UNIX NOTES Page 1UNIX/Linux Notes: Professor: Michael P. Harris v.20051201UNIX is a multi-user, multi-tasking operating system originally developed at AT&T Bell Laboratories. It provides programs for editing text, sending electronic mail, preparing tables, performing calculations and many other specialized functions that require separate application programs in other operating systems. One of the key identifying features of UNIX is its standardized directory and file structure.Typical UNIX/Linux root /Directory structure: │ ┌────┬────┬────┬────┬───────┬┴────────┬───┬───┬───┬────┐bin etc dev mnt lib lost+found home tmp sys boot unix │ │ │ default │(mounted ┌────┬────┬─┴───┬───┬───┬────┐ ┌───┬┴──┐volumes) mike teri ... etc bin lib spool hd0 fd0 sd0 (users home directories)There are many different versions of UNIX. One of the most important is the line of UNIX releases that started at AT&T, the latest being System V Release 4. Other important UNIX versions have come from the University of California at Berkeley; the latest is called BSD. Microsoft’s Xenix, a early popular microcomputer implementation of UNIX was originally based on an earlier AT&T release called System V. Linux is currently the leading popular “Open Source” implementation of a Unix-like standard operating system. POSIX is the validation standard, set for UNIX-like operating systems. Starting with Windows 2000 Pro, Windows 2000, XP, and 2003 are all now POSIX compliant. Other major versions of UNIX include SunOS, Solaris, SCO UNIX, AIX, HP/UX, ULTRIX, NOVELL UNIX (Univel), and the various implementations of the popular Linux OS.Since it started more than 35 years ago, UNIX has grown and changed in a different way from most operating systems. Many early UNIX users were computer and scientificprofessionals; more than a few of them extended UNIX by adding tools and functionality to do what they needed. UNIX was also used to develop a lot of the powerful networking systems that connect the world, such as Internet. So, whereas most operating systems were typically developed and controlled by one corporation, UNIX has been developed through a collective effort. This has meant more versions and somewhat more confusion than "standardized" operating systems like MSDOS & Windows. But it has also helped to make UNIX the flexible and incredibly rich and powerful operating system that it is today.UNIX and its derivatives were not designed as "user-friendly" operating systems, in fact, UNIX has, in the past, earned its label of "user-hostile." UNIX can be used the way it was originally designed, on typewriter-like terminals (ttys). Most modern versionsof UNIX can also work with window system GUIs (Graphical User Interface) which alloweach user to have more than one "terminal" on a single display. The X Window System(called X for short) is the most common UNIX window system. The appearance of X Windows may vary between systems due to different window managers. Four of the most common window managers are mwm (Motif Window Manager), olwm (Open Look Window Manager), CDE (Common Desktop Environment) and the new LinuxUNIX NOTES Page 2windows shells Gnome, KDE, fluxbox, and others.UNIX NOTES Page 3Getting Started:UNIX can be overwhelming with its barrage of details. To get started though, all you need to do is master just a few details:o How to Log in and out of your systemo Understand the Shell and how to control the system with control characterso Learn the important UNIX specific directories and fileso Manage UNIX files and directories, including listing, creating, copying, printing and removing files, and moving in and out of directorieso Work efficiently using UNIX pipes, filters, and multi-tasking.Logging In:Before you can start using UNIX and its facilities, the System Administrator has to set up a UNIX account for you with your login name, password, and home directory. At many sites, there will be a whole network of UNIX computers so you may also have to know the hostname of the computer that has your account as well. When you turn on your terminal you should see a message from the UNIX computer that looks something like:login:Logging in is the process of making your self know to the UNIX computer and getting into your account. On remote systems you will need to run a remote login program like telnet, rlogin, cu, or tip. In this case your login session might look similar to the following: (what you type is in bold)telnet mercury.delmar.eduSun Solaris OSmercury.delmar.edu: Solaris UNIX version 9.00.10login: mpharrisPassword: ********Last login: Wed Nov 28 14:34 CST 2005, from mercury.delmar.edumotd:The "crisis" of Today is the "joke" of TomorrowREMEMBER !!!We will be shutting down at 4:30pm for system backups.Fri Dec 2 12:24:48 CST 2005$_UNIX NOTES Page 4The UNIX Shell:Once you've logged into a UNIX computer, you're working with a program called the shell. The shell interprets the commands you enter, runs the program you've ask for, and generally coordinates what happens between you and the UNIX operating system. There are four shells in common use: the Bourne shell, Korn shell, Bash and C shell. For the novice the differences are slight however some to run some software or execute some program (especially shell scripts) you will need to know which shell you are using (ask your system administrator). The only immediate difference you will see isthat the Bourne, Korn, and Bash shells prompt you with $_ while the C shell most often uses %_ as the prompt. Certain keyboard commands (keystrokes) are interpreted by the shell, these are commonly called control characters. The basic control characters are:Ctrl-C or [DEL] Interrupt character (interrupts or cancel a command)Ctrl-D Returns you to UNIX command level. Used to signal end of input. ** Also logs you off of most UNIX systemsCtrl-H or [BACKSPACE] Erase character to left of cursorCtrl-Q Restart output after paused by Ctrl-SCtrl-S Pauses output to the screenCtrl-U Erase the whole input line so you can start overUNIX vs. MSDOSThe UNIX operating system has been around much longer than MSDOS. While MSDOS owes much of its original heritage to a single-user operating system named