I wrote a powershell script to compare the content of two folders:
$Dir1 ="d:\TEMP\Dir1"
$Dir2 ="d:\TEMP\Dir2"
function Test-Diff($Dir1, $Dir2) {
$fileList1 = Get-ChildItem $Dir1 -Recurse | Where-Object {!$_.PsIsContainer} | Get-Item | Sort-Object -Property Name
$fileList2 = Get-ChildItem $Dir2 -Recurse | Where-Object {!$_.PsIsContainer} | Get-Item | Sort-Object -Property Name
if($fileList1.Count -ne $fileList2.Count) {
Write-Host "Following files are different:"
Compare-Object -ReferenceObject $fileList1 -DifferenceObject $fileList2 -Property Name -PassThru | Format-Table FullName
return $false
}
return $true
}
$i = Test-Diff $Dir1 $Dir2
if($i) {
Write-Output "Test OK"
} else {
Write-Host "Test FAILED" -BackgroundColor Red
}
If I set a break point on Compare-Object
, and I run this command in console, I get the list of differences. If I run the whole script, I don't get any output. Why?
I'm working in PowerGUI Script Editor, but I tried the normal ps console too.
EDIT:
The problem is the check on the end of the script.
$i = Test-Diff $Dir1 $Dir2
if($i) {
Write-Output "Test OK"
...
If I call Test-Diff
without $i =
check, it works!
Test-Diff
returns with an array of objects and not with an expected bool value:
[DBG]: PS D:\>> $i | ForEach-Object { $_.GetType() } | Format-Table -Property Name
Name
----
FormatStartData
GroupStartData
FormatEntryData
GroupEndData
FormatEndData
Boolean
If I comment out the line with Compare-Object
, the return value is a boolean value, as expected.
The question is: why?
I've found the answer here: http://martinzugec.blogspot.hu/2008/08/returning-values-from-fuctions-in.html
Functions like this:
Function bar {
[System.Collections.ArrayList]$MyVariable = @()
$MyVariable.Add("a")
$MyVariable.Add("b")
Return $MyVariable
}
uses a PowerShell way of returning objects: @(0,1,"a","b") and not @("a","b")
To make this function work as expected, you will need to redirect output to null:
Function bar {
[System.Collections.ArrayList]$MyVariable = @()
$MyVariable.Add("a") | Out-Null
$MyVariable.Add("b") | Out-Null
Return $MyVariable
}
In our case, the function has to be refactored as suggested by Koliat.