#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>

int main() {

    extern int errno;

    char file[] = "temp";
    
    // opening file
    int desc_f = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0640);
    if (desc_f < 0) {
        perror("ERROR opening f_write.txt");
        exit(errno);
    }

    // writing to file

    int ret_write = 0;
    for (int i = 1; i <= 30; i++) {

        ret_write = write(desc_f, &i, sizeof(int));
        if (ret_write < 0) {
            perror("ERROR writing to f_write.txt");
            exit(errno);
        }

        sleep(1);
        if (i % 10 == 0) {
            lseek(desc_f, 0, SEEK_SET);
        }
    }

    // closing files

    int ret_close = 0;
    ret_close = close(desc_f);
    if (ret_close < 0) {
        perror("ERROR closing f_read.txt");
        exit(errno);
    }

    return EXIT_SUCCESS;
}