Powershell Get-ChildItem -Include/-Exclude doesn't filter if passed as an arg to a function

Question

Having a problem getting a filter argument to Get-ChildItem in a function

The following works fine and displays a whole list of files:

c:\temp\Get-ChildItem -Include deleteme.txt -Recurse

Now say I have the following script

file starts here

filename = GetLastFile.ps1

param([string] $filter)

$files = Get-ChildItem $filter

Write-Host $files #should print all matching files but prints nothing

$file = $files | Select-Object -Last 1;

$file.name #returns filename

file ends here

now trying to run the script>>

c:\temp.\GetLastFile.ps1 "-Include deleteme.txt -Recurse"

returns nothing.

suppling a filter . works fine, seems to be failing due to the -Include or -Exclude Any ideas?

Answer 1

I believe what is happening is your $filter parameter is being treated as a single string argument to the Get-ChildItem command. As such, unless you have a directory named "-Include deleteme.txt -Recurse", the command will always return nothing.

As for fixing your problem, well, there are a bunch of ways you could approach it. Probably one of the more versatile ways is to switch program behavior if the the $filter argument is passed, and instead of passing the entire filter string just pass the "deleteme.txt" string.

Answer 2

You're starting to get into an area where where Powershell 2.0 proxy functions can help. However, short of that, here's a simple way in PowerShell 2.0 to do this assuming all you need is -Include and -Recurse. Actually, I would recommend using -Filter instead it will do what you want and frankly it's quite a bit faster (4x on some of my tests) because -filter uses filesystem filtering provided by the OS whereas -include is processed by PowerShell.

param([string]$Filter, [switch]$Recurse)

$files = Get-ChildItem @PSBoundParameters

Write-Host $files #should print all matching files but prints nothing

$file = $files | Select-Object -Last 1;

$file.name #returns filename

The @ symbol is used to "splat" an array or hashtable across the parameters to a command. The $PSBoundParameters variable is an automatic variable new to PowerShell 2.0 that is defined in functions. It's a hashtable that contains all the bounded (named and positional) parameters e.g.:

PS> function foo($Name,$LName,[switch]$Recurse) { $PSBoundParameters }
PS> foo -Name Keith Hill -Recurse

Key                                                         Value
---                                                         -----
Name                                                        Keith
Recurse                                                     True
LName                                                       Hill

When you splat a hashtable like this against a command, PowerShell will map the key's (e.g. Recurse) value to the parameter named Recurse on the command.