PowerShell input to function not work when pipeling input

Question

I have a powershell function that I inherited. it works fine when using no input or providing a single server name as input.

Function works when running like this

Get-DiskUtil or

Get-DiskUtil computername

But if I try

Get-Content c:\psfiles\servers.txt | Foreach-Object {Get-DiskUtil} (this give the output of the local machine three times if I have three server listed in servers.txt).

or

Get-Content C:\psfiles\servers.txt | Get-DiskUtil

The result only gives the output of the local machine name and this error three times.

Can someone tell me why Get-Content does not work and how I might go about fixing this?

computername=$_ : The term 'computername=$_' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a 
path was included, verify that the path is correct and try again.
At D:\Data\WindowsPowerShell\Modules\MyFunctions\Get-DiskUtil.ps1:4 char:10
+ if ($_) {computername=$_}
+          ~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (computername=$_:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException

Get-DiskUtil:

Function Get-DiskUtil {
Param([string] $computername=$env:computername)
Process {
if ($_) {computername=$_}
gwmi win32_logicaldisk -fi "drivetype=3" -comp $computername |
Select @{Name="Computername";Expression={$_.systemName}},
DevicedID,
@{Name="SizeGB";Expression={"{0:N2}" -f ($_.Size/1GB)}},
@{Name="FreeGB";Expression={"{0:N2}" -f ($_.Freespace/1GB)}},
@{Name="UsedGB";Expression={"{0:N2}" -f (($_.Size-$_.FreeSpace)/1GB)}},
@{Name="PerFreeGB";Expression={"{0:P2}" -f ($_.Freespace/$_.size)}}
}
}

mjolinor · Accepted Answer · 2013-12-31 21:40:37Z

4

Looks like a simple typo to me. This line:

if ($_) {computername=$_}

should be:

if ($_) {$computername=$_}

There are many advantages to using advanced functions, but it's not required to have a function that accepts input from the pipeline.

answered Dec 31, 2013 at 21:40

mjolinor

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Comments

rerun · Accepted Answer · 2013-12-31 21:05:29Z

3

The issue is that you have created a function. Functions do not accept input from the pipeline you need to create an advanced function.

Function Get-DiskUtil {
     [CmdLetBinding]
     Param([parameter(Mandatory=$true,
        ValueFromPipeline=$true)]
          [string] $computername=$env:computername)
     )

This will allow that paramater to be taken in on the pipe line. Not you could also solve this by rearaging your calling code

Get-Content c:\psfiles\servers.txt | % {Get-DiskUtil $_}

answered Dec 31, 2013 at 21:05

rerun

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score 1 · Accepted Answer · 2013-12-31 22:04:07Z

1

All you need to do is add the [Parameter(ValueFromPipeline = $true)] attribute to your parameter declaration. You also need to declare the $ComputerName parameter as an array, since it will accept either a single value, or an array of values.

Here is the modified function.

function Get-DiskUtil {
    [CmdletBinding()]
    param(
        [Parameter(ValueFromPipeline = $true)]
        [string[]] $ComputerName = $env:COMPUTERNAME
    )

    process {
        Get-WmiObject -Class Win32_LogicalDisk -Filter "DriveType = 3" -ComputerName $ComputerName |
        Select-Object -Property @{Name="Computername"; Expression={$_.systemName} },
        DevicedID,
        @{ Name="SizeGB"; Expression={"{0:N2}" -f ($_.Size/1GB)}},
        @{ Name="FreeGB"; Expression={"{0:N2}" -f ($_.Freespace/1GB)}},
        @{ Name="UsedGB"; Expression={"{0:N2}" -f (($_.Size-$_.FreeSpace)/1GB)}},
        @{ Name="PerFreeGB"; Expression={"{0:P2}" -f ($_.Freespace/$_.size)}}
    }
}

# Call the function, passing in an array of values
'localhost','localhost' | Get-DiskUtil

edited Dec 31, 2013 at 22:04

answered Dec 31, 2013 at 21:26

user189198

2 Comments

emptyshell Over a year ago

This works as posted. Not declaring the $ComputerName is why I was getting the output error. Thank you very much and Happy New Year.

user189198 Over a year ago

Great! Glad to hear you're up and running! Cheers

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