Out-File似乎在使用UTF-8时强制BOM:
$MyFile = Get-Content $MyPath
$MyFile | Out-File -Encoding "UTF8" $MyPath
我怎么能写一个文件在UTF-8没有BOM使用PowerShell?
更新2021
自从10年前我写这个问题以来，PowerShell已经发生了一些变化。检查下面的多个答案，它们有很多有用的信息!
当前回答
注意:这个答案适用于Windows PowerShell;相比之下，在跨平台的PowerShell核心版(v6+)中，在所有cmdlet中，不含BOM的UTF-8是默认编码。
换句话说:如果您使用PowerShell [Core]版本6或更高版本，默认情况下您将获得无bom的UTF-8文件(您也可以显式地使用-Encoding utf8 / -Encoding utf8NoBOM请求，而使用-utf8BOM获得- bom编码)。 如果你正在运行Windows 10，并且你愿意在系统范围内切换到无bom的UTF-8编码——这可能会有副作用——甚至Windows PowerShell也可以一直使用无bom的UTF-8编码——请看这个答案。
为了补充M. Dudley自己简单而务实的回答(以及ForNeVeR更简洁的重新表述):
A simple, (non-streaming) PowerShell-native alternative is to use New-Item, which (curiously) creates BOM-less UTF-8 files by default even in Windows PowerShell: # Note the use of -Raw to read the file as a whole. # Unlike with Set-Content / Out-File *no* trailing newline is appended. $null = New-Item -Force $MyPath -Value (Get-Content -Raw $MyPath) Note: To save the output from arbitrary commands in the same format as Out-File would, pipe to Out-String first; e.g.: $null = New-Item -Force Out.txt -Value (Get-ChildItem | Out-String) For convenience, below is advanced function Out-FileUtf8NoBom, a pipeline-based alternative that mimics Out-File, which means: you can use it just like Out-File in a pipeline. input objects that aren't strings are formatted as they would be if you sent them to the console, just like with Out-File. an additional -UseLF switch allows you use Unix-format LF-only newlines ("`n") instead of the Windows-format CRLF newlines ("`r`n") you normally get.
例子:
(Get-Content $MyPath) | Out-FileUtf8NoBom $MyPath # Add -UseLF for Unix newlines
注意(Get-Content $MyPath)是如何包含在(…)中，这确保在通过管道发送结果之前打开、完整读取和关闭整个文件。为了能够写回相同的文件(在适当的位置更新它)，这是必要的。 一般来说，这种技术是不可取的，原因有二:(a)整个文件必须适合内存;(b)如果命令被中断，数据将丢失。
内存使用注意事项:
达德利先生自己的回答 和上面的New-Item替代方案要求首先在内存中构建整个文件内容，这对于大的输入集可能是个问题。 下面的函数不需要这样做，因为它是作为一个代理(包装器)函数实现的(关于如何定义这样的函数的简明摘要，请参阅这个答案)。
Out-FileUtf8NoBom函数源代码:
注意:该功能也可以作为麻省理工学院授权的Gist使用，并且今后只会维护它。
你可以直接使用以下命令安装它(虽然我个人可以向你保证这样做是安全的，但在直接执行脚本之前，你应该总是检查脚本的内容):
# Download and define the function.
irm https://gist.github.com/mklement0/8689b9b5123a9ba11df7214f82a673be/raw/Out-FileUtf8NoBom.ps1 | iex
function Out-FileUtf8NoBom {
<#
.SYNOPSIS
Outputs to a UTF-8-encoded file *without a BOM* (byte-order mark).
.DESCRIPTION
Mimics the most important aspects of Out-File:
* Input objects are sent to Out-String first.
* -Append allows you to append to an existing file, -NoClobber prevents
overwriting of an existing file.
* -Width allows you to specify the line width for the text representations
of input objects that aren't strings.
However, it is not a complete implementation of all Out-File parameters:
* Only a literal output path is supported, and only as a parameter.
* -Force is not supported.
* Conversely, an extra -UseLF switch is supported for using LF-only newlines.
.NOTES
The raison d'être for this advanced function is that Windows PowerShell
lacks the ability to write UTF-8 files without a BOM: using -Encoding UTF8
invariably prepends a BOM.
Copyright (c) 2017, 2022 Michael Klement <mklement0@gmail.com> (http://same2u.net),
released under the [MIT license](https://spdx.org/licenses/MIT#licenseText).
#>
[CmdletBinding(PositionalBinding=$false)]
param(
[Parameter(Mandatory, Position = 0)] [string] $LiteralPath,
[switch] $Append,
[switch] $NoClobber,
[AllowNull()] [int] $Width,
[switch] $UseLF,
[Parameter(ValueFromPipeline)] $InputObject
)
begin {
# Convert the input path to a full one, since .NET's working dir. usually
# differs from PowerShell's.
$dir = Split-Path -LiteralPath $LiteralPath
if ($dir) { $dir = Convert-Path -ErrorAction Stop -LiteralPath $dir } else { $dir = $pwd.ProviderPath }
$LiteralPath = [IO.Path]::Combine($dir, [IO.Path]::GetFileName($LiteralPath))
# If -NoClobber was specified, throw an exception if the target file already
# exists.
if ($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 System.IO.StreamWriter $LiteralPath, $Append
$htOutStringArgs = @{}
if ($Width) { $htOutStringArgs += @{ Width = $Width } }
try {
# Create the script block with the command to use in the steppable pipeline.
$scriptCmd = {
& Microsoft.PowerShell.Utility\Out-String -Stream @htOutStringArgs |
. { process { if ($UseLF) { $sw.Write(($_ + "`n")) } else { $sw.WriteLine($_) } } }
}
$steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
$steppablePipeline.Begin($PSCmdlet)
}
catch { throw }
}
process
{
$steppablePipeline.Process($_)
}
end {
$steppablePipeline.End()
$sw.Dispose()
}
}
其他回答
这是为我工作(使用“默认”而不是“UTF8”):
$MyFile = Get-Content $MyPath
$MyFile | Out-File -Encoding "Default" $MyPath
结果是没有BOM的ASCII。
[System.IO.FileInfo] $file = Get-Item -Path $FilePath
$sequenceBOM = New-Object System.Byte[] 3
$reader = $file.OpenRead()
$bytesRead = $reader.Read($sequenceBOM, 0, 3)
$reader.Dispose()
#A UTF-8+BOM string will start with the three following bytes. Hex: 0xEF0xBB0xBF, Decimal: 239 187 191
if ($bytesRead -eq 3 -and $sequenceBOM[0] -eq 239 -and $sequenceBOM[1] -eq 187 -and $sequenceBOM[2] -eq 191)
{
$utf8NoBomEncoding = New-Object System.Text.UTF8Encoding($False)
[System.IO.File]::WriteAllLines($FilePath, (Get-Content $FilePath), $utf8NoBomEncoding)
Write-Host "Remove UTF-8 BOM successfully"
}
Else
{
Write-Warning "Not UTF-8 BOM file"
}
如何使用PowerShell从文件中删除UTF8字节顺序标记(BOM)
注意:这个答案适用于Windows PowerShell;相比之下，在跨平台的PowerShell核心版(v6+)中，在所有cmdlet中，不含BOM的UTF-8是默认编码。
换句话说:如果您使用PowerShell [Core]版本6或更高版本，默认情况下您将获得无bom的UTF-8文件(您也可以显式地使用-Encoding utf8 / -Encoding utf8NoBOM请求，而使用-utf8BOM获得- bom编码)。 如果你正在运行Windows 10，并且你愿意在系统范围内切换到无bom的UTF-8编码——这可能会有副作用——甚至Windows PowerShell也可以一直使用无bom的UTF-8编码——请看这个答案。
为了补充M. Dudley自己简单而务实的回答(以及ForNeVeR更简洁的重新表述):
A simple, (non-streaming) PowerShell-native alternative is to use New-Item, which (curiously) creates BOM-less UTF-8 files by default even in Windows PowerShell: # Note the use of -Raw to read the file as a whole. # Unlike with Set-Content / Out-File *no* trailing newline is appended. $null = New-Item -Force $MyPath -Value (Get-Content -Raw $MyPath) Note: To save the output from arbitrary commands in the same format as Out-File would, pipe to Out-String first; e.g.: $null = New-Item -Force Out.txt -Value (Get-ChildItem | Out-String) For convenience, below is advanced function Out-FileUtf8NoBom, a pipeline-based alternative that mimics Out-File, which means: you can use it just like Out-File in a pipeline. input objects that aren't strings are formatted as they would be if you sent them to the console, just like with Out-File. an additional -UseLF switch allows you use Unix-format LF-only newlines ("`n") instead of the Windows-format CRLF newlines ("`r`n") you normally get.
例子:
(Get-Content $MyPath) | Out-FileUtf8NoBom $MyPath # Add -UseLF for Unix newlines
注意(Get-Content $MyPath)是如何包含在(…)中，这确保在通过管道发送结果之前打开、完整读取和关闭整个文件。为了能够写回相同的文件(在适当的位置更新它)，这是必要的。 一般来说，这种技术是不可取的，原因有二:(a)整个文件必须适合内存;(b)如果命令被中断，数据将丢失。
内存使用注意事项:
达德利先生自己的回答 和上面的New-Item替代方案要求首先在内存中构建整个文件内容，这对于大的输入集可能是个问题。 下面的函数不需要这样做，因为它是作为一个代理(包装器)函数实现的(关于如何定义这样的函数的简明摘要，请参阅这个答案)。
Out-FileUtf8NoBom函数源代码:
注意:该功能也可以作为麻省理工学院授权的Gist使用，并且今后只会维护它。
你可以直接使用以下命令安装它(虽然我个人可以向你保证这样做是安全的，但在直接执行脚本之前，你应该总是检查脚本的内容):
# Download and define the function.
irm https://gist.github.com/mklement0/8689b9b5123a9ba11df7214f82a673be/raw/Out-FileUtf8NoBom.ps1 | iex
function Out-FileUtf8NoBom {
<#
.SYNOPSIS
Outputs to a UTF-8-encoded file *without a BOM* (byte-order mark).
.DESCRIPTION
Mimics the most important aspects of Out-File:
* Input objects are sent to Out-String first.
* -Append allows you to append to an existing file, -NoClobber prevents
overwriting of an existing file.
* -Width allows you to specify the line width for the text representations
of input objects that aren't strings.
However, it is not a complete implementation of all Out-File parameters:
* Only a literal output path is supported, and only as a parameter.
* -Force is not supported.
* Conversely, an extra -UseLF switch is supported for using LF-only newlines.
.NOTES
The raison d'être for this advanced function is that Windows PowerShell
lacks the ability to write UTF-8 files without a BOM: using -Encoding UTF8
invariably prepends a BOM.
Copyright (c) 2017, 2022 Michael Klement <mklement0@gmail.com> (http://same2u.net),
released under the [MIT license](https://spdx.org/licenses/MIT#licenseText).
#>
[CmdletBinding(PositionalBinding=$false)]
param(
[Parameter(Mandatory, Position = 0)] [string] $LiteralPath,
[switch] $Append,
[switch] $NoClobber,
[AllowNull()] [int] $Width,
[switch] $UseLF,
[Parameter(ValueFromPipeline)] $InputObject
)
begin {
# Convert the input path to a full one, since .NET's working dir. usually
# differs from PowerShell's.
$dir = Split-Path -LiteralPath $LiteralPath
if ($dir) { $dir = Convert-Path -ErrorAction Stop -LiteralPath $dir } else { $dir = $pwd.ProviderPath }
$LiteralPath = [IO.Path]::Combine($dir, [IO.Path]::GetFileName($LiteralPath))
# If -NoClobber was specified, throw an exception if the target file already
# exists.
if ($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 System.IO.StreamWriter $LiteralPath, $Append
$htOutStringArgs = @{}
if ($Width) { $htOutStringArgs += @{ Width = $Width } }
try {
# Create the script block with the command to use in the steppable pipeline.
$scriptCmd = {
& Microsoft.PowerShell.Utility\Out-String -Stream @htOutStringArgs |
. { process { if ($UseLF) { $sw.Write(($_ + "`n")) } else { $sw.WriteLine($_) } } }
}
$steppablePipeline = $scriptCmd.GetSteppablePipeline($myInvocation.CommandOrigin)
$steppablePipeline.Begin($PSCmdlet)
}
catch { throw }
}
process
{
$steppablePipeline.Process($_)
}
end {
$steppablePipeline.End()
$sw.Dispose()
}
}
可以使用下面得到UTF8没有BOM
$MyFile | Out-File -Encoding ASCII
对于PowerShell 5.1，启用此设置:
控制面板，区域，管理，更改系统区域，使用Unicode UTF-8 全球语言支持
然后输入PowerShell:
$PSDefaultParameterValues['*:Encoding'] = 'Default'
或者，您可以升级到PowerShell 6或更高版本。
https://github.com/PowerShell/PowerShell
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