Ppt Os04 Unix 01

UNIX - J2EE (LC)Day 1

Course ObjectiveTo introduce the Unix Operating System To develop an ability to use general Unix commands To develop ability to write programs in shell To develop ability in using Unix utilities To introduce the security issues in Unix

Copyright 2005, Infosys Technologies Ltd

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ER/CORP/CRS/OS31/003 Version No: 1.00

This Course does not coverDifferences in command behavior in various Unix flavors Introduction/Implementation of System Calls System Administration in Unix Hacking/Tricky issues in using Unix commands Awk and sed programming


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ReferencesBrain W. Kernighan and Rob Pike, The UNIX Programming Environment. Stephen Prata, Advanced UNIX - A Programmers Guide. Stephen G. Kochan and Patrick H. Wood, Exploring the Unix System. James R. Groff, Paul N. Weinberg , Understanding Unix - A conceptual guide. Maurice J. Bach, The Design of the Unix Operating System


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Session PlanDay 1 Introduction to Unix Unix System Architecture Basic Unix Commands Processes in Unix Regular Expressions Introduction to vi editor


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Session PlanDay 2 Text Processing Commands Process oriented Commands File Handling Commands Types of Shell Shell Programming


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Session PlanDay 3 Unix Utilities Unix Program Development Tools Unix Communication Security Features


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Introduction to UnixWhat is Unix Unix is a very popular multi-user, multitasking, time-sharing operating system

Need for Unix in todays world Unix has become the operating system of choice for various engineering and scientific applications

Evolution of Unix Started in 1965 when AT&T, GE, IBM and Project MAC joined together to develop a time-sharing system named MULTICS (Multiplexed Information and Computing Service)


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Introduction to UnixFlavors of Unix AIX (Advanced IBM Unix) HP-UX ( Hewlett Packard Unix) MINIX (Minimal Unix) SCO UNIX SOLARIS XENIX LINUX, etc


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Features Of UnixThe important characteristic features are Portability Unix has been re-written in C , hence it can run on machines from microcomputers to mainframe computers

Security Without the proper username and passwords, it is not possible to work on Unix

Background Processing Jobs/Tasks are executed in the background with the minimal interaction from the user

Pipes Work with multiple commands at the same timeCopyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

Features Of Unix (Contd.) Redirection Tools Allow data to be re-directed between files as per the requirement of the user

Software Development Tools Unix supports any language that has an interpreter or compiler

Stable and Reliable Less prone to crashes

Communication Unix has commands which allow communication between different users connected to the system


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Features Of Unix (Contd.) Easy to write programs Unix hides machine architecture from the user

Hierarchical File System Easy to implement and maintain data

Shells Unix has different types of shells .viz. Bourne, C, Korn, etc


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System ArchitectureMajor components of Unix are : Kernel Monitors and controls the resources of a computer and allocates them among its users in an optimal manner

Shell Provides a processing environment for the user programs and acts like a command translator

Utilities Programs which are used for development purposes

User Applications Programs written by the user


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System Architecture

UserSHELLUNIX

UserSHELLOTHER APPLICATIONS

COMMANDSHARDWARE

DATABASEPACKAGES

KERNEL

COMPILERSSHELL

SHELL

User

User


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Processing EnvironmentUser Program Set of instructions written by the user

Process Instance of a program under execution

Shell Provides a processing environment for the user programs


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Structure of Unix File System

/ (root)

home bin sh

dev ls tty lp

etc

tmp

lib

usr

passwd shadow

Note: Different variants of UNIX differ slightly in the file system structure. But some of the basic folders are still the same.


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Inodes and Linking A directoryFILENAME INODE NUM FILENAME INODE NUM

Another directory

file1 file2

0221 0412 name1 file3 0221 0981

File1 and name1 are links with same inode numbersInode block #0412 #0221Copyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

Absolute Path and Relative PathThe Absolute Path The entire pathname starting from root(/) Example /home/trng10/file1.

The Relative Path The path relative to your present working directory Example cd ..


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How Unix Session Works.LOGIN SHELL ASKS FOR A COMMAND USER TYPES COMMAND SHELL EXECUTES UTILITY TO CARRY OUT COMMAND USER INTERACTS WITH UTILITY SHELL PROMPTS FOR NEXT COMMAND USER TYPES CONTROL-D LOGOUTCopyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

Login Sequence.Login id and password The /etc/passwd file and /etc/shadow file The /etc/profile file Shell prompt


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System Settings.The $PATH variable Shows the location of executables

Aliases Allows alternate name for commands

The tty, stty commands Early UNIX had different kind of terminals Today terminals are implemented as software For backward compatibility, tty and stty commands are used

The [ctrl-c] , [ctrl-d] and other keys


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Unix Command StructureUnix Command line structure command [options] [arguments]Microsoft Word Document


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General Unix Commandsls - List contents of a directory

ls [option] [filenames]

Microsoft Word ocu nt

cat - Concatenate and display files cat [option...] [file ...]Microsoft Word ocu nt


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General Unix Commandscp - Copy files cp [option...] [file1] [file2]Microsoft Word Document

mv - Move or rename files mv [option...] [file1] [file2]Microsoft Word Document


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General Unix Commandspwd - Display Working directory pwdMi r

cd - Change Working directory cd [Directory]Mi r


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t r t

t r t

General Unix Commandsmkdir - Make Directories mkdir [options] DirectoryNameMi r

rmdir - Remove DirectoriesMi r


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8 765 ()4 3 )2 1)0) (

rmdir [options] DirectoryName

' &%$ # " ! t r tt r t

General Unix Commandsrm - Remove files or directories rm [option...] file ...Micro o t or Docu ent

ln - Make link to files ln file1 [file2 ...] targetMicro o t or Docu ent


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C B A @9 C B A @9

General Unix Commandscal Calendar cal [options] [arguments]Microsoft Word Document

who Displays the users connected who [options]Microsoft Word Document


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General Unix Commandsmore Allows display page wise more [files]Micro o t or Docu ent

whoami Display usernameMicro o t or Docu ent


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S R QPI

whoami

H G F ED

Processes in UnixProcess: Instance of an application in memoryMi o o o u o n

Process related commands ps command


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Concept of stdin, stdout and stderr


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Standard FilesStandard Input (0) This file is opened by shell to accept information.

Standard Output (1) This file is opened by shell to direct output

Microsoft Word ocu nt

Standard Error (2) This file is opened by shell for writing error messages


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VU

T

Building Block PrimitivesRedirection of I/O: Input to a process can come from either keyboard or a file Output of a process can be sent to either screen or a file

Pipes Output of one program is piped as input to another program

Microsoft Word Document


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Special Files/dev/tty It is used to display on the terminal

/dev/null This file is used to suppress the output from being displayed Used for suppressing error messages from being displayed on the screen in programs

Mi r s t


e dcb WXa X` YX X W

rd t

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Regular ExpressionsWhat is it?String of ordinary and metacharacter which can be used to match more than one type of pattern. Uses character set * , [], ^, $, {}, etc.

Mi r s t


t srq fgp gi hg g f

rd t

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The Shell Metacharacters.* - Matches all filenames in current directory. ? - Matches a single character. [abc] - Matches a single character either a, b or c. [!abc] - Matches a single character which is not a, b or c. [a-c] Matches a single character which is within the range of a and c. ^abc Matches the pattern abc at the beginning of the line. abc$ - Matches the pattern abc at the end of the line.


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Unix.The Vi Editor.

Editor in UnixNeed for editor in Unix Types of editor Line Editor ed : UC Berkeley ex : Powerful than ed, Bell Systems

Full Screen Editor vi (stands for visual) vim vi improved emacs (GNU)


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The vi Editor.The important characteristic features are: Omnipresent Works on different Unix flavors

Fast Various operations are very fast

Powerful UNDO features Text in lines could be undone with very less effort


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The vi Editor.The limitations are: Less user-friendly No graphical user interface

Highly Case-sensitive Letter in small case has a different implementation in comparison with the same letter in upper case

Keystrokes could have more than one meaning A letter (of the same case) has different implementation across different modes.


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The vi Editor.Modes of working: Command Mode Keys are interpreted as commands

Insert Mode Keys are interpreted as data

Escape Mode Keys are interpreted for saving/exiting purposes


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vi Operating modes.

i, I , o, O, a, A ..

Command mode :Enter esc

Insert mode

Escape mode

:q


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Vi editor commandsTo move around h, j, k, l, ^D, ^U, G, 0, ^, $, w, b

Inserting/Deleting text i, a, I, A, r, R, o, O, dd, dw, c$, D, x, X.

Changing/Replacing text. cc, cw, c$, ~, J, u, . , yy, yw, p, P

File manipulation. :w, :wq, ZZ, :w!, :q, :q! , :![command]


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Searching a pattern/pattern Searches forward for first occurrence of a pattern.

?pattern Searches backward for first occurrence of a pattern.

n Repeats the last search.

N Repeats the last search command in opposite direction.


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Pattern Substitution.:s/ptn1/ptn2 Replaces first occurrence of ptn1 with ptn2.

: s/ptn1/ptn2/g Replaces all occurrences in the current line.

: m, n s/ptn1/ptn2/g Replaces all occurrences in lines m to n.

: ., $ s/ptn1/ptn2/g Replaces all occurrences from current line to end of file.


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Customizing vi.The set command :set all :set nu

The abbr command :abbr itl Infosys Technologies Ltd

The map command :map ^X :wq


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Vi Startup File.exrc vi reads .exrc before loading settings are permanent for a vi session


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Handling multiple files.vi file1 file2 file3 Opens all files one after another

:n Permits editing of next file in the buffer

: rew Permits editing of first file in buffer

: args Displays names of all files in the buffer

:f Displays the name of the current fileCopyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

System Variables.PATH Search path referred by Unix for any command. echo $PATH

HOME Indicates the home directory for the user. echo $HOME

Mic oso t o Doc e t


y u u x w v# ER/CORP/CRS/OS31/003 Version No: 1.00

System Variables (contd).PS1 Used for displaying & changing the primary prompt. echo $PS1

PS2 Used for changing the secondary prompt.

Mi r s t


rd t

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set command.set command Used for display all the environment variables. Shows the current values of system variables. Also allows conversion of arguments into positional parameters. Syntax : set

Mi r s t


rd t

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man command.A screenshot of the man command. Syntax: man [ ] indicates optional content

Type the letter q to quitCopyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

SummaryBackground Features of Unix Unix System Architecture Unix File System General Unix commands and utilities Processes Regular Expressions Vi Editor Modes of operationCopyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

Thank You!Copyright 2005, Infosys Technologies Ltd # ER/CORP/CRS/OS31/003 Version No: 1.00

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Ppt Os04 Unix 01