无法将参数绑定到参数'command'，因为它为null。电源外壳

Question

我有一个类似于以下代码的功能。它接收命令和命令参数。我必须在后台运行此命令并收集输出。但是最后一条语句让我很困惑

错误：

Cannot bind argument to parameter 'Command' because it is null.
+ CategoryInfo          : InvalidData: (:) [Invoke-Expression], ParameterBindingValidationException
+ FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.PowerShell.Commands.InvokeExpre
ssionCommand
+ PSComputerName        : localhost

码：

$cmd = 'Get-content'
$Arg = 'path to file'
$sb = "$cmd $Arg -ErrorVariable e -ErrorAction Stop"
invoke-Expression $sb #This printsoutput
$job = Start-job -ScriptBlock {Invoke-Expression $sb}
wait-job -id $job.Id
$job | Receive-job #this should print output but throwing error

我很确定最后一行是抛出错误的那一行。

Answer 1

$sb进入脚本块范围的另一种选择-argumentlist是使用$using:范围。（PowerShell 3+）

$cmd = 'Get-content'
$Arg = 'path to file'
$sb = "$cmd $Arg -ErrorVariable e -ErrorAction Stop"
$job = Start-job -ScriptBlock {Invoke-Expression $using:sb}
wait-job -id $job.Id
$job | Receive-job