循环中具有流程优先级的启动流程无法识别变量 [英] Start-Process with Process Priority in Loop doesn't recognize variable

问题描述

我在PowerShell中使用 FFmpeg .

I'm using FFmpeg with PowerShell.

我有一个循环，遍历一个mpg文件的文件夹，并将名称捕获到变量$inputName.

I have a loop that goes through a folder of mpg files and grabs the names to a variable $inputName.

FFmpeg然后将每个转换为mp4.

FFmpeg then converts each one to an mp4.

批处理

$files = Get-ChildItem "C:\Path\" -Filter *.mpg; 

foreach ($f in $files) {

    $inputName = $f.Name; #name + extension
    $outputName = (Get-Item $inputName).Basename; #name only

    ffmpeg -y -i "C:\Users\Matt\Videos\$inputName" -c:v libx264 -crf 25 "C:\Users\Matt\Videos\$outputName.mp4"
}

---

不起作用

具有流程优先级的批处理

---

Not Working

Batch Processing with Process Priority

$files = Get-ChildItem "C:\Path\" -Filter *.mpg; 

foreach ($f in $files) {

    $inputName = $f.Name; #name + extension
    $outputName = (Get-Item $inputName).Basename; #name only

    ($Process = Start-Process ffmpeg -NoNewWindow -ArgumentList '-y -i "C:\Users\Matt\Videos\$inputName" -c:v libx264 -crf 25 "C:\Users\Matt\Videos\$outputName.mp4"' -PassThru).PriorityClass = [System.Diagnostics.ProcessPriorityClass]::AboveNormal;
    Wait-Process -Id $Process.id 

}

如果我使用Start-Process PriorityClass设置了进程优先级"，则$inputName变量将不再被识别.

If I set the Process Priority using Start-Process PriorityClass, the $inputName variable is no longer recognized.

Error:
C:\Users\Matt\Videos\$inputName: No such file or directory

推荐答案

让我们讨论一些基本的东西.

Lets go over a few basic things.

在powershell中，我们喜欢管道|，它允许用户将信息从一个命令传递到另一个命令.

In powershell we love piping |, It allows use to pass the information from one command to another command.

一个很好的例子就是您拥有的ForEach.

A good example of this is the ForEach you have.

您可以代替Foreach($F in $Files)，将|用管道传输到foreach-object

Instead of Foreach($F in $Files) you can pipe | into a foreach-object

Get-ChildItem "C:\Path\" -Filter *.mpg | Foreach-Object{
    $_
}

管道|时，命令powershell将自动创建变量$_，该变量是在管道|中传递的对象

When Piping | a command powershell automatically creates the variable $_ which is the object that is passed in the pipe |

接下来的事情是报价"和'有两种类型.

The next thing is there are 2 types of quotes " and '.

如果使用'，则一切都是字面意义.例子

If you use ' then everthing is taken literally. Example

$FirstName = "TestName"
'Hey There $FirstName'

会回来

Hey There $FirstName

"允许您在其中使用变量.例子

While " allows you to use Variables in it. Example

$FirstName = "TestName"
'Hey There $FirstName'

会回来

Hey There TestName

现在，在解决此问题之前，还有最后一件事.在powershell中，我们有一个转义字符，也称为"tick".它位于带代字号的键盘上数字1旁边.您可以使用它来允许使用char，否则这些char会超出qoutes的范围.例子

Now one last thing before we fix this. In powershell we have a escape char ` aka a tick. Its located beside the number 1 on the keyboard with the tilde. You use it to allow the use of char that would otherwise break out of the qoutes. Example

"`"Hey There`""

会退货

"Hey There"

好的，现在我们已经涵盖了基础知识，可以修复脚本

OK so now that we covered the basics lets fix up the script

Get-ChildItem "C:\Users\Matt\Videos\" -Filter *.mpg -File | Foreach-Object{
    ($Process = Start-Process ffmpeg -NoNewWindow -ArgumentList "-y -i `"$($_.FullName)`" -c:v libx264 -crf 25 `"C:\Users\Matt\Videos\$($_.Name)`"" -PassThru).PriorityClass = [System.Diagnostics.ProcessPriorityClass]::AboveNormal;
    Try{
        Wait-Process -Id $Process.id
    }catch{
    }
}

在上述情况下，我改变了

In the case above I changed

在Get-ChildItem中添加-File以表示只希望返回文件而不是文件夹

Add -File to the Get-ChildItem to designate that you only want Files returned not folders

将|插入Foreach-Object

将-ArgumentList中的外部括号更改为双引号"而不是文字引号'

Changed the Outside Brackets in the -ArgumentList to be double quotes " instead of literal quotes '

删除了$InputName和$OutputName，取而代之的是Foreach-Object变量$_

Removed the $InputName and $OutputName in favor of the Foreach-Object variable $_

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