48 lines
959 B
C
48 lines
959 B
C
#include <semaphore.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/ipc.h>
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#include <sys/shm.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#define NUM_PROCESSES 5
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int main() {
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int shmid;
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int i, j, pid;
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sem_t* sems[NUM_PROCESSES];
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for (int i = 0; i < NUM_PROCESSES; i++) {
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shmid = shmget(IPC_PRIVATE, sizeof(sem_t), IPC_CREAT | 0600);
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sems[i] = (sem_t*)shmat(shmid, NULL, 0);
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}
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sem_post(sems[0]);
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for (int i = 0; i < NUM_PROCESSES; i++) sem_init(sems[i], 1, 0);
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// allow the first process to run
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sem_post(sems[0]);
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for (i = 0; i < NUM_PROCESSES; i++) {
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if ((pid = fork()) == 0) {
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break;
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}
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}
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if (pid == 0) {
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sem_wait(sems[i]);
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printf("I am child %d\n", i);
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for (j = i * 10; j < i * 10 + 10; j++) {
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printf("%d ", j);
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fflush(stdout);
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usleep(250000);
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}
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printf("\n\n");
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sem_post(sems[i + 1]);
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} else {
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for (i = 0; i < NUM_PROCESSES; i++) wait(NULL);
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}
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}
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