Unix Tutorial

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What is Unix?

Getting started

Hardware

Software

Basic Commands

vi Commands

Files

File Commands

Different types of file

File Redirection

Permissions

Pipelines / Filters

Directory

Directory Structure

Directory Command

Shell

Different types of shell

Compiling Program

Networking

Commands

Reference

Reference Commands

online help : Manpages

Useful links/Books

Search Engine

WHAT IS UNIX ?

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Unix operating systems all share two important characteristics:

• MULTITASKING:Unix system can run more than one program at a time.
• MULTIUSER :Unix can support more than one user at a time

There are many variations of Unix.

Name of Company	UNIX
Sun Microsystems	Solaris and Sun OS
Microsoft	XENIX
Silicon Graphics Inc(SGI)	IRIS
Novell	UNIXWare
University of Berkeley	BSD UNIX
AT & T	Unix SVR 3 ,Unix SVR 4
Hewlett-Packard (HP)	HP-UX
RedHat Software	RedHat Linux
Digital Equipment Corp(DEC)	ULTRIX, Digital UNIX

• Unix has more than 250 individual commands.These range from simple commands-for copying a file, for example-to the quite complex: those used in high-speed networking, file revision management, and software development.
• Unix is a multichoice system.As an example, Unix has three different primary command-line-based user interfaces(in Unix, the command-line user interface is called a shell): The three choices are the

1. Bourne shell,
2. C shell, and
3. Korn shell.

The UNIX operating system has three important features;

• The Kernel

The kernel is at the core of each UNIX system and is loaded in whenever the system is started up. It manages the entire resources of the system, presenting them to you and every other user as a coherent system. You do not need to know anything about the kernel in order to use a UNIX system. This information is provided for your information only.

Amongst the functions performed by the kernel are:

1. managing the machine's memory and allocating it to each process.
2. scheduling the work done by the CPU so that the work of each user is carried out as efficiently as is possible.
3. organising the transfer of data from one part of the machine to another.
4. accepting instructions from the shell and carrying them out. enforcing the access permissions that are in force on the file system.
• The Shell

Whenever you login to a Unix system you are placed in a program called the shell. You can see its prompt at the bottom left of your screen. To get your work done, you enter commands at this prompt. The shell acts as a command interpreter; it takes each command and passes it to the operating system kernel to be acted upon. It then displays the results of this operation on your screen.

• UNIX file system

Files are the integral part of your Unix system.A file system is a logical method for organising and storing large amounts of information in a way which makes it easily managable. The file is the smallest unit in which information is stored.