01 Introduction Unix Os

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Introduction to UNIXCET 421

Objectives

Motivate the use of UNIX

Introduce basic UNIX features (e.g. using directories, files)

Introduce vi and emacs



Contents

1. Background on UNIX

2. Starting / Finishing

3. Typing UNIX Commands

4. Commands to Use Right Away

5. UNIX help

continued



6. The UNIX File System

7. Working with Directories

8. Working with Files

9. Communicating with People

10. E-mail

11. vi/emacs



1.Background on UNIX

1.1. What is UNIX?

1.2. Histor y

1.3. Why use UNIX?



What is Unix?

A f ully featured moder n operating system

It is available in a variety of ³flavors.´

It¶s comprised of simple tools that perform a single f unction well.

These tools can be used together to perform complex tasks.



1.1. What is UNIX?

The UNIX Operating System (OS) is a large program (mostly coded in C) that tur ns the computer into a useable machine.

It provides a number of facilities:

management of hardware resources

director y and file system loading / execution / suspension of programs



History

Beginnings in 1969 AT & T Bell Laboratories

Ken Thompson and Dennis Richie

Working version (in 1970) on a DEC PDP 11/70

UNIX and C Relationship June 81: Berkeley UNIX 4.1 BSD (enhanced with vi , csh, and

virtual memory management )

1983: Berkeley UNIX 4.2 BSD (added TCP/IP networking,

sockets and a new file system) Later UNIX/32V, SYSTEM III, SYSTEM V

and then Linux



1.2.(Brief)

H

istory 1969 First UNIX at Bell Labs

1975 Bell Labs makes UNIX freeware

1970¶s Berkeley UNIX (BSD)

1980¶s TCP/IPMIT X-Windows

1990¶s The Web,LINUX



1.3. Wh

y Use UNIX? multi-tasking / multi-user

lots of software

networking capability

graphical (with command line)

easy to program

portable (PCs, mainframes, super -computers)

continued



free! (LINUX, FreeBSD, GNU)

popular

profitable1996 Sales: US$34.5 Billion, up 12%

not tied to one company

active community



UNIX Hardware is surrounded by the operating system

software

Operating system is called the system ker nel

The ker nel is the core of an operating system and manages the machine¶s hardware resources (including the processor and the memor y), and provides and controls the way any other software component canaccess these resources. The ker nel r uns with a higher privilege than other programs

(so-called user -mode programs). Comes with a number of user services and interfaces

Shell

Components of the C compiler

GUI or Command Line Interface



UNIX



M

odern UNIX Systems System V Release 4 (SVR4)

Solaris 9

4.4BSD

Linux



Unix is Made Up of ProcessesProcesses

Running ProgramsRunning ProgramsUser owned User owned

System ownedSystem owned

FilesFiles

Regular Files: Regular Files:

± ± DataData

± ± Executables <Executables <---- usually start a processusually start a process

Director y FilesDirector y Files

± ± Contain other files and directoriesContain other files and directories

Special FilesSpecial Files



UNIX Kernel



Modern UNIX Kernel



Unix Help

There is online help available on any Unix system.

The help system is call the "Unix man pages"set of help files and a command to view them.

the book has some of the same information, but you might need to check the man pages for your specific system for details.



RTFM

The acronym RTFM (commonly found innewgroups and other sources of information for Unix users and System Administrators) stands for:

Read The « Man page (or Read The « Manual).

It's common for beginners to str uggle instead of reading the man pages « it takes a while to get the hang of how to decipher the man pages.



Learning Unix

In class we will have:

lectures

demonstrations

thought exercises

You need to spend time playing on a Unix system to lear n!



Operating Systems

An Operating System controls (manages) hardware and software.

provides support for peripherals such as keyboard, mouse, screen, disk drives, «

software applications use the OS to communicate with peripherals.

The OS typically manages (starts, stops, pauses, etc) applications.



Single vs. Multitasking

Some old operating systems could only do one thing at a time (DOS).

Most moder n systems can support multiple applications (tasks) and some can support multiple users (at the same time).

Supporting multiple tasks/users means the OSmust manage memor y, CPU time, network interfaces, ...



User Interfaces

The User Interface is the software that supports interactions with a human.

Some operating systems directly provide a user interface and some don't.

Windows is an example of an Operating System that includes a user interface.

Unix (the OS) does not directly provide a user interface.



Unix and Users

Most flavors of Unix (there are many) provide the same set of applications to support humans

(commands and shells). Although these user interface programs are not

part of the OS directly, they are standardized enough that lear ning your way around one flavor

of Unix is enough.



Flavors of Unix

There are many versions of Unix that are used by lots of people:

SysV (from AT&T)BSD (from Berkeley)

Solaris (Sun)

IRIX (SGI)

AIX (IBM)

LINUX (free software)



POSIX

POSIX is a standard that describes a single interface to a Unix like operating system.

POSIX is not an implementation - it is a description!

Most vendors are supporting POSIX (by making sure their version of Unix adheres to the standard).



Unix History and Motivation

The first version of Unix came from AT&T in the early 1970s (Unix is old!).

Unix was developed by programmers and f or programmers.

Unix is designed so that users can extend the f unctionality - to build new tools easily and efficiently (this is important for programmers).



Some Basic Concepts

Unix provides a simple interface to peripherals (it's pretty easy to add support for a new

peripheral). Unix includes a basic set of commands that

allow the user to view/change the system resources (filesystem, processes, peripherals,

etc.).



What we will look at

In this course we will lear n about:

Unix user accounts

the core set of Unix commands

the Unix filesystem

A couple of special programs called "shells".

A number of commonly used applications:

Window system, text editors, programming tools.



The power of Unix is that you can

extend the basic commands We will also look at how to extend the basic

f unctionality of Unix:

customize the shell and user interface. string together a series of Unix commands to create

new f unctionality.

create custom commands that do exactly what we

want.



Our View of the World as Users

Unix Shell

Your ShellYour Shell

A shell is a process A shell is a process that acts as anthat acts as aninterface to the OS. It interface to the OS. It allows the user to r unallows the user to r un

programs individuallyprograms individuallyand together to and together to

accomplish a task.accomplish a task.



While graphical user interfaces are available and often used on Unix systems you must have a working knowledge of the standard command line utilities, pipes, and I/O redirection to benefit from the considerable strengths of Unix.

Use th

e command line



Simple Unix

Directory Structure/

usr etc home bin var ...

local bin ... class home ugrad ...

u1 u2 ...



Your First Command

Syntax: man topic

man provides online documentation on nearly ever ystandard command and configuration file.

Optional Syntax: man -k k eyword

man man for more details

Man(manual) -- Documentation is your friend



Special DirectoriesHome Director y /home/u1

~u1

~

A user generally has permission to freely manipulate files within this director y and its children.

Users start with their home director y as their pwd when they login.



Changing Directories The cd(Change Director y) command is used to change

directories

cd path

Paths can be relative or absolute

pwd reports present working director y

cd when entered by itself sets the pwd to the user¶s home director y.



Your Prompt Helps you Navigate

The default prompt on your user account tells you what director y is your pwd(where you are at the moment).

Some Examples:

csy12:~/bin>

csy12:/home

csy12:/usr /man



Other File System Utilities

ls Lists all files in a director y

cp Copies files

mv Moves files

rm Deletes files

mkdir Makes directories

rmdir Removes directories



Basic Syntax ls ls

cp cp source dest ORcp source « dir

mv mv source dest OR

mv source « dir

rm rm f ile

mkdir mkdir new directory name

rmdir rmdir directory to be removed



Other Comands

Ever y Unix distribution comes with hundreds of other standard commands that can be used for ever ything from viewing and

searching files to developing software.

Look through /bin, /usr /bin, and /usr /local/bin on most systems system and look at the man pages for the programs in those directories for more information.



Using Other Commands

Syntax: command file

cat Echoes file contents to the screen

grep Searches a file for a string

more Echos a file a line at a time

less Same as more but more features

wc Counts the words in a file and more

sort Sorts the contents of a file



Pipes and RedirectionThe Unix ³philosophy´ involves a set of generic tools which each do one thing well. Using these tools together

allows you to appreciate the power of the Unix command.

In Unix ever ything (including hardware devices) is treated as a File that can be read from and written to.



Pipes Pipes connect stdout of one command to stdin of

another comand.

i.e.

ls | less

cat student_list | grep senior | sort



I/O Redirection I/O redirection allows the user to change where input to

a command or output from a command goes to/comes

from.

cat student_list > outfile

program < infile

program < infile > outfile



Standard File HandlesEver y Unix process automatically comes with three file handles or descriptors.

These are:

Standard Input (stdin)

Keyboard

Standard Output (stdout)

Display

Standard Error (stderr)

Display (unbuff)



Three Default Open Files

Program

stdinstderr

stdout Buffer



Standard File Handles All standard shells provide a facility to re-map

these three file handles to other devices and files

in addition to other commands.

This allows one to use several simple Unix

commands to perform a complex task.



Pipes

Program 1

Program 2

Program 3

stdinPipe

stdout

Pipe

stdout

stdin



Shell/Environment Variables

Parent Process

VAR=1

Child Process

VAR=????

Shell Variables

Parent Process

VAR=1

Child Process

VAR=1

Environment Variables

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