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The C programming language made simple

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Practical example using semaphores (Login Queue)

#include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <semaphore.h> #define THREAD_NUM 16 sem_t semaphore; void* routine(void* args) { printf("(%d) Waiting in the login queue\n", *(int*)args); sem_wait(&semaphore); printf("(%d) Logged in\n", *(int*)args); sleep(rand() % 5 + 1); printf("(%d) Logged out\n", *(int*)args); sem_post(&semaphore); free(args); } int main(int argc, char *argv[]) { pthread_t th[THREAD_NUM]; sem_init(&semaphore, 0, 32); 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(&semaphore); return 0; }