Find number of file descriptor per process (initially 3 usually)

get-n-fds.c

int rm_fd_cache_get_fds_per_process(RmFdCache *self) {
    g_assert(self);

    int n = -1;

    struct rlimit rl;
    if(getrlimit(RLIMIT_NOFILE, &rl) == -1) {
        return -1;
    }

    struct pollfd *fds = g_malloc0(rl.rlim_cur * sizeof(struct pollfd));
    for(rlim_t i = 0; i < rl.rlim_cur; ++i) {
        fds[i].fd = i;
        fds[i].events = 0;
    }
    
    if(poll(fds, rl.rlim_cur, 0) == -1) {
        goto cleanup;
    }

    n = rl.rlim_cur;
    for(rlim_t i = 0; i < rl.rlim_cur; ++i) {
        n -= !!(fds[i].revents & POLLNVAL);
    }

cleanup:
    g_free(fds);
    return n;
}