introduction to linux1

7/28/2019 Introduction to Linux1

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Lab 1

INTRODUCTION

TO

LINUX


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What is Computer

A computer is an electronic device that

accepts information in the form ofdigitalized data and manipulates it for some

result based on a program or sequence of

instructions on how the data is to beprocessed.


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The Computer is a programmable finite

state machine which can perform precise

arithmetic and logical operations.

A programmable finite state machine is

one that can take a fixed range of values.The computer is called programmable

because it can be instructed to perform

tasks within its capacity.


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Computer System

Hardware Software Livewire(User)

Computer System


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HARDWARE

The physical circuitry and components areknown as hardware.

The hardware is categorized into five blocks.

Namely

Input Unit

Arithmetic Logic Unit(ALU)Control Unit

Memory

Output Unit


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CRT Display

Keyboard

Mouse

The Box

CD-ROMDrive

Floppy

Disk

Drive


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Software

Application Software System Software

Software


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What is a System Software?A computer program that controls the system hardware

system and interacts with application software;

Example- operating system.What is an Application Software?Application software (sometimes shortened toapplication) is any program designed to perform a

specific function directly for the user or, in some cases,

for another application program. Typical types of

application software include: Word processing,Electronic spreadsheet, Database, Email reader, Web

browser, Graphics software and so on.


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Operating System?

It is a set of programs that act as an interfacebetween the user and the hardware.

It is a system software that lies between

computer hardware (disk, Memory, Processoretc.) and the Application programs (WordProcessors, Web Browsers, spread Sheetsetc.)

It controls and co-ordinate the operation of acomputer system.


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What OS does?

It loads itself into the memory-Booting.

It loads the user program in the memory.

It loads the data required by the program in thememory.

Interprets the program instruction one at a time.

Sends instruction to the output device to display

the result on the screen. Uses the resources like memory, input and

output devices properly and efficiently.


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Major OS Functions

User Interface

Job/Task Management

Data Management

Device Management

Security


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Types of OS

Single User OS

Multi User OS

Multi Tasking OS Multi Processing

Real Time OS


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Linux OS

Linux is a free Unix-like operatingsystem Developed under the GNUGeneral Public License

It is a multi-user, multitasking OS withsupport for Networking

The source code for Linux is freelyavailable to everyone.


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History of Development!

The development of Linux started fromUNIX.

UNIX is a trade mark of AT & T,originally developed by Ken Thompson,

Dennis Ritchie and others back in 1970srunning on mainframes andmicrocomputers.

It is a multitasking and multi user OS.

Unix is mostly used in servers and webservers.

It is written with C language

It is a foundation for many OS like Linux,Novell etc. Ken Thompson, 1943

Dennis Ritchie, 1941


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History continues

Linux OS uses Unix as the base and gives

further more facilities and applications.

It was first released by its inventor LinusTorvalds in 1991.

In Linux GUI is made having Unix as its

core.

Linux is the ultimate Unix.


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History continues

Many vendors purchased the source code andhave developed their own versions.

IBM, HP, Sun etc.

The source code was also made free to collegesand universities.

UC Berkeley, and MIT have been on the front edge of

development since the beginning. As a lot of variations are appeared in various

versions, IEEE comes with a standard POSIX.1(Portable Operating System Interface for UNIX).


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Linux Came into Picture!!!

The down side of UNIX is that it is proprietary big and

expensive, especially for PC version.

This is where Linux comes in.

It was designed to be small, fast and inexpensive with

every functionality available.

Originally created by Linus Tovalds of university of

Helsinki, Finlald in 1991 using no code from AT & T. But partially from scratch and partially from using publicly

available PC based implementation of UNIX called

MINIX.


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Linux released!!! Finally Towards the end of 1991

Linux was made public and in Nov.

1991 version 0.10 was released.

In Dec 1991 version 0.11 wasreleased.

At the same time Torvalds made

source code free on the Internet and

asked to work with it.

Today's version of Linux is 2.6.12.x.

and freely downloadable from

www.kernel.org.

The Big Boss!

Linus Torvalds,

1969


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Linux Distributions

Several Companies and Organizations began

gathering and packaging Linux software together

in to useable forms called distributions Now there are almost more than 350

distributions available around the world!

The most popular distributions areRed Hat, SuSe, Debian, Slackware, Mandrake etc.


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Features of LINUX

Multi-user Multiple users can logged into and work on the system at the

same time.

Each user will have their own private area in the system where

they can customize their environments for use.

Multitasking

Can have many programs running at the same time for the user

Also Linux runs many of the system processes in the background

called Daemon processes, which remain ready for ever to serve

the request of a user. Graphical User Interface.

Hardware Support

Linux supports all most all well known hardware.

Networking Support


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Advantages!

Documentations like books, tutorials are freely

available for download in the web.

Also a project called Linux Documentation

project provides free materials

www.tldp.org

Help is available by professionals around theworld round the clock.


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Linux Commands


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What is a Command?

A command is an instruction telling acomputer to do something.

A command is an instruction to

perform a task in operating system


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Linux Commands

A command prompt looks like

[cs0203@linuxserver cpp]$

cs0203: user name linuxserver: machine name

cpp: current working directory


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Guidelines

All commands must always be entered in smallcase letters

Between command name and the options theremust be a space

The options are usually preceded by a - sign

Two or more options may be combined like

lsa -l as lsal

To repeat a command up-down arrow keys may beused


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Basic Linux Commands dateprints current date and time

Syntax:[cs0203@linuxserver cpp]$ date

O/P: Tue Nov 22 15:24:12 IST 2005

cal

Prints calander of current year Syntax:

[cs0203@linuxserver cpp]$cal 11 2005

O/P: November 2005

Su Mo Tu We Th Fr Sa1 2 3 4 5

6 7 8 9 10 11 12

13 14 15 16 17 18 19

20 21 22 23 24 25 26


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Basic Linux Commands

who (who am i) Displays the users logged in to the system

Syntax

[cs0203@linuxserver cpp]$who

O/P:ee05183 pts/278 Nov 22 15:23 (192.168.5.8)

et05428 pts/286 Nov 22 15:29 (192.168.5.9)

ee05410 pts/285 Nov 22 15:29 (192.168.5.10)

pwd Displays present working directory

Syntax:

[cs0203@linuxserver cpp]$pwd

O/P: /home/cs0230/cpp


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Basic Linux Commands

ls Lists files and folders of current directory

O/P:

squid.conf fontforge-20040529-1.i386.rpm squid.newsquid.conf golden collection mukeshpics

squidGuard.log indlinuxtcp ls -l

Long listing of files and folders of current directory

O/P:

-rw-r--r-- 1 cs01 cs01 2474 Oct 1 17:25 maze.cpp

drwxrwxr-x 4 cs01 cs01 4096 Oct 25 11:19 linux

lsal

List all files in the current working directory in long listing formatshowing permissions, ownership, size, and time and date stamp


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Getting Help

man

Displays the system manual

Command man displays information on man

Syntax :

[cs0203@linuxserver cpp]$man ls

info

Displays information in a different format

Command info displays information on man

Syntax:

[cs0203@linuxserver cpp]$info date


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What is a File?Any named collection of information stored on a disk.

Application programs and documents are examples of

files. You make a file when you create information (such

as text or graphics) using a program, give the material a

name and save it on a disk.

What is a Directory?It is a special kind of file that points to or contains

others files and directories. Directories can benested to any depth. Some software may refer to

directories and subdirectories by other names, such

as, folders, lockers, file drawer, etc.


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Creating a file touch

Creates an empty file Syntax:

[cs0203@linuxserver cpp]$touch test.txt

cat Used to create and display a file.

cat : displays file contentsSyntax:[cs0203@linuxserver cpp]$cat firstfile.txt

cat > : creates a file and save with ctrl+d

Syntax:[cs0203@linuxserver cpp]$cat > firstfile.txt

cat file1 file2 > file3 : concatenates contents of files file1 & file2 & storeit in file3(if it is not exist then newly created otherwise content of file3 is

overridden)Syntax:[cs0203@linuxserver cpp]$cat file1 file2 > file3

Cat file1 file2 >> file3 :concatenates content of files ,if file3 exist&contents some information then new content is appended.

Syntax:[cs0203@cat file1 file2 >>file3


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File related commands

mkdir

To create directory(s)

Syntax:

[cs0203@linuxserver cpp]$mkdir silicon cd

To change directory

Syntax:

[cs0203@linuxserver cpp]$cd silicon file

Display file type

Syntax:

[cs0203@linuxserver cpp]$file firstfile


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What is Path?Path is the specification of a file or directory in a hierarchical file

system using pathname separators ("/" in Unix)between

directories. The pathname tells the shell where in the directorytree to find a file. Files may be referred to by absolute pathname(also called full or complete pathname) orrelative pathname.Absolute path is a path relative to the root directory, the topmostnode of a hierarchical file system. Its first character must be a

pathname separator, e.g., the Unix forward slash . absolute

pathname is the full specification of a path beginning with the root

directory and including all directory levels the system passes

through to locate the file.relative pathname is the location of the file or directory relative tothe directory in which the user is currently located (the current

working directory).


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File commands contd. cp

Copies srcfile to destfile If destination file is present then overwrites

Else creates a new file with name destfile

Syntax:

[cs0203@linuxserver cpp]$cp test.c test1.c

clear

Clears the screen

Syntax:

[cs0203@linuxserver cpp]$clear shutdown

Shuts the system down.

Syntax:

[cs0203@linuxserver cpp]$shutdown

File commands contd


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File commands contd. mv

moves/renames a file or directory

mv : renaming

mv : moves to path directory

mv : moves with renaming

Syntax:

[cs0203@linuxserver cpp]$mv test.txt test1.c

rm

Removes/deletes a file

Syntax:

[cs0203@linuxserver cpp]$rm test.c rmdir

Removes/deletes an empty directory

Syntax:

[cs0203@linuxserver cpp]$rmdir cpp


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Some VI Commands


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vi is a screen-oriented text editor written by Bill Joy in 1976 .The name vi is derived from the shortest unambiguous

abbreviation for the command visual in ex.

vi editor works in 3 different modes

>> Command Mode

>> Insert Mode

>> Last Line Mode

INTRODUCTION TO VI EDITOR


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:Insert Mode

Command Mode

Last Line Mode

i, I, o, O, a, A

EscEsc or Enter


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[cs0203@linuxserver cpp]$vi

e.g [cs0203@linuxserver cpp]$vi firstcprog.cIf the file firstcprog.c exists then this command open the fileotherwise it will be created.

when vi editor starts it will be in command mode. To type we

must have to go to Insert mode.

Command to invoke Vi editor


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Operation on Vi Editor

Delete Operation

First move the cursor so that it covers the first character of thegroup you want to delete, then type the desired command as

below

x Delete only the current character D Delete to the end of the line

db Delete from the current character to the beginning of thecurrent word

de Delete from the current character to the end of thecurrent word

dd Delete the current line

dw Delete from the current character to the beginning of thenext word

[n]dd delete n lines from the current line.


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Operation on Vi Editor

Copy & Paste operation

p

Paste the specified buffer after the current cursor position or

line. If no buffer is specified (with the " command.) then 'p' uses

the general buffer.P

Paste the specified buffer before the current cursor position or

line. If no buffer is specified (with the " command.) then 'P' uses

the general buffer.

y

Yank(copy) the current line.

[n]yy

Yank n lines from the current line. The buffer can be specified

with the " command. If no buffer is specified, then the

general buffer is used.


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A

Append at the end of the current line.I

Insert from the beginning of a line.

O

(letter oh) Enterinsertmode in a new line above the current

cursor position.

aEnterinsertmode, the characters typed in will be inserted after

the current cursor position. A count inserts all the text that had

been inserted that many times.

i

Enterinsertmode, the characters typed in will be inserted before the

current cursor position. A count inserts all the text that had been

inserted that many times.

o

Enterinsertmode in a new line below the current cursor position.

Inserting New Text ( Change mode from Command to Insert)


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ZZ (in Command Mode)

Exit the editor, saving if any changes were made.

:w (in Last Line Mode)

Save the current document

:q (in Last Line Mode)

Exit the editor if no modification is made.

:wq (in Last Line Mode)

Exit the editor, saving if any changes were made.

:q! (in Last Line Mode)Exit the editor, without saving if any changes were made.

:wq! (in Last Line Mode)

Exit the editor, overrides the files saving if any changes

were made.

Saving and Quitti ng


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Search and Replace

As files become longer, you may need assistancelocating a particular instance of text.

Simple search / enter

n: next forward, N: next backward

Search-Exclusions/wild-card search

The special characters are: $ . * [ ] ^ \.The slash (/) starts a forward search. And (?) to

search backwards.


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Search and Replace

finding instances of a given string and replacingthem with a new string. It has the following

: line1, line2s/ oldstring / newstring

You specify the range of text for the search-and-

replace command with the line numbers line1 and line2. If you only give line1 and omit the comma,

then the command only affects that line. If you

give no line numbers, the command affects the

current line. The search-and-replace commandonly finds the first occurrence ofoldstringon theline.


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Search and Replace

You can repeat a search-and-replace on the currentline by typing an ampersand (&). To repeat it on adifferent line or group of lines, type:

: linenumber& or

: line1,line2&

The command g (for global) can be used with s

(substitute) to find and replace every occurrenceof a string pattern in an entire file.

The syntax of the global command is:

:g/string/commands


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Search and Replace

The global command finds each line in the filethat hasstringin it and then applies the commandsto it. You can combine the global and substitute itin the following manner:

:g/oldstring/s//newstring/g

You dont need to put oldstringin the searchstring part of the substitute command because theeditor already has the pattern from the globalcommand.

When specifying oldstring, you can use the specialcharacters as explained in the section SpecialCharacters. vi does not recognize specialcharacters in newstring, since it is performing are lacement not a search.


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Miscellaneous

u - undo last change U - undo all changes to the current line

J - join current line and the line below it

. - repeat the last command

:! - command invoke an external "command"

:%s/frog/toad/ -Replace the first occurrence of

"frog" with "toad" for all lines in the file.

dG - delete to end of the file

1G - move to the beginning of file . . .


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Set Command

set nu: This command is used to associate line numberswith the file On which you are working.

Syntax:

[esc]:set nu

Set ic:This command is used to ignore the case while

searching a pattern in the file.

Syntax:[esc]:set ic

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