Here is a chunk of code illustrating how PowerShell can use the FileSystemWatcher to synchronously watch a folder including subfolders for file changes:

$folder = $home 
$filter = '*'  


try
{
    $fsw = New-Object System.IO.FileSystemWatcher $folder, $filter -ErrorAction Stop
}
catch [System.ArgumentException]
{
    Write-Warning "Oops: $_"
    return
}

$fsw.IncludeSubdirectories = $true
$fsw.NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'

do
{
    $result = $fsw.WaitForChanged([System.IO.WatcherChangeTypes]::All, 1000)
    if ($result.TimedOut) { continue }
    
    $result
    Write-Host "Change in $($result.Name) - $($result.ChangeType)"

} while ($true)

This code would monitor your user profile for changes in files to the FileName and LastWrite properties.

A synchronous watcher keeps PowerShell busy, so in order to be able to abort the monitoring, a timeout of 1000ms is set. Every 1000ms, PowerShell returns control to you, and if you don’t press CTRL+C, the loop continues.

Note that a synchronous filesystemwatcher can miss changes: when a file change occurs and WaitForChange() returns, any subsequent change that occurs before WaitForChange() is called again will be missed.

If you don’t want to miss any changes, use an asynchronous approach (see next tip).


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