int seteuid(uid_t uid);
Declared, not implemented
IEEE Std 1003.1-2017
If uid is equal to the real user ID or the saved set-user-ID, or if the process has appropriate privileges,
seteuid() shall set the effective user ID of the calling process to uid; the real user ID and saved set-user-ID shall
seteuid() function shall not affect the supplementary group list in any way.
Upon successful completion, 0 shall be returned; otherwise, -1 shall be returned and
errno set to indicate the error.
seteuid() function shall fail if:
EINVAL- The value of the uid argument is invalid and is not supported by the implementation.
EPERM- The process does not have appropriate privileges and uid does not match the real user ID or the saved set-user-ID.