1. Introduction to UNIX

2. What is UNIX? An Operating System (OS) Mostly coded in C
Machine independence
It provides a number of facilities:
management of hardware resources
directory and file system
loading / execution / suspension of programs

3. History (Brief) 1969 1970’s 1980’s 1990’s First UNIX at Bell Labs
The MULTICS
Kernighan, Ritchie, Thompson
1970’s
Bell Labs makes UNIX freeware
Berkeley UNIX (BSD)
Bill Joy vi editor, C Shell
1980’s
System V release 4
TCP/IP
Sun Microsystems Solaris
Microsoft Xenix, SCO
MIT X-Windows
1990’s
GNU, LINUX
Stallman, Torvalds

4. Why Use UNIX? multi-tasking / multi-user lots of software
networking capability
graphical (with command line)
easy to program
portable (PCs, mainframes, super-computers)
continued

5. free! (LINUX, FreeBSD, GNU)
popular
profitable 1996 Sales: US$34.5 Billion, up 12%
not tied to one company
active community

6. Your Account Each user has their own space called their account.
Type your login ID and password to enter your account.
Only if the login ID and password match will you be let in.

7. Login to your Account
login: ad You type your ID and RETURN.
Password: You type your password and RETURN. It does not appear.
$ The UNIX prompt (or similar). You can now enter commands.

8. Logout from your Accountor
^D Press CONTROL and D together
exit

9. On-line Help man Manual pages Spacebar to go on; ^C to stop
man gnuchess
man man
apropos topic Lists commands related to topic
apropos game
apropos help

10. UNIX Books
The Unix Programming Environment, Brian W. Kernighan and Rob Pike. Prentice Hall, Inc., 1984.
Sumitabha Das, "Unix : Concepts and Applications"
A Student’s Guide to UNIX, Harley Hahn, McGraw-Hill, 1993
A Practical Guide to the UNIX System, Mark G. Sobell, Benjamin-Cummings, 3rd Edition, 1995

11. Kernel-Shell Relationship
Hardware
Kernel
Compilers
Internet Tools
Unix Commands
Database Packages
Other Application/ System Software
Shell
User

12. The Shell The UNIX user interface is called the shell.
The shell does 4 jobs repeatedly:
display
prompt
read
command
execute
command
the shell
process
command

13. Typing Commands
Try these:
date
cal
who
ls -a
man cal
clear

14. Changing your Password
The command is:
passwd
It will ask you for the new password twice.

15. Date Commands date Gives time and date cal Calendar cal 1997 cal 3

16. You and the System uptime Machine’s ‘up’ time
hostname Name of the machine
whoami Your name
who

17. Calculators expr e Simple arithmetic expr 3 + 5 + 7
bc Programmable Calculator

18. Some General Purpose Commands
date
locate
cal
more
who
passwd ls
echo
man
banner
clear
tty
uptime
uname
hostname
tput
quota
spell
whoami
ispell
apropos
cat
whatis
sort
which
pwd

19. Redirection, pipes , processes
Output can be redirected to a file with‘>‘:
ls > dir.txt
cal 2004 > year2004
Output can be appended to a file with ‘>>‘
cal 2004 > years
cal 2005 >> years
Pipes : sending the output of one program to the input of the other
ls | sort
who | sort
Processes : Running two commands sequentially
locate mj > xxx; date
locate usr > xxx &

20. The UNIX File System

21. The File
Ordinary Files
Directory Files
Device Files

22. The Parent Child Relationship
A simplified UNIX directory/file system: /
etc
bin
usr1
dev
tmp
. . .
. . .
. . .
date
. . .
faculty
cal mj

23. Some System Directories
/ root directory
/bin commands
/etc system data files (e.g. /etc/passwd)
/dev files representing I/O devices

24. Pathnames
A pathname is a sequence of directory names (separated by /’s) which identifies the location of a directory.
There are two sorts of pathnames
absolute pathnames
relative pathname

25. Absolute Pathnames
The sequence of directory names between the top of the tree (the root) and the directory of interest.
For example:
/bin
/etc/terminfo
/export/user/home/ad
/export/user/home/s /proj1

26. Relative Pathnames
The sequence of directory names below the directory where you are now to the directory of interest.
If you are interested in the directory proj1:
proj1 if you are in s
s /proj1 if you are in home
home/s /proj1 if you are in user

27. Commands and Pathnames
Commands often use pathnames.
For example:
/usr/games/fortune
cat /etc/passwd List the password file

28. Moving between Directories
s ’s home directory: s
proj1
proj2
hobby.c
. . .
. . .

29. If you are in directory s3910120 how do you move to directory proj1?
cd proj1
You are now in proj1. This is called the current working directory.

30. Move back to directory s3910120 (the parent directory):
pwd Print name of current working directory
Move back to directory s (the parent directory):
cd ..

31. When in proj1, move to proj2 with one command:
cd ../proj2
../proj2 is a relative pathname

32. Special Directory Names
/ The root directory
. The current working directory
.. The parent directory (of your current directory)

33. Examples cd / Change to root directory cd ~ Change to home directory
cd (Special case; means cd ~)
cd ../.. Go up two levels.

34. Investigate the System
Use cd
cat file List file
cd /etc
cat passwd
ls Directory listing
ls List current dir.
ls /etc List /etc

35. Making / Deleting / Renaming Directories
Usually, you can only create directories (or delete or rename them) in your home directory or directories below it.
mkdir Make a directory
rmdir Delete a directory
mv Rename a directory

36. Permissions ls –l /etc/passwd read, write, execute (r w x)
-rw-r--r root root Jul 28 16:19 /etc/passwd
read, write, execute (r w x)
rw- r-- r--
directory owner group everyone
chmod
-w, +w ….

37. Commands to work with files
cat > filename
less
head
tail cp mv rm wc
grep
spell
ispell

38. Communicating with People

39. Information on Others users Who else is logged on?
who Information on current users
ps What are people doing?
ps -au

40. Examine password info:
w What are people doing?
w -sh A shorter report
Examine password info:
more /etc/passwd
grep s38 /etc/passwd

41. Fingering People finger Info. on current users
finger -l Longer information
finger user Information on user (need not be logged in)
finger ad

42. finger @machine-name User info. for that machine finger @catsix
ping machine-name Is machine alive (on)?
ping catsix (^C to stop)

43. Your Finger Information
chfn Change your finger entry
finger also prints the contents of the .plan and .project files in your home directory. List ‘.’ files with:
ls -a

44. Talking Get out by typing ^C talk user Talk to user (on any machine)
talk ad
talk
Get out by typing ^C

45. write user Send a message to user on this machine
write ad
mesg n Switch off talk / write acceptance. mesg y Switch on

46. Sending E-mail Send mail : mail Add
Subject: Shoe Problem What colour are my shoes? I cannot see them at the moment because of my desk. - Jim ^D

47. The vi Editor Two modes Append a
Insert i
Command <ESC>
Append a
Replace character r, Replace word R …..
Deleting character x, Deleting line dd
Exit
Goto command mode press :wq ……

48. Filters
The UNIX programs that read some input, perform a simple transformation on it and write some output.
grep, egrep, fgrep
tr, dd, sort
Sed, awk – programmable filters

49. grep grep options pattern format filename(s) Some option
-c Counting number of occurrences
-n Line numbers along with lines
grep Mamata –e mamata database
grep [Mm]amata database

50. grep : Regular Expressions
Character sets
[mM] , [aeiou] , [a-zA-Z0-9]
Immediately preceeding character
G*, [gG]*
Matching a single character
2… A four character pattern starting with 2
.* A number of characters or none

51. grep : RE Specifying pattern boundaries c
Any non-special character c matches \c
Turn off any special meaning of character c ^
Beginning of line $
End of line .
Any single character
[…]
Any one of character in …; ranges like a-z are legal
[^…]
Any single character not in …; ranges are legal r*
Zero or more occurrences of r
r1r2
RE r1 followed by RE r2
Specifying pattern boundaries
^r pattern beginning with expression r
^[^r] pattern not beginning with expression r
r$ pattern ending with expression r

52. egrep : Regular Expressions
r+ : one or more occurrences of r
r? : zero or more occurrences of r
r1|r2 : r1 or r2
(r) : nested r

53. fgrep Searches for multiple patterns
Does not accept regular expression
Multiple patterns are separated by new line character.
The disadvantage of grep family is that none of them has a separate facility to identify fields.

54. sort
-f : eliminates distinction between uppercase and lowercase letters.
-n : numeric comparison
- r : largest to smallest
+m : comparison skips first m fields
+0 : beginning of the line
-u : discard duplicates

55. comm File comparison command Gives three columns of the output
Lines that occur only in file 1
Lines that occur only in file 2
Lines that occur in both
One or more columns can be suppressed
Comm –12 f1 f2

56. tr Transliteration of character in the input
tr a-z A-N
Mostly used for character conversion

57. Assignment
Try all the UNIX commands. Store the output in a file appropriately using redirection operators.
Read a word from the terminal and check if the spelling is correct. Suggest few alternatives.
Create a file using Vi. Store few names in the file. Search all the names containing the letter M or m.
Create another file using cat command
Compare both the files to find the differences
Use calculator commands to compute 5 arithmetic expressions.