Difference between pipeline ForEach-Object and -InputObject

September 9, 2024

I assume this has something to do with how the data is passed via the pipeline, but take the two examples below;

$someData = Get-ChildItem

$obj = ForEach-Object -InputObject $someData -Process {[pscustomobject] @{Name=$_.Name; LastWriteTime = $_.LastWriteTime}}

$obj2 = Get-ChildItem | % {[pscustomobject] @{Name=$_.Name; LastWriteTime = $_.LastWriteTime}}

The object types differ, although I expected both to be of type [PSCustomObject], only one is;

$obj.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                    
-------- -------- ----                                     --------                                                                                    
True     False    PSCustomObject                           System.Object                                                                               

$obj2.GetType()

IsPublic IsSerial Name                                     BaseType                                                                                    
-------- -------- ----                                     --------                                                                                    
True     True     Object[]                                 System.Array

When $Obj2 is passed into a Format-Table, I get the type of output I desire, i.e. an actual table of values. But $Obj provides somewhat useless Format-Table output. What’s happening behind the scenes?

>Solution :

ForEach-Object Documentation

When you use the InputObject parameter with ForEach-Object, instead of
piping command results to ForEach-Object, the InputObject value is
treated as a single object.