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

void run_test(int maxfd)
{
    int srcfd = STDERR_FILENO;
    int minfd = 1024;

    /* Linux kernel expands the file descriptor table exponentially, so
     * keep requesting a minimum file descriptor exponentially. */
    for ( ; minfd < maxfd; minfd *= 2) {
        int fd;
        do {
            fd = fcntl(srcfd, F_DUPFD, minfd);
        } while (fd == -1 && errno == EINTR);

        if (fd == -1) {
            if (errno != EMFILE)
                perror("fcntl");
            return;
        }
        close(fd);
    }
}

int main(int argc, char **argv)
{
    struct rlimit lim;
    if (argc > 1) {
        lim.rlim_max = lim.rlim_cur = strtol(argv[1], NULL, 0);
    } else {
        int n;
        FILE *f = fopen("/proc/sys/fs/nr_open","r");
        if (!f) {
            perror("fopen");
            return EXIT_FAILURE;
        }
        if (fscanf(f, "%d", &n) != 1)
            return EXIT_FAILURE;
        fclose(f);
        lim.rlim_max = lim.rlim_cur = n;
    }

    if (setrlimit(RLIMIT_NOFILE, &lim) == -1) {
        perror("setrlimit");
        return EXIT_FAILURE;
    }

    run_test(lim.rlim_cur);

    static const char msg[] = "success\n";
    int ok1 = write(STDOUT_FILENO, msg, strlen(msg)) == strlen(msg);
    return ok1 ? EXIT_SUCCESS : 255;
}