F GETPATH

This is untested code...

#if 0
        /* this would be nice... */
        if (fcntl(fd, F_GETPATH, fname) == -1) {
                strerror_r(errno, es, ES_LEN);
                fprintf(stderr, "fcntl(): %s\n", es);
                return -1;
        }
#else
        {
                const char t[PATH_MAX];
                struct stat a, b;
                snprintf(t, sizeof(t), "/proc/self/fd/%d", fd);
                if (readlink(t, fname, sizeof(fname)) == -1) {
                        strerror_r(errno, es, ES_LEN);
                        fprintf(stderr, "readlink(%s): %s\n", t, es);
                        return -1;
                }
 
                if (stat(fname, &a) == -1) {
                        strerror_r(errno, es, ES_LEN);
                        fprintf(stderr, "stat(%s): %s\n", fname, es);
                        return -1;
                }
                if (stat(t, &b) == -1) {
                        strerror_r(errno, es, ES_LEN);
                        fprintf(stderr, "stat(%s): %s\n", t, es);
                        return -1;
                }
 
                if (a.st_dev != b.st_dev || a.st_ino != b.st_ino) {
                        fprintf(stderr, "get_db(): tempoary file lost...\n");
                        return -1;
                }
        }
#endif