import subprocess
import stat
import os

suid_prog = './suid'

st = os.stat(suid_prog)
if not (st.st_mode & stat.S_ISUID):
    raise Exception("File %s is not setuid!" % suid_prog)
expected_uid = st.st_uid

if os.geteuid() == expected_uid:
    raise Exception("Already have uid %d, setuid won't do anything!" % expected_uid)

i = 1
while subprocess.call([suid_prog, str(expected_uid)]) == 0:
    i += 1
else:
    print 'Failed after %d tries!' % i