blocks|key|3945376|text|这是少数几种全局变量有用的情况之一，因为它们可以在整个会话中持续存在。在本例中，我使用它们来设置唯一的文件名(在本例中是今天的日期)，以记录到：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3945377|function+Write-Host($object)+
{
++++if($global:LogFile+-eq+$null)
++++{
++++++++$global:LogFile+=+".\LOG-$(Get-Date+-Format+'yyyy-MM-dd').txt"
++++}

++++$object+%7C+tee+$global:LogFile+-Append
}|code-block|syntax|javascript|3945378|-编辑：|3945379|在注释中，如果您希望在会话开始时有一个新文件，并在会话期间添加，我们仍然可以使用全局变量来确定会话的开始，但我们只需使用检查来删除开始时的文件，并将附加保留到Tee：|3945380|function+Write-Host($object)+
{
++++if($global:LogFile+-eq+$null)
++++{
++++++++$global:LogFile+=+".\LOG.txt"
++++++++Remove-Item+$global:LogFile+-ErrorAction+SilentlyContinue
++++}

++++$object+%7C+tee+$global:LogFile+-Append
}|3945381|-编辑2：|3945382|摘自第二条评论：|3945383|Remove-Item是一个不同的动物，因为它默认没有输出。实际上，获得任何输出的唯一方法是添加-Verbose参数。但是Tee-Object不会捕获冗长的流。为了解决这个问题，我们必须使用两个技巧。首先，我们指定带有重定向(about_Redirection)的-Verbose参数(以获取输出)，以将详细流(4)重定向到标准的成功(1)+/信息流。这将允许Tee-Object从Remove-Item+cmdlet捕获信息：|offset|length|style|CODE|3945384|Remove-Item+test.txt+-Verbose+4>&1+%7C+Tee-Object+out.txt|3945385|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_redirection?view=powershell-6^0|0|0|0|0|0|0|0|0|B|1C|8|1P|A|3O|8|50|A|5B|B|35|H|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|17|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|18|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|19|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|1B|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1C|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1D|8|@$S|1E|T|1F|U|V]|$S|1G|T|1H|U|V]|$S|1I|T|1J|U|V]|$S|1K|T|1L|U|V]|$S|1M|T|1N|U|V]|$S|1O|T|1P|U|V]]|9|@$S|1Q|T|1R|1|1S]]|A|$]]|$1|W|3|X|5|D|7|1T|8|@]|9|@]|A|$E|F]]|$1|Y|3|-4|5|6|7|1U|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

This is one of the few cases where global variables are useful, because they can persist through the entire session. In this example I am using them to set the unique filename (in this case today's date), to log to:

<pre><code>function Write-Host($object) 
{
 if($global:LogFile -eq $null)
 {
 $global:LogFile = ".\LOG-$(Get-Date -Format 'yyyy-MM-dd').txt"
 }

 $object | tee $global:LogFile -Append
}
</code></pre>

--- Edit: ---

From comments, if you want to have a new file on the start of session, and append during the session, we can still use the global variable to determine the start of a session, but we simply use the check to remove the file at the start, and leave the Append to the Tee:

<pre><code>function Write-Host($object) 
{
 if($global:LogFile -eq $null)
 {
 $global:LogFile = ".\LOG.txt"
 Remove-Item $global:LogFile -ErrorAction SilentlyContinue
 }

 $object | tee $global:LogFile -Append
}
</code></pre>

--- Edit 2: ---

From second Comments: 

<code>Remove-Item</code> is a different animal because it has no output by default. Indeed, the only way to get any output is to add the <code>-Verbose</code> parameter. But the <code>Tee-Object</code> doesn't capture the Verbose stream. To get around this, we have to use two tricks. First, we specify the <code>-Verbose</code> parameter (to get an output), with a redirect (<a href="https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_redirection?view=powershell-6" rel="nofollow noreferrer">about_Redirection</a>), to redirect the Verbose stream (4) to the standard Success (1) / Information stream. This would allow the <code>Tee-Object</code> to capture the information from the <code>Remove-Item</code> cmdlet:

<pre><code>Remove-Item test.txt -Verbose 4&gt;&amp;1 | Tee-Object out.txt
</code></pre>

blocks|key|3940879|text|您没有定义新的“会话”对您来说是什么，所以让我们使用变量$PID，它是PowerShell运行时所使用的进程ID。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3940880|理想情况下，您只需在文件名中包含这一部分，以便每个进程都有自己的日志。但是你在评论中说你不想要多个文件。在这种情况下，将PID写为文件中的第一行，并每次读取它。|3940881|function+Write-Host($object)+
{
++++$filename+=+'.\LOG.txt'

++++$logPID+=+Get-Content+-LiteralPath+$filename+-ReadCount+1+-ErrorAction+Ignore
++++$newSession+=+$logPID+-ne+$PID

++++if+($newSession)+{
++++++++$PID+%7C+Set-Content+-LiteralPath+$filename
++++}

++++$object+%7C+Tee-Object+-FilePath+$filename+-Append
}|code-block|syntax|javascript|3940882|entityMap^0|S|4|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

You don't define what a new "session" is to you, so let's use the variable <code>$PID</code>, which is the process ID that PowerShell is running as.

Ideally you'd just make this part of the file name so that each process has its own log. But you stated in comments that you don't want multiple files. In that case, write the PID as the first line in the file, and read it each time.

<pre class="lang-bsh prettyprint-override"><code>function Write-Host($object) 
{
 $filename = '.\LOG.txt'

 $logPID = Get-Content -LiteralPath $filename -ReadCount 1 -ErrorAction Ignore
 $newSession = $logPID -ne $PID

 if ($newSession) {
 $PID | Set-Content -LiteralPath $filename
 }

 $object | Tee-Object -FilePath $filename -Append
}
</code></pre>

blocks|key|3945472|text|我将为未来的搜索者提供一种替代方法。您可以获取当前进程的开始时间，将其与创建文件的时间进行比较，如果文件是在当前PID启动之前创建的，则可以删除该文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3945473|function+Write-Host
{
[cmdletbinding()]
Param([parameter(ValueFromPipeline=$true)]$object)
Begin{
++++$allObjects=New-Object+System.Collections.ArrayList
}
Process{
++++$allObjects.Add($object)%7Cout-null
}
End{
++++if((test-path+.\log.txt)+-and+(get-item+'.\LOG.txt').CreationTime+-lt+(Get-Process+-Id+$PID).StartTime){Remove-Item+.\LOG.txt}
++++$allObjects+%7C+tee+.\LOG.txt+-Append
}
}|code-block|syntax|javascript|3945474|此外，使用到高级函数的转换，您可以通过管道将某些内容传递给它，例如：|3945475|Get-Process+%7C+Write-Host|3945476|或者，我认为最简单的做法就是删除日志文件，这是脚本要做的第一件事。|3945477|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I'll offer an alternative method for future searchers. You can get what time your current process started at, compare it to when the file was created, and delete the file if it was created before your current PID was started.

<pre><code>function Write-Host
{
[cmdletbinding()]
Param([parameter(ValueFromPipeline=$true)]$object)
Begin{
 $allObjects=New-Object System.Collections.ArrayList
}
Process{
 $allObjects.Add($object)|out-null
}
End{
 if((test-path .\log.txt) -and (get-item '.\LOG.txt').CreationTime -lt (Get-Process -Id $PID).StartTime){Remove-Item .\LOG.txt}
 $allObjects | tee .\LOG.txt -Append
}
}
</code></pre>

Plus with the conversion to an advanced function you can just pipe things to it, such as:

<pre><code>Get-Process | Write-Host
</code></pre>

Or I suppose the simplest thing to do is just delete the log file as the first thing your script does.

I have a function to convert any <code>write-hosts</code> in the script (keeping them for coloring purposes later) to <code>tee</code> object

<pre><code>function Write-Host($object) 
{
 $object | tee .\LOG.txt -Append
}
</code></pre>

This currently appends to the file if it exists (or creates one if it doesnt)

i want to create one everytime a NEW session is started. only append to the file if you are in the same session

how do i do that?

Overwrite file if new session but append if same session

我有一个函数可以将脚本中的任何write-hosts (保留它们以便以后着色)转换为tee对象function Write-Host($object) {    $object | tee .\LOG.txt -Append}如果文件存在，则当前会将其附加到文件中(如果不存在，则创建一个文件)我想在每次启动新会话时创建...

问如果是新会话，则覆盖文件；如果是相同会话，则附加文件
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