Overview
Lecture P3: Unix What is an OS? Files
■ Abstraction for storage (disks).
■ File manipulation commands.
Processes.
■ Abstraction for processor (CPU).
■ Some useful commands.
Interactions.
■ Between files and processes.
■ I/O redirection and piles.
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Layers of Abstractions in Unix OS Operating Systems
Bare hardware. Multics (1965-1970)
Machine language. ■ Ambitious OS project at MIT.
Kernel. ■ Pioneered most of innovations in modern OS. User level (C programming). – file system Command level (shell). – protection Window system. – virtual machines
Hardware ■ A little ahead of its time.
Machine Kernel P User
Command
Windows
6 7 Unix History Operating Systems
Multics (1965-1970). Multics (1965-1970).
Unix / Linux (Thompson and Ritchie 1969). Unix / Linux (Thompson and Ritchie 1969).
■ Simplicity and elegance. – C language, bootstrapped implementation DOS. – integrated command structure – simplified, integrated file system Macintosh. – used by most programmers
■ Continued development at AT&T (1970’s) and "shepherding it out." Windows.
■ ■ Berkeley "BSD" (1978-1993): TCP/IP. OS definition under litigation.
■ Various flavors of commercial Unix (1980-1990).
■ Linux gave it new life (1991 - present).
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Files File Manipulation Commands
/ File. cat, more show the contents of a file % more xx ■ Sequence of bits.
■ A simple and powerful abstraction for bin lib etc u cp, rm, mv copy, remove, move permanent storage (disks). % cp xx yy copy file xx to yy ■ Extended for things beyond disks. % rm xx delete file xx aaclarke cs126 zrnye % rm * delete all files in current directory! "Everything in Unix is a file." % mv xx yy rename file xx to yy
ls list file names Directory. files submit %ls list al files in current directory ■ Sequence of files (and other directories). % ls *.c list all files ending in .c %ls-tr list all files, reverse-sorted by date Filename. stock mandel % ls -l list all file details (permissions, size) ■ Sequence of directory names on the path from "/" to the file. mand32.txt /u/cs126/files/mandel/mand32.txt
13 14 File Manipulation Commands Processes mkdir, rmdir make or remove directory Process.
% mkdir hello make a new directory named hello ■ An abstraction for the processor (CPU).
■ Almost every command is a process. pwd print name of current (working) directory Over 2,500 standard commands. cd change directory ■ Thousand more available. %cd.. to parent directory ■ EXTENSIBLE: can even add your own. %cd~ to my home directory %cd~xx to xx’s home directory chmod change read/write permissions % chmod 600 hello.c only you can read/write file hello.c % chmod 700 mandel for all files in directory mandel % chmod 644 index.html all Princeton students can read it
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Unix Commands Unix Commands: Text Processing lpr send file to printer grep, awk, perl pattern matching % lpr hello.c print file hello.c sort sort the lines of a file man, apropos online documentation % man ls get help on using ls command diff print out any lines where two files differ cal, date, xclock time utilities emacs, latex text processing % cal 9 2000 display calendar for September, 2000 % emacs hello.c edit file hello.c % date display current date ispell text processing bc, xcalc calculators % ispell readme spell-checker % xcalc graphical version of scientific calculator maple, matlab scientific computing
17 18 Unix Commands: Programming Unix Commands: Specialized for COS 126 emacs, xemacs text processing emacs126, xemacs126 use our customizations as default % emacs hello.c edit file hello.c % xemacs hello.c & cc, lcc, gcc, C compilers enscript126 pretty-print C code g++, javac C++, Java compilers % enscript126 hello.c % gcc hello.c compile C program hello.c gcc126 compile with warnings gdb, jdb C and Java debuggers % gcc126 hello.c
submit126 submit COS 126 assignment for grading % submit126 0 hello.c
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Unix Commands: Multimedia Unix Commands: Communication acroread, ghostview display documents mail, pine email % ghostview xx.ps display PostScript file xx.ps % acroread yy.pdf display Acrobat file yy.pdf rn read newsgroups xv, gs display graphics netscape browse web % xv giraffe.gif display graphics file giraffe.gif % gs mand.ps display graphics mand.ps telnet, rlogin, ssh login to remote computer xfig create figures ftp, sftp download files audiotool play or record music soffice StarOffice: free Office clone
21 22 Multiprocessing I/O Redirection and Pipes
Abstraction provided by operating system.
■ MULTIPLE "virtual" machines for your use.
■ Outgrowth of 1960s "time-sharing."
For COS126.
■ One window for editor. Unix ■ One window for UNIX % emacs hello.c & commands. [1] 18439 Ampersand % netscape & indicates "do this [2] 18434 in the background"
% jobs Note: can use ctrl-Z [1] + Running emacs hello.c and bg instead of & [2] - Running netscape
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Filters and Pipes Shell
Standard input, standard output. Command interface to UNIX. 3 ■ Abstract files for command interfaces. Just another programming language. mv file1 tmp; Redirection: ■ sequence of instructions a.out > saveanswer mv file2 file1; ■ Standard input from file. ■ variables sort < myfile > myfilesorted mv tmp file2 ■ Standard output to file. ■ branches, loops
4 Shell program to annoy Steve with email Piping: #!/bin/csh -f @ n = 0 ■ Connect standard output of one ls | wc -l > outputfile repeat 5 times while ($n < 5) command to standard input of the plotprog | lpr printf "Goodbye.\n" | next. gamblerall | avg email Shapiro mail -s "yo Hal!" [email protected] @ n = ($n + 1) Don't confuse redirection and piping. sleep 60 plotprog > lpr wait 1 minute end 5
25 26 Shell Graphics
EXTENSIBLE: add another command. ANSI C does not directly support graphical output.
■ rename a.out ■ Need help from operating system.
■ or chmod 700 a file containing shell commands ■ In this course we use "PostScript" to get cool pictures.
■ Don’t worry about details yet. Unix Unix % gcc avg.c % mv a.out avg phoenix.Princeton.EDU% cat ifs.ps % gamblerall | avg | lpr %! 50 50 translate 0 0 moveto 512 0 lineto Primary use. 256 512 lineto closepath stroke
■ low overhead "programming" to manipulate files and invoke /pt {0 360 arc fill} def commands 125.0 250.0 5.0 pt 312.5 125.0 5.0 pt 156.2 62.5 5.0 pt 328.1 31.2 5.0 pt 414.1 15.6 5.0 pt showpage phoenix.Princeton.EDU% gs ifs.ps 27 28
Graphics Graphics
ifs.c Game played on equilateral triangle, with vertices R, G, B. #include
■ Repeat the following: #define N 50000 B – pick a random vertex int randomInteger(int n) { ... } – move halfway between current point and vertex int main(void) { 2 int i, r; – draw a "dot" in color of vertex double x = 0.0, y = 0.0, x0, y0; 5
1 for (i = 0; i < N; i++) { What picture r = randomInteger(3); 3 emerges? 6 if (r == 0) { x0 = 0.0; y0 = 0.0; } else if (r == 1) { x0 = 512.0; y0 = 0.0; } 4 else { x0 = 256.0; y0 = 512.0; } x = (x0 + x) / 2.0; 0 y = (y0 + y) / 2.0; R G printf("%f %f\n", x, y); } return 0; } 29 30 Graphics
Text output is boring.
■ Replace and add printf() statements to create PostScript.
■ Use gs to view PostScript file.
ifs.c . . .
printf("%%!\n 50 50 translate\n"); printf("/pt {0 360 arc fill} def\n"); printf("0 0 moveto 512 0 lineto "); draw enclosing printf("256 512 lineto closepath stroke\n"); triangle
for (i = 0; i < N; i++) { . . . printf("%f %f 1.0 pt\n", x, y); }
printf("showpage\n");
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