux systems are not

affected by those industries’ orientation because of it capacity to run on any kind of computers,

even aging x486-based computers with limited amounts of RAM.

# Linux is a true multi-tasking operating system similar to his brother UNIX. That means that if a

program crashes you can kill it and continue working with confidence.

#Another benefit is that Linux is practically immunized against all kinds of viruses that we find in

other operating systems. To date we have found only two viruses that were effective on Linux

systems.

Unix Components

Kernel

The computer programs that allocate the system resources and coordinate all the details of the computer's internals is called the operating system or kernel.

Cell

Users communicate with the kernel through a program known as the shell. The shell is a command line interpreter; it translates commands entered by the user and converts them into a language that is understood by the kernel. C Shell, Bourne Shell and Korn Shell are most famous shells which are available with most of the Unix variants.

Commands and Utilities

There are various command and utilities which you would use in your day to day activities.  cp, mv, cat  and  grep  etc. are few examples of commands and utilities. There are over 250 standard commands plus numerous others provided through 3rd party software. All the commands come along with various optional options.

Files and Directories

All data in UNIX is organized into files. All files are organized into directories. These directories are organized into a tree-like structure called the file system.

File Management in Unix

All data in UNIX is organized into files. All files are organized into directories. These directories

are organized into a tree-like structure called the file system.

Thare are three basic types of files in unix

Ordinary  Files

An ordinary file is a file on the system that contains data, text, or program instructions. In this tutorial, you look at working with ordinary files.

Directories

Directories store both special and ordinary files. For users familiar with Windows or Mac OS, UNIX directories are equivalent to folders.

Special Files

Some special files provide access to hardware such as hard drives, CD-ROM drives, modems, and Ethernet adapters. Other special files are similar to aliases or shortcuts and enable you to access a single file using different names.