Working with the Unix OS

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Figure 49. Tie breaker rule Process Scheduling priority = (CPU_usage / 2) + 60 Process B has an initial higher user level priority. Process A runs first "ready to run" for longer time. Real Time Processing - hard-coded into kernel - not standard UNIX 173 Figure 50. Fair Share Scheduler
Process Scheduling System Calls for Time #include #include extern long times(); main() { int i; /* tms is data structure containing <strong>the</strong> 4 time elements */ struct tms pb1, pb2; long ptl, pt2; ptl = times(&pb1); for (i = 0; i < 10; i++) if (fork() == 0) child (i); for (i = 0; i < 10; i++) wait((int *) 0); pt2 = times(&pb2); printf("parent real %u user %u sys %u cuser %u csys %u\n", pt2 - ptl, pb2.tms_utime - pb1.tms_utime, pb2.tms_stime - pb1.tms_stime, pb2.tms_cutime - pb1.tms_cutime, pb2.tms_cstime - pb1.tms_cstime); } child(n) int n; { int i; struct tms cb1, cb2; long tl, t2; } tl = times(&cb1); for (i = 0; i < 10000; i++) ; t2 = times(&cb2); printf("child %d: real %u user %u sys %u\n", n, t2 - tl, cb2.tms_utime - cb1.tms_utime, cb2.tms_stime - cb1.tms_stime); exit(0); Figure 51. Program Using Timer #include #include #include main(argc, argv) int argc; char *argv[ ]; { extern unsigned alarm(); extern wakeup(); struct stat statbuf; time_t axtime; if (argc != 2) { printf("only 1 arg\n"); exit(0); stime(p } axtime = (time_t) 0; value), for (;;) time(tloc), times (tbuffer), alarm { /* find out file access time */ if (stat (argv[1], &statbuf) == -1) { printf("file %s not <strong>the</strong>re\n", argv[1]); exit(0); } if (axtime != statbuf.st_atime) { printf("file %s accessed\n", argv[1]); axtime = statbuf.st_atime; } signal(SIGALRM, wakeup); /* reset for alarm */ alarm(60); pause(); /* sleep until signal */ } } wakeup() { } Figure 52. Alarm Call 174
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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 $append then tee -a
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C Programming - Basics main() { int
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C Programming - Basics e.g. i += 2
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External Variables A C program cons
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C Programming - Basics main.c #incl
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C Programming - Basics default: pri
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C Programming - Basics struct tnode
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Unix Tools 4. UNIX TOOLS Tools of t
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Unix Tools Korn shell ! .profile HI
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Unix Tools grep "$name" $PHONEBOOK
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Unix Tools awk '$3 > 0 { print $1,
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Unix Tools END { print max, maxline
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Unix Tools Let an example input fil
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Unix Tools Brown eqn 1 # output Jon
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Development Tools Make looks at the
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Development Tools /* compute size o
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Development Tools #endif #line cons
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Development Tools 1.1 5 lines Retri
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Development Tools In Emacs, you may
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Development Tools */ %{ #define YYS
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C Libraries 6. C LIBRARIES Input an
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C Libraries } while (!feof(fp1)) pu
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C Libraries } free(p); /* what is w
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C Libraries } if ((fp->flag&( _READ
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C Libraries /* dirwalk: apply fcn t
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C Libraries } switch (pid=fork()){
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C Libraries What is curses? - libra
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C Libraries } if ((fd=fopen(argv[1]
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Introduction to kernel 7. INTRODUCT
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82 Introduction to kernel Programs
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Introduction to kernel } { printf("
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Introduction to kernel The kernel r
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Introduction to kernel UNIX Interna
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Introduction to kernel File System
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Introduction to kernel Every proces
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Processes I Process States 1. Execu
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Processes I } printf("%d %s\n", cnt
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Processes I dup (and other similar
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Processes I The u area contains - p
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Processes I The Context of a Proces
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Processes I Process Control use and
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Processes I Although the processes
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Processes I Handling Signals - proc
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Processes I USER=neville PATH=/user
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Processes I ! Shadow Password /etc/
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struct timeval { long tv_sec; /* se
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Processes I F_SETFL set status flag
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Processes I process is the child pr
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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 (
Page 133 and 134: Processes II int readline(int fd, c
Page 135 and 136: Processes II { } char process_name[
Page 137 and 138: Processes II - Pipe in a single pro
Page 139 and 140: Processes II System V IPC - message
Page 141 and 142: Processes II int msgctl(int msqid,
Page 143 and 144: Processes II For every semop operat
Page 145 and 146: Processes II /* client loop */ mesg
Page 147 and 148: I/O Subsystem Drivers frequently sl
Page 149 and 150: I/O Subsystem Terminal Drivers - In
Page 151 and 152: I/O Subsystem Canonical Mode algori
Page 153 and 154: I/O Subsystem Raw Mode Raw mode is
Page 155 and 156: Figure 43. Pushing a Module onto a
Page 157 and 158: Interprocess Communication } { ptra
Page 159 and 160: Interprocess Communication T ID KEY
Page 161 and 162: Interprocess Communication }; int m
Page 163 and 164: Interprocess Communication for (i=0
Page 165 and 166: Interprocess Communication /* struc
Page 167 and 168: Interprocess Communication ! Compar
Page 169 and 170: … connect(sockfd,(struct sockaddr
Page 171 and 172: Interprocess Communication Address
Page 173 and 174: Process Scheduling Page Tables and
Page 178 and 179: Process Scheduling Clock - restart
Page 180 and 181: Process Scheduling Figure 57. Mappi
Page 182 and 183: Figure 62. Sequence of Swapping Ope
Page 184 and 185: Buffer Cache The kernel takes buffe
Page 186 and 187: Buffer Cache The kernel places the
Page 188 and 189: Buffer Cache Process B will find th
Page 190 and 191: Unix Administration 14. UNIX ADMINI
Page 192 and 193: Unix Administration Example output
Page 194 and 195: Unix Administration *) IN=-mtime -2
Page 196 and 197: Unix Administration Load /Unix kern
Page 198 and 199: Unix Administration for (i=0; i&i d
Page 200 and 201: Unix Administration fi done echo $s
Page 202 and 203: Unix Administration New Software !
Page 204 and 205: Unix Security Example: group name:g
Page 206 and 207: Unix Security $ crypt < exam320.Z >
Page 208 and 209: Unix Security - exported filesystem
Page 210 and 211: Unix Security system(cmdstr); $ ech
Page 212: Unix Security - repairs damaged use
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Working with the Unix OS

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