TOPIC: DEL
Changing file timestamps using Windows PowerShell
29th October 2014Recently, a timestamp got changed on an otherwise unaltered file on me and I needed to change it back. Luckily, I found an answer on the web that used PowerShell to do what I needed, and I am recording it here for future reference. The possible commands are below:
$(Get-Item temp.txt).creationtime=$(Get-Date "27/10/2014 04:20 pm")
$(Get-Item temp.txt).lastwritetime=$(Get-Date "27/10/2014 04:20 pm")
$(Get-Item temp.txt).lastaccesstime=$(Get-Date "27/10/2014 04:20 pm")
The first of these did not interest me, since I wanted to leave the file creation date as it was. The last write and access times were another matter because these needed altering. The Get-Item commandlet brings up the file, so its properties can be set. Here, these include creationtime, lastwritetime and lastaccesstime. The Get-Date commandlet reads in the provided date and time for use in the timestamp assignment. While PowerShell itself is case-insensitive, I have opted to show the camel case that is produced when you are tabbing through command options for the sake of clarity.
The Get-Item and Get-Date have aliases of gi and gd, respectively, and the Get-Alias commandlet will show you a full list while Get-Command (gcm) gives you a list of commandlets. Issuing the following gets you a formatted list that is sent to a text file:
gcm | Format-List > temp2.txt
There is some online help, but it is not quite as helpful as it ought to be, so I have popped over to Microsoft Learn whenever I needed extra enlightenment. Here is a command that pops the full thing into a text file:
Get-Help Format-List -full > temp3.txt
In fact, getting a book might be the best way to find your way around PowerShell because of all its commandlets and available objects.
For now, other commands that I have found useful include the following:
Get-Service | Format-List
New-Item -Name test.txt -ItemType "file"
The first of these gets you a list of services, while the second creates a new blank text file for you, and it can create new folders for you too. Other useful commandlets are below:
Get-Location (gl)
Set-Location (sl)
Copy-Item
Remove-Item
Move-Item
Rename-Item
The first of the above is like the cwd or pwd commands that you may have seen elsewhere, in that the current directory location is given. Then, the second will change your directory location for you. After that, there are commandlets for copying, deleting, moving and renaming files. These also have aliases, so users of the legacy Windows command line or a UNIX or Linux shell can use something that is familiar to them.
Little fixes like the one with which I started this piece are all good to know, but it is in scripting that PowerShell really is said to show its uses. Having seen the usefulness of such things in the world on Linux and UNIX, I cannot disagree with that, and PowerShell has its own IDE too. That may be just as well, given how much there is to learn. That especially is the case when you might need to issue the following command in a PowerShell session opened using the Run as Administrator option just to get the execution as you need it:
Set-ExecutionPolicy RemoteSigned
Issuing Get-ExecutionPolicy will show you if this is needed when the response is: Restricted. A response of RemoteSigned shows you that all is in order, though you need to check that any script you then run has no nasty payload in there, which is why execution is restrictive in the first place. This sort of thing is yet another lesson to be learnt with PowerShell.
Creating empty text files and changing file timestamps using Windows Command Prompt & Powershell
17th May 2013Linux and UNIX have the touch command for changing the creation dates and times for files. However, it also creates empty text files for you as well. In fact, there are times when I feel the need to do this sort of thing on Windows too and the following command accomplishes the deed when run in a Command Prompt window:
type nul > command.bat
Essentially, null output is sent to a file that is created anew, command.bat in this case. Then, you can edit it in Notepad (or whatever is your choice of text editor) and add in what you need. This will not work in PowerShell, so you need another command for that:
New-Item command.bat -type file1
This uses the New-Item command, which also can be used to create folders as well if you so desire. Then, the command becomes the following:
New-Item c:\commands -type directory1
Note that file1 in the previous example has become directory1 and there is the -force option should you need to overwrite what already exists for some reason...
That other use of the UNIX/Linux touch command can be performed from the Command Prompt too, and here is an example command:
copy /b file.txt +,,
The /b switch switches on binary behaviour for the copy command, though that appears to be the default action anyway. The + operator triggers concatenation and ,, gets around not having a defined destination because you cannot copy a file over itself. If that were possible, then there would no need for special syntax for changing the date and time for a file.
For doing the same thing with PowerShell, try the following:
(GetChildItem test.txt).LastWriteTime=Get-Date
The GetChildItem command has aliases of gci, dir and ls and the last two of these give away its essential purpose. Here, it is used to pick out the test.txt file so that its timestamp can be replaced with the current date and time returned by the Get-Date command. The syntax looks a little more complex, even if it achieves the same end. Somehow, that touch command is easier to explain. Are Linux and UNIX that complicated, after all?