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about_Remote_Variables

Updated: May 8, 2014

Applies To: Windows PowerShell 4.0

TOPIC
    about_Remote_Variables

SHORT DESCRIPTION
    Explains how to use local and remote variables in remote
    commands.
    
LONG DESCRIPTION
    You can use variables in commands that you run on remote
    computers. Simply assign a value to the variable and then
    use the variable in place of the value.

    By default, the variables in remote commands are assumed
    to be defined in the session in which the command runs. You
    can also use variables that are defined in the local session,
    but you must identify them as local
    variables in the command.


 USING REMOTE VARIABLES

    Windows PowerShell assumes that the variables used in remote
    commands  are defined in the session in which the command runs.

    In the following example, the $ps variable is defined in the
    temporary  session in which the Get-WinEvent command runs.


        PS C:\>Invoke-Command -ComputerName S1 -ScriptBlock {$ps = "Windows PowerShell"; Get-WinEvent -LogName $ps}


    
    Similarly, when the command runs in a persistent session (PSSession), 
    the remote variable must be defined in the same PSSession.
         
    
        PS C:\>$s = New-PSSession -ComputerName S1

        PS C:\>Invoke-Command -ComputerName S1 -ScriptBlock {$ps = "Windows PowerShell"}

        PS C:\>Invoke-Command -Sessions $s -ScriptBlock {Get-WinEvent -LogName $ps}
    

 USING LOCAL VARIABLES


    You can also use local variables in remote commands, but you must
    indicate that the variable is defined in the local session.

    Beginning in Windows PowerShell 3.0, you can use the Using scope
    modifier to identify a local variable in a remote command.

    The syntax of Using is as follows:
     
       The syntax is:
           $Using:<VariableName>       


    In the following example, the $ps variable is created in the local
    session, but is used in the session in which the command runs. The
    Using scope modifier identifies $ps as a local variable.


        PS C:\>$ps = "Windows PowerShell"
        PS C:\>Invoke-Command -ComputerName S1 -ScriptBlock {Get-WinEvent -LogName $Using:ps}


    You can also use the Using scope modifier in PSSessions. 


        PS C:\>$s = New-PSSession -ComputerName S1

        PS C:\>$ps = "Windows PowerShell"

        PS C:\>Invoke-Command -Sessions $s -ScriptBlock {Get-WinEvent -LogName $Using:ps}





 USING LOCAL VARIABLES IN WINDOWS POWERSHELL 2.0

    You can use local variables in a remote command by defining parameters
    for the remote command and using the ArgumentList parameter of the 
    Invoke-Command cmdlet to specify the local variable as the parameter
    value.
     
    This command format is valid on Windows PowerShell 2.0 and later versions
    of Windows PowerShell.

    
      -- Use the param keyword to define parameters for the remote command. 
         The parameter names are placeholders that do not need to match the
         name of the local variable. 

      -- Use the parameters defined by the param keyword in the command.


      -- Use the ArgumentList parameter of the Invoke-Command cmdlet to
         specify the local variable as the parameter value.


     For example, the following commands define the $ps variable in the local 
     session and then use it in a remote command. The command uses $log as 
     the parameter name and the local variable, $ps, as its value.

      C:\PS>$ps = "Windows PowerShell"

      C:\PS>Invoke-Command -ComputerName S1 -ScriptBlock {param($log) Get-WinEvent -logname $log} -ArgumentList $ps

 KEYWORDS
    about_Using

     
 SEE ALSO
    about_Remote
    about_PSSessions
    about_Scopes
    Enter-PSSession
    Invoke-Command
    New-PSSession



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