CODEWITHSUNDEEP
powershell
gurpsone
gurpsone

Reputation: 483

Compare LastWriteTime in an 'if' statement in PowerShell

I want to run something like the below script every 10 minutes.

I have file A and file B. Every 10 minutes, I want to check if File A is newer than File B. If so, I want to set the LastWriteTime of file B to the current date. I believe my if statement is wrong... How can I fix it?

$a = Get-Item c:\users\testuser\desktop\test.xml | select LastWriteTime

$b = Get-Item C:\users\testuser\Desktop\test.swf | select LastWriteTime

if($a < $b)
{
    $b.LastWriteTime = (Get-Date)
}

I think in the above example, I'm only setting the variable $b to the current date...I want to set the LastWriteTime of the actual file to the current date.

Upvotes: 2

Views: 5398

Answers (3)

bart
bart

Reputation: 198

Try this. It worked for me in PowerShell 5.

In order to change the date of LastWriteTime, you have to write to file again, for example,

$a = Get-Item fileA.txt
$b = Get-Item fileB.txt

if(($a.LastWriteTime) -lt ($b.LastWriteTime))
{
    fileB.txt | add-content -Value ''
}

Upvotes: 1

Tyler Helder
Tyler Helder

Reputation: 624

You could do something similar to the following to change the last write time of a file:

$File1 = Get-ChildItem -Path "C:\Temp\test1.txt"
$File2 = Get-ChildItem -Path "C:\Temp\test2.txt"

#System.IO is a namespace of the file class in .NET and GetLastWriteTime/SetLastWriteTime are methods of this class.
if ([System.IO.File]::GetLastWriteTime($File1) -lt [System.IO.File]::GetLastWriteTime($File2))
    {
        Write-Output  "File1 LastWriteTime is less than File2, Setting LastWriteTime on File2."
            ([System.IO.File]::SetLastWriteTime($File2,(Get-Date)))
    }
ELSE
    {
        Write-Output "File1 LastWriteTime is not less than File2 LastWriteTime."
    }

More information on the Namespace, .NET class, and associated methods used in the above code can be found Here.

Hope this helps!

Upvotes: 2

Janis S.
Janis S.

Reputation: 2626

Try using the less than operator in the if statement and using the Get-ChildItem to get the file instead of the LastWriteTime property.

$a = Get-ChildItem tst1.txt  
$b = Get-ChildItem tst2.txt 

if(($a.LastWriteTime) -lt ($b.LastWriteTime))
{ 
    $b.LastWriteTime = (Get-Date) 
}

Learn more about operators here.

Upvotes: 4

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