#include<pthread.h>#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<string.h>#include<semaphore.h>#define THREAD_NUM 4sem_t sem;
void* routine(void* args){
int index = *(int*)args;
int semVal;
sem_wait(&sem);
sleep(index + 1);
sem_getvalue(&sem, &semVal);
printf("(%d) Current semaphore value after wait is %d\n", index, semVal);
sem_post(&sem);
sem_getvalue(&sem, &semVal);
printf("(%d) Current semaphore value after post is %d\n", index, semVal);
free(args);
}
intmain(int argc, char *argv[]){
pthread_t th[THREAD_NUM];
sem_init(&sem, 0, 4);
int i;
for (i = 0; i < THREAD_NUM; i++) {
int* a = malloc(sizeof(int));
*a = i;
if (pthread_create(&th[i], NULL, &routine, a) != 0) {
perror("Failed to create thread");
}
}
for (i = 0; i < THREAD_NUM; i++) {
if (pthread_join(th[i], NULL) != 0) {
perror("Failed to join thread");
}
}
sem_destroy(&sem);
return0;
}
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