Month of Lunches - Day 6

Today we are going to Cover something that I had touched on previously in Day 4. PowerShell and its use of Objects.

Every time that you run a cmdlet in PowerShell and get output to your screen you are seeing text. But under the hood PowerShell is actually creating objects (unless otherwise told). There is a ton of information that you cannot see immediately, but if you know where and how to look there is a wealth of information. For example, as I stated previously running the Get-Process command only displays 8 or so pieces of information but if you export it to a CSV or HTML file you will see that there are 60+ columns of information that are actually within the output.

Don explains the way PowerShell is actually handling this data better than anyone for me to date. What you are seeing as a table when its displayed is actually made up of four things. To make this easier to visualize lets export our process list to CSV file. Open your PowerShell windows and type:

                Get-Process | Export-CSV <path>\<filename>

Open the CSV file you just created and follow along. What PowerShell is actually showing is:

1.        Objects: Each row of the CSV file is actually an individual object.

2.        Properties: These are the columns. Each column header has a name and these are the properties of that object.

3.        Methods: These are not actually shown. Methods are the actions that can be taken against any or all of the objects.

4.        Collection: This is basically the entire table. It is the sum of all the objects, or rows, there associated properties, or columns, and the methods, or actions, that can be taken against them.

PowerShell creates and uses these objects for a couple of reasons. The first of which Don points out is that Windows is an object oriented operating system, and most of its programs are object oriented. Windows being object oriented makes it extremely easy for PowerShell to use these objects and create its own.  The Second reason is for ease of use. Using objects makes parsing the data infinitely easier.

Ok so you don’t want to have to output everything to CSV or HTML to find out what the properties and methods are do you? No, of course not. Well this is where Get-Member comes in. You can pipe nearly every command to Get-Member, or its alias GM,  cmdlet and it will display all the associated properties and methods. There are actually several different kinds of properties (ScriptProperty, Property, NoteProperty, and AliasProperty) but these are not important right now. They are all just properties for now. Let's take a look at them.

                Get-Process | GM

This will display all of associated 60+ properties, methods, and events of the collection. This is important because you can display and sort these properties in whatever fashion you want with a couple of cmdlets. Select-Object and Sort-Object.

Say you wanted to display a list of running process' in order by name, and you wanted to display only the  Name, Memory Usage, ID, and Start Time. You could run the following command

                Get-Process | Select-Object -property name,VM,ID,StartTime | sort-object -property name

Or you could shorten it with alias'

                Get-Process | Select -prop name,vm,id,starttime | sort -prop name

As you can see with the Select-Object you can specify multiple properties by separating them with commas, but do not use spaces. PowerShell will see that as the start of a new variable and error. This can be done with any cmdlet that has multiple properties. You could also specify methods in this manner but the important ones have cmdlets of their own (method: Kill , cmdlet: Stop-Process).

Just remember that almost everything in PowerShell is an object that has properties, and they can be manipulated. Everything is an object until you tell it not to be.