pipeline.ps1.txt

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Helpful notes from the presentation
"Understanding the Pipeline - Get your one-liners to work!"
    "It will always work -- if you know how"

Jason Helmick
2009


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# First Problem - ByValue

Get-Service | Stop-Service
 Sending    |   Receiving

1. What kind of object is sent across the pipeline
        To Determine: Get-Service | gm
        Answer: ServiceController

2. Does the receiving cmdlet have any parameters that accept
    pipeline input BYVALUE

        To Determine: Get-Help Stop-Service -Full
        Answer: Yes
                -Name <String>
                -InputObject <ServiceController>

Solution: Because THe passed object is same type as -InputObject 
            (ServiceController) The two cmdlets work together.

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# Second Problem - ByPropertyName

Get-Service | Stop-Process
 Sending    |   Receiving

1. What kind of object is sent across the pipeline?
        To Determine: Get-Service | gm
        Answer: ServiceController

2. Does the receiving cmdlet have any parameters that accept
    pipeline input BYVALUE?

        To Determine: Get-Help Stop-Process -Full
        Answer: Yes
                -InputObject <Process>

        *Note: Because the Passed object has a different type
            (ServiceController) than -InputObject (process) There is 
            no ByValue connection
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3. What parameters of Stop-Process accept pipeline input ByPropertyName?

        To Determine: Get-Help Stop-Process -Full
        Answer: Yes            
                -Name (Process name)
                -ID (Process ID)

4. Is there a property of the sending cmdlet that matches the parameter 
    name of the receiving cmdlet?

        To Determine: Get-Service | gm
        Answer: Yes
                Name


Solution: Because THe passed object has a property with the same name (Name)
             as the parameter (-Name) on the receiving cmdlet - this works.
            

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# Third Problem - ByPropertyName

Get-ADComputer -Filter * | Get-Service -name bits
        Sending          |        Receiving

1. What kind of object is sent across the pipeline?
        To Determine: Get-ADComputer -Filter * | gm
        Answer: ADComputer

2. Does the receiving cmdlet have any parameters that accept
    pipeline input BYVALUE?

        To Determine: Get-Help Get-Service -Full
        Answer: Yes
                -InputObject <ServiceController>

        Note: Because the Passed object has a different type
            (ADComputer) than -InputObject (ServiceController) There is 
            no ByValue connection
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3. What parameters of Get-Service accept pipeline input ByPropertyName?

        To Determine: Get-Help Get-Service -Full
        Answer: Yes            
                -Name (Service name)
                -ComputerName (ComputerName)

4. Is there a property of the sending cmdlet that matches the parameter 
    name of the receiving cmdlet?

        To Determine: Get-ADComputer -Filter * | gm 
        Answer: Yes - But its the wrong one we want - it matches to -Name.
                Name (Computer names)

        Note: Because the Passed object has a different property name (Name)
            than the desired parameter on the receiving cmdlet (-ComputerName)
            this doesn't work as we expect.
            

Solution: To match the property (Name) to the parameter (-ComputerNAme) create
            your own custom property in-flight using the Select-Object cmdlet.

 Get-Adcomputer -filter * | Select-Object -Property @{n='ComputerName';e={$_.name}} | 
 Get-Service -name bits
            

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# Fourth Problem - The parenthetical

Get-Adcomputer -filter * | Get-WmiObject -Class win32_bios
        Sending          |        Receiving

1. What kind of object is sent accross the pipeline?
        To Determine: Get-ADComputer -Filter * | gm
        Answer: ADComputer

2. Does the receiving cmldet have any parameters that accept
    pipeline input BYVALUE or ByPropertyName

        To Determine: Get-Help Get-WmiObject -Full
        Answer: NO!

        Note: This cmdlet does not except ANY pipeline input, so
                a new tactic to solving the problem must be used.
                
Solution:The cmdlet Get-WmiObject supports -ComputerName with an argument of 
            object type <String[]>. You need to fill this argument with the data, but it must 
            be of type <String>.
            
            
Example:
   
        1. Get-Adcomputer -filter * | Select-Object -Property name | gm
        # Not type string - won't work
        
        2. Get-Adcomputer -filter * | Select-Object -ExpandProperty name | gm
        # -ExpandProperty - This makes the type <string> - This will work.

Get-WmiObject -Class win32_bios -ComputerName (Get-Adcomputer -filter * | Select-Object -ExpandProperty name)
 
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 Resources:
 
    For more help on working with the pipeline, see the book
    "Learn Windows PowerShell in a Month of Lunches" - chapter 9
    Or go to http://www.PowerShell.Org and post a question in the forums.        

    
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