Working with Cmdlets

Cmdlets provide the basic foundation for working with a computer from within the Windows PowerShell. Although there are many different cmdlets with many different available uses, cmdlets all have common features. I'll examine these common features in this section.

Using Windows PowerShell Cmdlets

At the Windows PowerShell prompt, you can get a complete list of cmdlets available by typing help *-*. To get help documentation on a specific cmdlet, type help followed by the cmdlet name, such as:

help get-variable

Table 6-2 provides a list of cmdlets you'll commonly use for administration. Although there are many other cmdlets available, these are the ones you're likely to use the most.

Table 6-2: Cmdlets Commonly Used for Administration
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Cmdlet Name	Description
ConvertFrom-SecureString	Export a secure string to a safe format.
ConvertTo-SecureString	Create a securestring from a normal string.
Get-Alias	Returns alias names for cmdlets.
Get-AuthenticodeSignature	Gets the signature object associated with a file.
Get-Credential	Gets a credential object based on a password.
Get-Date	Gets the current date and time.
Get-EventLog	Gets the log data from the Windows log files.
Get-ExecutionPolicy	Gets the effective execution policy for the current shell.
Get-Host	Gets host information.
Get-Location	Displays the current location.
Get-MshDrive	Gets the drive information for the specified Msh drive.
Get-Service	Gets a list of services.
Import-Alias	Imports an alias list from a file.
New-Alias	Creates a new cmdlet-alias pairing.
New-Service	Creates a new service.
Push-Location	Pushes a location to the stack.
Read-Host	Reads a line of input from the host console.
Restart-Service	Restarts a stopped service.
Resume-Service	Resumes a suspended service.
Set-Alias	Maps an alias to a cmdlet.
Set-AuthenticodeSignature	Places an Authenticode signature in a script or other file.
Set-Date	Sets the system date and time on the host system.
Set-ExecutionPolicy	Sets the execution policy for the current shell.
Set-Location	Sets the current working location to a specified location.
Set-Service	Makes and sets changes to the properties of a service.
Start-Service	Starts a stopped service.
Start-Sleep	Suspends shell or script activity for the specified period.
Stop-Service	Stops a running service.
Suspend-Service	Suspends a running service.
Write-Output	Writes an object to the pipeline.

Using Cmdlet Parameters

All cmdlet parameters are designated with an initial dash (-). To reduce the amount of typing required, some parameters are position-sensitive such that you can sometimes pass parameters in a specific order without having to specify the parameter name. For example, with get-service, you don't have to specify the -Name parameter, you can simply type:

Get-service ServiceName

where ServiceName is the name of the service you want to examine, such as:

Get-service MSExchangeIS

This command line returns the status of the Microsoft Exchange Information Store service. Because you can use wildcards, such as *, with name values, you can also type get-service mse* to return the status of all Microsoft Exchange–related services.

All cmdlets support the common set of parameters listed in Table 6-3. However, for you to use these parameters, you must run the cmdlet in such a way that these parameters are returned as part of the result set.

Table 6-3: Common Cmdlet Parameters
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Parameter Name	Description
-Confirm	Pauses processes and requires the user to acknowledge the action before continuing. Remove- and Disable- cmdlets have this parameter.
-Debug	Provides programming-level debugging information about the operation.
-ErrorAction	Controls the command behavior when an error occurs.
-ErrorVariable	Sets the name of the variable (in addition to the standard error) in which to place objects for which an error has occurred.
-OutBuffer	Sets the output buffer for the cmdlet.
-OutVariable	Sets the name of the variable in which to place output objects.
-Verbose	Provides detailed information about the operation.
-WhatIf	Allows the user to view what would happen if a cmdlet were run with a specific set of parameters. Remove- and Disable- cmdlets have this parameter.

Understanding Cmdlet Errors

When you work with cmdlets, you'll encounter two standard types of errors:

• Terminating errors Errors that halt execution

• Nonterminating errors Errors that cause error output to be returned but do not halt execution

With both types of errors, you'll typically see error text that can help you resolve the problem. For example, an expected file might be missing, or you may not have sufficient permissions to perform a specified task.

Using Cmdlet Aliases

For ease of use, Windows PowerShell lets you create aliases for cmdlets. An alias is an abbreviation for a cmdlet that acts as a shortcut for executing the cmdlet. For example, you can use the alias gsv instead of the cmdlet name get-service.

Table 6-4 provides a list of commonly used default aliases. Although there are many other aliases, these are the ones you'll use most frequently.

Table 6-4: Commonly Used Cmdlet Aliases
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Alias	Cmdlet
clear, cls	Clear-Host
Diff	Compare-Object
cp, copy	Copy-Item
Epal	Export-Alias
Epcsv	Export-Csv
Foreach	ForEach-Object
Fl	Format-List
Ft	Format-Table
Fw	Format-Wide
Gal	Get-Alias
ls, dir	Get-ChildItem
Gcm	Get-Command
cat, type	Get-Content
h, history	Get-History
gl, pwd	Get-Location
gps, ps	Get-Process
Gsv	Get-Service
Gv	Get-Variable
Group	Group-Object
Ipal	Import-Alias
Ipcsv	Import-Csv
R	Invoke-History
Ni	New-Item
Mount	New-MshDrive
Nv	New-Variable
rd, rm, rmdir, del, erase	Remove-Item
Rv	Remove-Variable
Sal	Set-Alias
sl, cd, chdir	Set-Location
sv, set	Set-Variable
Sort	Sort-Object
Sasv	Start-Service
Sleep	Start-Sleep
spps, kill	Stop-Process
Spsv	Stop-Service
write, echo	Write-Output

You can define additional aliases using the Set-Alias cmdlet. The syntax is:

Set-alias aliasName cmdletName

Where aliasName is the alias you want to use and cmdletName is the cmdlet for which you are creating an alias. The following example creates a "go" alias for the get-process cmdlet:

Set-alias go get-process

To use your custom aliases whenever you work with Windows PowerShell, enter the related command line in your profile.