Working with the Unix OS

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C Libraries int li; /* number of lines on the screen */ int co; /* number of columns on the screen */ char *msg="Welcome to UNIX" ; if ((name=getenv("TERM")) == NULL) { fprintf(stderr, "%s: can't find terminal type\n", argv[0]); exit(1); } switch (tgetent(buff, name)) { case -1: fprintf(stderr, "%s: can't read termcap file\n", argv[0]); exit(1); case 0: fprintf(stderr, "%s: can't find entry for %s\n", argv[0],name); exit(1); } } cl = tgetstr("cl",&ap); cm = tgetstr("cm",&ap); co = tgetnum("co"); li = tgetnum("li"); printf(%s%s%s\n", cl, tgoto(cm, (co/2)-(strlen(msg)/2),li/2), msg); 79
Introduction to kernel 7. INTRODUCTION TO KERNEL What is an Operating System? What does it do ? Why do we need one? An operating system performs two main functions: ! Resource sharing - among simultaneous users - central processor memory input/output devices ! Provision of a virtual machine - raw piece of hardware - input/output - extremely complex programming - memory - virtual memory - filing system - locate by name not physical location protection and error handling - program interaction - e.g. pipes - program control - user interacts via command language Types of operating systems - single user systems - e.g. DOS - process control - industrial process - feedback - failsafe - file interrogation systems - database - fast response - transaction processing - frequently modified database - general purpose systems - multi-access - interactive Operating System Functions - job sequencing job control language interpretation - error handling I/O handling - Interrupt handling scheduling - resource control protection - multi-access good interface to user - accounting of computer resources Operating System Characteristics ! concurrency switching from one activity to another protecting one activity from the effects of another synchronizing activities that are mutually dependent ! sharing advantages | disadvantages cost saving resource allocation building on work of others simultaneous access to data sharing data simultaneous execution removing redundancy protection against corruption ! long term storage convenience of keeping data in computer essay access, protection against interference/system failure ! nondeterminacy OS must be determinate - same program run today or tomorrow with same data should produce same results. indeterminate - must respond to unpredictable order of events 80
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UNIVERSITY OF ATHENS DEPARTMENT OF
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Figure 27. Driver Entry Points.....
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Introduction to Unix ! Execution ma
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Introduction to Unix It works in th
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Introduction to Unix * matches 0 or
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Introduction to Unix vi file-name s
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Introduction to Unix 1,$s/^/>>/ 1,$
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Introduction to Unix ! Special Devi
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Introduction to Unix Working with F
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Introduction to Unix ! Communicatio
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Unix Shells 2. UNIX SHELLS Back Quo
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Unix Shells ! CASE Statement case t
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Unix Shells two lines !Y@Y@Z@Z@ZY c
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Unix Shells if $append then tee -a
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C Programming - Basics main() { int
Page 31 and 32: C Programming - Basics e.g. i += 2
Page 33 and 34: External Variables A C program cons
Page 35 and 36: C Programming - Basics main.c #incl
Page 37 and 38: C Programming - Basics default: pri
Page 39 and 40: C Programming - Basics struct tnode
Page 41 and 42: Unix Tools 4. UNIX TOOLS Tools of t
Page 43 and 44: Unix Tools Korn shell ! .profile HI
Page 45 and 46: Unix Tools grep "$name" $PHONEBOOK
Page 47 and 48: Unix Tools awk '$3 > 0 { print $1,
Page 49 and 50: Unix Tools END { print max, maxline
Page 51 and 52: Unix Tools Let an example input fil
Page 53 and 54: Unix Tools Brown eqn 1 # output Jon
Page 55 and 56: Development Tools Make looks at the
Page 57 and 58: Development Tools /* compute size o
Page 59 and 60: Development Tools #endif #line cons
Page 61 and 62: Development Tools 1.1 5 lines Retri
Page 63 and 64: Development Tools In Emacs, you may
Page 65 and 66: Development Tools */ %{ #define YYS
Page 67 and 68: C Libraries 6. C LIBRARIES Input an
Page 69 and 70: C Libraries } while (!feof(fp1)) pu
Page 71 and 72: C Libraries } free(p); /* what is w
Page 73 and 74: C Libraries } if ((fp->flag&( _READ
Page 75 and 76: C Libraries /* dirwalk: apply fcn t
Page 77 and 78: C Libraries } switch (pid=fork()){
Page 79 and 80: C Libraries What is curses? - libra
Page 81: C Libraries } if ((fd=fopen(argv[1]
Page 85 and 86: 82 Introduction to kernel Programs
Page 87 and 88: Introduction to kernel } { printf("
Page 89 and 90: Introduction to kernel The kernel r
Page 91 and 92: Introduction to kernel UNIX Interna
Page 93 and 94: Introduction to kernel File System
Page 95 and 96: Introduction to kernel Every proces
Page 97 and 98: Processes I Process States 1. Execu
Page 99 and 100: Processes I } printf("%d %s\n", cnt
Page 101 and 102: Processes I dup (and other similar
Page 103 and 104: Processes I The u area contains - p
Page 105 and 106: Processes I The Context of a Proces
Page 107 and 108: Processes I Process Control use and
Page 109 and 110: Processes I Although the processes
Page 111 and 112: Processes I Handling Signals - proc
Page 113 and 114: Processes I USER=neville PATH=/user
Page 115 and 116: Processes I ! Shadow Password /etc/
Page 117 and 118: struct timeval { long tv_sec; /* se
Page 119 and 120: Processes I F_SETFL set status flag
Page 121 and 122: Processes I process is the child pr
Page 123 and 124: Processes I Rules about sharing of
Page 125 and 126: Processes II 9. PROCESSES (II) FORK
Page 127 and 128: Processes II /* background.c */ #in
Page 129 and 130: Processes II } while (1){ printf("p
Page 131 and 132: Processes II } /* child */ signal (
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Processes II int readline(int fd, c
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Processes II { } char process_name[
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Processes II - Pipe in a single pro
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Processes II System V IPC - message
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Processes II int msgctl(int msqid,
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Processes II For every semop operat
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Processes II /* client loop */ mesg
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I/O Subsystem Drivers frequently sl
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I/O Subsystem Terminal Drivers - In
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I/O Subsystem Canonical Mode algori
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I/O Subsystem Raw Mode Raw mode is
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Figure 43. Pushing a Module onto a
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Interprocess Communication } { ptra
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Interprocess Communication T ID KEY
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Interprocess Communication }; int m
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Interprocess Communication for (i=0
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Interprocess Communication /* struc
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Interprocess Communication ! Compar
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… connect(sockfd,(struct sockaddr
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Interprocess Communication Address
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Process Scheduling Page Tables and
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Figure 49. Tie breaker rule Process
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Process Scheduling Clock - restart
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Process Scheduling Figure 57. Mappi
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Figure 62. Sequence of Swapping Ope
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Buffer Cache The kernel takes buffe
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Buffer Cache The kernel places the
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Buffer Cache Process B will find th
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Unix Administration 14. UNIX ADMINI
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Unix Administration Example output
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Unix Administration *) IN=-mtime -2
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Unix Administration Load /Unix kern
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Unix Administration for (i=0; i&i d
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Unix Administration fi done echo $s
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Unix Administration New Software !
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Unix Security Example: group name:g
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Unix Security $ crypt < exam320.Z >
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Unix Security - exported filesystem
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Unix Security system(cmdstr); $ ech
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Unix Security - repairs damaged use
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Working with the Unix OS

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