Today's modern computing world makes use of a vast variety of data stores, including the file store, the certificate store, the Registry, etc. With previous tools, each of these data stores are accessed using different and incompatible tools, making it hard for the admin to learn, use, and master. PowerShell take a different approach through the use of providers and standard cmdlets.
A PowerShell provider is a software component that sits between the actual data store and the standard cmdlets. The standard cmdlets call into the provider to return the relevant data and present it in a admin-friendly way. To aid in conversion, PowerShell provides aliases for these standard cmdlets. The provider architecture is shown at http://msdn2.microsoft.com/en-us/library/ms714658.d2eb7674-3a27-4baf-91b7-b8eaf1e8ab2c(en-us,VS.85).gif.
To illustrate this, let's look at the two data stores, the filesystem and the Registry:
PSH [D:\foo]:dirDirectory: Microsoft.PowerShell.Core\FileSystem::D:\foo Mode LastWriteTime Length Name ---- ------------- ------ ---- d---- 14/10/2007 12:04 bar PSH [D:\foo]:cd barPSH [D:\foo\bar]:lsDirectory: Microsoft.PowerShell.Core\FileSystem::D:\foo\bar Mode LastWriteTime Length Name ---- ------------- ------ ---- -a--- 14/10/2007 12:04 8 foobar.txt PSH [D:\foo\bar]:cd hklm: PSH [HKLM:\]:lsHive: Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE SKC VC Name Property --- -- ---- -------- 4 0 HARDWARE {} 87 0 SOFTWARE {} 8 0 SYSTEM {} PSH [HKLM:\]:dir .\software\microsoft\powershellHive: Microsoft.PowerShell.Core\Registry::HKEY_LOCAL_MACHINE\software\microsoft\ powershell SKC VC Name Property --- -- ---- -------- 4 2 1 {Install, PID}
In this example, we use both the Dir and LS aliases to examine two separate data stores: the filesystem and the Registry. Both aliases are to the Get-ChildItem standard cmdlet, which allows both Linux/Unix and Dos/Windows users to use familiar names to perform common and familiar operations. There are several more standard cmdlets:
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Clear-ItemDeletes the contents of an item, but does not delete the item.
Clear-ItemPropertyDeletes the value of a property, but does not delete the property itself.
Copy-ItemCopies an item from one location to another within a namespace.
Copy-ItemPropertyCopies a property and value from a specified location to another location.
Get-ChildItemGets the items and child items in one or more specified locations.
Get-ItemPropertyRetrieves the properties of a specified item.
Get-ItemGets the item at the specified location.
Invoke-ItemInvokes the provider-specific default action on the specified item.
Move-ItemMoves an item from one location to another.
New-ItemCreates a new item in a namespace.
Move-ItemPropertyMoves a property from one location to another.
Rename-ItemRenames an item in a Windows PowerShell provider namespace.
New-ItemPropertySets a new property of an item at a location.
Remove-ItemDeletes the specified items.
Remove-ItemPropertyDeletes the property and its value from an item.
Rename-ItemPropertyRenames a property of an item.
Set-ItemChanges the value of an item to the value specified in the command.
Set-ItemPropertySets the value of a property at the specified location.
This list represents a number of new cmdlets for the admin to learn. In order to minimise the learning curve, PowerShell provides common aliases for each of these standard cmdlet, e.g., Get-ChildItem is aliased to GCI, DIR, and LS. You can get a list of these aliases as follows:
PSH [D:]:get-alias * | where {$_.definition -like "*item*"} | ft -auto
CommandType Name Definition
---------- ---- ----------
Alias cli Clear-Item
Alias clp Clear-ItemProperty
Alias cpi Copy-Item
Alias cpp Copy-ItemProperty
Alias gci Get-ChildItem
Alias gi Get-Item
Alias gp Get-ItemProperty
Alias ii Invoke-Item
Alias mi Move-Item
Alias mp Move-ItemProperty
Alias ni New-Item
Alias ri Remove-Item
Alias rni Rename-Item
Alias rnp Rename-ItemProperty
Alias rp Remove-ItemProperty
Alias si Set-Item
Alias sp Set-ItemProperty
Alias cp Copy-Item
Alias ls Get-ChildItem
Alias mv Move-Item
Alias rm Remove-Item
Alias rmdir Remove-Item
Alias copy Copy-Item
Alias del Remove-Item
Alias erase Remove-Item
Alias move Move-Item
Alias rd Remove-Item
Alias ren Rename-ItemThese aliases enable you to start using PowerShell and PowerShell providers straight away using the names of the DOS/Windows/Unix/Linux commands you are already familiar with. They also avoid you needing to learn new cmdlets in order to get any value from PowerShell.
The aliases and standard cmdlets call into a provider to obtain the relevant information (the contents of the current working file store folder, the current node in the Registry, etc.). PowerShell comes with several providers, and you can add more. Providers built into PowerShell include Alias, Environment, FileSystem, Function, Registry, Variable, and Certificate. Additional third-party providers include SQL Server, One-Note and Microsoft Compute Cluster.
With the provider, you can use the New-PSDrive to create new drives. These drives can then be used as normal drives in the standard cmdlets and related aliases. For example:
PSH [D:\foo]:New-PSDrive -name scripts -psProvider Filesystem -root d:\fooName Provider Root ---- -------- ---- scripts FileSystem D:\foo PSH [D:\foo]:dir scripts:Directory: Microsoft.PowerShell.Core\FileSystem::D:\foo Mode LastWriteTime Length Name ---- ------------- ------ ---- d---- 14/10/2007 12:04 bar
In this manner, you can create new drives that are more meaningful than C: and D:. To see what drives are available, you can use the Get-PSDrive cmdlet as shown here (note the new scripts drive we created in the previous example):
PSH [D:\foo]: Get-PSDrive Name Provider Root ---- -------- ---- Alias Alias C FileSystem C:\ cert Certificate \ D FileSystem D:\ E FileSystem E:\ Env Environment F FileSystem F:\ Feed FeedStore Function Function HKCU Registry HKEY_CURRENT_USER HKLM Registry HKEY_LOCAL_MACHINE L FileSystem L:\ R FileSystem R:\ S FileSystem S:\ scripts FileSystem D:\foo T FileSystem T:\ U FileSystem U:\ Variable Variable Y FileSystem Y:\
With these drives, you can perform actions like Dir ENV: to get a list of environment variables or dir Variable: to see a list of variables in use. For more help on providers, type Get-Help about_providers at the PowerShell prompt. And for more detailed information about providers and how to build one, see http://msdn2.microsoft.com/en-us/library/ms714636.aspx.