Access function inside filesystemwatcher event function powershell - function

Question

I want access a function inside filesystemwatcher created event function. I tried using a global function but i never see output on console.
#Script Parameters
param(
[Parameter(Mandatory=$True, position=1)]
[String]$path
)
#Global Function
function global:myFunction (){
Write-Host "myFunction"
}
#FileSystemWatcher properties
$fsw = New-Object System.IO.FileSystemWatcher
$fsw.Path = $path
$fsw.Filter = ""
$fsw.IncludeSubDirectories = $True
$fsw.EnableRaisingEvents = $True
#Created event function
Register-ObjectEvent -InputObject $fsw -EventName Created -Action{
$global:myFunction #trying to access global function
}

Answer 1

Your only problem is a syntax confusion about how to invoke a global function:
$global:myFunction # WRONG - looks for *variable*
looks for a variable named myFunction in the global scope.
Omit the $ to call the function:
global:myFunction # OK - calls function
That said, given that all scopes in a given session by default see global definitions, you don't need the global: scope specifier - simply invoke myFunction:
The only time you need global: explicitly is if there's a different myFunction definition in the current scope or in an ancestral scope, and you want to explicitly target the global definition.
Without global:, such a different definition would shadow (hide) the global definition.
To put it all together:
# Script Parameters
param(
[Parameter(Mandatory=$True, position=1)]
[String]$path
)
# Global Function
function global:myFunction {
param($FullName)
Write-Host "File created: $FullName"
}
# FileSystemWatcher properties
$fsw = New-Object System.IO.FileSystemWatcher
$fsw.Path = $path
$fsw.Filter = ""
$fsw.IncludeSubDirectories = $True
$fsw.EnableRaisingEvents = $True
# Created-event function
$eventJob = Register-ObjectEvent -InputObject $fsw -EventName Created -Action {
myFunction $EventArgs.FullPath # Call the global function.
}
Note that I've extended the code to pass the full filename of the newly created file to myFunction, via the automatic $EventArgs variable.
Alternatives:
Modifying the global scope from a script can be problematic due to the potential for name collisions, not least because global definitions linger even after the script terminates.
Therefore, consider:
either: moving the code of function myFunction directly into the -Action script block.
or: calling a (possibly temporary) script file from the -Action script block.
Also note that event action blocks typically write output to the success output stream, not directly to the host with Write-Host - if they need to produce output at all - where it can be collected on demand via the Receive-Job cmdlet.

Answer 2

You could specify explicitly your function inside Action scriptblock. Like so
#FileSystemWatcher properties
$fsw = New-Object System.IO.FileSystemWatcher
$fsw.Path = $path
$fsw.Filter = ""
$fsw.IncludeSubDirectories = $True
$fsw.EnableRaisingEvents = $True
#Created event function
Register-ObjectEvent -InputObject $fsw -EventName Created -Action {
#Describe your function here
function global:myFunction (){
Write-Host "myFunction"
}
#There call your function
global:myFunction
}