Linux系統編程22 文件系統 - 文件屬性和FAT文件系統

1 umask
umask：防止產生權限過鬆的文件

umask 命令是用 umask()封裝的。
代碼中也可以使用 umask:

NAME
umask - set file mode creation mask

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

   mode_t umask(mode_t mask);

2 文件權限的更改和管理

NAME
chmod, fchmod, fchmodat - change permissions of a file

SYNOPSIS
#include <sys/stat.h>

   int chmod(const char *pathname, mode_t mode);
   int fchmod(int fd, mode_t mode);

3 粘住位
t位，現在常用於給特定的目錄設置t位，如 根目錄下的 tmp 目錄
drwxrwxrwt 最後一位是t位，這樣 各個用戶 對 tmp 這個目錄以及中文件 的操作就會比較特殊化了。

mhr@ubuntu:~/work/linux/wenjianxitong/20$ 
mhr@ubuntu:~/work/linux/wenjianxitong/20$ ls / -l
total 100
drwxr-xr-x   2 root root  4096 Apr  8 22:58 bin
drwxr-xr-x   3 root root  4096 May  1 03:40 boot
drwxrwxr-x   2 root root  4096 Sep  2  2019 cdrom
drwxr-xr-x  18 root root  3980 May  3 08:50 dev
drwxr-xr-x 132 root root 12288 May  3 08:50 etc
drwxr-xr-x   3 root root  4096 Sep  2  2019 home
lrwxrwxrwx   1 root root    33 May  1 03:40 initrd.img -> boot/initrd.img-4.4.0-178-generic
lrwxrwxrwx   1 root root    33 May  1 03:40 initrd.img.old -> boot/initrd.img-4.4.0-177-generic
drwxr-xr-x  22 root root  4096 Sep  2  2019 lib
drwxr-xr-x   2 root root  4096 Apr  8 22:55 lib64
drwx------   2 root root 16384 Sep  3  2019 lost+found
drwxr-xr-x   4 root root  4096 Sep  2  2019 media
drwxr-xr-x   3 root root  4096 Sep  2  2019 mnt
drwxr-xr-x   2 root root  4096 Sep  2  2019 opt
dr-xr-xr-x 245 root root     0 May  3 08:49 proc
drwx------   3 root root  4096 Apr 23 05:34 root
drwxr-xr-x  26 root root   820 May  4 19:13 run
drwxr-xr-x   2 root root 12288 Apr  8 22:58 sbin
drwxr-xr-x   2 root root  4096 Apr  8 23:00 snap
drwxr-xr-x   2 root root  4096 Apr 20  2016 srv
dr-xr-xr-x  13 root root     0 May  3 08:49 sys
drwxrwxrwt  12 root root  4096 May  4 19:17 tmp
drwxr-xr-x  11 root root  4096 Apr 20  2016 usr
drwxr-xr-x  14 root root  4096 Apr 20  2016 var
lrwxrwxrwx   1 root root    30 May  1 03:40 vmlinuz -> boot/vmlinuz-4.4.0-178-generic
lrwxrwxrwx   1 root root    30 May  1 03:40 vmlinuz.old -> boot/vmlinuz-4.4.0-177-generic
mhr@ubuntu:~/work/linux/wenjianxitong/20$ 

4 文件系統 ：FAT UFS
文件系統: 文件或數據的存儲和管理
待補充…