powershell - "(gl -stack)"和 "gl -stack"之间的区别

Question

我只是想知道为什么在括号之间嵌入表达式时会得到两个不同的成员列表，例如gl-stack。看起来，如果没有括号，表达式就会被完全求值，并且结果会立即传递到下一个管道组件。但通过括号，集合中的单个对象将被一一传递，以便为集合中的对象而不是集合本身调用 Get-Member。请参阅以下 PowerShell 交互，了解 Get-Location -Stack 的示例。

提前致谢!

PS C:\temp\loc1> pushd
PS C:\temp\loc1> pushd ..\loc2
PS C:\temp\loc2> gl -stack

Path
----
C:\temp\loc1
C:\temp\loc1


PS C:\temp\loc2> gl -stack | gm


   TypeName: System.Management.Automation.PathInfoStack

Name          MemberType Definition
----          ---------- ----------
Clear         Method     System.Void Clear()
Contains      Method     bool Contains(System.Management.Automation.PathInfo...
CopyTo        Method     System.Void CopyTo(System.Management.Automation.Pat...
Equals        Method     bool Equals(System.Object obj)
GetEnumerator Method     System.Collections.Generic.Stack`1+Enumerator[[Syst...
GetHashCode   Method     int GetHashCode()
GetType       Method     type GetType()
Peek          Method     System.Management.Automation.PathInfo Peek()
Pop           Method     System.Management.Automation.PathInfo Pop()
Push          Method     System.Void Push(System.Management.Automation.PathI...
ToArray       Method     System.Management.Automation.PathInfo[] ToArray()
ToString      Method     string ToString()
TrimExcess    Method     System.Void TrimExcess()
Count         Property   System.Int32 Count {get;}
Name          Property   System.String Name {get;}


PS C:\temp\loc2> (gl -stack) | gm


   TypeName: System.Management.Automation.PathInfo

Name         MemberType Definition
----         ---------- ----------
Equals       Method     bool Equals(System.Object obj)
GetHashCode  Method     int GetHashCode()
GetType      Method     type GetType()
ToString     Method     string ToString()
Drive        Property   System.Management.Automation.PSDriveInfo Drive {get;}
Path         Property   System.String Path {get;}
Provider     Property   System.Management.Automation.ProviderInfo Provider {...
ProviderPath Property   System.String ProviderPath {get;}

Answer 1

Get-Location -Stack返回 PathInfoStack正如你所看到的那样。该对象源自Stack<T>它实现了 ICollection。当您将表达式放入 () 中时PowerShell 计算该表达式。如果结果是一个集合，则对其进行迭代并输出。您可以通过这个简单的函数看到相同的结果:

PS> function GetArray() { ,@(1,2,3) }
PS> GetArray | Foreach {$_.GetType().FullName}
System.Object[]
PS> (GetArray) | Foreach {$_.GetType().FullName}
System.Int32
System.Int32
System.Int32