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/* Store the privileged ID for later verification */
uid_t privid = geteuid();

/*  Code intended to run with elevated privileges   */

/* Temporarily drop privileges */
if (seteuid(getuid()) != 0) {
  /* Handle error */
}

/*  Code intended to run with lower privileges  */

if (need_more_privileges) {
  /* Restore Privileges */
  if (seteuid(privid) != 0) {
    /* Handle error */
  }

  /*  Code intended to run with elevated privileges   */
}

/* ... */

/* Restore low privileges if needed */
if (geteuid() != privid) {
  if (seteuid(privid())) {
    /* Handle Error */
  }
}

/* Permanently drop privileges */
if (setuid(getuid()) != 0) {
  /* Handle error */
}

if  (setuid(0) != -1) {
  /* Privileges can be restored, handle error */
}

/*  Code intended to run with lower privileges  */