Basic Cmdlets

PowerShell will happily provide a list of all registered cmdlets using Get-Command. Here's a partial list:

 CommandType     Name                  Definition -----------     ----                  ---------- Cmdlet          Add-Content           Add-Content [-Path] <String[]> [-Value] <Ob... Cmdlet          Add-History           Add-History [[-InputObject] <PSObject[]>] [... Cmdlet          Add-Member            Add-Member [-MemberType] <PSMemberTypes> [-... Cmdlet          Add-PSSnapin          Add-PSSnapin [-Name] <String[]> [-PassThru]... Cmdlet          Clear-Content         Clear-Content [-Path] <String[]> [-Filter <... Cmdlet          Clear-Item            Clear-Item [-Path] <String[]> [- Force] [-Fi... Cmdlet          Clear-ItemProperty    Clear-ItemProperty [-Path] <String[]> [-Nam... Cmdlet          Clear-Variable         Clear-Variable [-Name] <String[]> [-Include... Cmdlet          Compare-Object         Compare-Object [- ReferenceObject] <PSObject... Cmdlet          ConvertFrom-SecureString ConvertFrom-SecureString [- SecureString] <... Cmdlet          Convert-Path             Convert-Path [-Path] <String[]> [-Verbose]... 

In Chapter 9, we'll talk you through output formatting, which helps prevent information from getting lost "off the edge" of PowerShell's 80-column display window.

Using Get-Command is a good way to inventory what your capabilities within PowerShell are. For any given cmdlet, Get-Command tells you more about it. For example, the following example describes what the Set-Alias cmdlet does:

 PS C:\>Get-Command Set-Alias 

The following example produces a lengthy description of the Set-Alias cmdlet, along with details about each argument, examples of how the cmdlet is used, and so forth.

 PS C:\>Get-Help Set-Alias 

Tip 

Try using Help instead of Get-Help; Help isn't an alias, but rather a built-in function. It calls Get-Help and display the output one page at a time, making it easier to read lengthy entries.

Get-Help can also be used to help discover new cmdlets. For example, if you want to create a new service, but aren't sure what the proper cmdlet would be, Get-Help can help you find out:

 PS C:\>Get-Help *Service 

The * wildcard tells Get-Help to display a list of help topics related to services; since there's a help topic for each cmdlet, you'll also be looking at a list of cmdlets related to services.

Parameters

Many cmdlets can accept parameters that are passed by name using a hyphen, then the parameter (or argument) name followed by a space, and then the value you're passing to the parameter. The following example creates a new file.

 PS C:\>New_Item -type file "myfile.txt" 

Notice the -type parameter, which is given the values file and a filename. When parameters are passed by name, they can be passed in any order. Some parameter names may be abbreviated such as -db for -debug. Valid abbreviations are always listed in the command's help.

Ubiquitous Parameters

Most cmdlets support a set of ubiquitous parameters, which are always optional. This means ubiquitous parameters such as those listed below don't need to be specified if you don't want to use them.

• -Debug (-db). Instructs the cmdlet to provide additional programmer-level detail about the operation.

• -ErrorAction (-ea). Controls the behavior of the cmdlet when an error occurs. Values can be NotifyContinue (which is the default), NotifyStop, SilentContinue, SilentStop, and Inquire.

• -ErrorVariable (-ev). Specifies the name of a variable that will store all objects that encountered an error while processing. The specified variable is processed in addition to the built-in $ERROR variable.

• -OutVariable (-ov). Specified the name of a variable in which to place all objects that are output from the cmdlet.

• -Verbose (-vb). Instructs the cmdlet to produce additional output about its actions and progress.