在linux 中，文件的三种时间权限

在linux 中，文件有3中属性 atime(access time),mtime(modification time),ctime(change time)三种
使用stat 命令可以看到节点的inode信息
[21:22:19 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 802h/2050d Inode: 133995 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2014-12-03 21:22:14.566170356 +0800
Modify: 2014-12-03 21:22:14.566170356 +0800
Change: 2014-12-03 21:22:14.566170356 +0800

读取文件，会使atime发生变化
[21:22:24 root()@localhost ~]# cat kiwi
You have new mail in /var/spool/mail/root
[21:23:49 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 802h/2050d Inode: 133995 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2014-12-03 21:23:49.465170247 +0800
Modify: 2014-12-03 21:22:14.566170356 +0800
Change: 2014-12-03 21:22:14.566170356 +0800

修改文件内容会导致mtime发生变化，其他两个时间属性同时也会发生变化。
我们要注意，在redhat 6中，修改只有在发生实际修改的时候，文件的三个时间属性才会发生变化
[21:26:54 root()@localhost ~]# vi kiwi
[21:27:09 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 7 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 134620 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2014-12-03 21:27:09.918170106 +0800
Modify: 2014-12-03 21:27:09.918170106 +0800
Change: 2014-12-03 21:27:09.933170076 +0800

改变文件权限，改变文件属组，增加减少文件硬链接的数目等操作都会导致其inode信息发生变化，因此执行这样的操作的时候，会改变文件的ctime属性
改变文件属组导致ctime变化
[21:30:44 root()@localhost ~]# chown oracle:oinstall kiwi
[21:31:22 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 7 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 134615 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 500/ oracle) Gid: ( 500/oinstall)
Access: 2014-12-03 21:30:41.924168555 +0800
Modify: 2014-12-03 21:30:41.924168555 +0800
Change: 2014-12-03 21:31:22.104169997 +0800
改变文件权限导致ctime变化
[21:31:27 root()@localhost ~]# ls -l kiwi
-rw-r--r-- 1 oracle oinstall 7 Dec 3 21:30 kiwi
[21:34:28 root()@localhost ~]# chmod 777 kiwi
[21:34:36 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 7 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 134615 Links: 1
Access: (0777/-rwxrwxrwx) Uid: ( 500/ oracle) Gid: ( 500/oinstall)
Access: 2014-12-03 21:30:41.924168555 +0800
Modify: 2014-12-03 21:30:41.924168555 +0800
Change: 2014-12-03 21:34:36.241169603 +0800
增加硬链接导致ctime变化
[21:35:52 root()@localhost ~]# ln kiwi kiwilink
[21:36:10 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 7 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 134615 Links: 2
Access: (0777/-rwxrwxrwx) Uid: ( 500/ oracle) Gid: ( 500/oinstall)
Access: 2014-12-03 21:30:41.924168555 +0800
Modify: 2014-12-03 21:30:41.924168555 +0800
Change: 2014-12-03 21:36:10.309169867 +0800
删除硬链接导致ctime变化
[21:36:16 root()@localhost ~]# rm -rf kiwilink
[21:37:00 root()@localhost ~]# stat kiwi
File: `kiwi'
Size: 7 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 134615 Links: 1
Access: (0777/-rwxrwxrwx) Uid: ( 500/ oracle) Gid: ( 500/oinstall)
Access: 2014-12-03 21:30:41.924168555 +0800
Modify: 2014-12-03 21:30:41.924168555 +0800
Change: 2014-12-03 21:37:00.557169513 +0800