无法在 powershell 中使用 bcdedit filelds 进行编辑 - 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

为什么我不能在 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 中的以下命令:

For example, in cmd.exe the following command:

bcdedit /set {GUID} description "OS2"

成功完成，更改了指定 GUID 的描述字段，但是当我从 Powershell 执行相同操作时，出现以下错误:

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.

有人可以向我解释一下吗?

Can someone explain this to me?

推荐答案

将包含在 {...} 中的值作为 literal 传递(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，即具有特殊性的字符在 PowerShell 中不加引号的意思(它们包含一个 脚本块)，在这种情况下，这恰好导致 { 和 } 简单地获得 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`-转义未加引号的元字符单独:
bcdedit/set `{340E0E1A-01EC-4A33-A850-8D6A09FD4CE9`} 描述OS2"

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

自 PSv3 起可用的通用替代方案是使用所谓的停止解析符号，--%，按原样传递所有剩余参数，没有 PowerShell 的解释(除了扩展 %...% 封闭的环境变量引用):

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"

警告:虽然 --% 如果您的所有参数都是文字，则按预期工作，但在您的情况下，一般情况下它会阻止您使用 PowerShell 变量 和 表达式 作为参数中的/，并且可能会产生其他意外的副作用 - 请参阅这个答案.

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.

除非需要对 PowerShell 变量和表达式进行插值，否则 --% 允许按原样重复使用 cmd.exe 命令行，而无需担心PowerShell 的引用(转义)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(未加引号时具有特殊含义的字符)与 cmd.exe 不同，并且数量更多:

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:

( ) , { } ; @ $ # 

^{<、>、@ 和 # 仅在 开始令牌.
< 保留供未来使用，从 PowerShell 7.0 开始}

^{<, >, @ 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 %...%-enclosed 变量名(例如, %PATH%)，而 PowerShell 需要 $-prefixed 变量名(例如，$env:PATH 或$HOME) 或 $(...) 封闭表达式(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(以及在 PowerShell 中，还有子表达式扩展)也在 "..."(双引号字符串)中执行.

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

'...'(单引号字符串)是 PowerShell 中的 文字 字符串(内容按原样使用，没有插值)，而 ' 对 cmd.exe 没有特殊意义.

'...' (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.

要将元字符视为文字，您有两种选择:

To treat metacharacters as literals, you have two options:

• 将它们括在带引号的字符串中:

• Enclose them in quoted strings:

• cmd.exe 和 PowerShell:将它们包含在 "..." 中(但可能会插入任何变量引用/子表达式也包含在字符串中)；例如，"|".
• 仅限 PowerShell:将它们括在 '...' 中；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., '|'

逃避他们单独:

• PowerShell:`-转义它们(反引号)；例如，`|
  • 这也适用于 "..."，尽管它只需要转义 $ 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.
    • 这仅适用于 "..." 的外部，遗憾的是，它不适用于转义 % 以抑制变量扩展 -请参阅此答案了解完整故事.
    • 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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