Windows PowerShell is a command line shell and scripting language for Windows that supersedes the CMD.exe shell and batch language. PowerShell is also an automation engine for Windows that provides functionality similar to Windows Script Host and VBScript.
Description of Windows PowerShell
Windows PowerShell is a command line shell and scripting language for Windows that supersedes the CMD.exe shell and batch language. PowerShell is also an automation engine for Windows that provides functionality similar to Windows Script Host and VBScript. The PowerShell engine is hostable allowing PowerShell functionality to be accessed from within custom applications including other PowerShell hosts such as PowerShell ISE, PowerGUI and PowerShellPlus.
PowerShell is built on top of the Microsoft .NET Framework and exposes much of the capabilities of the .NET Framework through the PowerShell scripting language. And since .NET allows for interop with COM, you can also script COM objects.
PowerShell 2.0 is integrated with Windows 7 and Windows Server 2008 R2, and is available for Windows XP SP3, Windows Server 2003 SP2 and Windows Vista SP1 and SP2. Powershell 5.0 is currently the standard on Windows 10 and Server 2012 R2.
Example Usage
# List all processes using > 100 MB of PagedMemory in descending sort order
C:\PS> Get-Process | Where {$_.PagedMemorySize -gt 100MB} | Sort -Desc
# PowerShell can also evaluate expressions
C:\PS> "Hello World!"
Hello World!
C:\PS> (98.6 - 32) * 5/9
37
# Production orientation allows experimentation and confirmation
C:\PS> Get-ChildItem C:\Users\John *.bak -r |
Where {$_.LastWriteTime -gt (Get-Date).AddDays(-7)} |
Remove-Item -WhatIf
What if: Performing operation "Remove File" on Target "C:\Users\John\foo.bak"
C:\PS> Get-Process iexp* | Stop-Process -Confirm
Confirm
Are you sure you want to perform this action?
Performing operation "Stop-Process" on Target "iexplore (7116)".
[Y] Yes [A] Yes to All [N] No [L] No to All [S] Suspend [?] Help (default is Y):
Common Gotchas
Executing EXEs via a path with spaces requires quoting the path and the use of the call operator - &
C:\PS> & 'C:\Program Files\Windows NT\Accessories\wordpad.exe'
Calling PowerShell functions does not require parenthesis or comma separated args. PowerShell functions should be called just like a cmdlet. The following examples demonstrates the problem caused by this issue e.g.:
C:\PS> function Greet($fname, $lname) {"My name is '$lname', '$fname' '$lname'"}
C:\PS> Greet('James','Bond') # Wrong way to invoke this function!!
My name is '', 'James Bond' ''
Note that both 'James' and 'Bond' are packaged up as a single argument (an array) that is passed to the first parameter. The correct invocation is:
C:\PS> Greet James Bond
My name is 'Bond', 'James' 'Bond'
Note that in PowerShell 2.0, the use of Set-StrictMode -version 2.0 will catch this type of problem.
Enabling Scripts
Before you can run custom PowerShell scripts (.ps1 files), you need to enable the execution of unsigned scripts. Otherwise, attempting to run a script will produce an error:
.\test.ps1 : File C:\test.ps1 cannot be loaded because running
scripts is disabled on this system. For more information, see
about_Execution_Policies at http://go.microsoft.com/fwlink/?LinkID=135170.
At line:1 char:1
+ .\test.ps1
+ ~~~~~~~~~~
+ CategoryInfo : SecurityError: (:) [], PSSecurityException
+ FullyQualifiedErrorId : UnauthorizedAccess
You can set the script execution policy with the Set-ExecutionPolicy cmdlet:
# Allow scripts to be run by all users. This command requires admin privileges
Set-ExecutionPolicy Unrestricted
# Allow scripts to be run by the current user. This does not require special privileges
Set-ExecutionPolicy Unrestricted -Scope CurrentUser
Resources
