PowerShell 字符串插值语法

Question

我总是使用以下语法来确保变量在字符串中展开：

"my string with a $($variable)"

我最近运行进入以下语法：

"my string with a ${variable}"

它们等价吗？有什么区别吗？

Answer 1

${variable} 是包含 特殊字符 .

的变量名称的语法

（参见 about_Variables -> 包含特殊字符的变量名 )

示例：

${var with spaces} = "value"
"var with spaces: ${var with spaces}"

所以在你的情况下，它基本上与简单地写 $variable

相同

Answer 2

补充：

${...}（将变量名括在{和}中）确实是如果变量名称包含 特殊字符 ，例如 空格、. 或 -，则总是 是必需的].

不特别的是_和-surprisingly and problematically-?.
注意：在 [=32= 的上下文中，: 总是被解释为终止 PowerShell 驱动器引用 ]代表所有环境变量）。

在字符串扩展（插值）的上下文中"..."，还有另一个 使用 ${...} 的原因，即使变量名称本身不需要它：

如果您需要从紧跟在非空白字符之后的变量名中区分出来，特别是包括::

$foo = 'bar'  # example variable

# INCORRECT: PowerShell assumes that the variable name is 'foobarian', not 'foo'
PS> "A $foobarian."
A .  # Variable $foobarian doesn't exist -> reference expanded to empty string.

# CORRECT: Use {...} to delineate the variable name:
PS> "A ${foo}barian."
A barbarian.

# INCORRECT: PowerShell assumes that 'foo:' is a *namespace* (drive) reference
#            (such as 'env:' in $env:PATH) and FAILS:
PS> "$foo: bar"
Variable reference is not valid. ':' was not followed by a valid variable name character. 
Consider using ${} to delimit the name.

# CORRECT: Use {...} to delineate the variable name:
PS> "${foo}: bar"
bar: bar

有关 PowerShell 字符串扩展规则的全面概述，请参阅 this answer。

请注意，在传递未加引号的参数[=71]的情况下，隐式应用字符串扩展时，您需要相同的技术=]到一个命令；例如：

# INCORRECT: The argument is treated as if it were enclosed in "...", # so the same rules apply. Write-Output $foo:/bar # CORRECT Write-Output ${foo}:/bar

最后，一个有点晦涩的替代方法是 `-转义变量名后的第一个字符，但问题是这仅适用于不属于 [=49= 的字符]转义序列（参见about_Special_Characters）：

# OK: because `: is not an escape sequence.
PS> "$foo`: bar"
bar: bar

# NOT OK, because `b is the escape sequence for a backspace character.
PS> "$foo`bar"
baar # The `b "ate" the trailing 'r' of the variable value
     # and only "ar" was the literal part.

PowerShell 字符串插值语法

PowerShell string interpolation syntax

powershell

syntax

string-interpolation