Working with PowerShell Objects

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+Working with PowerShell Objects
+====
+When cmdlets are executed in PowerShell, the output is an Object, as opposed to only returning text.
+This provides the ability to store information as properties.
+As a result, handling large amounts of data and getting only specific properties is a trivial task.
+
+As a simple example, the following function retrieves information about storage Devices on a Linux or MacOS operating system platform.
+This is accomplished by parsing the output of an existing command, *parted -l* in administrative context, and creating an object from the raw text by using the *New-Object* cmdlet.
+
+```PowerShell
+Function Get-DiskInfo {
+    $disks = sudo parted -l | Select-String "Disk /dev/sd*" -context 1,0
+    $diskinfo = @()
+    foreach ($disk in $disks) {
+        $diskline1 = $disk.ToString().Split("`n")[0].ToString().Replace('  Model: ','')
+        $diskline2 = $disk.ToString().Split("`n")[1].ToString().Replace('> Disk ','')
+        $i = New-Object psobject -Property @{'Friendly Name' = $diskline1; Device=$diskline2.Split(': ')[0]; 'Total Size'=$diskline2.Split(':')[1]}
+        $diskinfo += $i
+    }
+    $diskinfo
+}
+```
+
+Execute the function and store the results as a variable.
+Now retrieve the value of the variable.
+The results are formatted as a table with the default view.
+
+*Note: in this example, the disks are virtual disks in a Microsoft Azure virtual machine.*
+
+```PowerShell
+PS /home/psuser> $d = Get-DiskInfo
+[sudo] password for psuser:
+PS /home/psuser> $d
+
+Friendly Name            Total Size Device
+-------------            ---------- ------
+Msft Virtual Disk (scsi)  31.5GB    /dev/sda
+Msft Virtual Disk (scsi)  145GB     /dev/sdb
+
+```
+
+Passing the variable down the pipeline to *Get-Member* reveals available methods and properties.
+This is because the value of *d$* is not just text output.
+The value is actually an array of .Net objects with methods and properties.
+The properties include Device, Friendly Name, and Total Size.
+
+```PowerShell
+PS /home/psuser> $d | Get-Member
+
+
+   TypeName: System.Management.Automation.PSCustomObject
+
+Name          MemberType   Definition
+----          ----------   ----------
+Equals        Method       bool Equals(System.Object obj)
+GetHashCode   Method       int GetHashCode()
+GetType       Method       type GetType()
+ToString      Method       string ToString()
+Device        NoteProperty string Device=/dev/sda
+Friendly Name NoteProperty string Friendly Name=Msft Virtual Disk (scsi)
+Total Size    NoteProperty string Total Size= 31.5GB
+```
+
+To confirm, we can call the GetType() method interactively from the console.
+
+```PowerShell
+PS /home/psuser> $d.GetType()
+
+IsPublic IsSerial Name                                     BaseType
+-------- -------- ----                                     --------
+True     True     Object[]                                 System.Array
+```
+
+To index in to the array and return only specific objects, use the square brackets.
+
+```PowerShell
+PS /home/psuser> $d[0]
+
+Friendly Name            Total Size Device
+-------------            ---------- ------
+Msft Virtual Disk (scsi)  31.5GB    /dev/sda
+
+PS /home/psuser> $d[0].GetType()
+
+IsPublic IsSerial Name                                     BaseType
+-------- -------- ----                                     --------
+True     False    PSCustomObject                           System.Object
+```
+
+To return a specific property, the property name can be called interactively from the console.
+
+```PowerShell
+PS /home/psuser> $d.Device
+/dev/sda
+/dev/sdb
+```
+
+To output a view of the information other than default, such as a view with only specific properties selected, pass the value to the *Select-Object* cmdlet.
+
+```PowerShell
+PS /home/psuser> $d | Select-Object Device, 'Total Size'
+
+Device   Total Size
+------   ----------
+/dev/sda  31.5GB
+/dev/sdb  145GB
+```
+
+Finally, the example below demonstrates use of the *ForEach-Object* cmdlet to iterate through the array and manipulate the value of a specific property of each object.
+In this case the Total Size property, which was given in Gigabytes, is changed to Megabytes. 
+Alternatively, index in to a position in the array as shown below in the third example.
+
+```PowerShell
+PS /home/psuser> $d | ForEach-Object 'Total Size'
+ 31.5GB
+ 145GB
+
+PS /home/psuser> $d | ForEach-Object {$_.'Total Size' / 1MB}
+32256
+148480
+
+PS /home/psuser> $d[1].'Total Size' / 1MB
+148480
+```