Working with the Unix OS

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141 Processes II segment the kernel maintains. #include #include /* defines ipc-perm structure */ struct shrnid_ds { struct ipc_perm shrn_perm; /* operation perm struct */ int shrn_seqsz; /* segment size */ struct XXX shrn_YYY; /* hardware & implementation dependent information */ ushort shrn_lpid; /* pid of last operation */ ushort shrn_cpid; /* creator pid */ ushort shrn_nattch; /* current # attached */ ushort shrn_cnattch; /* in-core # attached */ time_t shrn_atime; /* last attach time */ time_t shrn_dtime; /* last detach time */ time_t shrn_ctime; /* last change time */ }; int shrnget(key_t key, int size, int shrnflag); /* used to create or open access to an existing shared memory segment */ shrnflag 0400 SHM_R read by owner 0200 SHM_W write by owner 0040 SHM_R >> 3 read by group 0020 SHM_W >> 3 write by group 0004 SHM_R >> 6 read by world 0002 SHM_W >> 6 write by world IPC_CREAT IPC_EXCL char *shrnat(int shrnid, char *shraddr, int shrnflag); /* returns the starting address of shared memory segment */ if shrnaddr == 0 system selects address for the caller else if value for shrnflag specifies SHM_RND, shared memory is attached at the address specified by the shrnaddr argument rounded down by SHMLBA (lower boundary address) else shared memory is attached at the address specified by the shrnaddr argument int shrndt(char *shrnaddr); /* detaches the segment but does not delete the shared memory segment */ int shrnctl(int shrnid, int cmd, struct shrnid_ds *buf); /* a cmd of IPC_RMID removes a shared memory segment from the system */ See shared_memory.c The two process wait for access to the shared memory by waiting for a semaphore's value to become greater than zero. This is the most efficient way to wait for the resource, since it is the kernel that does all semaphore operations and the kernel puts a process to sleep when it has to wait for a semaphore. ! Busy-waiting - instead of sleeping - keep trying to obtain resource /* server loop */ mesgptr->mesg_flag = 0; /* signal client */ while (mesgptr->mesg_flag == 0) ; /* wait for client to process */
Processes II /* client loop */ mesgptr->mesg_flag = 1; /* signal server */ while (mesgptr->mesg_flag == 1) ; /* wait for server to process */ ! Multiple Buffers /* typical program loop */ while ( (n = read(fdin, buff, BUFFSIZE» > 0) /* process the data */ write (fdout, buff, n); Sockets and TLI Sockets are a form of IPC provided by BSD4.3 TLI, Transport Layer Interface is a form of IPC provided by System V. Both provide communication between processes on the same system and between processes on different systems. 142
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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
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 (
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: Processes II For every semop operat
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 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
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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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