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

#define MY_TEST_DIR_NAME "my_test_dir"
#define MY_TEST_UID_1 42
#define MY_TEST_UID_2 43
#define MY_TEST_GROUP 2222

static void testDir(int flags)
{
    system("ls -ld " MY_TEST_DIR_NAME);

    /*
     * Open the directory.
     */
    int fd = open(MY_TEST_DIR_NAME, flags | O_NOFOLLOW);
    if (fd < 0) {
        fprintf(stderr, "Couldn't open directory (%s)\n", strerror(errno));
        return;
    }
    system("ls -ld " MY_TEST_DIR_NAME);

    /*
     * Give it away.
     */
    if (fchown(fd, MY_TEST_UID_1, MY_TEST_GROUP) != 0) {
        fprintf(stderr, "Can't do first change of ownership (%s)\n", 
                strerror(errno));
        close(fd);
        return;
    }
    system("ls -ld " MY_TEST_DIR_NAME);

    /*
     * Give it away again.
     */
    if (fchown(fd, MY_TEST_UID_2, MY_TEST_GROUP) != 0) {
        fprintf(stderr, "Can't do second change of ownership (%s)\n", 
                strerror(errno));
        close(fd);
        return;
    }
    system("ls -ld " MY_TEST_DIR_NAME);

    printf("All OK!\n");
    close(fd);
}

int main(int argc, char ** argv)
{
    /*
     * Parse the args.
     */
    if (argc != 3) {
        fprintf(stderr, "Usage: %s [O_RDONLY|O_WRONLY] mode\n", argv[0]);
        exit(1);
    }

    int flags;
    if (strcmp(argv[1], "O_RDONLY") == 0) {
        flags = O_RDONLY;
    } else if (strcmp(argv[1], "O_WRONLY") == 0) {
        flags = O_WRONLY;
    } else {
        fprintf(stderr, "Argument must be O_RDONLY or O_WRONLY\n");
        exit(1);
    }

    int mode = (int)strtol(argv[2], NULL, 0);

    /*
     * Will only work as root.
     */
    if (geteuid() != 0) {
        fprintf(stderr, "Must run test as root.\n");
        exit(1);
    }

    /*
     * Create a directory.
     */
    if (mkdir(MY_TEST_DIR_NAME, mode) < 0) {
        fprintf(stderr, "Can't create directory(%s)\n", strerror(errno));
        exit(1);
    }

    testDir(flags);

    /*
     * Delete the directory.
     */
    if (rmdir(MY_TEST_DIR_NAME) < 0) {
        fprintf(stderr, "Can't delete directory(%s)\n", strerror(errno));
        exit(1);
    }

    exit(0);
}