Keeping with the theme of my last blog post, let’s talk a little more about Powershell basics. More specifically, let’s talk about the basics of reusing your Powershell scripts. Most DBAs have their library of scripts that they take with them from job to job, helping them be more effective at their job. Whether it’s SQL, Powershell, or some other language, experienced data professionals always make sure to retain their work for when they’ll need it again.
Enter the profile. This is actually a concept that’s been around for a long, long while in the *nix world. The concept is simple: There is a script that runs every time you start up a session in your shell, configuring your environment. Many times in *nix, this will configure system variables like PATH or HOME, but you can also use it to load custom functions and aliases within your shell.
The Microsoft team borrowed this concept when constructing the Powershell language. We have access to a profile (well, 4 of them) that help us configure and customize our own environments. Similar *nix, it’s a .ps1 script that runs every time you open a new session. This allows you a lot of flexibility for reuse of your code.
Getting Started
As linked above, there are 4 different types of profiles you can use. We won’t focus on these different profiles, but instead stay with the basic profile: the one that applies to the current user and the current host (in these examples, the ISE). To view your profile, open it up in your text editor of choice by referencing the $profile system variable:
ise $profile
If you don’t currently have a profile, you’ll probably get an error about the file not existing. To fix this, create the file:
New-Item -ItemType File -Path $profile -Force
Vioala! You now have a completely empty profile, which is what you will see when you try and open it again.
So Now What?
I can hear the internal dialog now:
“Woo hoo! A profile!”
“Ummm…yeah. That’s great. But what do we do with it?”
“…….”
“That’s what I was thinking, too.
I don’t want to leave you hanging, so let’s start making use of it. The first order of business with the profile is to use it for customizing your environment. Since I am a SQL DBA, I like to load up the SQLPS module and the SMO objects. This means any time I’m in Powershell, I’ve got the SQL Server cmdlets and objects ready to go.
Next up, I have a function I wrote a while back for reporting on the available disk space on a server. It’s very handy and I use it almost every day. The code is not original, but I wrapped it in a function to save myself a LOT of typing. Usually, you’d package such a function in a module. I ended putting it in my profile because it was easy. I also add to an alias to save myself even more typing.
This means I end up with a profile that looks a lot like this:
#load SMO library [System.Reflection.Assembly]::LoadWithPartialName('Microsoft.SqlServer.SMO') | out-null #Load SQLPS Module Import-Module SQLPS -DisableNameChecking #Set Aliases New-Alias -Name gfs -Value Get-FreeSpace function Get-FreeSpace{ <# .SYNOPSIS Uses WMI to get capacity and freespace for all disks/mounts on a host. .DESCRIPTION Uses WMI Win32_Volume to query logical disks and provide drive size and usage for all logical disks and mountpoints. If no parameter is given, localhost is used. Otherwise the host name should be passed. Mike Fal (http://www.mikefal.net) 2012-10-10 .PARAMETER host - Name of machine information is being queried from, defaults to localhost .EXAMPLE Get-FreeSpace "CCX-SQL-PRD-01" #> param([string] $hostname = ($env:COMPUTERNAME)) gwmi win32_volume -computername $hostname | where {$_.drivetype -eq 3} | Sort-Object name ` | ft name,@{l="Size(GB)";e={($_.capacity/1gb).ToString("F2")}},@{l="Free Space(GB)";e={($_.freespace/1gb).ToString("F2")}},@{l="% Free";e={(($_.Freespace/$_.Capacity)*100).ToString("F2")}} }
Now if I had just added this to my profile and wanted to load it into the current session, I’d just have to execute it, like so:
. $profile
This loads the profile, running it as if it were any other .ps1 script (because it is).
The Power of the Profile
Using this, I have a customized Powershell environment ready to go any time I start. It lets me use Powershell the way I want to, allowing me to extend my shell with my own custom code or pre-packaged modules that I need access to. I’ve talked several times before about building Powershell tools, but at some point we all need a toolbox. By leveraging the profile, you can start building your own custom Powershell toolbox that you can rely on.
Want to know more? You can learn about Powershell profiles right from the shell itself: Get-Help about_profiles. How cool is that?