Create powershell cmdlet that processes each path received from dir

Question

I'm trying to create a cmdlet written in powershell that can accept each path from dir command and run a powershell function on this path. Example:

PS> dir *.ext | Convert-xyz

Here's what I tried below. Except, it only processes the first item listed by dir *.ext and then exits.

function Convert-xyz {

    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$True,
                   ValueFromPipeline=$True,
                   ValueFromPipelineByPropertyName=$True)]
        [string[]]$path,

        [string[]]$function
    )

    foreach ($pathi in $path) {
        Write-Host -ForegroundColor "Yellow" "`nPath: $pathi"
        foreach ($funct in $function) {
            write-host -ForegroundColor "Green" "Function: $funct"
            switch($funct) {
                "reflow"   {reflow  ($pathi);  break}
                "desquare" {desquare($pathi);  break}

                default   {
                    write-host -ForegroundColor "Red" "Unknown function: $funct"
                }
            }
        }
    }
    Write-Host "End"

} #function

You'll need a foreach in there, something like dir *.exe | %{convert-xyz} — Nick
– Nick, Commented Jan 10, 2018 at 20:37
Aside: Your function calls are not correct semantically. PowerShell functions are not called with ( ). The calls should beshould be reflow $pathi and desquare $pathi, not reflow ($pathi) and desquare ($pathi). — Bill_Stewart
– Bill_Stewart, Commented Jan 10, 2018 at 20:39

Ansgar Wiechers · Accepted Answer · 2018-01-10 20:57:50Z

For handling pipeline input you'll want to put your processing code in a Process {} block.

function Convert-xyz {
    [CmdletBinding()]
    Param(
        [Parameter(Mandatory=$true,
                   ValueFromPipeline=$true,
                   ValueFromPipelineByPropertyName=$true)]
        [string[]]$path,

        [string[]]$function
    )

    Process {
        foreach ($pathi in $path) {
            Write-Host -ForegroundColor "Yellow" "`nPath: $pathi"
            foreach ($funct in $function) {
                Write-Host -ForegroundColor "Green" "Function: $funct"
                switch ($funct) {
                    "reflow"   {reflow   $pathi; break}
                    "desquare" {desquare $pathi; break}
                    default    {
                        Write-Host -ForegroundColor "Red" "Unknown function: $funct"
                    }
                }
            }
        }
    }

    End {
        Write-Host "End"
    }
} #function

The content of that block is run for every input from the pipeline (which doesn't come as an array, but one item at a time).

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