c4-3 test of umask

#include "apue.h"
#include <fcntl.h>

#define RWRWRW (S_IRUSR |S_IWUSR |S_IRGRP |S_IWGRP |S_IROTH |S_IWOTH )

int
main(void )
{
    umask(0);
    if (creat("foo",RWRWRW) < 0)
        err_sys("create error");
    umask(S_IRGRP |S_IWGRP | S_IROTH | S_IWOTH);
    if (creat("bar",RWRWRW) < 0)
        err_sys("create error");
    exit(0);

}

ubuntu@ubuntu-virtual-machine:~/Desktop/apue$ umask

0002

ubuntu@ubuntu-virtual-machine:~/Desktop/apue$  ls -l foo bar

-rw------- 1 ubuntu ubuntu 0 2011-12-28 20:09 bar

-rw-rw-rw- 1 ubuntu ubuntu 0 2011-12-28 20:09 foo

ubuntu@ubuntu-virtual-machine:~/Desktop/apue$ umask

0002

ubuntu@ubuntu-virtual-machine:~/Desktop/apue$ umask -S

u=rwx,g=rwx,o=rx

PS：

子进程修改自己的文件模式屏蔽字，对父进程没有影响

文件最后的属性为：

mask&0777

 建立文件 ：  664 ＝ 0666-0002
  建立目录：  775 = 0777 - 0002