PowerShell：CLI 调用的转义规则

发布于 2025-01-16 13:14:43 字数 1343 浏览 0 评论 0原文

据我所知，当使用 -Command 选项从 cmd.exe 调用 PowerShell 时，转义规则本质上是 Linux 中使用的规则。因此，您使用反斜杠 (\)，而不是通常的反引号 (`)。

这就是说，您不写：

C:\> powershell -c "echo `"That's a single quote: ' `""

而是

C:\> powershell -c "echo \"That's a single quote: ' \""

得到：

That's a single quote: '

这与您在 Linux 终端中键入的内容完全相同：

~ >>> bash -c "echo \"That's a single quote: ' \""

如果我没记错的话，此功能名为 PSNativeCommandArgumentPassing。但比较在一定程度上是有效的。事实上，在 Linux 下，你可以写：

~ >>> bash -c "echo \"That's a double quote: \\\" \""

得到：

That's a double quote: "

而等效的 PowerShell 行：

C:\> powershell -c "echo \"That's a double quote: \\\"  \""

给出

The string is missing the terminator: ".

通过反复试验，我意识到：

C:\> powershell -c "echo \"That's a double-quote: `""  \""

可以按预期工作。

你能向我解释一下`""背后的逻辑是什么吗？

另外，从 powershell.exe 而不是 cmd.exe 调用 PowerShell 时，等效命令是什么？

原文

As I have learned, when invoking PowerShell from cmd.exe, with the -Command option, escaping rules are essentially those used in Linux. So you use a backslash (\), rather than the usual backtick (`).

This is to say that you don't write:

C:\> powershell -c "echo `"That's a single quote: ' `""

but

C:\> powershell -c "echo \"That's a single quote: ' \""

to get:

That's a single quote: '

And this is the exact equivalent of what you would type in a Linux terminal:

~ >>> bash -c "echo \"That's a single quote: ' \""

If I am not wrong, this feature is named PSNativeCommandArgumentPassing.
But comparisons work up to a certain point. In fact, under Linux you write:

~ >>> bash -c "echo \"That's a double quote: \\\" \""

to get:

That's a double quote: "

while the equivalent PowerShell line:

C:\> powershell -c "echo \"That's a double quote: \\\"  \""

gives

The string is missing the terminator: ".

By trial and error, I realised that:

C:\> powershell -c "echo \"That's a double-quote: `""  \""

works as expected.

Can you explain to me what is the logic behind: `""?

Also, what are the equivalent commands when calling PowerShell from powershell.exe, rather than cmd.exe?

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夏至、离别 2025-01-23 13:14:43

tl;dr

仅在 PowerShell 的命令行上，使用 \" 将 " 传递到-c (-Command) 应该执行的代码。
- 只有在生成的代码中，PowerShell 通常将 " 转义为 `" 才适用，因此您可能必须组合两种转义技术：`\".
  - 您的尝试，`""，具有相同的效果，但它不可靠。^[1]
- \" 对于 PowerShell 自身的命令行解析来说，工作稳健，但可能会根据情况中断 cmd.exe 端的调用 /em> - 请参阅底部部分以获取解决方法。
从 PowerShell 调用 CLI（外部控制台应用程序）时，不仅会首先应用 PowerShell 自己的不同引用规则（支持 '...' 代码> 字符串，嵌入" 内的 "..." 转义为 `")，这是 PowerShell 7.2.x 之前长期存在的错误另外< /em> 需要转义 " 字符。当嵌入外部程序参数时使用 \ （仅）；请参阅此答案。

此功能名为PSNativeCommandArgumentPassing

否；此功能 - 在 PowerShell 7.3 中成为正式功能（请参阅此答案） - 不会出现玩，因为：

它通常在您通过其 CLI 调用的旧版 Windows PowerShell 版本中不可用，powershell.exe （而现代的跨平台 PowerShell（核心） 版本的 CLI 是 pwsh.exe)
它仅适用于来自 PowerShell 会话内部的调用。
它旨在解决从 PowerShell 调用带有嵌入式 " 或空字符串参数的外部程序时长期存在的问题 - 请参阅这个答案。
- 因此，链接的答案解决了您的最后问题：
  - <块引用>
    此外，从 powershell.exe（而不是 cmd.exe）调用 PowerShell 时的等效命令是什么？
- 简而言之：不幸的是，至少在 PowerShell 7.2.x 之前，您必须另外手动使用 " 转义 " 字符。 嵌入外部程序参数（仅）。

为什么以下内容在 cmd.exe 中有效：

powershell -c "echo \"That's a single quote: ' \""

PowerShell 仅将 \ 识别为其命令行上的转义字符，< /strong> 与其他 CLI 保持一致。
在 PowerShell 会话内，只有 `（反引号）用作转义字符。
警告：虽然 \" 转义 " 在两个 PowerShell 版本中均一致 >在PowerShell（命令行解析）方面，在某些情况下它可能会破坏cmd.exe自己的解析 - 请参阅底部部分。
当通过以下方式调用 PowerShell CLI 时-c (-Command) 并执行一段 PowerShell 源代码，该代码（-c 后面的参数）被解析分两个阶段：
- 首先，所有未转义的 " 字符都被剥离，其中转义的 (\"）被保留且未转义。
- 只有然后才是解析结果并作为PowerShell代码执行。

因此，PowerShell 最终执行的是逐字记录：

echo "That's a single quote: ' "

从上面可以看出为什么这不起作用：

:: SYNTAX ERROR
powershell -c "echo \"That's a double quote: \\\"  \""

PowerShell最终尝试逐字执行，

echo "That's a double quote: \" "

这是一个语法错误，因为在PowerShell内部会话 \不转义 " -仅 `" 或 - 在 "..." 内，或者 - "" 。

从上面可以看出为什么这（大部分）有效：

:: Works, but not robustly
powershell -nop -c "echo \"That's a double-quote: `""  \""

""有时，但并不总是作为 \";^[1] 这里就是这样 - 另见底部部分。
结果，PowerShell 最终逐字执行以下命令，该命令有效，因为传递的转义 " 现在是 `-转义，因为它需要位于 PowerShell 内“...”字符串：
```
 echo "这是一个双引号：`" "
```

为了避免脆弱的 "" 转义，最好通过组合所需的 ` 来制定此命令 -使用命令行转义\-转义 - 即 `\" - 但请参阅底部部分以获得完全可靠的解决方案：

powershell -nop -c "echo \"That's a double-quote: `\"  \""

避免 cmd 上的解析问题。 exe端，\"的安全替代品：

而\"转义" 在两个 PowerShell 版本上一致地工作 PowerShell（命令行解析）端，在某些情况下它可以破坏cmd.exe自己的解析相比之下，使用。从任务计划程序等无 shell 环境调用时，\" 是安全的。

虽然有解决方法，但不幸的是，它们是 PowerShell 特定版本：

在 Windows PowerShell 中 (powershell.exe)
使用"^""（原文如此）代替\"
在PowerShell（核心）中（v6+，pwsh.exe）
- 使用 "" 代替 \"

重要提示：

< p>这些解决方法要求将整个代码传递给-c（-Command) 作为单个，“...” - 封闭参数。
-c (-Command) 还接受多个参数 - 可以单独用双引号引起来或not - 在这种情况下，它只是在剥离未转义的 " 之后连接这些参数，以形成要执行的代码。这种技术在某些情况下允许您摆脱 \"-逃脱（例如， powershell -c \"Between 2 & 3`\"\"，但是(a)它需要你密切关注命令cmd.exe的哪些部分将显示为未加引号，(b) 需要您 ^ 转义任何 cmd.exe 元字符，例如 &，以及 (c)总是执行空白规范化，即将多个空格折叠成每个空格。

以下调用旨在逐字打印 Between 2 &，演示一下：

:: BREAKS, because cmd.exe sees `&` as *outside a double-quoted string*
powershell -c " \" Between 2 & 3`\" \" "

:: PowerShell (Core) workaround
pwsh -c " "" Between 2 & 3`"" "" "

:: Windows PowerShell workaround
powershell -c " "^"" Between 2 & 3`"^"" "^"" "

^{[1] "" 位于 "..." 内的示例不存在工作是powershell -c "echo \" Nat `""King`"" Cole \""：它打印 Nat "King"，而不是 Nat "King" Cole Cole，即第二个转义的 " 丢失（但是，它在 pwsh.exe 中可以正常工作，正如底部部分所述）。最终不值得猜测 powershell.exe -c 如何准确地解析嵌入的 "" 序列，因为它显然不可靠，并且确实存在可靠的替代方案（\" 或者，来自 cmd.exe，也可 "^""）。}

tl;dr

On PowerShell's command line only, use \" to pass a " through to the code that -c (-Command) should execute.
- Only in the resulting code does PowerShell's usual escaping of " as `" apply, so you may have to combine the two escaping techniques: `\".
  - Your attempt, `"", had the same effect, but it doesn't work reliably.^[1]
- \" works robustly with respect to PowerShell's own parsing of its command line, but can situationally break calls on the cmd.exe side - see the bottom section for workarounds.
When calling CLIs (external console applications) from PowerShell, not only do PowerShell's own, different quoting rules apply first (support for '...' strings, embedded " inside "..." escaped as `"), a long-standing bug up to PowerShell 7.2.x additionally requires escaping " chars. with \ when embedded in external-program arguments (only); see this answer.

this feature is named PSNativeCommandArgumentPassing

No; this feature - which became official in PowerShell 7.3 (see this answer) - does not come into play, because:

it generally isn't (and won't be) available in the legacy Windows PowerShell edition that you're invoking via its CLI, powershell.exe (whereas the modern, cross-platform PowerShell (Core) edition's CLI is pwsh.exe)
it only applies to calls from inside a PowerShell session.
it is designed to address a long-standing problem when calling external programs with embedded " or empty-string string arguments from PowerShell - see this answer.
- Therefore, the linked answer addresses your last question:
  - Also, what are the equivalent commands when calling PowerShell from powershell.exe, rather than cmd.exe?
- In short: unfortunately, up to at least PowerShell 7.2.x you'll have to additionally, manually escape " chars. with " embedded in external-program arguments (only).

Why the following works from cmd.exe:

powershell -c "echo \"That's a single quote: ' \""

PowerShell only recognizes \ as an escape character on its command line, for consistency with other CLIs.
- Inside a PowerShell session, only ` (backtick) serves as the escape character.
- Caveat: While \" to escape " works consistently in both PowerShell editions on the PowerShell (command-line parsing) side, situationally it can break cmd.exe's own parsing - see the bottom section.
When the PowerShell CLI is invoke via -c (-Command) with a piece of PowerShell source code to execute, that code (the argument(s) following -c is parsed in two stages:
- First, all unescaped " chars. are stripped, wheres escaped ones (\") are kept and unescaped.
- Only then is the result parsed and execute as PowerShell code.

Therefore, what PowerShell ends up executing is verbatim:

echo "That's a single quote: ' "

From the above follows why this does not work:

:: SYNTAX ERROR
powershell -c "echo \"That's a double quote: \\\"  \""

PowerShell ends up trying to execute verbatim

echo "That's a double quote: \" "

which is a syntax error, because inside a PowerShell session \ doesn't escape " -only `" or - inside "...", alternatively - "" do.

From the above follows why this (mostly) works:

:: Works, but not robustly
powershell -nop -c "echo \"That's a double-quote: `""  \""

"" sometimes, but not always works as an alternative to \";^[1] here it does - see also the bottom section.
As a result, PowerShell ends up executing the following verbatim, which works, because the escaped " that was passed through is now `-escaped, as it needs to be inside a PowerShell "..." string:
```
 echo "That's a double-quote: `"  "
```

To avoid the brittle "" escaping, it is better to formulate this command by combining the required `-escaping with the command-line \-escaping - i.e. `\" - but see the bottom section for a fully robust solution:

powershell -nop -c "echo \"That's a double-quote: `\"  \""

Avoiding parsing problems on the cmd.exe side, a safe alternative to \":

While \" to escape " works consistently in both PowerShell editions on the PowerShell (command-line parsing) side, situationally it can break cmd.exe's own parsing. By contrast, using \" is safe when calling from no-shell environments such as Task Scheduler.

While there are workarounds, they are, unfortunately PowerShell edition-specific:

In Windows PowerShell (powershell.exe)
- Use "^"" (sic) instead of \"
In PowerShell (Core) (v6+, pwsh.exe)
- Use "" instead of \"

Important:

These workarounds require that the whole code to pass to -c (-Command) be passed as a single, "..."-enclosed argument.
-c (-Command) also accepts multiple arguments - which may individually be double-quoted or not - in which case it simply concatenates these arguments, after having stripped unescaped ", to form the code to execute. This technique situationally allows you to get away with \"-escaping (e.g., powershell -c \"Between 2 & 3`\"\", but (a) it requires you to pay close attention to which parts of the command cmd.exe will see as unquoted, (b) would require you to ^-escape any cmd.exe metacharacters such as & in those parts, and (c) invariably performs whitespace normalization, i.e. folds runs of multiple spaces into a single one each.

The following calls, designed to print verbatim Between 2 & 3" , demonstrate this:

:: BREAKS, because cmd.exe sees `&` as *outside a double-quoted string*
powershell -c " \" Between 2 & 3`\" \" "

:: PowerShell (Core) workaround
pwsh -c " "" Between 2 & 3`"" "" "

:: Windows PowerShell workaround
powershell -c " "^"" Between 2 & 3`"^"" "^"" "

^{[1] An example of where "" inside "..." doesn't work is powershell -c "echo \" Nat `""King`"" Cole \"": instead of Nat "King" Cole, it prints Nat "King Cole, i.e. the second escaped " is missing (it would work fine in pwsh.exe, however, as discussed in the bottom section). It's ultimately not worth speculating how, precisely, embedded "" sequences are parsed by powershell.exe -c, given that it demonstrably isn't reliable and that reliable alternatives do exist (\" or, from cmd.exe, also "^"").}