#define _GNU_SOURCE
#include <pwd.h>
#include <stdio.h>
#include <unistd.h>

char* cuserid(char* buf) {
  struct passwd pw, *ppw;
  long pwb[256];
  if (getpwuid_r(geteuid(), &pw, (void*)pwb, sizeof pwb, &ppw))
    return 0;
  snprintf(buf, L_cuserid, "%s", pw.pw_name);
  return buf;
}