Working with the Unix OS

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Processes I System V provides times system call #include #include long times(struct tms *ptr); struct tms ( time_t tms_utime; /* user time */ time_t tms_stime; /* system time */ time_t tms_cutime; /* user time, children */ time_t tms_cstime; /* system time, children */ }; long time(long *ptr); /* seconds since 00:00:00 GMT, 1 Jan 1970 */ ! Input and Output - Unix system calls for I/O open, read, write etc direct entry points into kernel - Standard I/O library higher level interface between process and kernel features: buffering, line-by-line input, formatted output ! System Calls #include int open(char pathname int oflag[, int mode]); returns a file descriptor if successful, else -1 oflag O_RDONLY O_WRONLY O_RDWR O_NDELAY O_APPEND O_CREAT O_TRUNC O_EXCL open for reading only open for writing only open for reading and writing do no block on open or read or write append to end of file on each write create the file is it does not exist if file exist, truncate to zero length error if O_CREAT & file already exist int creat(char *pathname, int mode); int close{int fildes); int read{int fildes, char *buff, unsigned int nbytes); returns number of bytes read if successful, else -1 int write{int fildes, char *buff, unsigned int nbytes); returns actual number of bytes written long lseek{int fildes, long offset, int whence); whence 0 position offset from beginning of file current 1 position plus offset 2 position set to size of file plus offset int dup{int fildes); returns a new file descriptor - same file position int fcntl{int fildes, int cmd, int arg); used to change the properties of an open file cmd F_DUPFD duplicate file descriptor F_SETFD set the close-on-exec flag via arg F_GETFD return the close-on-exec flag via arg 115
Processes I F_SETFL set status flags via arg F_GETFL return status flags via arg F_GETLK, F_SETLK, F_SETLKW record locking #include device specific operations int ioctl (int fildes, unsigned long request, char *arg); intended for device specific operations ! signals Notification to a process that an event has occurred "software interrupt" usually occur asynchronously. - by one process to another process - by the kernel to a process #include Name Description Default action ISIGALRM Alarm clock Terminate ISIGBUS Bus error Terminate core ISIGCLD Death of child process Discarded ISIGEMT EMT instruction Terminate core ISIGFPE FPE instruction Terminate core ISIGHUP Hangup Terminate ISIGILL Illegal instruction Terminate core ISIGINT Interrupt character Terminate ISIGIOT IOT instruction Terminate core ISIGKILL Kill Terminate ISIGPIPE Write on pipe no one read it Terminate ISIGPOLL Select event on stream device Terminate ISIGPWR Power fail Terminate ISIGQUIT Quit character Terminate core ISIGSEGV Segmentation violation Terminate core ISIGSYS Bad argument to system call Terminate core ISIGTERM Software termination signal Terminate ISIGTRAP Trace trap Terminate core ISIGUSRl User defined signal 1 Terminate ISIGUSR2 User defined signal 1 Terminate - How and when are signals sent? 1. kill system call (kill is a misnomer) allows a process to sending process and send a signal to another process. To send a signal, the receiving process must both have the same effective user ID. 2. kill command is also used to send signals 3. terminal-generated signals e.g. interrupt character AC generates SIGINT signal 4. hardware conditions e.g. floating point error generates SIGFPE error 5. software conditions the kernel causes signals to be generated e.g. SIGURG out-of-band data arrives on a socket - What can a process do with a signal? 1. Provide a function called a signal handler 2. Ignore a signal (except SIGKILL terminate any process) 3. Allow the default action to occur - To handle a signal from within a process: #include int (*signal (int sig, void (*func) (in))) (int); signal: is a function that returns a pointer to a function that returns an integer. 116
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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
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 and 82: C Libraries } if ((fd=fopen(argv[1]
Page 83 and 84: Introduction to kernel 7. INTRODUCT
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: struct timeval { long tv_sec; /* se
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 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
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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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