1.c

#include <stdio.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <errno.h>

#define FILENAME "./test"

#define FLAGS (O_RDWR | O_CREAT)

#define MODE (S_IRUSR)

int main(void)
{
    int fd;

    fd = open(FILENAME, FLAGS, MODE, 1, 2, 3, 4, 5);
    printf("fd = %d\n", fd);
    if (fd == -1)
    {
        printf("errno = %d, ENOENT = %d\n", errno, ENOENT);
        perror("open");
        return -1;
    }

    close(fd);

    return 0;
}