Simple PowerShell LastWriteTime compare - file

Question

I need a PowerShell script that can access a file's properties and discover the LastWriteTime property and compare it with the current date and return the date difference.
I have something like this...
$writedate = Get-ItemProperty -Path $source -Name LastWriteTime
...but I can not cast the LastWriteTime to a "DateTime" datatype. It says, "Cannot convert "#{LastWriteTime=...date...}" to "System.DateTime".

Answer 1

Try the following.
$d = [datetime](Get-ItemProperty -Path $source -Name LastWriteTime).lastwritetime
This is part of the item property weirdness. When you run Get-ItemProperty it does not return the value but instead the property. You have to use one more level of indirection to get to the value.

Answer 2

(ls $source).LastWriteTime
("ls", "dir", or "gci" are the default aliases for Get-ChildItem.)

Answer 3

I have an example I would like to share
$File = "C:\Foo.txt"
#retrieves the Systems current Date and Time in a DateTime Format
$today = Get-Date
#subtracts 12 hours from the date to ensure the file has been written to recently
$today = $today.AddHours(-12)
#gets the last time the $file was written in a DateTime Format
$lastWriteTime = (Get-Item $File).LastWriteTime
#If $File doesn't exist we will loop indefinetely until it does exist.
# also loops until the $File that exists was written to in the last twelve hours
while((!(Test-Path $File)) -or ($lastWriteTime -lt $today))
{
#if a file exists then the write time is wrong so update it
if (Test-Path $File)
{
$lastWriteTime = (Get-Item $File).LastWriteTime
}
#Sleep for 5 minutes
$time = Get-Date
Write-Host "Sleep" $time
Start-Sleep -s 300;
}

Answer 4

(Get-Item $source).LastWriteTime is my preferred way to do it.

Answer 5

I can't fault any of the answers here for the OP accepted one of them as resolving their problem. However, I found them flawed in one respect. When you output the result of the assignment to the variable, it contains numerous blank lines, not just the sought after answer. Example:
PS C:\brh> [datetime](Get-ItemProperty -Path .\deploy.ps1 -Name LastWriteTime).LastWriteTime
Friday, December 12, 2014 2:33:09 PM
PS C:\brh>
I'm a fan of two things in code, succinctness and correctness. brianary has the right of it for succinctness with a tip of the hat to Roger Lipscombe but both miss correctness due to the extra lines in the result. Here's what I think the OP was looking for since it's what got me over the finish line.
PS C:\brh> (ls .\deploy.ps1).LastWriteTime.DateTime
Friday, December 12, 2014 2:33:09 PM
PS C:\brh>
Note the lack of extra lines, only the one that PowerShell uses to separate prompts. Now this can be assigned to a variable for comparison or, as in my case, stored in a file for reading and comparison in a later session.

Answer 6

Slightly easier - use the new-timespan cmdlet, which creates a time interval from the current time.
ls | where-object {(new-timespan $_.LastWriteTime).days -ge 1}
shows all files not written to today.

Answer 7

Use
ls | % {(get-date) - $_.LastWriteTime }
It can work to retrieve the diff. You can replace ls with a single file.