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#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/select.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <sys/types.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#define NSEM 3
char *mem;
void quit(signum)
int signum;
{
shmdt(mem);
exit(1);
}
int main(argc, argv)
int argc;
char **argv;
{
int shmid, semid, i, pid, id;
char *mem;
struct sembuf sb;
if (argc < 2) {
printf("usage: writer [id]\n");
exit(1);
}
id = atoi(argv[1]);
if ((shmid = shmget(52, 1<<14, IPC_CREAT | 0666)) == -1){
perror("shmget: shmget failed");
exit(1);
}
if ((mem = shmat(shmid, NULL, 0)) == (char *) -1) {
perror("shmat");
exit(1);
}
printf("Wshmid: %x\n", shmid);
if ((semid = semget(shmid, NSEM, 0)) == -1) {
perror("Wsemget: ");
exit(1);
}
signal(SIGQUIT, quit);
srand(time(NULL));
while (1) {
rand() % id;
sb.sem_num = 0; sb.sem_op = -1; sb.sem_flg = 0;
semop(semid, &sb, 1);
for (i = 0; i < 1<<14; i++) {
mem[i]= 0x30 + id;
}
sb.sem_op = 1;
semop(semid, &sb, 1);
sleep(rand() % ((id * 2) + 1));
}
}
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