无法在Powershell中使用bcdedit filelds编辑-cmd.exe命令行失败 [英] Unable to edit with bcdedit filelds in powershell - cmd.exe command line fails

问题描述

为什么不能在PowerShell中使用 bcdedit 编辑描述字段？

Why can't I edit the description field using bcdedit in PowerShell?

例如，在 cmd.exe 以下命令：

bcdedit /set {GUID} description "OS2"

成功完成，更改了指定GUID的描述字段，但是当我执行相同操作时Powershell发生错误，我得到以下错误：

completes successfully, changing the description field for the specified GUID, but when I do the same thing from Powershell, I get the following error:

The set command specified is not valid.
Run "bcdedit /?" for command line assistance.
The parameter is incorrect.

有人可以向我解释吗？

推荐答案

要传递包含在 {...} 中的值作为 literal （如-is）在PowerShell中，您必须引用它；例如：

To pass a value enclosed in {...} as a literal (as-is) in PowerShell, you must quote it; e.g.:

bcdedit /set "{340E0E1A-01EC-4A33-A850-8D6A09FD4CE9}" description "OS2"

{和} 与 cmd.exe 不同，它们是元字符，即在PowerShell中使用无引号时具有特殊含义的字符（它们包含一个 script块），在这种情况下恰好导致 {和} 已删除。

引用可以防止这种情况。

{ and }, unlike in cmd.exe, are metacharacters, i.e., characters that have special meaning in PowerShell when used unquoted (they enclose a script block), which in this case happens to result in { and } simply getting removed.
Quoting prevents that.

或者，您可以 `-分别转义未引号的元字符 ：

bcdedit / set`{340E0E1A -01EC-4A33-A850-8D6A09FD4CE9`}说明 OS2

Alternatively, you can `-escape the unquoted metacharacters individually:
bcdedit /set `{340E0E1A-01EC-4A33-A850-8D6A09FD4CE9`} description "OS2"

一个通用替代版本，自PSv3起可用 ，就是使用所谓的 停止解析符号，-％ ，w hich照原样传递所有剩余参数，无需PowerShell解释（扩展％...％-封闭的环境变量引用除外）：

A generic alternative, available since PSv3, is to use the so-called stop-parsing symbol, --%, which passes all remaining arguments as-is, without interpretation by PowerShell (with the exception of expanding %...%-enclosed environment-variable references):

bcdedit --% /set {340E0E1A-01EC-4A33-A850-8D6A09FD4CE9} description "OS2"

注意：虽然-％可以按预期工作您的参数是文字，就像您遇到的情况一样，通常会阻止您将 PowerShell变量和表达式用作/在参数中，并且可能会有其他意外副作用-请参见此答案。

Caveat: While --% works as expected if all your arguments are literals, as in your case, in general it prevents you from using PowerShell variables and expressions as / in arguments, and can have other unexpected side effects - see this answer.

除非需要内插PowerShell变量和表达式， -％允许按原样重用 cmd.exe 命令行，而不必担心PowerShell的报价（escapi ng）要求。

Unless interpolation of PowerShell variables and expression is needed, --% allows reuse of cmd.exe command lines as-is, without having to worry about PowerShell's quoting (escaping) requirements.

通常， PowerShell的元字符（未引用时具有特殊含义的字符）与 cmd.exe 和更多：

Generally, PowerShell's metacharacters (characters that have special meaning when unquoted) are different from cmd.exe's and much more numerous:

除了 cmd.exe 的元字符。

& | < >

PowerShell具有：

PowerShell has:

( ) , { } ; @ $ # 

<sup>< ，> ， @ 和＃仅具有特殊含义在令牌的开始中。

< 保留供未来使用，例如PowerShell 7.0的</sup>

^{<, >, @ and # only have special meaning at the start of a token.
< is reserved for future use, as of PowerShell 7.0}

除此之外，关于变量扩展（插值）：

• cmd.exe 仅扩展 ％...％括起来的变量名（例如，％PATH％），而 PowerShell要求 $ 前缀的变量名（例如 $ env：PATH 或 $ HOME ）或 $（...）括起来的表达式（子表达式运算符）

• cmd.exe only expands %...%-enclosed variable names (e.g., %PATH%), whereas PowerShell requires $-prefixed variable names (e.g., $env:PATH or $HOME) or $(...)-enclosed expressions (subexpression operator)

• 在两个解释器中，变量扩展（在PowerShell中还包括子表达式扩展）也在 ... （双引号字符串）内执行

• In both interpreters, variable expansion (and, in PowerShell, also subexpression expansion) is also performed inside "..." (double-quoted strings).

'...'（单用引号括起来的字符串）是PowerShell中的文字字符串（内容按原样使用，不带插值），而'对<$没有特殊含义完全是c $ c> cmd.exe 。

'...' (single-quoted strings) are literal strings in PowerShell (contents is used as-is, without interpolation), whereas ' has no special meaning to cmd.exe at all.

要处理元字符作为 literals ，您有两个选择：

To treat metacharacters as literals, you have two options:

• 带引号的字符串 ：

• Enclose them in quoted strings:

• 两个 cmd.exe 和PowerShell：将它们包含在 ... 中（但可能还会对字符串中包含的任何变量引用/子表达式进行插值）；例如， | 。


• 仅PowerShell：将它们包含在'...';例如，'|'



• Both cmd.exe and PowerShell: enclose them in "..." (but potentially with interpolation of any variable references / subexpressions also enclosed in the string); e.g., "|".
• PowerShell only: enclose them in '...'; e.g., '|'

转义它们单独 ：

Escape them individually:



• PowerShell：` -逃避他们（反引号）；例如，`|
  
  
  
  
  • 这在内也有效 ... ，尽管只有需要来转义 $ 以防止变量/子表达式扩展。
  
  
  • PowerShell: `-escape them (backtick); e.g., `|
    • This also works inside "...", although there it is only needed to escape $ so as to prevent variable / subexpression expansion.
    

    • 这仅对<$ c的外部有效$ c> ... ，可悲的是，它不能转义％来抑制变量扩展-请参见完整答案的答案。
    
    
    • This only works outside of "...", and sadly, doesn't work for escaping % to suppress variable expansion - see this answer for the full story.

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