PowerShell 中的 echo 和 Write-Host 有什么区别？

Question

我对 PowerShell 中 echo 和 Write-Host 之间的区别感到困惑。我有两个文件，POC.ps1 和 validatePath.ps1。这些文件在我的本地机器上，我正在使用Invoke-Command 在远程机器上运行它们。我正在使用 PowerShell v3.0。

要执行这两个脚本，我使用以下命令：

.\POC.ps1 -filename C:\Users  -user Blaine

这是两个文件：

POC.ps1：

param($filename, $user)

echo $filename
echo "This"
echo $user

$responseObject = Invoke-Command testcomputer -FilePath .\validatePath.ps1  -ArgumentList($filename, $user) -AsJob

while($responseObject.State -ne "Completed")
{

}

$result = Receive-Job -Id $responseObject.Id -Keep
echo $result

这就是事情变得奇怪的地方......

validatePath.ps1：

Param([string] $filename,
      [string] $user)

function ValidatePath( $filename, $user, $fileType = "container" )
{
    Write-Host "This is the file name: $filename"
    Write-Host "This is user: $user"  <--- Notice I'm using Write-Host here
    $fileExist = $null
    if( -not (test-path $filename -PathType $fileType) )
    {
        throw "$user, the path $filename does not exist!"

    }
    else
    {
         Write-Host "This is the second part"
         echo $filename found!
    }
    Write-Host "This is the third part"
    return $fileExist
}


try
{

    ValidatePath($filename, $user)
}
catch
{
    $e = $_.Exception
    echo $e
}

当我运行上面的脚本时，输出如下：

C:\Users
This
Blaine
This is the file name: C:\Users Blaine
This is user:  <--- Notice where this line is?
This is the second part
This is the third part
C:\Users
Blaine
found!

但如果我将validatePath.ps1 更改为：

Param([string] $filename,
      [string] $user)

function ValidatePath( $filename, $user, $fileType = "container" )
{
    Write-Host "This is the file name: $filename"
    echo "This is user: $user" <---notice I'm using Echo here
    $fileExist = $null
    if( -not (test-path $filename -PathType $fileType) )
    {
        throw "$user, the path $filename does not exist!"

    }
    else
    {
         Write-Host "This is the second part"
         echo $filename found!
    }
     Write-Host "This is the third part"
    return $fileExist
}


try
{

    ValidatePath($filename, $user)
}
catch
{
    $e = $_.Exception
    echo $e
}

这是输出：

C:\Users
This
Blaine
This is the file name: C:\Users Blaine
This is the second part
This is the third part
This is user: <---- Notice where this line is now?
C:\Users
Blaine
found!

您会注意到“这是用户：”这一行位于不同的位置。为什么是这样？为什么echo 与Write-Host 的工作方式不同？

更新：

更奇怪的是，如果我像这样重新运行脚本两次：

POC.ps1：

param($filename, $user)

echo $filename
echo "This"
echo $user

$responseObject = Invoke-Command CAPTESTPK01 -FilePath .\validatePath.ps1  -ArgumentList $filename, $user -AsJob

while($responseObject.State -ne "Completed")
{

}

$result = Receive-Job -Id $responseObject.Id -Keep
echo $result


$filename = "C:\saddfasdfj"

#Here I run the command again, using a different file name
$responseObject = Invoke-Command CAPTESTPK01 -FilePath .\validatePath.ps1  -ArgumentList $filename, $user -AsJob

while($responseObject.State -ne "Completed")
{
   if($responseObject.State -eq "Failed")
   {
        echo "Failed"
        $result = Receive-Job -Id $responseObject.Id -Keep
        echo $result
        break
   }
}

$result = Receive-Job -Id $responseObject.Id -Keep
echo $resul

当在validatePath.ps1 中使用echo 时，它给了我这个输出：

C:\Users
This
Blaine
This is the file name: C:\Users
This is the second part
This is the third part
This is user: Blaine <---- This line is here
C:\Users
found!
This is the file name: C:\saddfasdfj
This is user: Blaine <---- But now it's here, where it should be? Wth?
Blaine, the path C:\saddfasdfj does not exist!

Answer 1

echo 是 Write-Output 的别名，它写入 Success 输出流。这允许通过管道处理输出或重定向到文件中。 Write-Host 直接写入控制台，因此无法进一步重定向/处理输出。

Answer 2

echo 是 Write-Output 的别名。 Write-Host 直接写入“屏幕”，Write-Output 写入管道。如果管道没有输入到其他命令中，它最后也会在“屏幕”上结束。您看到的不同之处在于，Write-Host 直接写入屏幕，Write-Output 首先通过管道并在 Write-Host 之后最终出现在屏幕上。

使用 Write-Output 可以将输出通过管道/重定向到文件或另一个命令，而 Write-Host 不能。应该根据您的需要使用它们。

请参阅here 了解更多信息。