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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