#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

int main(void) {
    const char *path = "ostep_ch39_demo.tmp";
    int fd = open(path, O_CREAT | O_RDWR | O_TRUNC, 0644);
    if (fd < 0) {
        perror("open");
        return 1;
    }
    const char msg[] = "hello from files\n";
    ssize_t n = write(fd, msg, sizeof(msg) - 1);
    if (n != (ssize_t)(sizeof(msg) - 1)) {
        perror("write");
        close(fd);
        unlink(path);
        return 1;
    }
    if (lseek(fd, 0, SEEK_SET) < 0) {
        perror("lseek");
        close(fd);
        unlink(path);
        return 1;
    }
    char buf[32];
    ssize_t r = read(fd, buf, sizeof(buf) - 1);
    if (r < 0) {
        perror("read");
        close(fd);
        unlink(path);
        return 1;
    }
    buf[r] = '\0';
    printf("wrote %zd bytes, read back: %s", n, buf);
    close(fd);
    if (unlink(path) != 0) {
        perror("unlink");
        return 1;
    }
    printf("unlinked successfully\n");
    return 0;
}