Powershell: Piping values from one function to another

Question

I have two functions one which outputs a set of directories And one needs to receive that set and do a foreach on it, however it seems the second function is only receiving one of the directories (the last one).

What am I doing wrong.

Get-Directories {
    return Get-ChildItem | Where-Object { $_.PSIsContainer -eq $True }
}
function Invoke-Build {
    [CmdletBinding()]
    Param(
    [Parameter(Mandatory=$True,ValueFromPipeline=$True,ValueFromPipelineByPropertyName=$True)]
    [string[]]$directories
)
Write-Output $dir
foreach ($dir in $directories) {
    Set-Location $dir
    Build
    Set-Location ..
}

Get-Directories | Invoke-Build

The output though is just the last directory found by Get-Directories. I need the second function to accept array input as I plan to make it do things asynchronously.

Use process{...} block.

user4003407
– user4003407

2016-01-22 09:05:52 +00:00
Commented Jan 22, 2016 at 9:05 — user4003407
– user4003407, Commented Jan 22, 2016 at 9:05

Maurice · Accepted Answer · 2016-01-22 09:35:53Z

1

You need to include a PROCESS block in your Invoke-Build function.

function Invoke-Build 
{
  [CmdletBinding()]
  Param
  (
    [Parameter(Mandatory = $True,
               ValueFromPipeline = $True,
               ValueFromPipelineByPropertyName = $True)]
    [string[]]$directories
  )

  PROCESS 
  {
    Write-Output $directories
  }
}

If you call the function like this:

"dir1", "dir2", "dir3" | Invoke-Build

The function will iterate over the directories one at a time.

More Information on implementing pipeline support can be found here: http://learn-powershell.net/2013/05/07/tips-on-implementing-pipeline-support/

answered Jan 22, 2016 at 9:35

Maurice

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Comments

wnbates · Accepted Answer · 2016-01-22 09:26:28Z

0

PetSerAl's comment was spot on.

I changed the second function as follows

function Invoke-Build {
    [CmdletBinding()]
    Param(
        [Parameter(Mandatory=$True,ValueFromPipeline=$True,ValueFromPipelineByPropertyName=$True)]
        [string[]]$directories
    )
    Begin { Write-Output "Starting" }
    Process {
        Set-Location $_
        build
        Set-Location ..
    }
    End { Write-Output "Done" }

answered Jan 22, 2016 at 9:26

wnbates

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1 Comment

Kiran Reddy Over a year ago

you can also use the foreach inside the process block to specify an array of values ( when not using the pipeline)

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