#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

int main(void) {
    int fd = open("./csie_trains/train_902001", O_RDWR);
    struct flock fl = {
        .l_type = F_WRLCK, .l_whence = SEEK_SET, .l_start = 0, .l_len = 0};
    // First, check if the file is locked (Assume that fd was opened before
    // here)
    if (fcntl(fd, F_GETLK, &fl) == -1) {
        perror("fcntl F_GETLK");
        exit(69);
    }
    printf("%d\n", fl.l_type);
}