//http://blog.chinaunix.net/uid-24549279-id-71355.html

 /*

  ============================================================================

  Name        : test.c

  Author      : blank

  Version     :

  Copyright   : Your copyright notice

  Description : 程序4-4 chmod函数实例

  ============================================================================

 */

 #include <fcntl.h>

 #include "ourhdr.h"

 int main(int argc, char *argv[])

 {

     struct stat  buf;

     if (stat("foo", &buf) < ){

         err_sys("stat error for foo");

     }

     /*

      * turn on set-group-ID and turn off group-execute

      */

     if (chmod("foo", (buf.st_mode & ~S_IXGRP) | S_ISGID) < ){

         err_sys("chmod error for foo");

     }

     /*

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

      */

     if (chmod("bar", (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) < ){

         err_sys("chmod error for bar");

     }

     exit();

 }