github.com/stuarqi/moby@v1.13.1/contrib/syscall-test/setgid.c (about)

     1  #include <sys/types.h>
     2  #include <unistd.h>
     3  #include <stdio.h>
     4  
     5  int main() {
     6  	if (setgid(1) == -1) {
     7  		perror("setgid");
     8  		return 1;
     9  	}
    10  	return 0;
    11  }