Consider the following Powershell script, which searches for folders in C:\ with a 'og' in their name:
PS C:\> (ls | %{$_.Name} | ?{$_.Contains("og")}) PerfLogs Program Files setup.log
Now I narrow down the search to get only one item:
PS C:\> (ls | %{$_.Name} | ?{$_.Contains("Prog")}) Program Files
The strange thing is that the first operation yields an array, whereas the second operation (which is IMHO semantically the same operation, so it should yield the same type of result) yields a string. This can be seen in the following result:
PS C:\> (ls | %{$_.Name} | ?{$_.Contains("og")}).Length 3 PS C:\> (ls | %{$_.Name} | ?{$_.Contains("Prog")}).Length 13
This can be very irritating, since apparently there are less folders which match 'og' than those who match 'Prog'.
Evidently, PowerShell implicitly 'unboxes' a single-item array to a single object, and we never get an array of length 1. It seems that every time I want to count the results coming over the pipeline, I have to check if I'm dealing with an array or not.
How can I prevent this from happening? How do you deal with this?
Best Answer
And zero item results to
$null
.You can't.
Use the array constructor (
@(...)
) to force a collection (possibly with zero or one elements) return: