CSC 414 Chapter, Spring 2008

1.1 Applied Operating System Concepts Workshop on Using UNIX: An Introduction Tutorial 1.2 Applied Operating System Concepts Workshop Objectives • teach the basic system utility commands to get you started with UNIX. 1.3 Applied Operating System Concepts Workshop Materials • Workshop notes: copies of all slides and supplemental materials. • Hands-on Exercises 1.4 Applied Operating System Concepts Workshop Contents • Log in and log out of a UNIX system • File and directory management • Communicating with others • Background processes • Input and output files • Pipes and filters 1.5 Applied Operating System Concepts tserver tserver 198.77.88.191 198.77.88.191 Workshop Setup 1.6 Applied Operating System Concepts Using UNIX: An Introduction Tutorial 1.7 Applied Operating System Concepts What This Workshop Covers • Log in and log out of a UNIX system • File and directory management • Communicating with others • Background processes • Input and output files • Pipes and filters 1.8 Applied Operating System Concepts UNIX Features • Multi-user and multi-tasking • Hierarchical filesystem • User-selectable command language (shell) • Compatible file, device, and interprocess I/O • X Window system • Network communication services 1.9 Applied Operating System Concepts UNIX Compared with other OS • Mature and stable OS • Large user community • Vendor-independent OS • Network-portable window system (X) • Runs on range of hardware (PC - Cray) • Common Open System Environment (COSE) • Engineering WS and Internet servers. 1.10 Applied Operating System Concepts UNIX done it first • Multitasking - 1972 • Long file name - 1970 • Right button for menu - 1988 • Multi-user with file protection - 1970 • Almost all OS now support TCP/IP, NFS, WWW, and Java, all of which were developed on UNIX 1.11 Applied Operating System Concepts Command-line Based vs GUI • Things can be done beyond what the designers thought of • Search and process text files quickly, ask me about “grep”, “sed”, and “awk” • There is no GUI interface for every thing. 1.12 Applied Operating System Concepts Versions of UNIX • AT&T - System V Release 4 • University of California at Berkeley - BSD 4.4 • Xenix • POSIX • SunOS, Solaris • SCO UNIX • AIX • HP/UX • LINUX 1.13 Applied Operating System Concepts Connecting to UNIX • Directly connected – console – workstation – dumb terminal • From other systems – telnet / rlogin – X terminal – kermit/procomm 1.14 Applied Operating System Concepts Logging in/out • Log in – Connect to the UNIX system – Press ENTER key several times, if needed – At the log in prompt, type your userid (case sensitive) and press ENTER key. – At the password prompt, type your password (case sensitive) and press ENTER key. • Log out – exit or logout – Ctrl-d 1.15 Applied Operating System Concepts Changing Passwords • When – First time – Frequently (4~6 months) • How $ passwd – old passwd is required • What password to choose? – more than 6-8 character long – Mixed lower and upper case alphabetical + punctuation – avoid names, dates, numbers, common words, ... 1.16 Applied Operating System Concepts UNIX Shell • UNIX Shell – user interface to the system – interprets commands – run programs • Types – Bourne (sh), Korn (ksh), C (csh), Bourne Again (bash) • Prompt – “I’m ready and waiting for your command” – usually “%”, “$”, or “>“ – customizable Kernel Hardware Applications shells user user 1.17 Applied Operating System Concepts UNIX Command Format <command> <options> <arguments> • First word is the command • The rest, if any, are options and arguments • Commands are case sensitive and mostly in lowercase • A command may or may not have arguments $ date $ ls -l • Arguments are usually files or directories $ ls -al /etc 1.18 Applied Operating System Concepts Commands (2) • Options: – single letters – prefixed with a dash “-” – combined or separated (e.g., -al = -a -l) – come before other arguments • Spaces must be inserted between commands, options, arguments • Multiple commands are separated by a semicolon “;” and they are executed sequentially. • Control characters: Ctrl-c, Ctrl-h, Ctrl-z, … • On-line help (man pages) 1.19 Applied Operating System Concepts UNIX Filesystem tmp tmp zoman yusuf badr home home usr usr etc etc bin bin thesis bin mail ch1.tex ls hosts // ... ... ... ... ... ... ... ... ... ... User home directory root directory 1.20 Applied Operating System Concepts File and Directory Names • Case sensitive • Any character • Avoid “/”, “>“, “ “, “!”, – they are legal but hard to use with shells • Length: 14 characters • Must be unique inside its directory • Wildcards – “*” any number of characters – “?” any single character – “[ ]” Any one of the characters between the brackets 1.21 Applied Operating System Concepts pathnames • pathname: is an address that locates a directory or a file in the UNIX file system. • Absolute pathname: always starts with “/” /home/zoman/thesis/ch1.tex • Relative pathname: never starts with “/” thesis/ch1.tex • Relative pathname up: using “..” ../thesis/ch1.tex 1.22 Applied Operating System Concepts Directory Navigation • Moving around $ cd /etc $ cd thesis/fig $ cd .. • Where am I $ pwd /home/zoman • Creating/removing $ mkdir GoodStuff $ rmdir BadStuff 1.23 Applied Operating System Concepts Directory Navigation (2) • File listing $ ls - normal list $ ls -a - normal list + plus hidden files $ ls -l - long list $ ls -al - long list + hidden files $ ls -F - normal list + file type 1.24 Applied Operating System Concepts bash$ ls -l total 306 -rwxr-xr-x 1 zoman zoman 30 Aug 26 1996 ChModAll -rwx------ 1 zoman zoman 50 Aug 26 1996 Dis -rwxr-xr-x 1 zoman zoman 92 Aug 26 1996 MyClean -rwxr----- 1 zoman zoman 156 Aug 26 1996 chksp -rwxr----- 1 zoman zoman 31 Aug 26 1996 d2t -rwx------ 1 zoman zoman 35 Aug 26 1996 dvi2ps -rwxr-x--x 1 zoman zoman 40960 Aug 26 1996 hcal -rwxr-x--x 1 zoman zoman 32768 Aug 26 1996 hdate -rwx------ 1 zoman zoman 21 Aug 26 1996 mps -rwx------ 1 zoman zoman 22 Aug 26 1996 pa -rwxr-x--- 1 zoman zoman 73728 Aug 26 1996 praytime -rwx------ 1 zoman zoman 42 Aug 26 1996 spl bash$ Long Listing Files type access permission # of links ownergroup size (bytes) modification date and time name 1.25 Applied Operating System Concepts Access Permissions • Access permission on a file control what can be done to the file contents • Access permission on a directory where the file is kept control whether the file can be renamed or removed • To access a directory, access permission should be allowed for all of its parent directories all the way up to the root. 1.26 Applied Operating System Concepts Access Permissions • First character shows the file type: – directory (d) – plain file (-) -rwxr-xr-x -rwxr-xr-x  The rest, specify three types of users  owner  group  others rwx rwxr-x r-xr-x r-x  who are allowed to  (r) read  (w) write  (x) execute 1.27 Applied Operating System Concepts Protecting Your Files • -r-- --- --- (400) protect it from accidental editing • -rw- --- --- (600) only you who can edit/read the file • -rw- r-- r-- (644) only you who can edit, others read • -rw- rw- rw- (666) public file! • dr-x r-x r-x (555) anyone can list but can’t create/delete/rename files • dr-x --- --- (500) only you who do that • drwx --- --- (700) you can do anything but not others • drwx r-x r-x (755) you can do anything, others only list • drwx rwx rwx (777) anyone can do anything! 1.28 Applied Operating System Concepts Changing Access Permissions chmod permission files • Character Method $ chmod a=r-x file $ chmod u=rw- file $ chmod ugo+r file $ chmod go-w file • Numerical Method $ chmod 744 file $ chmod 600 file 1.29 Applied Operating System Concepts owner group others -rwxrwxrwx -rwxr-xr-x -rw-r--r-- -r-------- Numerical Access Permissions 111111111 777 777 111101101 755 755 110100100 644 644 100000000 400 400 1.30 Applied Operating System Concepts Viewing and Editing Files • Listing files – cat – head – tail • Listing files page per page – more – less • Editing files – vi – pico – emacs 1.31 Applied Operating System Concepts File Manipulation • Copy – cp • move (rename) – mv • remove (delete) – rm 1.32 Applied Operating System Concepts Communicating with others • who - who is currently using the system • talk - interactive messaging $ talk user $ talk user@host.anme • e-mail programs – mail - simple and old email program – pine - simple and easy to use email program – elm - powerful email program 1.33 Applied Operating System Concepts Input/Output Redirection • Usually programs read from the keyboard and write output and error messages to the screen. • Each running program opens three files: standard input, standard output, and standard error associated with the keyboard, screen, and screen, respectively. • Input can be obtained (directed) from a file using “<“ and “<<“. • Output can be written (directed) to a file using “>“ and “>>“. 1.34 Applied Operating System Concepts Piping and Filtering • Consider $ ls /etc > list.temp $ more list.temp $ rm list.temp • Compare with $ ls /etc | more • Piping – directing the output of one command to the input of another – pipe symbol “|”. 1.35 Applied Operating System Concepts Piping and Filtering (2) • grep – one of the most useful filters in UNIX. – searches line-by-line for a specified pattern – outputs any line that matches the pattern $ grep “zoman” /etc/passwd $ grep -l “[Zz]oman” .* * • advance filters, check man pages – sed – awk 1.36 Applied Operating System Concepts Multi-tasking • Time sharing: many processes running “virtually” at the same time. • Each has a process identification number PID • Viewing processes $ ps $ ps -ef 1.37 Applied Operating System Concepts Background vs Foreground Processes • Foreground process – one at a time $ sleep -60 – lock the terminal until it is done • Background processes – one or more can run at the same time in the background – free up the terminal $ sleep -60 & $ sleep -60 Ctrl-z $ bg 1.38 Applied Operating System Concepts Canceling/Stopping Processes • Canceling a foreground process Ctrl-c • Killing a background process $ kill pid - get the pid using ps command $ kill -9 pid 1.39 Applied Operating System Concepts Customizing Your Account • .profile - ksh, bsh • .login, .cshrc - csh • .bash_profile, .bashrc - bash # .bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment PATH=$PATH:$HOME/bin ENV=$HOME/.bashrc USERNAME="" export USERNAME ENV PATH 1.40 Applied Operating System Concepts Suggested Reading List • Learning the UNIX Operating System Grace Todino, John Strang, and Jerry Peek, O’Reilly Associates, 1994 • A Student’s Guide to UNIX Harely Hahn, McGraw-Hill, 1993 • UNIX Power Tools Jerry Peek, Tim O’reilly, Mike Loukides, and others, O’Reilly & Associates and Random House Electronic Pub. 1993 • UNIX in a Nutshell (System V & Solaris 2.0) Daniel Gilly and staff of O’Reilly Associates, 1992. • The UNIX Programming Environment Brin Kernighan and Rob Pike, Prentice-Hall, 1984 1.41 Applied Operating System Concepts IMPORTANT UNIX Concepts • Environment and Shell Variables – These allow you to customize your UNIX environment – They are different in terms of their SCOPE  SCOPE determines the visibility of a variable 1.42 Applied Operating System Concepts Other IMPORTANT UNIX Concepts • Environment Variable – Examples are TERM and DISPLAY – Set a particular variable to a value by using the setenv command – You can print the value of a particular variable or all the environment variable using the printenv command 1.43 Applied Operating System Concepts % Environment Variables % • Examples – To set environment variables – % setenv TERM vt100 – % setenv DOG Goofy – print out the terminal type – % printenv TERM – vt100 – print out all environment variables – % printenv 1.44 Applied Operating System Concepts Shell Variables • Shell variables are similar to Environment variables except they have a limited scope, i.e., they exist only in the shell which they are defined. • Environment variables on the other hand, exist in all its children shells • To illustrate this concept, let us look at the following example 1.45 Applied Operating System Concepts Environment vs. Shell Variables % set prompt = "Parent Shell > " Parent Shell > setenv DOG Goofy Parent Shell > set mouse=Mickey Parent Shell > printenv DOG Goofy Parent Shell > echo $mouse Mickey Parent Shell > xterm & (YOU SHOULD NOW HAVE A NEW xterm WINDOW) THIS IS KNOWN AS “SPAWNING A NEW (OR CHILD) PROCESS” 1.46 Applied Operating System Concepts Environment vs. Shell Variables (IN THE NEW xterm WINDOW, DO THE FOLLOWING) % set prompt = "Child Shell > " Child Shell > printenv DOG Goofy Child Shell > echo $mouse mouse: Undefined variable. 1.47 Applied Operating System Concepts Environment vs. Shell Variables Child Shell > setenv DOG Pluto Child Shell > set mouse=Minnie Child Shell > printenv DOG Pluto Child Shell > echo $mouse Minnie Child Shell > exit (THE xterm WINDOW SHOULD NOW GO AWAY - THIS PROCESS HAS NOW BEEN KILLED) 1.48 Applied Operating System Concepts Environment vs. Shell Variables Parent Shell > Parent Shell > printenv DOG Goofy Parent Shell > echo $mouse Mickey Parent Shell > 1.49 Applied Operating System Concepts Environment & Shell Variables Why is this important? UNIX uses Environment and Shell Variables control a number of processes Customizes your working environment Variables used for UNIX Scripts They are typically defined and initialized in your .login and .cshrc files 1.50 Applied Operating System Concepts Useful Shell Variables filec #Allows file completion path #List of command directories cdpath #List of candidate directories to cd into history #Number of commands to remember 1.51 Applied Operating System Concepts What is shell programming? • Shell programming – automate a set of UNIX commands. – Just like any programming language – “wrappers”  black box a customized collection of UNIX commands. – Example of shell programs .login .cshrc 1.52 Applied Operating System Concepts .login file set path=($HOME/bin /usr/local/bin \ /usr/ucb /usr/sbin /bin /usr/bin \ /usr/bin/X11 .) stty dec new tset -I -Q set mail=/usr/spool/mail/$USER set editmode = emacs umask 077 biff n date 1.53 Applied Operating System Concepts .cshrc file if ($?prompt) then set notify set history = 100 set savehist = 100 alias pd pushd alias pop popd alias vt100 "set term = vt100" endif 1.54 Applied Operating System Concepts When these files are executed? .cshrc – is automatically executed when you start a new shell .login – only gets executed once when you first login Can be re-executed by giving the source command % source .cshrc 1.55 Applied Operating System Concepts Other useful .login and .cshrc entries set filec set cdpath=(~ ~rvrpci/pub ~/mythesis) Other common entries set path=( $path /usr/local/bin) set path=(/usr/local/bin $path) 1.56 Applied Operating System Concepts User defined shell program • Determine name of command • Determine input, output, and option arguments • Determine UNIX commands to execute • Establish error trapping • Make shell program executable 1.57 Applied Operating System Concepts A simple shell program • dd command to swap bytes % dd if=input.dat of=output.dat bs=2 conv=swab • Very difficult to remember • Very little utility to non-UNIX geeks (normal people) 1.58 Applied Operating System Concepts We would rather see... % swap_bytes input.dat output.dat 1.59 Applied Operating System Concepts Special Shell Variables Set % swap_bytes input.dat output.dat $0 $1 $2 $argv[1] $argv[2] command 1.60 Applied Operating System Concepts Another Special Shell Variables % swap_bytes input.dat output.dat $#argv Indicates how many arguments are present In this case, 2