#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

//#define HASSETUGID 0
#define HASGETRESUID 1

main()
{
  printf ("uid=%d, euid=%d, gid=%d, egid=%d\n", getuid(), geteuid(), getgid(), getegid());
#if defined(HASSETUGID)
  printf ("issetugid()=%d" % issetugid());
#endif

#if defined(HASGETRESUID)
  uid_t ruid, euid, suid;
  gid_t rgid, egid, sgid;
  if ((getresuid(&ruid, &euid, &suid) == 0) &&
      (getresgid(&rgid, &egid, &sgid) == 0)) {
    printf ("ruid=%d, euid=%d, suid=%d\n", ruid, euid, suid);
    printf ("rgid=%d, egid=%d, sgid=%d\n", rgid, egid, sgid);
  }
#endif

  unsigned int oldeuid;
  oldeuid = geteuid();
  if (seteuid(0) != 0) {
    printf ("cannot setuid(0)\n");
  } else {
    printf ("can setuid(0)\n");
  }
}