basic_unix_tutorial.pdf

A Basic UNIX Tutorial

This tutorial comprises fourteen sections, each of which addresses a fundamental aspect of UNIX

computing. It concentrates on illustrating the central concepts by providing short explanations, along

with examples, and exercises.

This tutorial covers the "Introduction to UNIX" and "Intermediate UNIX" workshops offered

by the Idaho State University Computer Center. Check the ISU workshop schedule to see

when the workshops are offered.

Table of Contents

What Is UNIX?

A broad description of the UNIX operating system.

Accessing UNIX Systems

General methods of accessing UNIX computers.

Logging In and Logging Out

Gaining access to your UNIX account.

The UNIX Shell

How to enter UNIX commands.

Files and Directories

Storing and manipulating files.

Input/Output Redirection

How to manage input and output.

Pipelines and Filters

Creating processing pipelines.

Processes and Multitasking

Managing processes.

Interaction and Job Control

More on managing processes.

Text Editing with Emacs

Creating and editing text files with the emacs editor.

The Execution Environment

The environment under which shell commands and programs run.

Customizing the Shell

Personalizing your UNIX shell environment.

Interactive Use of the Shell

Tips and tricks to enhance your efficiency with the command line interface.

The UNIX Filesystem

A closer look at UNIX files and directories.

I DAHO S TATE U NIVERSITY

Contact: webmaster@isu.edu

Revised: February 5, 1997

URL: http://www.isu.edu/departments/comcom/workshops/unix/

Author: Jonathan Byrd

Section 1: What Is Unix?

Unix is an operating system . The job of an operating system is to orchestrate the various parts of the

computer -- the processor, the on-board memory, the disk drives, keyboards, video monitors, etc. --

to perform useful tasks. The operating system is the master controller of the computer, the glue that

holds together all the components of the system, including the administrators, programmers, and

users. When you want the computer to do something for you, like start a program, copy a file, or

display the contents of a directory, it is the operating system that must perform those tasks for you.

More than anything else, the operating system gives the computer its recognizable characteristics. It

would be difficult to distinguish between two completely different computers, if they were running

the same operating system. Conversely, two identical computers, running different operating

systems, would appear completely different to the user.

Unix was created in the late 1960s, in an effort to provide a multiuser, multitasking system for use by

programmers. The philosophy behind the design of Unix was to provide simple, yet powerful

utilities that could be pieced together in a flexible manner to perform a wide variety of tasks.

The Unix operating system comprises three parts: The kernel, the standard utility programs, and the

system configuration files.

The kernel

The kernel is the core of the Unix operating system. Basically, the kernel is a large program that is

loaded into memory when the machine is turned on, and it controls the allocation of hardware

resources from that point forward. The kernel knows what hardware resources are available (like the

processor(s), the on-board memory, the disk drives, network interfaces, etc.), and it has the necessary

programs to talk to all the devices connected to it.

The standard utility programs

These programs include simple utilities like cp, which copies files, and complex utilities, like the

shell that allows you to issue commands to the operating system.

The system configuration files

The system configuration files are read by the kernel, and some of the standard utilities. The Unix

kernel and the utilities are flexible programs, and certain aspects of their behavior can be controlled

by changing the standard configuration files. One example of a system configuration file is the

filesystem table "fstab" , which tells the kernel where to find all the files on the disk drives. Another

example is the system log configuration file "syslog.conf", which tells the kernel how to record the

various kinds of events and errors it may encounter.

Section 2: Accessing a Unix System

There are many ways that you can access a Unix system. If you want the fullest possible access to

the computer's commands and utilities, you must initiate a login session. The main mode of initiating

a login session to a Unix machine is through a terminal , which usually includes a keyboard, and a

video monitor.

When a terminal establishes a connection to the Unix system, the Unix kernel runs a process called a

tty to accept input from the terminal, and send output to the terminal. When the tty process is created,

it must be told the capabilities of the terminal, so it can correctly read from, and write to, the

terminal. If the tty process receives incorrect information about the terminal type, unexpected results

can occur.

Console

Every Unix system has a main console that is connected directly to the machine. The console is a

special type of terminal that is recognized when the system is started. Some Unix system operations

must be performed at the console. Typically, the console is only accessible by the system operators,

and administrators.

Dumb terminals

Some terminals are referred to as "dumb" terminals because they have only the minimum amount of

power required to send characters as input to the Unix system, and receive characters as output from

the Unix system.

Personal computers are often used to emulate dumb terminals, so that they can be connected to a

Unix system.

Dumb terminals can be connected directly to a Unix machine, or may be connected remotely,

through a modem, a terminal server, or other network connection.

Smart terminals

Smart terminals, like the X terminal, can interact with the Unix system at a higher level. Smart

terminals have enough on-board memory and processing power to support graphical interfaces. The

interaction between a smart terminal and a Unix system can go beyond simple characters to include

icons, windows, menus, and mouse actions.

Network-based access modes

Unix computers were designed early in their history to be network-aware. The fact that Unix

computers were prevalent in academic and research environments led to their broad use in the

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