143 lines
4.5 KiB
HTML
143 lines
4.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<HEAD>
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<TITLE>The Source</TITLE>
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<META NAME="description" CONTENT="The Source">
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<META NAME="keywords" CONTENT="lpg">
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<A NAME="tex2html1370" HREF="node82.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A> <A NAME="tex2html1368" HREF="node73.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A> <A NAME="tex2html1364" HREF="node80.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif"></A> <A NAME="tex2html1372" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME="tex2html1371" HREF="node82.html">7 Sound Programming</A>
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<B>Up:</B> <A NAME="tex2html1369" HREF="node73.html">shmtool: An interactive shared </A>
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<B> Previous:</B> <A NAME="tex2html1365" HREF="node80.html">Examples</A>
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<BR> <P>
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<H4><A NAME="SECTION00744740000000000000">The Source</A></H4>
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<P>
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<P>
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<HR><PRE>
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#include <stdlib.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#include <ctype.h>
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#include <string.h>
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#define SEGSIZE 100
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void usage();
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void writeshm(int shmid, char *segptr, char *text);
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void changemode(int shmid, char *mode);
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void removeshm(int shmid);
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void readshm(int shmid, char *segptr);
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main(int argc, char *argv[])
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{
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key_t key;
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int shmid, cntr;
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char *segptr;
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if(argc == 1)
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usage();
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/* Create unique key via call to ftok() */
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key = ftok(".", 'S');
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/* Open the shared memory segment - create if necessary */
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if((shmid = shmget(key, SEGSIZE, IPC_CREAT|IPC_EXCL|0666)) == -1)
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{
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printf("Shared memory segment exists - opening as client\n");
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/* Segment probably already exists - try as a client */
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if((shmid = shmget(key, SEGSIZE, 0)) == -1)
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{
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perror("shmget");
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exit(1);
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}
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}
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else
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{
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printf("Creating new shared memory segment\n");
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}
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/* Attach (map) the shared memory segment into the current process */
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if((segptr = (char *)shmat(shmid, 0, 0)) == (char *)-1)
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{
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perror("shmat");
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exit(1);
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}
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switch(tolower(argv[1][0]))
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{
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case 'w': writeshm(shmid, segptr, argv[2]);
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break;
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case 'r': readshm(shmid, segptr);
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break;
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case 'd': removeshm(shmid);
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break;
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case 'm': changemode(shmid, argv[2]);
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break;
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default: usage();
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}
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}
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writeshm(int shmid, char *segptr, char *text)
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{
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strcpy(segptr, text);
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printf("Done...\n");
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}
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readshm(int shmid, char *segptr)
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{
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printf("segptr: %s\n", segptr);
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}
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removeshm(int shmid)
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{
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shmctl(shmid, IPC_RMID, 0);
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printf("Shared memory segment marked for deletion\n");
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}
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changemode(int shmid, char *mode)
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{
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struct shmid_ds myshmds;
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/* Get current values for internal data structure */
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shmctl(shmid, IPC_STAT, &myshmds);
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/* Display old permissions */
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printf("Old permissions were: %o\n", myshmds.shm_perm.mode);
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/* Convert and load the mode */
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sscanf(mode, "%o", &myshmds.shm_perm.mode);
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/* Update the mode */
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shmctl(shmid, IPC_SET, &myshmds);
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printf("New permissions are : %o\n", myshmds.shm_perm.mode);
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}
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usage()
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{
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fprintf(stderr, "shmtool - A utility for tinkering with shared memory\n");
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fprintf(stderr, "\nUSAGE: shmtool (w)rite <text>\n");
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fprintf(stderr, " (r)ead\n");
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fprintf(stderr, " (d)elete\n");
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fprintf(stderr, " (m)ode change <octal mode>\n");
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exit(1);
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}</PRE>
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<HR>
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<P>
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<BR> <HR>
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<P><ADDRESS>
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<I>Converted on: <BR>
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Fri Mar 29 14:43:04 EST 1996</I>
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</ADDRESS>
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