When invoking remote commands, one often wants to use local values as arguments to the remote command. This post explains how to do that. <\/p>\n
Let’s start with a simple example. Below you can see how Get-Process is invoked in a remote session when the Id parameter is set to 0:<\/p>\n
PS> $s = New-PSSession -Computer localhost\nPS> Invoke-Command -Session $s -Script { Get-Process -Id 0<\/strong> }\nHandles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName PSComputerName\n------- ------ ----- ----- ----- ------ -- ----------- --------------\n 0 0 0 24 0 0<\/strong> Idle localhost<\/pre>\nPassing local values<\/h3>\n
What if we want to calculate the value of the Id parameter programmatically, instead of hard-coding it to a particular integer? Well, script blocks can declare parameters and the param block can be used to pass a value to the command that is being invoked. In the following example, we declare the $processId parameter in the script block and then use the Args parameter of Invoke-Command to set the value of $processId to $pid, which is the process ID of the current Windows PowerShell process.<\/p>\n
PS> $s = New-PSSession -ComputerName localhost\nPS> Invoke-Command -Session $s -Script { param($processId)<\/strong> Get-Process -Id $processId<\/strong> } -Args $pid<\/strong>\nHandles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName PSComputerName\n------- ------ ----- ----- ----- ------ -- ----------- --------------\n 533 13 46160 37456 198 6.07 9488<\/strong> powershell<\/strong> localhost<\/pre>\nThe example above demonstrates that Get-Process was invoked with a process id of the local Windows PowerShell console. Invoke-Command takes whatever you pass in the Args parameter and binds it to script block’s parameters in the remote session. Note that above I simply passed in a value of a local $pid variable, but any local expression (not just a simple variable dereference) can be used instead.<\/p>\n
Referring to remote variables<\/h3>\n
A different behavior takes place when you don’t declare script block parameters using the "param" keyword:<\/p>\n
PS> $s = New-PSSession -ComputerName localhost\nPS> Invoke-Command -Session $s -Script { Get-Process -Id $pid<\/strong> }\nHandles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id<\/strong> ProcessName PSComputerName\n------- ------ ----- ----- ----- ------ -- ----------- --------------\n 329 10 21216 33524 154 7.63 6596 wsmprovhost<\/strong> localhost<\/pre>\nIn this case $pid is an unbound variable and Windows PowerShell assumes that it refers to the $pid variable in the remote session. Therefore, as you can see Get-Process returns the process that hosts the remote session. <\/p>\n
Magic $args variable<\/h3>\n