Prof. Powershell

My Favorite PowerShell 4 Features (Part 2)

Prof. PowerShell is back again to share another batch of his favorite tweaks in the latest version of Powershell.

• By Jeffery Hicks
• 12/17/2013

See Also:

• My Favorite PowerShell 4 Features (Part 1)

In the previous lesson I highlighted some of my favorite features in PowerShell 4.0. Here are a few more. These are items that I think you might want to use immediately in your PowerShell management tasks.

Get-FileHash
Years ago I wrote a function to derive a file hash based on the MD5, SHA1 or SHA256 algorithms. This came in handy when verifying a file copy. Now PowerShell 4.0 has a Get-FileHash cmdlet that does the same thing. Give the cmdlet the path to a file and the hashing algorithm and you'll get a checksum. Valid algorithms are SHA1, SHA256, SHA384, SHA512, MACTripleDES, MD5 and RIPEMD160. The default is SHA256.

PS C:\> get-filehash .\unattend.xml | Select Hash

Hash
----
A281E0CB7C2A7858DED2CEBBDD383B58604C2C4E1CB8E04A11773C466E4797FA

The result is an object with the algorithm and hash. You could get the file hash of an entire directory and save it.

PS C:\> dir scripts -file | get-filehash -Algorithm MD5 | export-csv c:\work\scripthash.csv

Or verify that a file was copied correctly.

PS C:\> $before = Get-FileHash C:\scripts\CHI-CORE01.mof -Algorithm MD5
PS C:\> $after = copy C:\scripts\CHI-CORE01.mof -Destination \\chi-fp02\SalesData -PassThru | get-filehash -Algorithm MD5
PS C:\> compare-object $before $after -Property hash

As long as the file copies OK, Compare-Object won't return anything.

Get Process Owner
Another enhancement that I think IT Pros will like is the ability to display process owner with Get-Process.

PS C:\> get-process -IncludeUserName

You can see the result here:

Having access to this information offers up some interesting possibilities. How about displaying all non-system owned processes?

PS C:\> get-process -IncludeUserName | where {$_.username -match "globomantics"} |group Username

Count Name                      Group
----- ----                      -----
6 GLOBOMANTICS\jeff         {System.Diagnostics.Process (conhost), Syste...
1 GLOBOMANTICS\rgbiv        {System.Diagnostics.Process (notepad)}

The caveat is that only works locally. You can't get user names with Get-Process using –Computername. However, you can use PowerShell remoting.

PS C:\> invoke-command {get-process -IncludeUserName | where Username } -comp chi-hvr2 | out-gridview -title "CHI-HVR2 Processes"

I ran this from a Windows 8.1 system to a Windows Server 2012 R2 server.

But because the command is running on the remote server, you can use remoting from any version of PowerShell. Here's a command from a PowerShell 2.0 session querying processes on Windows 8.1.

PS C:\> invoke-command {get-process -includeusername | where {$_.username -match "globomantics"}} -comp chi-win81.globomantics.local -Credential globomantics\administrator

However, as you can see in the screen shot, PowerShell 2.0 doesn't know by default about the new property.

But all that means is that you need to take an extra step to display it.

PS C:\> invoke-command {get-process -includeusername | where {$_.username –match  "globomantics"}} -comp chi-win81.globomantics.local -Credential globomantics\administrator | Format-table ID,ProcessName,WS,Username –auto

Here's the result:

Sure, it isn't as elegant but it works.

PowerShell 4.0 has much to offer an IT Pro so I hope you'll get your hands on it and give it a go. Oh, and be sure to reread help even for cmdlets you think you know just in case there is some little enhancement that might be just what you need.