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已翻译by Luox	Delete Linux touch command - Why do we need to change Timestamp.md
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翻译ing Luoxcat
Linux touch command - Why do we need to change Timestamp?
================================================================================
We may use touch command in Linux to create an empty file. Of course we can use another command such as vi, nano or any editing tools to do it. But you may need more steps do it. But do know it that the main function of touch command is not create an empty file?
### What is touch command ###
As we know, every file has timestamp attached to it. This time stamp is access time and modification time. Touch command is a command for file access and modification time.
### Why we need touch ###
Since touch command description is to change timestamp, we may wonder why do we need to change timestamp? This question also comes to our mind. But then, we think there is a reason why we need it. If you are participating in open source projects over sea, then timestamp may become important. Compiling a source code files may need a same region of timestamp. If not, the program may failed to compiled.
### Run touch without options ###
To use touch command is quite simple. Just type :
$ touch file_name
Please take a look a screenshot below.
![Touch command](http://linoxide.com/wp-content/uploads/2014/01/touch.png)
**File_1.txt** originally has timestamp 12:42. After we do touch command, it changed to 17:08. By default, touch will change the file timestamp into current time.
### Change only Access time ###
As we mention before that every file has Access time and Modify time attached to the file. File_1.txt above has timestamp 17:08. We can see more detail about it.
![Detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_stat.png)
We see that **Access** time and **Modify** time has the same value which is 17:08:35 and the timezone is GMT +7.
Now if we want to change only the Access time, we need to use **-a** option.
$ touch -a file_1.txt
![Touch -a option](http://linoxide.com/wp-content/uploads/2014/01/touch_a.png)
As you see, the **Access time is changed** into 17:51:37 but the **Change time is still** 17:08:35
### Change only Modify time ###
To do this, we can use **-m** option. Now we will use **file_2.txt** as an example.
![File_2.txt detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_stat_file_2.png)
$ touch -m file_2.txt
![Touch -m option](http://linoxide.com/wp-content/uploads/2014/01/touch_m.png)
Now the **Modify time is change from 12:42:20 to 17:57:20. Please note**, that the Change field value will always keep record when the file is accessed or modified.
### Change into custom timestamp ###
Both -**a and -m** option will change the file timestamp into current time. We can also possible to change it into custom timestamp. To do this, use **-t** option.
From file_2.txt above example, we knew that its time stamp are :
12:42:20 for Access time
17:57:20 for Modify time
2014-01-14 for the date
Let say we want to change it into **09:58:27** for **both Access time and Modify time and 12 January 2014**. To do this, we can use this command :
$ touch -t 201401120958.27 file_2.txt
![Touch using -t option](http://linoxide.com/wp-content/uploads/2014/01/touch_t.png)
**-t** option is consist of :
#### [[CC]YY]MMDDhhmm [.SS] ####
CC - The first two digits of the year
YY - The second two digits of the year
MM - The month of the year [01-12]
DD - The day of the month [01-31]
hh - The hour of the day [00-23]
mm - The minute of the hour [00-59]
SS - The second of the minute [00-61]
### Another way to change date and time ###
If you feel that the **[[CC]YY]MMDDhhmm [.SS]** format is not comfortable for you, we can use -d option. Here’s an example how to use **-d** option.
#### Change the date to specific date ####
For example we have file named file_3.txt with attributes as shown in the picture below.
![File_3.txt detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/stat_file_3.png)
Now **we want to change the date** from 14 January 2014 to 10 December 2013. We can use with this command :
$ touch -d ‘10-December-2013’ file_3.txt
![Change date using -d option](http://linoxide.com/wp-content/uploads/2014/01/touch_d_date.png)
We see now that the date for Access and Modify entries is changed into 10 December 2013.
### Change the timezone ###
If we want to change it into time in specific GMT, we can also use with **-d** option. Let’s return the file_3.txt into the current time.
$ touch file_3.txt
![Reset file_3.txt timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_return_file_3.png)
We can see that file_3.txt has GMT +0700 timezone. To change it into GMT3 timezone, we can use this command.
$ touch -d GMT3 file_3.txt
![Change into GMT3 timezone](http://linoxide.com/wp-content/uploads/2014/01/touch_gmt3.png)
Now the time is change into 10:00:00 AM
### Combining values using -d option ###
There is something cool using **-d** option. Please take a look at the picture below.
![Change date using keyword](http://linoxide.com/wp-content/uploads/2014/01/touch_next_sunday.png)
We can use the word ‘**next Sunday**’ and combine it with GMT 3 values, and touch command can still recognize it. The date is changed into 21 January 2014, where the current date is 14 January 2014.
Here’s another example of **-d** option.
First, we reset file_3.txt into current date and time.
$ touch file_3.txt
![Reset file_3.txt timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_reset_file_3.png)
Then we do this command :
$ touch -d ‘1 year ago 13:43:07’ file_3.txt
![Change date using keyword](http://linoxide.com/wp-content/uploads/2014/01/touch_d_year_ago.png)
Touch even recognize a word ‘**1 year ago**’. The date and time is now changed into 14 January 2013 and 13:43:07 time.
### Create an empty file ###
When you run touch command and the destination file is not exist, then touch will create an empty file with the same name.
$ touch file_10.txt
![Create an empty file](http://linoxide.com/wp-content/uploads/2014/01/touch_file_10.png)
### Create multiple files at the same time ###
To create multiple files, you can put the file names separated by space.
$ touch doc_10.txt doc_20.txt doc_30.txt
![Create multiple files](http://linoxide.com/wp-content/uploads/2014/01/touch_multiple_files.png)
### Conclusion ###
Touch will useful for you if you are dealing with a timestamp of files and directories. As usual you can always type **man touch** or **touch --help** to display its manual page to explore more detail.
--------------------------------------------------------------------------------
via: http://linoxide.com/linux-command/linux-touch-command/
译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出

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Linux touch 命令 - 为什么我们需要改变时间戳？
================================================================================
我们可能在 Linux 下运用 touch 命令创建一个空文件。当然我们也可以使用其他命令例如 vi, nano 或是任意一个编辑工具来实现。但是你可能需要更多的步骤来完成操作。其实你要知道 touch 命令的主要功能并不是为了创建一个空文件哦。
### 什么是 touch 命令 ###
众所周知，每个文件都被附有时间戳。这个时间戳记包括访问时间和修改时间。而 Touch 命令主要就是用来修改文件的访问时间和修改时间。
### 为什么我们需要使用 touch 命令 ###
既然 touch 命令描述的是改变时间戳，那么我们可能会想为什么我们需要去改变时间戳呢?这个问题会引发我们的深思。然而，我想有个理由可以解释为什么我们需要使用它。如果你参加了一个跨海的开源项目，那么时间戳可能变得很重要。编译源代码文件可能需要同一地区的时间戳。如果未统一，程序可能会编译失败。
### 不带任何选项下运行 touch ###
最简单的使用 touch 命令。只需键入：
$ touch file_name
请观察下面的一张截图。
![Touch command](http://linoxide.com/wp-content/uploads/2014/01/touch.png)
**File_1.txt**原来的时间戳是 12:42。在我们使用 touch 命令后，它改变为了 17:08。由此看出，默认情况下，touch 会将文件的时间戳改为当前时间。
### 只改变访问时间 ###
正如我们之前提到的，每个文件都附有访问时间和修改时间。上面的时间戳是 17:08。我们可以看更多的细节。
![Detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_stat.png)
我们发现**访问**时间和**修改**时间的值是相同的都是 17:08:35 ,还有它们属于同一时区 GMT +7。
如果现在我们要只改变访问时间，我们需要使用**-a**选项。
$ touch -a file_1.txt
![Touch -a option](http://linoxide.com/wp-content/uploads/2014/01/touch_a.png)
如你所见，**访问时间变为**了 17:51:37 ,但是**修改时间仍为**17:08:35。[译注：原文为 Change time(状态改变时间)应是作者笔误]
### 只改变修改时间 ###
我们可以使用**-m**选项来实现。现在我们用**file_2.txt**作个示例。
![File_2.txt detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_stat_file_2.png)
$ touch -m file_2.txt
![Touch -m option](http://linoxide.com/wp-content/uploads/2014/01/touch_m.png)
现在**修改时间从 12:42:20 改为了 17:57:20。请注意**,当文件被访问或修改时，状态改变时间域的值总会对其记录。
### 更改为自定义时间戳 ###
**-a**和**-m**选项都会将文件的时间戳改为现在当前时间。当然我们也可以更改为自定义时间戳。使用**-t**选项实现。
从上面示例示例中的 file_2.txt，我们看出它的时间戳是：
访问时间:12:42:20
修改时间:17:57:20
执行日期:2014-01-14
假如我们想要将**访问时间和修改时间**改为**2014年1月12日 09:58:27**。我们可以用下列命令来完成：
$ touch -t 201401120958.27 file_2.txt
![Touch using -t option](http://linoxide.com/wp-content/uploads/2014/01/touch_t.png)
**-t** 选项语法组成 :
#### [[CC]YY]MMDDhhmm [.SS] ####
CC - 年份的前两位
YY - 年份的后两位
MM - 月份 [01-12]
DD - 日期 [01-31]
hh - 时 [00-23]
mm - 分 [00-59]
SS - 秒 [00-61]
### 改变日期和时间的另一种方式 ###
如果你觉得**[[CC]YY]MMDDhhmm [.SS]**格式不适合你，我们也可以使用 -d 选项。下面是**-d**选项使用的一个示例。
#### 更改指定日期 ####
举例来说，我们有个名为 file_3.txt 的文件，它的相关属性在下面的截图中展示了。
![File_3.txt detail timestamp](http://linoxide.com/wp-content/uploads/2014/01/stat_file_3.png)
现在**我们要将日期2014年1月14日改为2013年12月20日**。可以使用下列命令：
$ touch -d ‘'10-December-2013' file_3.txt
![Change date using -d option](http://linoxide.com/wp-content/uploads/2014/01/touch_d_date.png)
不出意料，访问时间和修改时间的日期已经改为了2013年12月10日。
### 改变时区 ###
如果我们想改变指定GMT的时间，我们也可以使用**-d**选项。先让file_3.txt 移回当前时间。
$ touch file_3.txt
![Reset file_3.txt timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_return_file_3.png)
不难发现 file_3.txt 的时区为 GMT +0700。要改为 GMT3 时区，我们只需要键入如下命令：
$ touch -d GMT3 file_3.txt
![Change into GMT3 timezone](http://linoxide.com/wp-content/uploads/2014/01/touch_gmt3.png)
好的，现在时间已经改为了 10:00:00 AM。
### 结合参数下使用-d选项 ###
还可以用很酷的方式使用**-d**选项。请观察下面的图片。
![Change date using keyword](http://linoxide.com/wp-content/uploads/2014/01/touch_next_sunday.png)
我们可以将单词 **next Sunday** 和 GMT 3合成一个值，而 touch 命令仍然能识别它。日期已经改为了2014年1月21日，而当前的日期为2014年1月14日。
还有另一个**-d**选项的示例。
首先，我们要将file3_3.txt重置到当前日期和时间。
$ touch file_3.txt
![Reset file_3.txt timestamp](http://linoxide.com/wp-content/uploads/2014/01/touch_reset_file_3.png)
然后我们尝试这个命令：
$ touch -d ‘1 year ago 13:43:07’ file_3.txt
![Change date using keyword](http://linoxide.com/wp-content/uploads/2014/01/touch_d_year_ago.png)
太震撼了，Touch 甚至能识别单词‘**1 year ago**’。现在的日期以及时间已经改为了2013年1月14日,13:43:07。
### 创建一个空文件 ###
当你运行 touch 命令目标文件不存在时，touch 会创建一个同名的空文件。
$ touch file_10.txt
![Create an empty file](http://linoxide.com/wp-content/uploads/2014/01/touch_file_10.png)
### 同时创建多个文件 ###
你可以用空格将目标文件分割开来，以此来创建多个文件。
$ touch doc_10.txt doc_20.txt doc_30.txt
![Create multiple files](http://linoxide.com/wp-content/uploads/2014/01/touch_multiple_files.png)
### 总结 ###
如果你要处理关于文件或目录的时间戳问题，那么 Touch 会对你很有用的。一如既往得你也可以键入**man touch**或**touch --help**来显示帮助页面了解更多细节。
--------------------------------------------------------------------------------
via: http://linoxide.com/linux-command/linux-touch-command/
译者：[Luoxcat](https://github.com/Luoxcat) 校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出