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0206 | The pipeline - Deeper

How the pipeline really works | The 4 step solution​

1 | ByValue | match by value​

  • example 
    # match by -InputObject <ServiceController[]> 
    # (ByValue)
    get-service | stop-service -whatif
  • the object types must match
  • first, check what kind of objects are going through the pipeline 
    <command> | get-member
  • then check the receiving commands parameters 
    get-help <recevi-command> -full
  • accepting pipeline input? --> true (ByValue) AND object type match

2 | ByPropertyName | match by propertyname​

  • name of the property coming across must match the name of the property on the receiving end
  • example 
    # ByPropertyName
    # -Name <String[]> -- Name -> Name
    get-service | stop-process -whatif
    # ByPropertyName
    # -Path
    get-process calc | dir

3 | What if my property doesn't match | Customize it!​

  • if the propertynames do not match, fix them in flight
  • example 
    # get all the computer names and check for the bits service on each of them
    # ByPropertyName: Name <-> ByPropertyName: ComputerName <String[]>
    get-adcomputer -filter * | get-service -name bits
    # fix with customcolumns/calculated properties
    get-adcomputer -filter * | select -property name, @{name='ComputerName';expression={$_.name}}
    # or the same as
    get-adcomputer -fileter * | select -property name, @{n='NewName';e={$_.name}}
    # or
    get-adcomputer -fileter * | select -property name, @{label='NewName';e={$_.name}}
    # or
    get-adcomputer -fileter * | select -property name, @{l='NewName';e={$_.name}}
    # and then leave the "name" column out
    get-adcomputer -filter * | select -property @{name='ComputerName';expression={$_.name}}
    # finally -- pass it through
    get-adcomputer -filter * | select -property @{n='ComputerName';e={$_.name}} | get-service -name bits

4 | The Parenthetical | When all else fails​

  • no match by value, by propertyname and no renaming will fix it
  • only by string, no objects
  • example 
    # -computername expects string computernames --> select only by the name AND conv to string
    get-wmiobject -class win32_bios -computername (get-adcomputer -filter * | select -expandproperty name)
    # or since PSv3
    get-wmiobject -class win32_bios -computername (get-adcomputer -filter * ).name
    # or use get-ciminstance instead of get-wmiobject
    get-help get-ciminstance
    # or with script blocks
    get-adcomputer -filter * | get-wmiobject -class win32_bios -computername {$_.Name}