PowerShell:Start作业中的$input到底是什么？

考虑以下代码。我只是使用

-InputObject

参数将一个32位有符号整数数组

[Int32[]]

传入

启动作业

cmdlet

$Job = Start-Job -ScriptBlock { $input.GetType().FullName; } -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;

该代码的结果是：

System.Management.Automation.Runspaces.PipelineReader`1+<GetReadEnumerator>d__0[[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

但是，我收到了一条错误消息：

方法调用失败，因为[System.Int32]不包含名为“ReadToEnd”的方法。 +CategoryInfo:InvalidOperation:（：）[]，运行时异常 +FullyQualifiedErrorId:MethodNotFound +PSComputerName:localhost

然后我想，我将使用

PSBase

属性来获取“真实”对象

但随后我收到一条类似的错误消息：

方法调用失败，因为[System.Management.Automation.PSInternalMemberSet]不包含名为“ReadToEnd”的方法。 +CategoryInfo:InvalidOperation:（ReadToEnd:String）[]，运行时异常 +FullyQualifiedErrorId:MethodNotFound +PSComputerName:localhost

我注意到在这种困惑周围有一种神秘感，但它让我更加困惑。显然，

PipelineReader

类有一个名称混乱的属性

4\u this

，它有一个

Read（）

方法，使用

Get Member

实际上看不到该方法

底线：当通过

启动作业

cmdlet上的

-InputObject

参数提交输入时，是否有人知道如何简单地“展开”

$input

自动变量的内容，以便我可以单独处理对象

这个脚本应该只返回

1

，而不是

1、2、3

$Job = Start-Job -ScriptBlock { $input[0]; } -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;

资料来源：

总之：

$input

是一个自动变量，它以枚举器的形式包含整个管道，与管道中的“当前对象”不同

下面是一个如何使用它的示例

function test {
    #$input is an enumerator that you should use $input | foreach-object { } to access the objects.

    #To to get all items you could e.g. convert the enumerator to an array.
    $arr = @($input)

    #If you need to use the $input enumerator for something else, you need to call .Reset() first as the enumerator has reached the end.
    $input.Reset()

    #Print some values from the data
    $arr.count
    $arr[0]
}

PS> "hello", "world" | test


2
hello

更新：这里有证据证明这也适用于您的

启动作业

场景。对样本进行注释以解释

$Job = Start-Job -ScriptBlock { 
    #Read the complete pipeline to an array
    $data= @($input)
    "`$data is an $($data.GetType().Name) with $($data.count) objects"

    #Unlike in a pipeline, where the `Start-Job` command would be called once per object like `Start-Job ...... -InputObject $_`, 
    #you're inputing a single `object[]` object the the pipeline. So you only have one item in your $input pipeline.

    #Get our inputobject (our array)
    $arr= $data[0]
    "`$arr is an $($arr.GetType().Name)"

    #Use array
    "$($arr[0]) is less than $($arr[1]) which is less than $($arr[2])"
} -InputObject @(1,2,3);

Wait-Job -Job $Job;
Receive-Job -Keep $Job;

Id     Name            PSJobTypeName   State         HasMoreData     Location             Command                  
--     ----            -------------   -----         -----------     --------             -------                  
54     Job54           BackgroundJob   Completed     True            localhost             ...                     
$data is an Object[] with 1 objects
$arr is an ArrayList
1 is less then 2 which is less then 3

并证明我关于管道的“理论”。以下是流水线版本：

$Job = 1, 2, 3 | Start-Job -ScriptBlock { 
    #Read the complete pipeline to an array
    $data= @($input)
    "`$data is an $($data.GetType().Name) with $($data.count) objects"

    #Now the command is run per object, so the $input enumerator contained our 3 seperate Int32 values.

    #Get a single object in the pipeline
    $OneOfTheValues= $data[0]
    "`$OneOfTheValues is an $($OneOfTheValues.GetType().Name)"

    #Use data
    "$($data[0]) is less than $($data[1]) which is less than $($data[2])"
}

Wait-Job -Job $Job;
Receive-Job -Keep $Job;

Id     Name            PSJobTypeName   State         HasMoreData     Location             Command                  
--     ----            -------------   -----         -----------     --------             -------                  
58     Job58           BackgroundJob   Completed     True            localhost             ...                     
$data is an Object[] with 3 objects
$OneOfTheValues is an Int32
1 is less then 2 which is less then 3

---

所以我坚持我最初的答案。行为相同，您只是以不同的方式使用管道/cmdlet。：）

大概

$input

是一个枚举器，就像在标准管道中一样。 为了处理项目，我们应该使用带有 自动变量

$\uuu

或在

端的另一个管道中传递
$input
块（如果未指定，则隐式）

也许还有其他方法可以枚举
$input
的项，但它们是
据我所知，在实践中不经常使用。
这似乎有效：

$Job = Start-Job -ScriptBlock { $input.movenext();$input.current[0] } -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;

$Job=Start Job-ScriptBlock{$（$input）[0]；}-InputObject@（1,2,3）
对你有用吗？是的，但是你能进一步解释一下
$input
是什么吗？这就是我最终想要理解的。我想我有一个更好的例子。指示枚举器中的
$input
，不能像数组那样对其进行索引。请尝试以下操作：
$Job=Start Job-ScriptBlock{$input.getEnumerator（）[0]}-InputObject@（1,2,3）
Start Job
不会以这种方式运行。看看我的例子。
$Job = Start-Job -ScriptBlock { 
    #Read the complete pipeline to an array
    $data= @($input)
    "`$data is an $($data.GetType().Name) with $($data.count) objects"

    #Unlike in a pipeline, where the `Start-Job` command would be called once per object like `Start-Job ...... -InputObject $_`, 
    #you're inputing a single `object[]` object the the pipeline. So you only have one item in your $input pipeline.

    #Get our inputobject (our array)
    $arr= $data[0]
    "`$arr is an $($arr.GetType().Name)"

    #Use array
    "$($arr[0]) is less than $($arr[1]) which is less than $($arr[2])"
} -InputObject @(1,2,3);

Wait-Job -Job $Job;
Receive-Job -Keep $Job;

Id     Name            PSJobTypeName   State         HasMoreData     Location             Command                  
--     ----            -------------   -----         -----------     --------             -------                  
54     Job54           BackgroundJob   Completed     True            localhost             ...                     
$data is an Object[] with 1 objects
$arr is an ArrayList
1 is less then 2 which is less then 3

$Job = 1, 2, 3 | Start-Job -ScriptBlock { 
    #Read the complete pipeline to an array
    $data= @($input)
    "`$data is an $($data.GetType().Name) with $($data.count) objects"

    #Now the command is run per object, so the $input enumerator contained our 3 seperate Int32 values.

    #Get a single object in the pipeline
    $OneOfTheValues= $data[0]
    "`$OneOfTheValues is an $($OneOfTheValues.GetType().Name)"

    #Use data
    "$($data[0]) is less than $($data[1]) which is less than $($data[2])"
}

Wait-Job -Job $Job;
Receive-Job -Keep $Job;

Id     Name            PSJobTypeName   State         HasMoreData     Location             Command                  
--     ----            -------------   -----         -----------     --------             -------                  
58     Job58           BackgroundJob   Completed     True            localhost             ...                     
$data is an Object[] with 3 objects
$OneOfTheValues is an Int32
1 is less then 2 which is less then 3

# process each item separately
$Job = Start-Job -ScriptBlock {process{$_}} -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;

# process the whole $input
$Job = Start-Job -ScriptBlock {$input | %{$_}} -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;

# compare with script blocks in standard pipelines

# each item
@(1,2,3) | . {process{$_}}

# whole input
@(1,2,3) | . {$input | %{$_}}

$Job = Start-Job -ScriptBlock { $input.movenext();$input.current[0] } -InputObject @(1,2,3);
Wait-Job -Job $Job;
Receive-Job -Keep $Job;