PowerShell 范围标识符 [英] PowerShell Scope Identifier

问题描述

我是 PowerShell 新手，试图更好地理解作用域.有没有办法从范围内识别范围?某些变量或函数会给我某种范围名称或范围 Guid 或范围 ID 吗?

I'm a PowerShell newbie, trying to understand scopes better. Is there a way to identify a scope from within the scope ? Some variable or function that would give me scope name or scope Guid or scope Id of some sort ?

例如，我如何知道局部作用域是否为全局作用域?

How could I, for example, know if the local scope is the global scope ?

推荐答案

例如，我如何知道局部作用域是否为全局作用域?

How could I, for example, know if the local scope is the global scope?

[bool] $isGlobalScope = -not $(try { Get-Variable -Scope 1 PSHOME } catch { })

$PSHOME 是一个 自动变量 带有选项 AllScope，因此根据定义，它存在于每个范围内.它还具有选项Constant，这意味着它既不能删除也不能修改.

$PSHOME is an automatic variable with option AllScope, so it is by definition present in each and very scope. It also has option Constant, which means that it cannot neither removed nor modified.

通过询问Get-Variable 要从 parent 范围中检索此变量，-Scope 1，如果您在全局范围内，则操作 失败，因为全局作用域是整个作用域层次结构的根，因此没有父作用域.

By asking Get-Variable to retrieve this variable from the parent scope, -Scope 1, the operation fails if you're in the global scope, because the global scope is the root of the entire scope hierarchy and therefore has no parent.

结果是:

• 如果您不在全局范围内，Get-Variable 调用 succeeds 并返回一个 非空字符串(PowerShell 的主路径).

• If you're not in the global scope, the Get-Variable call succeeds and returns a nonempty string (PowerShell's home path).

• 布尔-not 运算符 将该字符串强制转换为 Boolean ([bool])，其计算结果为 $false，假设非空字符串被视为 $true(无论其内容如何)并应用否定.

• The Boolean -not operator coerces that string to a Boolean ([bool]), which evaluates to $false, given that nonempty strings are considered $true (irrespective of their content) and negation is applied.

如果您在全局范围内，则尝试访问 -Scope 1 会导致 statement-terminating 错误，这会导致触发 catch 块noreferrer">try/catch/finally 语句.

If you are in the global scope, the attempt to access -Scope 1 causes a statement-terminating error, which triggers the catch block of the try / catch / finally statement.

• 由于 catch 块不执行任何操作，它的行为类似于表达式上下文中的 $null
• -not 将 $null 强制转换为布尔值.$null 在布尔上下文中是 $false，因此 -not 的否定计算结果为 $true，表明代码在全局范围内运行.

• Since the catch block takes no action, it behaves like $null in an expression context
• -not coerces $null to a Boolean. $null is $false in a Boolean context, so the negation with -not evaluates to $true, indicating that the code runs in the global scope.

注意:线程/后台作业和远程会话都有自己的全局作用域，上面的测试无法区分它们.

Note: Thread / background jobs and remote sessions have their own global scopes, and the test above cannot distinguish between them.

^{注意:这个答案的原始形式建议将 (Get-PSCallStack).Count -eq 1 作为测试；Get-PSCallStack 输出 [System.Management.Automation.CallStackFrame] 实例，以相反的顺序描述对当前作用域的调用链.因此，但是，此测试不会通过 dot-sourcing.}

^{Note: The original form of this answer suggested (Get-PSCallStack).Count -eq 1 as a test; Get-PSCallStack outputs [System.Management.Automation.CallStackFrame] instances that describe the chain of invocations to the current scope in reverse order. Therefore, however, this test doesn't detect running in the global scope via dot-sourcing.}

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