Working with the Unix OS

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I/O Subsystem Control Terminal Terminal on which the user logs into the system. When a user presses DELETE, BREAK, RUBOUT, QUIT keys the interrupt handler invokes the line discipline, which sends a signal to all processes in the control process group. Indirect Terminal Drivers /dev/tty - current terminal /dev/console - console device Login algorithm login /* procedure for logging in */ { getty process executes: set process group (setpgrp system calO; open tty line; /* sleeps until opened */ if (open successful) { exec login program: prompt for user name; turn off echo, prompt for password; if (successful) /* matches password in letclpasswd */ { put tty in canonical mode (ioctl); exec shell; } else count login attempts, try again up to a point; } } Figure 41. Loggin in Streams - different drivers tend to duplicate functionality - a full-duplex connection between a process and a device driver - a set of linear linked queue pairs, one for input and one for output Each queue contains: - open procedure - close procedure - put - to pass message into queue - service - to execute queue - pointer to next queue in stream - pointer to list of messages awaiting service - pointer to private data structure - maintains state of queue - flags - high and low water marks - flow control Figure 42. A Stream after Open 151
Figure 43. Pushing a Module onto a Stream I/O Subsystem Figure 44. Windowing VT on Physical Terminal /* assume file descriptors 0 and 1 already refer to physical tty */ for (;;) /* loop */ { select (input); /* wait for some line with input */ read input line; switch (line with input data) { case physical tty: /* input on physical tty line */ if (control command) /* e.g. create new window */ { open a free pseudo-tty; fork a new process: if (parent) { push a msg discipline on mpx side; continue; /* back to for loop */ } /* child here */ close unnecessary file descriptors; open other member of pseudo-tty pair, get stdin, stdout, stderr; push tty line discipline; exec shell; /* looks like virtual tty */ } /* "regular" data from tty coming up for virtual tty */ demultiplex data read from physical tty, strip off headers and write to appropriate pty; continue; /* back to for loop */ case logical tty: /* a virtual tty is writing a window */ encode header indicating what window data is for; write header and data to physical tty; continue; /* back to for loop */ } } Figure 45. Pseudo-code for Multiplexing Windows 152
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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
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 (
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: I/O Subsystem Raw Mode Raw mode is
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 176 and 177: Figure 49. Tie breaker rule Process
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 !
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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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