在命令行上设置公共属性值 [英] Setting Public Property Values on the Command Line

问题描述

在命令行上设置公共属性值 msi 遵循模式

MyInstaller.msi PUBLICPROPERTY="someValue"

这适用于命令提示符"又名 cmd.exe 和 powershell.

This works on "Command Prompt" aka cmd.exe and powershell.

但是

MyInstaller.msi PUBLICPROPERTY=""

在 powershell 中没有像预期的那样工作.我希望它将 PUBLICPROPERTY 设置为 null，但它将 PUBLICPROPERTY 设置为值 "CURRENTDIRECTORY="C:\temp\msi\""(它确实像 cmd.exe 预期的那样工作).

does not work like expected in powershell. I expected that it sets PUBLICPROPERTY to null but it sets PUBLICPROPERTY to the value "CURRENTDIRECTORY="C:\temp\msi\"" (it does work like expected with cmd.exe).

为什么 powershell 和 cmd.exe 的行为不同，如何解决?

Why do powershell and cmd.exe behaviour different, and how can it be fixed?

推荐答案

PowerShell，在必要的 Windows 上，在幕后对您的论点进行重新引用.

这种不可见的重新引用并不总是按预期工作，例如在这种情况下.

您可以通过调整引用来解决问题:

You can solve the problem by tweaking your quoting:

... PUBLICPROPERTY=`"`"  # `-escape the " chars.

... 'PUBLICPROPERTY=""'  # use enclosing '...', so " chars. can be used as-is

请注意，如果您想在参数中包含 PowerShell 变量/表达式的值，则使用 '...' 将不起作用.

Note that using '...' won't work if you want to include the values of PowerShell variables / expressions in the argument.

此外，在 PSv3+ 中，您可以使用 --%，停止解析符号，使 PowerShell 按原样传递剩余参数，就好像您从 cmd.exe/一个批处理文件(包括%OS%等环境变量引用的扩展).

Additionally, in PSv3+ you can use --%, the stop-parsing symbol, to make PowerShell pass the remaining arguments through as-is, as if you had called from cmd.exe / a batch file (including expansion of environment-variable references such as %OS%).

... --% PUBLICPROPERTY=""

同样，您将无法以这种方式在参数中引用 PowerShell 变量或表达式.

Again, you won't be able to reference PowerShell variables or expressions in the arguments that way.

至于没有上述技术会发生什么:

As for what happens without the techniques above:

• PUBLICPROPERTY="someValue" 变成
  PUBLICPROPERTY=someValue

PUBLICPROPERTY="some Value"，由于空格，变成
"PUBLICPROPERTY=some Value"，即整个参数都包含在"..."中.

PUBLICPROPERTY="some Value", due to whitespace, becomes
"PUBLICPROPERTY=some Value", i.e., the entire argument is enclosed in "...".

PowerShell-在内部诸如PUBLICPROPERTY="someValue"之类的参数的引号被去除:如果您将这样的参数传递给PowerShellcmdlet 或函数，它只会看到 PUBLICPROPERTY=someValue.

PowerShell-internally an argument such as PUBLICPROPERTY="someValue" has its quotes stripped: if you pass such an argument to a PowerShell cmdlet or function, it will see just PUBLICPROPERTY=someValue.

在将这样的值传递给外部程序时，PowerShell 会根据情况决定是否需要双引号，但该引用只会应用于整个参数 - " 字符的初始位置丢失.

On passing such a value on to an external program, PowerShell decides situationally whether double-quoting is needed, but that quoting is then only ever applied to the entire argument - the initial placement of the " chars. is lost.

因此，PUBLICPROPERTY="someValue" 变成了 PUBLICPROPERTY=someValue 并按原样传递，因为它包含没有嵌入空格，因此 PowerShell 不应用双引号.

Thus, PUBLICPROPERTY="someValue" turns into PUBLICPROPERTY=someValue and is passed on as-is, because it contains no embedded whitespace, so PowerShell applies no double-quoting.

相比之下，PUBLICPROPERTY="some Value" 变成了 PUBLICPROPERTY=some Value，作为 "PUBLICPROPERTY=some Value" 传递>，因为空格的存在需要双引号才能将值保留为单个参数.

By contrast, PUBLICPROPERTY="some Value" turns into PUBLICPROPERTY=some Value, which is passed on as "PUBLICPROPERTY=some Value", because the presence of whitespace requires double-quoting in order to preserve the value as a single argument.

请注意，PowerShell 只对传递给外部程序的参数应用双-引用，因为这是唯一可以假定所有人都能理解的引用样式程序.

Note that PowerShell only ever applies double-quoting to arguments passed to external programs, because that is the only style of quoting that can be assumed to be understood by all programs.

重新引用逻辑随着时间的推移发生了变化，并且具有令人遗憾的是，由于向后兼容性问题，这些错误仍然存​​在.

The re-quoting logic has changed over time and has bugs, which, regrettably, are here to stay due to backward compatibility concerns.

例如，'3 " of rain' 变成了 "3 " of rain"，它被破坏，因为嵌入" 缺少转义；解决方法是预测并明确执行 PowerShell 应该自动执行的操作:将嵌入的 " 转义为\" 为了外部程序的利益:'3 \" of rain'

E.g, '3 " of rain' becomes "3 " of rain", which is broken, because the embedded " lacks escaping; the workaround is to anticipate that and explicitly do what PowerShell should be doing automatically: escape the embedded " as \" for the benefit of the external program: '3 \" of rain'

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