1. Introduction to Unix Lesson 8

2. Introduction to UNIX

3. What is an operating system? Operating system Communications Accounting Input/ Output Command Interpreter Security Scheduling Memory Management Program Development Tools

4. The UNIX operating system Scheduler Allows more than one person to use the system at the same time. Shares the system’s resources among the users, allowing each a slice of the resources. Programs running in memory are called processes File system A directory structure used to organize files in UNIX Shell The UNIX system’s command interpreter A program that reads the lines you type and interprets them. Sits between the user and the internals of the system

5. History of UNIX In 1965 Bell joined GE and MIT in a project to develop a new OS called Multics Wanted to provide simultaneous computer access to a large community of users A smaller version written by some at Bell including Ken Thompson and Dennis Ritchie for PDP-7, later ported to PDP-11 (in 1971). Name came as play on Multics – Unics, or UNIX Thompson started to develop a Fortran compiler for Unix, but ended up developing B language. B was an interpretive language with the inherent speed problems characteristic of such languages Decided to improve on it so created next language, C In 1973 Unix rewritten in C

6. Unix Popularity grows… At the time (70’s) AT&T was not allowed to market computer products. Universities were requesting copies of Unix for educational purposes. By 1977 Unix system sites had grown to about 500 of which 125 were universities. Unix popular in phone companies and you can see heavy influence in phone equipment. In 1982 AT&T combined several versions and created UNIX System III. Other additions were made and System V was born in 1983. UC-Berkeley had developed a variant for VAX machines which was called BSD. By 1984 there were about 100,000 sites running UNIX

7. The variations of UNIX BSD (Berkeley Software Distribution) XENIX – version for microcomputers developed by MS SunOS – UNIX variation by Sun POSIX – an independent effort to define a standard OS environment – actually a family of standards. System V release 4 (SVR4) – combined elements of System V release 3, BSD, SunOS, and Xenix to provide a common environment Solaris – a version for Sun, 2.3 was POSIX compliant. Linux – PC version by Linus Torvalds in 1991. IRIX – a proprietary version used by Silicon Graphics HP-UX – variant developed and sold by HP AIX – IBM’s version for use on IBM workstations

8. Some differences to be aware of for Microsoft OS users UNIX is case sensitive, thus CC FILE1 is not the same as cc file1 UNIX is open source, thus source code is readily available for it. UNIX is not proprietary (as a whole) so its evolution is not controlled by a single organization/corporation NT/2000 and UNIX are both multitasking, but UNIX also is multiuser (supports simultaneous users)

9. UNIX file system / binetcusrdevhome sh date who hosts passwd hosts.equiv src bin games tty1 hda1 cdrom user1 user2 user3 Redhat file1.rhosts

10. LINUX A number of different versions Redhat BSD Slackware Caldera Debian Incorporates the use of shells Bash (Bourne again shell) variation on traditional Bourne shell – default. pdksh (Public Domain Korn Shell) variation on original UNIX Korn shell. tcsh – an enhanced version of the original Berkley C shell csh.

11. Some common Linux functions FunctionProgram Editorsvi, emacs Shellsbash, tcsh, pdksh Text processingtetex, troff Toolsawk (gawk– file/DB manipulation) Network programstelnet, ftp Electronic mailElm, Pine

12. Programming languages available C/C++ JAVA LISP Prolog Ada Perl Tcl/Tk Fortran-to-C translator Pascal-to-C translator Compiler tools (lex and yacc (flex and bison))

13. Interacting with the Linux OS The Shell is the interface between the user and the Linux OS How you interact with the system will depend on how the system was configured. Command Line Interpreter GUI Gnome KDE

14. Gnome

15. KDE

16. Some common CLI commands ls – provide list of files in current directory ls -l  provides additional info on each file ls -a  lists all files in the directory (hidden) ls -al  combines the above two ls doc*  lists files that start with doc Wildcards: * for any set of characters, ? for single character. cp – copy a file cp fileone filetwo  copies fileone into filetwo, creating filetwo if it needs to cd – change directory cd docs  changes current directory to docs cd /  changes to root directory cd..  changes to parent directory

17. Some more commands rm – remove (delete) a file rm fileone  deletes fileone rm file*  deletes all files that begin with ‘file’ rm *  deletes all files rm * file  deletes all files (space between * and file) cat – display contents of a file cat fileone  displays contents of fileone more – displays contents of a file screen by screen more fileone  displays contents of fileone

18. And just a few more commands mv – renames or moves a file mv fileone newname  renames ‘fileone’ to be ‘newname’ mv fileone docs/fileone  moves fileone from current directory to ‘docs’ directory mv fileone docs/newname  moves fileone from current directory to ‘docs’ directory and renames it mkdir – create a directory in current directory mkdir docs  creates a directory called ‘docs’ mkdir /home/gwhite/docs  creates a directory called ‘docs’ in directory /home/gwhite rmdir – remove directory rmdir docs  removes directory called ‘docs’

19. A couple more quick Linux commands pwd lists current working directory chmod 777 Changes permission of to allow anybody to access it chmod 700 Changes permission of to allow only the owner to access it

20. And more who – lists all users currently connected along with when, how long, and where they logged in. finger – provides information about other users on your network logout – logs you out of the system (ends your session) halt – shuts down Linux

21. Some commands everybody should know passwd – used to change your password. man – used to obtain information about a topic apropos – used to find commands that are related to keyword

22. Devices Files and directories contained on different HW devices (e.g. floppy drives, CD’s) and hard disk partitions are called file systems. The Linux partition used to install the Linux system on is called the root partition. The root partition ( indicated by a single slash, /) contains the main file system and user subdirectories. To access files on another file system, say a CD-ROM, you need to attach that file system to your main system. Attaching a file system is called mounting the file system.

23. Mounting a file system The first step is to set up an empty directory to which you want to mount the file system. Most Linux distributions, including Red Hat, have pre-created directories for this purpose. /mnt/cdrom /mnt/floppy To mount a floppy, for example, you would: mount device mountpoint mount /dev/fd0 /mnt/floppy When done, you need to unmount the device: umount device-or-mointpoint (*** notice the spelling ***) umount /mnt/floppy Make sure you aren’t still using that device or it won’t let you unmount it. These are sysadmin commands and not user commands!

24. Archive files The tar utility (tape archive) creates archives for files and directories. The tar utility is ideal for making backup copies of files or for combining several files into a singe file for transmission. Command examples: tar cvf myarch.tar mydir Creates archive of mydir directory and calls the single file myarch.tar (the ‘v’ displays each filename as it is archived).` tar xf myarch.tar Extracts all files and subdirectories from the file myarch.tar

25. Compressed Archives A compressed archive is an archive file created with tar and then compressed with gzip. It will generally have.tar.gz as extensions. To install such a file, you first need to uncompress it with gunzip, then extract it with tar. gunzip savefile.tar.gz tar xvf savefile.tar Instead of gunzip, you may also use gzip –d You may also combine both with: tar xzvf savefile.tar.gz

26. Installation of software packages rpm is used to manage and install software packages. The –i option is used to install software rpm –i newsoftwarefile RPM stands for “RedHat Package Manager” An RPM software package operates as its own installation program for a software application. Linux software applications often consist of multiple files that may need to be installed in different directories. The program is most likely installed in /usr/bin Installation may also require changes to config files

27. C gcc (compiler for C), g++ (compiler for C++) A sample C program (stored in file hello.c) #include int main() { (void) printf(“Hello, World!\n”); return0; /* just to be nice */ } gcc –o hello hello.c (-o says executable version to be called hello) now to invoke we type “hello”

28. Makefiles game: main.o edit.o gcc –o game main.o edit.o main.o: main.c gcc –c main.c edit.o: edit.c gcc –c edit.c $ make gcc –c main.c gcc –c edit.c gcc –o game main.o edit.o $ If we were to edit main.c, then $ make gcc –c main.c gcc –o game main.o edit.o $ File named makefile

29. Editing -- the vi editor Still one of the most widely used editors in the UNIX world today A keyboard-based editor (emacs is another) Uses the keyboard to specify commands and receive user input Certain keys perform certain functions Delete, insert, cursor movement, save, quit

30. vi commands To edit a file with vi vi If exists it will load that file, if it doesn’t it will create it. To exit, type ‘:’ This moves the cursor to the command line at the bottom of the screen, then ‘q’ quits the editor ‘q!’ quits without saving ‘w’ will save the file

31. vi commands The vi editor in Linux (actually Vim) allows you to use the arrow keys to move around. To insert text ‘a’ enters text after the cursor ‘i’ enters text before the cursor To stop entering text, hit To delete text ‘dw’ deletes the word the cursor is on ‘dd’ deletes the line the cursor is on ‘x’ deletes the character the cursor is on and also work To search / searches forward for ‘n’ repeats previous search