Every file on your computer has a timestamp, which contains the access and modification time for a file, but did you know that you can change that timestamp? Here’s how to do it.
Using the Touch Command
The “touch” command is available pretty much anywhere that you can get the Bash shell, which includes Linux or Windows with Cygwin installed. Here’s the options for the command:
If you want to check the file timestamp, you can do so with this command:
Obviously you should make sure to replace “file” with your file’s name.
-a and -m options
These two options update the access and modification time respectively. Using them should be no problem at all. Here is the syntax:
touch –a file
This will update “file”s access time to the current date and time. You can replace the (-a) options with (-m) to do the same but for the modification time. If the file doesn’t exist, an empty file with the same name will be created in the current directory.
If you use this option, touch won’t do anything at all if the file specified doesn’t exist. Look:
touch –c omar
In the above example touch will do nothing as “omar”, the file not the person, doesn’t exist.
This option might come in handy if you want to copy a timestamp from a file to another file. Like so:
touch –r file1 file2
Where “file1” is the reference file and “file2” is the file that will be updated. If you want to copy the timestamp to more than one file you can provide them all in the command as well and they will be created simultaneously.
touch –r file1 file2 file3 file4
-d and –t options
Both (-d) and (-t) options do the same thing, which is setting the same arbitrary timestamp for access and modification times. The difference is that (-d) uses free format human readable date, this means that you can use “Sun, 29 Feb 2004 16:21:42″ or “2004-02-29 16:21:42” or even “next Thursday”. This option is complex to fully describe it here. On the other hand (-t) uses a simple stamp that you are confined to use. The stamp is [[CC]YY]MMDDhhmm[.ss]. [CC] is for century and you may ignore it and ignore the seconds as well. If you ignore [CC] the command will substitute it depending on what you enter as year. If you specify the year with only two digits, then CC is 20 for years in the range (0~68) and 19 for years in (69~99).
touch –t 3404152240 file
touch –t 8804152240 file
In the first command the file timestamps will be set to: 15th April 2034 10:40 PM. While the second command will set it to: 15th April 1988 which is in a different century. If no year is specified it will be set to the current year. Example:
touch –t 04152240 file
This will set the timestamp to 15th April 2011 10:40 PM because it is 2011 by the time of writing this article.
Combining Options to Set Arbitrary Individual Access and Modification Times
The (-a) and (-m) options only updates the timestamps to current time and the (-d) and (t) options sets both access and modification timestamps to the same time. Assume you only only want to set the access time to the 5th of June 2016 at 5:30 PM, How would you do that? Well, you’ll use (-a) and (-t) to both set an arbitrary time and apply it only for the access timestamp. Example:
touch –at 1606051730 file
touch –a -t 1606051730 file
And if you want to do the same for the modification time just substitute (-at) with (-mt). It’s easy.
Creating Empty Files
The second and most famous usage of the touch command is creating empty files. This might sound stupid, why would anyone sensibly overload his computer with empty nonsense files but it really comes to use when, for example, you are working on a project and want to keep track of progress with dates and times. So you’ll have a folder with the project’s name and use touch to create empty files with the events as names of file. In other words, you can use it to create logs. Example:
Now you have a file signifying the completion of stage 1 of the project at the time of creating this file and you can see this time by issuing the command:
You can find touch useful in different ways depending on what you do. If you know more good uses for touch then share it in the comments or read more about the touch command by visiting its man page online or in a terminal by issuing the command “man touch”.
- Published 09/22/11