fgetpwent_r
extern struct passwd *fgetpwent_r(FILE *, struct passwd *, char *, int);
fgetpwent_r(f, b->result, b->buffer, b->buflen));
while (fgetpwent_r(src, &cur, buf, sizeof (buf)) != NULL) {
while (!found && fgetpwent_r(fp, result, buffer, buflen) != NULL) {