test case to make os.getuid() and os.geteuid() return different results

I got the same uid and euid even though the file belongs to root and has the suid bit set. Does anybody know how to make a test case to let getuid() and geteuid() return different results? Thanks.

$ cat main.py 
#!/usr/bin/env python3

import os
print(os.getuid())
print(os.geteuid())
$ dir
total 4.0K
-rwsr-xr-x 1 root staff 154 2021/02/02-10:48:27 main.py
$ ./main.py 
504
504
$ id 

EDIT: I tried a C program. uid and euid are still the same.

$ cat main.c
// vim: set noexpandtab tabstop=2:
#include <unistd.h>
#include <sys/types.h>
#include <stdio.h>

int main() {
    uid_t uid = getuid();
    uid_t euid = getuid();
    printf("%dn", uid);
    printf("%dn", euid);
}
$ ls -l ./main.exe
-rwsr-xr-x 1 root dialout 16656 Feb  2 12:14 ./main.exe
$ ./main.exe
504
504

Answer

Typo!

uid_t euid = getuid();

should read

uid_t euid = geteuid();

Then the C program will work. Don’t make setuid #! scripts. That’s not implemented for security reasons.

The suidperl story contains within it the description of why setuid won’t work on #! scripts.