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touch
在linux中，touch的主要作用是创建不存在的文件或者改变已有文件的时间戳。
每个文件都有自己的时间戳，包括访问时间/存取时间（access time）修改时间（modify time），touch命令可以用来修改文件时间戳。让自己的文件更加整齐规范
- 创建文件
[root@localhost test]# touch file{1..10}.txt
[root@localhost test]# ls
file10.txt file2.txt file4.txt file6.txt file8.txt
file1.txt file3.txt file5.txt file7.txt file9.txt- 修改时间戳
[root@localhost test]# ls -l file1.txt
-rw-r--r--. 1 root root 0 May 10 11:45 file1.txt
[root@localhost test]# echo "123"> file1.txt
[root@localhost test]# cat file1.txt
123
[root@localhost test]# touch file1.txt
[root@localhost test]# cat file1.txt
123
[root@localhost test]# ls -l file1.txt
-rw-r--r--. 1 root root 0 May 10 11:47 file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 11:47:37.313572609 -0400
Modify: 2016-05-10 11:47:37.313572609 -0400
Change: 2016-05-10 11:47:37.313572609 -0400
提示：touch一个已经存在的文件，会修改文件的时间戳，将原来文件的时间戳11:45改为了11:47（包括访问时间和修改时间以及状态改变时间（change time）），但是不会改变文件内容。
- touch参数
-a 或–time=atime或–time=access或–time=use 只更改存取时间/访问时间。
-c 或–no-create 不建立任何文档。
-d 使用指定的日期时间，而非现在的时间。
-f 此参数将忽略不予处理，仅负责解决BSD版本touch指令的兼容性问题。
-m 或–time=mtime或–time=modify 只更改修改时间。
-r 把指定文档或目录的日期时间，统统设成和参考文档或目录的日期时间相同。
-t 使用指定的日期时间，而非现在的时间。
- 更新访问时间（参数-a）
[root@localhost test]# touch -a file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 12:42:52.415574001 -0400
Modify: 2016-05-10 12:31:40.145571990 -0400
Change: 2016-05-10 12:42:52.415574001 -0400- 更新修改时间（参数-m）
[root@localhost test]# touch -m file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 12:42:52.415574001 -0400
Modify: 2016-05-10 12:46:10.966574061 -0400
Change: 2016-05-10 12:46:10.966574061 -0400提示：状态改变时间（change time）会随着访问时间(access time)或修改时间（modify time）更新
- 更细时间戳为指定时间（参数-t或者-d）
[root@localhost test]# touch -t 201605101645.33 file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 16:45:33.000000000 -0400
Modify: 2016-05-10 16:45:33.000000000 -0400
Change: 2016-05-10 12:51:41.637573079 -0400[root@localhost test]# touch -d '10-MAY-2013 17:00:11' file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2013-05-10 17:00:11.000000000 -0400
Modify: 2013-05-10 17:00:11.000000000 -0400
Change: 2016-05-10 13:08:08.639572248 -0400
[root@localhost test]# touch -d 'a year ago 19:00:1' file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2015-05-10 16:00:01.000000000 -0400
Modify: 2015-05-10 16:00:01.000000000 -0400
Change: 2016-05-10 13:09:41.633570947 -0400
[root@localhost test]# touch -d CST15 file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 17:00:00.000000000 -0400
Modify: 2016-05-10 17:00:00.000000000 -0400
Change: 2016-05-10 12:59:52.207573643 -0400
[root@localhost test]# touch -d 'next Monday CST15' file1.txt
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-16 17:00:00.000000000 -0400
Modify: 2016-05-16 17:00:00.000000000 -0400
Change: 2016-05-10 13:01:15.396571448 -0400
-t参数的格式[[CC]YY]MMDDhhmm .[SS]。两个参数都不会更新状态改变时间戳
- 将两个文件的时间戳同步（参数-r）
[root@localhost test]# stat file1.txt
File: `file1.txt'
Size: 4 Blocks: 8 IO Block: 4096 regular file
Device: 802h/2050d Inode: 12845069 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2015-05-10 16:00:01.000000000 -0400
Modify: 2015-05-10 16:00:01.000000000 -0400
Change: 2016-05-10 13:09:41.633570947 -0400
[root@localhost test]# stat file2.txt
File: `file2.txt'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 802h/2050d Inode: 12845070 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2016-05-10 11:45:30.052578051 -0400
Modify: 2016-05-10 11:45:30.052578051 -0400
Change: 2016-05-10 11:45:30.052578051 -0400
[root@localhost test]# touch -r file1.txt file2.txt
[root@localhost test]# stat file2.txt
File: `file2.txt'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 802h/2050d Inode: 12845070 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2015-05-10 16:00:01.000000000 -0400
Modify: 2015-05-10 16:00:01.000000000 -0400
Change: 2016-05-10 13:11:21.579573112 -0400