Viewing Object Structure (Get-Member)

Because objects play such a central role in Windows PowerShell, there are several native commands designed to work with arbitrary object types. The most important one is the Get-Member command.

The simplest technique for analyzing the objects that a command returns is to pipe the output of that command to the Get-Member cmdlet. The Get-Member cmdlet shows you the formal name of the object type and a complete listing of its members. The number of elements that are returned can sometimes be overwhelming. For example, a process object can have over 100 members.

To see all of the members of a Process object and page the output so you can view all of it, type:

PS> Get-Process | Get-Member | Out-Host -Paging

The output from this command will look something like this:

TypeName: System.Diagnostics.Process

Name MemberType Definition

---- ---------- ----------

Handles AliasProperty Handles = Handlecount

Name AliasProperty Name = ProcessName

NPM AliasProperty NPM = NonpagedSystemMemorySize

PM AliasProperty PM = PagedMemorySize

VM AliasProperty VM = VirtualMemorySize

WS AliasProperty WS = WorkingSet

add_Disposed Method System.Void add_Disposed(Event...

...

We can make this long list of information more usable by filtering for elements we want to see. The Get-Member command lets you list only members that are properties. There are several forms of properties. The cmdlet displays properties of any type if we set the Get-MemberMemberType parameter to the value Properties. The resulting list is still very long, but a bit more manageable:

PS> Get-Process | Get-Member -MemberType Properties

TypeName: System.Diagnostics.Process

Name MemberType Definition

---- ---------- ----------

Handles AliasProperty Handles = Handlecount

Name AliasProperty Name = ProcessName

...

ExitCode Property System.Int32 ExitCode {get;}

...

Handle Property System.IntPtr Handle {get;}

...

CPU ScriptProperty System.Object CPU {get=$this.Total...

...

Path ScriptProperty System.Object Path {get=$this.Main...

...

Note:

The allowed values of MemberType are AliasProperty, CodeProperty, Property, NoteProperty, ScriptProperty, Properties, PropertySet, Method, CodeMethod, ScriptMethod, Methods, ParameterizedProperty, MemberSet, and All.

There are over 60 properties for a process. The reason Windows PowerShell often shows only a handful of properties for any well-known object is that showing all of them would produce an unmanageable amount of information.

Note:

Windows PowerShell determines how to display an object type by using information stored in XML files that have names ending in .format.ps1xml. The formatting data for process objects, which are .NET System.Diagnostics.Process objects, is stored in PowerShellCore.format.ps1xml.

If you need to look at properties other than those that Windows PowerShell displays by default, you will need to format the output data yourself. This can be done by using the format cmdlets.

Posted in: Software| Tags: PowerShell Handle Alias Object Structure Get-Member out-Hosting Paging Process Property ProcessName Allowed MemberType Determine

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Interpreting Standard Aliases

Unlike the aliases described above, which were designed for name-compatibility with other interfaces, the aliases built into Windows PowerShell are generally designed for brevity. These shorter names can be typed quickly, but are impossible to read if you do not know what they refer to.

Windows PowerShell tries to compromise between clarity and brevity by providing a set of standard aliases that are based on shorthand names for common verbs and nouns. This allows a core set of aliases for common cmdlets that are readable once you know the shorthand names. For example, in standard aliases the verb Get is abbreviated to g, the verb Set is abbreviated to s, the noun Item is abbreviated to i, the noun Location is abbreviated to l, and the noun Command is abbreviated to cm.

Here is a brief example to illustrate how this works. The standard alias for Get-Item comes from combining g for Get and i for Item: gi. The standard alias for Set-Item comes from combining s for Set and i for Item: si. The standard alias for Get-Location comes from combining g for Get and l for Location, gl. The standard alias for Set-Location comes from combining s for Set and l for Location, sl. The standard alias for Get-Command comes from combining g for Get and cm for Command, gcm. There is no Set-Command cmdlet, but if there were, we would be able to guess that the standard alias comes from s for Set and cm for Command: scm. Furthermore, people familiar with Windows PowerShell aliasing who encounter scm would be able to guess that the alias refers to Set-Command.

Creating New Aliases

You can create your own aliases using the Set-Alias cmdlet. For example, the following statements create the standard cmdlet aliases discussed in Interpreting Standard Aliases:

Set-Alias -Name gi -Value Get-Item

Set-Alias -Name si -Value Set-Item

Set-Alias -Name gl -Value Get-Location

Set-Alias -Name sl -Value Set-Location

Set-Alias -Name gcm -Value Get-Command

Internally, Windows PowerShell uses commands like these during startup, but these aliases are not changeable. If you attempt to actually execute one of these commands, you will get an error explaining that the alias cannot be modified. For example:

PS> Set-Alias -Name gi -Value Get-Item

Set-Alias : Alias is not writeable because alias gi is read-only or constant and cannot be written to.

At line:1 char:10

+ Set-Alias <<<< -Name gi -Value Get-Item

Posted in: Others Software| Tags: Interpreting Standard Alias Describe Set-Commad Encounter Scm Furthermore Familiar

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