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Using a FileSystemWatcher from PowerShell
# Start-FileSystemWatcher.ps1 - File System Watcher in Powershell.
# Brought to you by MOBZystems, Home of Tools
# https://www.mobzystems.com/code/using-a-filesystemwatcher-from-powershell/
[CmdletBinding()]
Param(
# The path to monitor
[Parameter(Mandatory=$true, Position=0)]
[string]$Path,
# Monitor these files (a wildcard)
[Parameter(Position=1)]
[string]$Filter = "*.*",
# Monitor subdirectories?
[switch]$Recurse,
# Execute ths block on Created
[scriptblock]$CreatedAction,
# Execute ths block on Deleted
[scriptblock]$DeletedAction,
# Execute ths block on Changed
[scriptblock]$ChangedAction,
# Execute ths block on Renamed
[scriptblock]$RenamedAction,
# Check for ESC every ... seconds
[int]$KeyboardTimeout = -1,
# Redirect output of the actions to this log file, if specified
[string]$LogFile = ''
)
# Helper function to set up variables $_, $eventArgs and $e
Function DoAction(
# The action to execute. Is one of the script arguments $ChangedAction, $CreateAction, etc.
[scriptblock]$action,
# The name of the file, local to the path being watched
[string]$_,
# The [PSEventsArgs] object returned from Wait-Event
[System.Management.Automation.PSEventArgs]$eventArgs,
# For Renamed this is a RenamedEventArgs object, for the others a FileSystemEventArgs
# FileSystemEventArgs has ChangeType, FullPath and Name;
# RenamedEventArgs adds OldFullPath and OldName
$e
)
{
# Execute the action and catch its output
$output = Invoke-Command $action
if ($output) {
# Write to output
Write-Output $output
# And to log file if we have to
if ($LogFile -ne '') {
Write-Output $output >> $LogFile
}
}
}
# Sanity check: you have to provide at least one action
if (!$CreatedAction -and !$DeletedAction -and !$ChangedAction -and !$RenamedAction) {
Write-error "Specify at least one of -CreatedAction, -DeletedAction, -ChangedAction or -RenamedAction"
return
}
# Remove all event handlers and events
@( "FileCreated", "FileDeleted", "FileChanged", "FileRenamed" ) | ForEach-Object {
Unregister-Event -SourceIdentifier $_ -ErrorAction SilentlyContinue
Remove-Event -SourceIdentifier $_ -ErrorAction SilentlyContinue
}
# Do the file watching on the $Path argument's full path
[string]$fullPath = (Convert-Path $Path)
# Set up the file system watcher with the full path name of the supplied path
[System.IO.FileSystemWatcher]$fsw = New-Object System.IO.FileSystemWatcher $fullPath, $Filter -Property @{IncludeSubdirectories = $Recurse;NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite, DirectoryName'}
# Register an event handler for all actions, if provided:
if ($CreatedAction) {
Register-ObjectEvent $fsw Created -SourceIdentifier "FileCreated"
}
if ($DeletedAction) {
Register-ObjectEvent $fsw Deleted -SourceIdentifier "FileDeleted"
}
if ($ChangedAction) {
Register-ObjectEvent $fsw Changed -SourceIdentifier "FileChanged"
}
if ($RenamedAction) {
Register-ObjectEvent $fsw Renamed -SourceIdentifier "FileRenamed"
}
[string]$recurseMessage = ''
if ($Recurse) {
$recurseMessage = " and subdirectories"
}
[string]$pathWithFilter = Join-Path $fullPath $Filter
if ($KeyboardTimeout -eq -1) {
Write-Host "Monitoring '$pathWithFilter'$recurseMessage. Press Ctrl+C to stop."
} else {
Write-Host "Monitoring '$pathWithFilter'$recurseMessage. Press ESC to cancel in at most $KeyboardTimeout seconds, or Ctrl+C to abort."
}
# Start monitoring
$fsw.EnableRaisingEvents = $true
[bool]$exitRequested = $false
do {
# Wait for an event
[System.Management.Automation.PSEventArgs]$e = Wait-Event -Timeout $KeyboardTimeout
if ($e -eq $null) {
# No evet? Then this is a timeout. Check for ESC
while ($host.UI.RawUI.KeyAvailable) {
$k = $host.UI.RawUI.ReadKey("NoEcho,IncludeKeyUp,IncludeKeyDown")
if (($k.Character -eq 27) -and !$exitRequested) {
Write-Host "ESC pressed. Exiting..."
$exitRequested = $true
}
}
} else {
# A real event! Handle it:
# Get the name of the file
[string]$name = $e.SourceEventArgs.Name
# The type of change
[System.IO.WatcherChangeTypes]$changeType = $e.SourceEventArgs.ChangeType
# The time and date of the event
[string]$timeStamp = $e.TimeGenerated.ToString("yyyy-MM-dd HH:mm:ss")
Write-Verbose "--- START [$($e.EventIdentifier)] $changeType $name $timeStamp"
switch ($changeType) {
Changed { DoAction $ChangedAction $name $e $($e.SourceEventArgs) }
Deleted { DoAction $DeletedAction $name $e $($e.SourceEventArgs) }
Created { DoAction $CreatedAction $name $e $($e.SourceEventArgs) }
Renamed { DoAction $RenamedAction $name $e $($e.SourceEventArgs) }
}
# Remove the event because we handled it
Remove-Event -EventIdentifier $($e.EventIdentifier)
Write-Verbose "--- END [$($e.EventIdentifier)] $changeType $name $timeStamp"
}
} while (!$exitRequested)
if ($CreatedAction) {
Unregister-Event FileCreated
}
if ($DeletedAction) {
Unregister-Event FileDeleted
}
if ($ChangedAction) {
Unregister-Event FileChanged
}
if ($RenamedAction) {
Unregister-Event FileRenamed
}
Write-Host "Exited."
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