如何在PowerShell中正确/全局设置UTF-8(无BOM)文件? [英] How to cat a UTF-8 (no BOM) file properly/globally in PowerShell?

问题描述

创建文件utf8.txt.确保编码为UTF-8(无BOM).将其内容设置为€

在cmd.exe中:

type utf8.txt > out.txt

out.txt的内容为€

在PowerShell(v4)中:

cat .\utf8.txt > out.txt

或

type .\utf8.txt > out.txt

Out.txt的内容是€

如何全局使PowerShell正常工作?

解决方案

注意:此答案是关于 Windows PowerShell (最高v5.1)的； PowerShell [em，v6 +] ，PowerShell的跨平台版本，现在幸运地默认为无BOM UTF-8 输入和输出.

---

Windows PowerShell，与基础.NET框架不同 ^[1] ，则使用以下默认值:

输入 上的

• :不带BOM(字节顺序标记)的文件假定位于系统的 默认编码，即 旧版 单字节编码，通过控制面板配置).

• 在 output 上:默认情况下，>和>>重定向操作符会生成 UTF-16 LE 文件(其中确实有-并且需要-BOM).

消耗文件并生成的cmdlet通常支持-Encoding参数，该参数使您可以显式指定编码.
在PowerShell v5.1之前，显式使用基础Out-File cmdlet是更改编码的唯一方法.
在 PowerShell v5.1 + 中，>和>>成为Out-File的有效别名，允许您通过$PSDefaultParameterValues首选项更改>和>>的编码行为.多变的;例如:
$PSDefaultParameterValues['Out-File:Encoding'] = 'utf8'.

为使PowerShell能够正确处理UTF-8，必须将其同时指定为输入和输出编码 ^[2] ，但请注意，在输出上，PowerShell 始终会向UTF-8文件添加BOM.

应用于您的示例:

Get-Content -Encoding utf8 .\utf8.txt | Out-File -Encoding utf8 out.txt

要在PowerShell中创建没有 BOM 的UTF-8文件，请参见此答案我的.

---

^{[1]默认情况下，.NET框架使用(无BOM)UTF-8进行输入和输出.
PowerShell和建立在其上的.NET框架之间的这种有意的行为差异是不寻常.}

^{[2] Get-Content确实会自动识别带有BOM的 的UTF-8文件.}

Create a file utf8.txt. Ensure the encoding is UTF-8 (no BOM). Set its content to €

In cmd.exe:

type utf8.txt > out.txt

Content of out.txt is €

In PowerShell (v4):

cat .\utf8.txt > out.txt

or

type .\utf8.txt > out.txt

Out.txt content is €

How do I globally make PowerShell work correctly?

解决方案

Note: This answer is about Windows PowerShell (up to v5.1); PowerShell [Core, v6+], the cross-platform edition of PowerShell, now fortunately defaults to BOM-less UTF-8 on both in- and output.

---

Windows PowerShell, unlike the underlying .NET framework^[1] , uses the following defaults:

• on input: files without a BOM (byte-order mark) are assumed to be in the system's default encoding, which is the legacy Windows code page ("ANSI" code page: the active, culture-specific single-byte encoding, as configured via Control Panel).

• on output: the > and >> redirection operators produce UTF-16 LE files by default (which do have - and need - a BOM).

File-consuming and -producing cmdlets do usually support an -Encoding parameter that lets you specify the encoding explicitly.
Prior to PowerShell v5.1, using the underlying Out-File cmdlet explicitly was the only way to change the encoding.
In PowerShell v5.1+, > and >> became effective aliases of Out-File, allowing you to change the encoding behavior of > and >> via the $PSDefaultParameterValues preference variable; e.g.:
$PSDefaultParameterValues['Out-File:Encoding'] = 'utf8'.

For PowerShell to handle UTF-8 properly, you must specify it as both the input and output encoding^[2] , but note that on output, PowerShell invariably adds a BOM to UTF-8 files.

Applied to your example:

Get-Content -Encoding utf8 .\utf8.txt | Out-File -Encoding utf8 out.txt

To create a UTF-8 file without a BOM in PowerShell, see this answer of mine.

---

^{[1] The .NET framework uses (BOM-less) UTF-8 by default, both for in- and output.
This - intentional - difference in behavior between PowerShell and the .NET framework it is built on is unusual.}

^{[2] Get-Content does, however, automatically recognize UTF-8 files with a BOM.}

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