execve() vs system()

setuid 관련 문서들을 보다가 어느 대학의 시험지 내용같은걸 찾았는데요
아래문제의 b 항목이 제가 질문한 것입니다.
아래의 소스코드 그대로 테스트해보니
system 을 이용했을때는 shadow 가 보이는데
execve 를 이용할때는 안보이더군요
OS 마다 다른걸까요?;
제가 테스트해본 OS 는 데비안 리눅스입니다 커널버전이 정확히 몇인지는 기억이...

5. (15 points) The difference between system() and execve().
(a) Write a program that simply calls system("/bin/cat /etc/shadow"), and make it a
set-root-uid program. Run it using a regular user account in both Minix and Linux. Describe
and explain your observation. For example, if you get a “permission denied” message, you need
to explain why it is denied.

(b) Still use the same program, but replace system() with execve() (see the following code).
Run the program using a regular user account in both Minix and Linux. Describe and explain
your observation. If the observation is different from that of the previous program, you need to
explain what causes such a difference, and which call is more secure.

int main()
{
char *argv[3];
argv[0] = "/bin/cat";
argv[1] = "/etc/shadow";
argv[2] = 0;
/* system("/bin/cat /etc/shadow"); */
execve("/bin/cat", argv, 0);
return 0;
}