[Pthread][Semaphore] Pthread + semaphore to create synchronize

Semaphore (programming) 1

C code

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>

void *thread_function(void *arg);
sem_t bin_sem;

#define WORK_SIZE 1024
char work_area[WORK_SIZE];

int main() {
    int res;
    pthread_t a_thread;
    void *thread_result;

/* Initial Semaphore 0 */
    res = sem_init(&bin_sem, 0, 0);
    if (res != 0) {
        perror("Semaphore initialization failed");
        exit(EXIT_FAILURE);
    }
    res = pthread_create(&a_thread, NULL, thread_function, NULL);
    if (res != 0) {
        perror("Thread creation failed");
        exit(EXIT_FAILURE);
    }

    printf("Input some text. Enter 'end' to finish\n");
    while(strncmp("end", work_area, 3) != 0) {
        fgets(work_area, WORK_SIZE, stdin);
        sem_post(&bin_sem); /* Increase Semaphore to 1 ( 0 + 1 ) */
    }
    printf("\nWaiting for thread to finish...\n");
    res = pthread_join(a_thread, &thread_result);
    if (res != 0) {
        perror("Thread join failed");
        exit(EXIT_FAILURE);
    }
    printf("Thread joined\n");
    sem_destroy(&bin_sem);
    exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
    sem_wait(&bin_sem); /* decrease Semaphore to 0 ( 1 - 1 ) */
    while(strncmp("end", work_area, 3) != 0) {
        printf("You input %d characters\n", strlen(work_area) -1);
        sem_wait(&bin_sem);  /* wait for another Semaphore, because the value is 0 now */
    }
    pthread_exit(NULL);
}

Result

Input some text. Enter 'end' to finish
This is my first pthread and semaphore.
You input 39 characters
end

Waiting for thread to finish...
Thread joined

Reference

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1. Semaphore (programming) ↩