#define _GNU_SOURCE
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

char* __randname(char*);

char* mktemp(char* template) {
    size_t l = strlen(template);
    int retries = 100;
    struct stat st;

    if (l < 6 || memcmp(template + l - 6, "XXXXXX", 6)) {
        errno = EINVAL;
        *template = 0;
        return template;
    }

    do {
        __randname(template + l - 6);
        if (stat(template, &st)) {
            if (errno != ENOENT)
                *template = 0;
            return template;
        }
    } while (--retries);

    *template = 0;
    errno = EEXIST;
    return template;
}