05.Working with providers

What are providers?

A PowerShell provider, or PSProvider, is an adapter. It’s designed to take some kind of data storage, such as Windows Registry, Active Directory, or even the local filesystem, and make it look like a disk drive.

You can see a list of installed PowerShell providers right within the shell:

Get-PSProvider

You use a provider to create a PSDrive. A PSDrive uses a single provider to connect to data storage.

Get-PSDrive

The PSProvider adapts the data store, and the PSDrive makes it accessible.

Get-Command -Noun *item*

Because it’s probably the one you’re most familiar with, we’ll start with the filesystem—the FileSystem PSProvider.

Understanding how the filesystem is organized

The filesystem is organized around two main types of objects—folders and files. Folders are also a kind of container, capable of containing both files and other folders. Files aren’t a type of container; they’re more of an endpoint object.

PowerShell doesn’t use the terms file and folder. Instead, it refers to these objects by the more generic term item.

Set-Item

------------------ Example 1: Create an alias ------------------

Set-Item -Path alias:np -Value "c:\windows\notepad.exe"

---- Example 2: Change the value of an environment variable ----

Set-Item -Path env:UserRole -Value "Administrator"

------------ Example 3: Modify your prompt function ------------

Set-Item -Path function:prompt -Value {'PS '+ (Get-Date -Format t) + " " + (Get-Location) + '> '}

------- Example 4: Set options for your prompt function -------

Set-Item -Path function:prompt -Options "AllScope,ReadOnly"

Some PSProviders don't support item properties. For example, the Environment PSProvider is what's used to make the ENV: drive available in PowerShell. This drive provides access to the environment variables, but as the following example shows, they don't have item properties:

Get-ItemProperty -Path Env:\PSModulePath

Navigating the filesystem

Using wildcards and literal paths

• -Path: Wildcards are permitted.
• -LiteralPath: No characters are interpreted as wildcards.

Note that -LiteralPath isn't positional; if you plan to use it, you have to type -LiteralPath.

Working with other providers

PowerShell includes the following aliases for Write-Output:

- All platforms:   - `echo`

- Windows:   - `write`

Write-Output

----- Example 1: Get objects and write them to the console -----

$P = Get-Process
Write-Output $P

----------- Example 2: Pass output to another cmdlet -----------

Write-Output "test output" | Get-Member

---------- Example 3: Suppress enumeration in output ----------

Write-Output 1,2,3 | Measure-Object

Count : 3
...

Write-Output 1,2,3 -NoEnumerate | Measure-Object

Count : 1
...

Windows Commands	Description	Linux + macOS
echo TEXT	Print TEXT to the terminal
echo TEXT > TARGET	Print TEXT to a file named TARGET
echo TEXT >> TARGET	Append TEXT to TARGET

Lab

NOTE For this lab, you need any computer running PowerShell v7.1 or later.

Complete the following tasks from a PowerShell prompt:

1. Create a new directory called Labs.
2. Create a zero-length file named /Labs/Test.txt (use New-Item).
3. Is it possible to use Set-Item to change the contents of /Labs/Test.txt to -TESTING? Or do you get an error? If you get an error, why? The FileSystem provider doesn’t support this action. You use Write-Output to add text content from PowerShell into a file:
   • Write-Output "First line text." > TARGET
   • Write-Output "Second line text content" >> TARGET
4. Using the Environment provider, display the value of the system environment variable PATH.
5. Use help to determine what the differences are between the -Filter, -Include, and -Exclude parameters of Get-ChildItem. -Include and -Exclude must be used with –Recurse or if you’re querying a container. -Filter uses the PSProvider’s filter capability, which not all providers support. For example, you could use DIR –filter in the filesystem.