#include <sys/types.h>
#include <sys/stat.h>

#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char **argv)
{
	struct stat statbuf;

	if ( stat("foo", &statbuf) == -1 ) {
		perror("can't stat foo");
		exit(1);
	}

	/* turn off group execute and turn on set-group-ID */
	if ( chmod("foo", (statbuf.st_mode & ~S_IXGRP) | S_ISGID) == -1 ) {
		perror("can't chmod foo");
		exit(1);
	}

	/* set absolute mode to rw-r--r-- */

	if ( chmod("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) == -1 ) {
		perror("can't chmod bar");
		exit(1);
	}

	exit(0);
}