Category: One-Liner

As silly as this may sound, learning how to find what you’re looking for in PowerShell is key if you want to learn PowerShell quickly and easily.  PowerShell is a rather unique language in that most of the information you will need to use the language is retrievable by using the language itself.  The problem for newcomers to PowerShell who like to dive right in when learning something and who don’t want to read through lots of documentation to get started is that they need to know some PowerShell to learn more about PowerShell and what it can do.

When I first started learning PowerShell I was fortunate to be able to see PowerShell presented twice, both times by Jeffrey Snover, the “father” of PowerShell.  In both presentations as he wrapped things up he mentioned that if there’s one thing you should make sure that you take with you about PowerShell it’s a set of five cmdlets that are key to learning more about PowerShell.  They are (in no particular order): Get-Help, Get-Command, Get-Member, Get-PSDrive and Get-Alias.

Rather than pulling the documentation about these cmdlets into this article, I thought it would be more useful to follow the KISS principle and list a series of questions you might ask yourself about PowerShell accompanied with the PowerShell script (mostly one-liners) that can be used to answer those very questions primarily using the cmdlets I mentioned above.  Here are the questions and their answers to help get you started.

I’ve heard PowerShell cmdlets all follow a verb-noun syntax.  What verbs are available in PowerShell?

Get-Command -CommandType Cmdlet | Group-Object -Property Verb -NoElement

What cmdlets use the verb “out”?

Get-Command -Verb Out

What cmdlets use the noun “command”?

Get-Command -Noun Command

What examples are available for the Tee-Object cmdlet?

Get-Help Tee-Object -examples

What is the full help information for Tee-Object?

Get-Help Tee-Object -Full | Out-Host -Paging
# Note: I could have replaced “Out-Host -Paging” with “more” and the result would have been the same

What are the non-common parameters of Set-Location (with their documentation)?

Get-Help Set-Location -Parameter *

What cmdlets have a parameter like “path”?

Get-Help * -Parameter *path* | Sort-Object -Property Name

What general PowerShell help topics are available?

Get-Help -Category HelpFile,Provider

I need general help on operators.  Where can I find that information?

Get-Help -Category HelpFile,Provider | Where-Object { (Get-Help $_.Name | Out-String).Contains(“operator”) }

Now that I see the help topics and providers that reference the keyword “operator”, how do I see the details?

Get-Help about_operator
Get-Help Variable
# etc.

What aliases are defined for the ForEach-Object cmdlet?

Get-Alias | Where-Object {$_.Definition -eq “ForEach-Object”}

I’ve heard PowerShell even treats the registry as a drive.  What other drives are there?

Get-PSDrive

How do I start browsing the Registry in PowerShell?

Set-Location HKLM: # or cd HKLM:
Get-ChildItem # or dir
Set-Location Software # or cd Software
# etc.

I noticed that there is a drive for environment variables.  How do I use that to check the value of my Path environment variable?

(Get-Item env:Path).Value

How do I add all of my installed PowerShell snapins to the current session so that I can use their cmdlets too?

Get-PSSnapin -Registered | ForEach-Object { if ((Get-PSSnapin $_.Name -ErrorAction SilentlyContinue) -eq $null) { Add-PSSnapin $_.Name } }

(Note: More useful one-liners using Get-PSSnapin can be found here.)

I need to enumerate a bunch of services and then do other things.  Since these are enumerated as objects, how can I tell what I can do with them (i.e. how can I tell what properties and methods they have)?

Get-Service | Get-Member

Are there other basic questions that you think should be on this list?  After learning how to find the information you need within PowerShell, what has been your biggest stumbling block?  Let me know in the comments!

Kirk out.

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By default PowerShell v1.0 comes with 44 variables preinstalled.  Some of these variables are used to configure the maximum number of objects that PowerShell supports, others are used to configure output preferences for scripts, and there are more with many other purposes.  As a script author, it is very useful to understand what the variables are used for so that you can take advantage of them in your scripts.

Fortunately, the wonderful folks at Microsoft who created PowerShell embedded tons of help documentation about PowerShell directly within the shell.  So learning what variables are used for is simple as long as you know how to get the information (which isn’t always that simple for newcomers).

Here’s a useful one-liner that can be used to produce a detailed list of all PowerShell variables.  The output includes the variable name, type, description, value, and options set on the variable.  It also includes a custom member called DisplayValue which is a more detailed view of the data that the variable contains.  Here’s the one-liner, split across multiple lines to improve readability:

Get-ChildItem -Path Variable: `
       | Add-Member `
              -Name Type `
              -MemberType ScriptProperty `
              -Value { $this.GetType().FullName } `
              -PassThru `
       | Add-Member `
              -Name DisplayValue `
              -MemberType ScriptProperty `
              -Value { (Get-Variable -Name $this.Name -Scope 1 -ValueOnly | Format-List -Property * | Out-String).Trim("`r`n") } `
              -PassThru `
       | Sort-Object -Property Name `
       | Format-List -Property Name,Type,Description,Value,DisplayValue,Options `
       | Out-Host -Paging

For the most part, the output of this one-liner provides enough of a description for each variable to explain what it is used for.  Some variables that don’t have descriptions are easily understood by looking at their DisplayValue.  A few might be confusing though.  The $ variable (which you would use in your script as $$) contains the last token in the last command that was run.  The ^ variable ($^ in your script) contains the first token in the last command that was run.  The error variable ($error) contains the history of errors encountered during the current PowerShell session.  You can clear this history at any time by running the $error.Clear() command.

If you are authoring a PowerShell extension (an extension may be a PowerShell snapin, a set of functions, PowerShell scripts, etc) and if your extension adds additional global variables that will be useful to consumers of your extension, I strongly encourage you to provide enough details in the variable description that PowerShell continues to be a self-documenting scripting environment.  The self-documenting nature of PowerShell is unique and incredibly beneficial to PowerShell users.  Please continue to promote this through your own PowerShell work.

If there are any system variables that you are having a hard time with, or that you feel I should have described in more detail in this post because they just aren’t intuitive, feel free to let me know in the comments and I’ll help you out as best as I can.

Kirk out.

Technorati Tags: PowerShell, PoSh, Poshoholic, Essential PowerShell
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