Powershell 运行作业时的参数解释

为什么上面的代码块会引发以下错误

$h = "host1.example.com"
$code = {
  $(Get-WmiObject -Class "Win32_ComputerSystem" -Namespace "root\cimv2" -ComputerName $h)
}
$timeout = 5
$jobstate = $(Wait-Job -Job ($job = $(Start-Job -ScriptBlock $code)) -Timeout $timeout)
$wmicomobj = $(Receive-Job -Job $job)

无法验证参数“ComputerName”上的参数。参数为null或 空的。请提供一个不为null或空的参数，然后重试该命令 再一次。 +CategoryInfo:InvalidData:（：）[Get WMIOObject]，ParameterBindingValidationException +FullyQualifiedErrorId:ParameterArgumentValidationError，Microsoft.PowerShell.Commands.GetWmiObjectCommand +PSComputerName:localhost

---

我想用它来实现在循环中获取多个主机的WMI对象时的超时。但首先，我需要通过作业执行获得结果。

脚本块中无法使用脚本全局范围中定义的变量，除非您使用

using

限定符：

Cannot validate argument on parameter 'ComputerName'. The argument is null or empty. Supply an argument that is not null or empty and then try the command again. + CategoryInfo : InvalidData: (:) [Get-WmiObject], ParameterBindingValidationException + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.PowerShell.Commands.GetWmiObjectCommand + PSComputerName : localhost 或者将它们作为参数传入，如下所示：

$code = {
  Get-WmiObject -Class "Win32_ComputerSystem" -Namespace "root\cimv2" -ComputerName $using:h
}

$code = {
  Param($hostname)
  Get-WmiObject -Class "Win32_ComputerSystem" -Namespace "root\cimv2" -ComputerName $hostname
}
$jobstate = Wait-Job -Job ($job = $(Start-Job -ScriptBlock $code -ArgumentList $h)) -Timeout $timeout

或者像这样：

$code = {
  Get-WmiObject -Class "Win32_ComputerSystem" -Namespace "root\cimv2" -ComputerName $using:h
}

$code = {
  Param($hostname)
  Get-WmiObject -Class "Win32_ComputerSystem" -Namespace "root\cimv2" -ComputerName $hostname
}
$jobstate = Wait-Job -Job ($job = $(Start-Job -ScriptBlock $code -ArgumentList $h)) -Timeout $timeout