Technology Tales

Adventures & experiences in contemporary technology

Changing file timestamps using Windows PowerShell

29th October 2014

Recently, 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)

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 very 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.

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