At Tech Ed in Orlando last week John Waters picked up "Windows PowerShell Unleashed by Tyson Kopczynski" and as John has a eye for cool technology I did likewise and got hooked on PowerShell.  I'm not usually a live-on-the-command-line-love-batch-files kind of guy but PowerShell covers enough ground in a powerful and consistent way that I'm considering adding this to my technology toolbox.  Although PowerShell is intended for system administrator use, there may be a place for PowerShell in development to do limited testing against .NET objects, task automatation and general exploration.  In any case it's a great toy and a hoot to play with.

PowerShell has several important differences from cmd.exe. 

• PowerShell lets you use NET FCL objects, COM objects and even your own .NET classes.
• PowerShell scripts can be code signed (see Windows PowerShell Unleashed by Tyson Kopczynski for detailed steps).  Previous scripting environments like Windows Scripting Host (WSH) opened large security holes.  This feature allows scripts from trusted sources to be run.
• PowerShell is object based, not text based.  This eliminates parsing and reformatting to use the output from a command.
• PowerShell provides a consistent interface. 
  • You can navigate through files, the certificate store, environmental variables and the registry, all using commands you already know. 
  • Commands confirm to the pattern verb-name, i.e. "get-service" to cut down on memorization.  There are aliases for historic DOS and UNIX commands so you can list a directory with the PowerShell native "get-childitem", UNIX style "ls" or DOS "dir". 
  • PowerShell lets you locate and interrogate available commands and objects.
• PowerShell is extensible.  You can create your own commands in a .NET assembly and register them for use in PowerShell.  There are several other points of extensibility including providers for navigation, types and formatting.

Here's a sample session of PowerShell to give you a very brief notion of how it works.  Be aware that this is only scratching the surface of the possibilities for PowerShell.  Let's say we want to work with Windows services, so we need to know what commands are available:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> get-command *service

CommandType     Name                                                Definition
-----------     ----                                                ----------
Cmdlet          Get-Service                                         Get-Service [[-Name] <String[]>] [-Include <Stri...
Cmdlet          New-Service                                         New-Service [-Name] <String> [-BinaryPathName] <...
Cmdlet          Restart-Service                                     Restart-Service [-Name] <String[]> [-Force] [-Pa...
Cmdlet          Resume-Service                                      Resume-Service [-Name] <String[]> [-PassThru] [-...
Cmdlet          Set-Service                                         Set-Service [-Name] <String> [-DisplayName <Stri...
Cmdlet          Start-Service                                       Start-Service [-Name] <String[]> [-PassThru] [-I...
Cmdlet          Stop-Service                                        Stop-Service [-Name] <String[]> [-Force] [-PassT...
Cmdlet          Suspend-Service                                     Suspend-Service [-Name] <String[]> [-PassThru] [...

From here we can see what services are available for SQL Server:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> get-service MSSQL*

Status   Name               DisplayName
------   ----               -----------
Running  MSSQL$NRLAPTOP2    MSSQL$NRLAPTOP2
Running  MSSQL$SQLEXPRESS   SQL Server (SQLEXPRESS)
Running  MSSQL$TELERIK      MSSQL$TELERIK
Running  MSSQLSERVER        SQL Server (MSSQLSERVER)
Stopped  MSSQLServerADHe... SQL Server Active Directory Helper
Running  MSSQLServerOLAP... SQL Server Analysis Services (MSSQL...

Now we want to stop the MSSQLSERVER service and any dependant services:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> stop-service "MSSQLSERVER" -force

If we re-run get-service we can see that the service is stopped:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> get-service mssql*

Status   Name               DisplayName
------   ----               -----------
Running  MSSQL$NRLAPTOP2    MSSQL$NRLAPTOP2
Running  MSSQL$SQLEXPRESS   SQL Server (SQLEXPRESS)
Running  MSSQL$TELERIK      MSSQL$TELERIK
Stopped  MSSQLSERVER        SQL Server (MSSQLSERVER)
Stopped  MSSQLServerADHe... SQL Server Active Directory Helper
Running  MSSQLServerOLAP... SQL Server Analysis Services (MSSQL...

You can also interrogate the service objects using the get-member command. For example you could take the service objects returned by get-service and direct them to the get-member command using the "|" pipe symbol. The following is only a partial listing.

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> get-service | get-member

   TypeName: System.ServiceProcess.ServiceController

Name                      MemberType    Definition
----                      ----------    ----------
Name                      AliasProperty Name = ServiceName
Close                     Method        System.Void Close()
Continue                  Method        System.Void Continue()
CreateObjRef              Method        System.Runtime.Remoting.ObjRef CreateObjRef(Type requestedType)
Dispose                   Method        System.Void Dispose()
Equals                    Method        System.Boolean Equals(Object obj)
ExecuteCommand            Method        System.Void ExecuteCommand(Int32 command)
get_DependentServices     Method        System.ServiceProcess.ServiceController[] get_DependentServices()
get_DisplayName           Method        System.String get_DisplayName()
get_MachineName           Method        System.String get_MachineName()
get_ServiceHandle         Method        System.Runtime.InteropServices.SafeHandle get_ServiceHandle()

What about navigation?  If I want to change locations in the file system of course there's "CD" or the PS native "set-location". What's unique here is that you can navigate the registry, environmental variables, certificate stores or any other system that PS has a provider for (yes, you can write your own providers).  For example the following is perfectly legal:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> cd env:
PS Env:\> dir

Name                           Value
----                           -----
Path                           C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program Files\ATI Technolo...
TEMP                           C:\DOCUME~1\NOELRI~1\LOCALS~1\Temp
SESSIONNAME                    RDP-Tcp#1
PATHEXT                        .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.PSC1
USERDOMAIN                     NRLAPTOP
PROCESSOR_ARCHITECTURE         x86

You could image using CD to navigate hiearchical database information in this way (to what practical end I do not know, but it is amusing). Find out what PowerShell drives are available on your machine by using get-psdrive:

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> get-psdrive

Name       Provider      Root                                                                           CurrentLocation
----       --------      ----                                                                           ---------------
Alias      Alias
C          FileSystem    C:\                                    Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug
cert       Certificate   \
D          FileSystem    D:\
Env        Environment
Function   Function
HKCU       Registry      HKEY_CURRENT_USER
HKLM       Registry      HKEY_LOCAL_MACHINE
Variable   Variable

Use get-psprovider to find the providers on your system.  See the MSDN for examples of writing your own provider. 

PS C:\Clients\Falafel\Projects\FalafelCmdletLibrary\bin\Debug> Get-PSProvider

Name                 Capabilities                                      Drives
----                 ------------                                      ------
Alias                ShouldProcess                                     {Alias}
Environment          ShouldProcess                                     {Env}
FileSystem           Filter, ShouldProcess                             {C, D}
Function             ShouldProcess                                     {Function}
Registry             ShouldProcess                                     {HKLM, HKCU}
Variable             ShouldProcess                                     {Variable}
Certificate          ShouldProcess                                     {cert}

You can download PowerShell at http://www.microsoft.com/technet/scriptcenter/topics/msh/download.mspx.  It comes with the install and docs for "Getting Started", "Quick Reference" and "Users Guide".