In PowerShell, there are lots of commands that gives tabular data, e.g.
get-process
In PS, we have some terminologies that describes different parts of these tables:
- collection: This refers to the whole table.
- object: single row in the table
- property: column in the table
- method: action that you can take on a given row (object)
Now to see what methods you can apply to each object in get-process, we do:
PS C:\> Get-Service | get-member TypeName: System.ServiceProcess.ServiceController Name MemberType Definition ---- ---------- ---------- Name AliasProperty Name = ServiceName RequiredServices AliasProperty RequiredServices = ServicesDependedOn Disposed Event System.EventHandler Disposed(System.Object, System.EventArgs) Close Method void Close() Continue Method void Continue() CreateObjRef Method System.Runtime.Remoting.ObjRef CreateObjRef(type requestedType) Dispose Method void Dispose(), void IDisposable.Dispose() GetType Method type GetType() . ...etc.
On our machine, one of the get-service collection’s object is called “browser”:
PS C:\> Get-Service -Name browser
Status Name DisplayName
—— —- ———–
Running browser Computer Browser
Let’s say we wan to apply the “GetType” method on this object, then we do this using the following syntax:
PS C:\> (Get-Service -Name browser).GetType() IsPublic IsSerial Name BaseType -------- -------- ---- -------- True False ServiceController System.ComponentModel.Component
This in turn can have it’s own methods:
PS C:\> (Get-Service -Name browser).GetType() | Get-Member TypeName: System.RuntimeType Name MemberType Definition ---- ---------- ---------- AsType Method type AsType() Clone Method System.Object Clone(), System.Object ICloneable.Clone() Equals Method bool Equals(System.Object obj), bool Equals(type o), bool _MemberInfo.Equa... FindInterfaces Method type[] FindInterfaces(System.Reflection.TypeFilter filter, System.Object f...
Note: here is another example of using methods, but this time for “get-date”.
PS C:\> get-date 03 December 2015 13:37:59 PS C:\> (Get-date).ToShortTimeString() 13:38 PS C:\>
Here is another very popular way of accessing a method:
PS C:\> $date = Get-Date PS C:\> $date 03 December 2015 13:38:52 PS C:\> $date.ToShortTimeString() 13:38 PS C:\>
In Powershell, a “method” is simply a way of telling the object to do something, usually to itself. This concept, i.e. treating a table as a “collection” of “objects” means that you can work with data more easily (especially when compared to unix where you need to use grep, awk, and sed). In Powershell, you can extract data based on property names, and object’s field entries. By default, the get-process
command only shows a subset of properties, because the screen isn’t big enough to show all of them. However the command will show all the properties if you pipe it to a file. If you want to see all the available properties and methods for a collection, you need to use the get-member command. E.g. for get-process, you do:
get-process | get-member
Note, that sometimes you may need to use “-force” to access to the complete list, i.e.:
get-process | get-member -force
Note, everything about a collection, i.e. properties, object, are referred to as a member. Hence that’d where get-member gets it’s name from. When you use get-member, you will discover a number of different types of properties:
- aliasproperty
- scriptproperty
- noteproperty
- property
You can ignore the various types and just think of them all as the same thing.
Now lets start by manipulating objects in a table. For get-process, if you want to re-arrange the rows based on the virtualmemory (vm) property, then do this:
get-process | sort-object -property VM
This sorts it by vm, followed by id:
get-process | sort-object -property VM,id
If you want to specify which property (columns) to output, then do:
get-process | select-object -Property ProductVersion,FileVersion
If you want to view the first 10 lines, you can do this using the select-object command:
get-process | select-object -Property ProductVersion,FileVersion | select-object -first 10
Similarly for the last 10 lines you do:
get-process | select-object -Property ProductVersion,FileVersion | select-object -last 10
If you want to filter out rows, like we do in linux using grep, awk, and sed, then we need to use where-object. This will be covered later.
Note: When you look at the help files of any command that outputs a tabular output, you will find that they don’t give a whole list of all available properties (columns), that’s why you have to use the get-member command instead to get all this info.