注意：此答案适用于Windows PowerShell；相比之下，在跨平台的PowerShell Core版本（v6 +）中，所有cmdlet 的默认编码是不带BOM的 UTF-8 。
换句话说：如果您使用的是PowerShell [Core]版本6或更高版本
，则默认情况下会获得无BOM的UTF-8文件（也可以使用-Encoding utf8/ 显式请求-Encoding utf8NoBOM，而使用 -BOM编码获得-utf8BOM）。
为了补充达德利（M. Dudley）自己简单而务实的答案（以及ForNeVeR更为简洁的表述））：
为了方便起见，这里的先进功能Out-FileUtf8NoBom，基于管道的替代，模仿Out-File，这意味着：
- 你可以像使用它
Out-File在管道中。
- 不是字符串的输入对象将被格式化，就像将它们发送到控制台一样
Out-File。
例：
(Get-Content $MyPath) | Out-FileUtf8NoBom $MyPath
请注意如何使用(Get-Content $MyPath)括起来(...)，以确保在通过管道发送结果之前，打开，完整读取和关闭整个文件。为了能够写回相同的内容，这是必需的文件（在适当位置更新它），。
但是，通常不建议使用此技术，原因有两个：（a）整个文件必须适合内存；（b）如果命令中断，数据将丢失。
关于的注释 内存使用的说明：
- M. Dudley自己的答案要求首先在内存中建立整个文件的内容，这对于大文件可能是有问题的。
- 下面的功能仅对此稍有改进：仍然首先缓冲所有输入对象，但随后生成它们的字符串表示形式并将其逐个写入输出文件。
的源代码Out-FileUtf8NoBom（也可作为MIT许可的Gist获得）：
<#
.SYNOPSIS
Outputs to a UTF-8-encoded file *without a BOM* (byte-order mark).
.DESCRIPTION
Mimics the most important aspects of Out-File:
* Input objects are sent to Out-String first.
* -Append allows you to append to an existing file, -NoClobber prevents
overwriting of an existing file.
* -Width allows you to specify the line width for the text representations
of input objects that aren't strings.
However, it is not a complete implementation of all Out-String parameters:
* Only a literal output path is supported, and only as a parameter.
* -Force is not supported.
Caveat: *All* pipeline input is buffered before writing output starts,
but the string representations are generated and written to the target
file one by one.
.NOTES
The raison d'être for this advanced function is that, as of PowerShell v5,
Out-File still lacks the ability to write UTF-8 files without a BOM:
using -Encoding UTF8 invariably prepends a BOM.
#>
function Out-FileUtf8NoBom {
[CmdletBinding()]
param(
[Parameter(Mandatory, Position=0)] [string] $LiteralPath,
[switch] $Append,
[switch] $NoClobber,
[AllowNull()] [int] $Width,
[Parameter(ValueFromPipeline)] $InputObject
)
#requires -version 3
# Make sure that the .NET framework sees the same working dir. as PS
# and resolve the input path to a full path.
[System.IO.Directory]::SetCurrentDirectory($PWD.ProviderPath) # Caveat: Older .NET Core versions don't support [Environment]::CurrentDirectory
$LiteralPath = [IO.Path]::GetFullPath($LiteralPath)
# If -NoClobber was specified, throw an exception if the target file already
# exists.
if ($NoClobber -and (Test-Path $LiteralPath)) {
Throw [IO.IOException] "The file '$LiteralPath' already exists."
}
# Create a StreamWriter object.
# Note that we take advantage of the fact that the StreamWriter class by default:
# - uses UTF-8 encoding
# - without a BOM.
$sw = New-Object IO.StreamWriter $LiteralPath, $Append
$htOutStringArgs = @{}
if ($Width) {
$htOutStringArgs += @{ Width = $Width }
}
# Note: By not using begin / process / end blocks, we're effectively running
# in the end block, which means that all pipeline input has already
# been collected in automatic variable $Input.
# We must use this approach, because using | Out-String individually
# in each iteration of a process block would format each input object
# with an indvidual header.
try {
$Input | Out-String -Stream @htOutStringArgs | % { $sw.WriteLine($_) }
} finally {
$sw.Dispose()
}
}