Introduction to UNIX

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. 1969 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 History (Brief)

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 • profitable1996 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 Account logout or ^D Press CONTROL and D together or 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. User Other Application/ System Software Shell Unix Commands User Shell Hardware Internet Tools Database Packages Kernel Shell Compilers Shell User User Kernel-Shell Relationship

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 3 2005 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 cal 7 1962 cal 9 1752

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. 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 Some General Purpose Commands

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/s3910120/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 s3910120 s3910120/proj1 if you are in home home/s3910120/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 • s3910120’s home directory: s3910120 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. pwd Print name of current working directory • Move back to directory s3910120(the parent directory): cd ..

31. When in proj1, move to proj2with 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 -rw-r--r-- 1 root root 2365 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. 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 finger @ratree.psu.ac.th • ping machine-name Is machine alive (on)? ping catsix (^C to stop)

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

44. Talking • talk user Talk to user(on any machine) talk ad talk bill-gates@ratree.psu.ac.th 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 ProblemWhat colour are my shoes? I cannot see them at the moment because of my desk.- Jim^D

47. The vi Editor • Two modes • 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