Chapter 3 Quick Reference

Open table as spreadsheet

To	Do This
Produce a listing of all variables defined in a Windows PowerShell session	Use the Set-Location cmdlet to change location to the variable PSDrive, then use the Get-ChildItem cmdlet
Obtain a listing of all the aliases	Use the Set-Location cmdlet to change location to the alias PSDrive, then use the Get-ChildItem cmdlet to produce a listing of aliases. Pipeline the resulting object into the Where-Object cmdlet and filter on the name property for the appropriate value
Delete a directory that is empty	Use the Remove-Item cmdlet and supply the name of the directory
Delete a directory that contains other items	Use the Remove-Item cmdlet and supply the name of the directory and specify the recurse argument
Create a new text file	Use the New-Item cmdlet and specify the - path argument for the directory location. Supply the name argument, and specify the type argument as file. Example: new-item -path C:\Mytest -name Myfile.txt-type file
Obtain a listing of registry keys from a registry hive	Use the Get-ChildItem cmdlet and specify the appropriate PSDrive name for the -path argument. Complete the path with the appropriate registry path. Example: gci -path HKLM:\software
Obtain a listing of all functions on the system	Use the Get-ChildItem cmdlet and supply the PSDrive name of function:\ to the path argument. Example: gci -path function:\

Chapter 4: Using PowerShell Scripts

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Overview

After completing this chapter, you will be able to:

Understand the reasons for writing Windows PowerShell scripts
Make the configuration changes required to run Windows PowerShell scripts
Understand how to run Windows PowerShell scripts
Understand how to break lines
Understand the use of variables and constants
Create objects in a Windows PowerShell script
Call methods in a Windows PowerShell script

With the ability to perform so many actions from inside Windows PowerShell in an interactive fashion, you may wonder , “Why do I need to write scripts?” For many network administrators, one-line PowerShell commands will indeed solve many routine problems. This can become extremely powerful when the commands are combined into batch files and perhaps called from a login script. However, there are some very good reasons to write Windows PowerShell scripts. We will examine them as we move into this chapter. All the scripts mentioned in this chapter can be found in the corresponding scripts folder on the CD.

Why Write Windows PowerShell Scripts

Perhaps the number one reason to write a Windows PowerShell script is to address recurring needs. As an example, consider the activity of producing a directory listing. The simple Get- ChildItem cmdlet does a good job, but after you decide to sort the listing and filter out only files of a certain size , you end up with the command shown here:

Get-ChildItem c:\fso  Where-Object {$_.Length -gt 1000}  Sort-Object -Property

name

Even using Tab Completion , the previous command requires a bit of typing. One way to shorten it would be to create a user -defined function, and we will examine that technique later. For now, the easiest solution is to write a Windows PowerShell script. The DirectoryListWithArguments.ps1 script is shown here:

DirectoryListWithArguments.ps1

foreach ($i in $args) {Get-ChildItem $i  Where-Object {$_.length -gt 1000}  Sort-Object -property name}

The DirectoryListWithArguments.ps1 script takes a single, unnamed argument that allows the script to be modified when it is run. This makes the script much easier to work with and adds flexibility.

An additional reason that network administrators write Windows PowerShell scripts is to run the script as a scheduled task. In the Windows world, there are multiple task scheduler engines. Using the WIN32_ScheduledJob Windows Management Instrumentation (WMI) class, you can create, monitor, and delete scheduled jobs. This WMI class has been available since the Windows NT 4 days. On Windows XP and Windows Server 2003, the schtasks .exe utility offers more flexibility than the WIN32_ScheduledJob WMI class. On Windows Vista, a Schedule.Service object is available to simplify configuration of scheduled jobs.

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The ListProcessesSortResults.ps1 script is a script that a network administrator may want to schedule to run several times a day. It produces a list of currently running processes and writes the results out to a text file as a formatted and sorted table.

ListProcessesSortResults.ps1

$args = "localhost","loopback","127.0.0.1" foreach ($i in $args) {$strFile = "c:\mytest\"+ $i +"Processes.txt" Write-Host "Testing" $i "

please

wait ..."; Get-WmiObject -

computername

$i -class win32_process  Select-Object name, processID, Priority, ThreadCount, PageFaults, PageFileUsage  Where-Object {!$_.processID -eq 0}  Sort-Object -property name  Format-Table  Out-File $strFile}

One other reason for writing Windows PowerShell scripts is that it makes it easy to store and share both the “secret commands” and the ideas behind the scripts. For example, suppose you develop a script that will connect remotely to workstations on your network and search for user accounts that do not require a password. Obviously, an account without a password is a security risk! After some searching around, you discover the WIN32_UserAccount WMI class and develop a script that performs to your expectation. Because this is likely a script you would want to use on a regular basis, and perhaps share with other network administrators in your company, it makes sense to save it as a script. A sample of such a script is AccountsWithNoRequiredPassword.ps1 , which is seen here.

AccountsWithNoRequiredPassword.ps1

$args = "localhost" foreach ($i in $args) {Write-Host "Connecting to" $i "please wait ..."; Get-WmiObject -computername $i -class win32_UserAccount  Select-Object Name, Disabled, PasswordRequired, SID, SIDType  Where-Object {$_.PasswordRequired -eq 0}  Sort-Object -property name  Write-Host}