UNIT 2 LAB 4: CREATING LOOPING STATEMENTS

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1 OVERVIEW In a script, it is often necessary to perform the same operation repeatedly until some condition exists. This could be reading the lines of text in a file or reading input from the keyboard until a specific key is pressed. These tasks are normally handled using a looping statement. In this lab, you will practice creating looping statements to repeat a task for a specific number of iterations, until a specific condition exists, or until all the items in an array are read. OBJECTIVES 5.1. Use input and output commands Use looping constructs Initialize data structures Use arithmetic, string, and logical operators PREREQUISITES Lab - Creating Selection Statements is complete. SCENARIO Your organization is investigating the use of the command line and scripting for network administration. You have previously created parts of a menu based inventory script. In this lab, we will add some further functionality to the script using looping statements. TASKS 1. Logon to the DC-1 virtual machine with an administrative account. 2. Open the PowerShell ISE. 3. Open the Get-Inventory-Sw.ps1 and save it as Get-Inventory2.ps1 4. Get-Inventory2.ps1 should now be displayed in the script pane. We will be editing this script in this lab. ADDING A WHILE LOOP One of the issues you had with the previous script was that it could only process one option at a time before the script would exit. In this step, you will add a While loop so that the script will keep running until the user presses the X key to exit. To add a loop to the Get-Inventory2.ps1 script, perform the following steps: 1. Before any code in the Main Body section add the following code: While ( $menu_choice -ne X ) { 2. Remove the code in the statement block for X option, leaving only the Write-Host statement about Exiting

2 3. Place a closing curly brace } at the end of the script to match the opening curly brace in the While statement. 4. The main body of the script should look like the screen shown below. Figure 1 - Script Main Body 5. Correct any errors in the script and then save the script. 6. Run the script and test the operation. You should see output similar to the screen below. 7. Notice each time an option is chosen the menu is displayed again. To prevent the multiple menus inert the following line at the top of the while loop before the line that displays the menu. Clear-Host Figure 2 - Script Output

3 8. Run the script and verify it works. 9. You may notice that you don t see the output from each option because the loop is executing too quickly. To slow down your script so that you can see the information displayed on the console, add the following command before the final curly brace for the While statement. Start-Sleep -Seconds Save your script and test it. It should now work correctly. In the next section, we ll make some of the menu options work. 11. The code in the Main Body of your script should look like the screen shown below. Some comments have been added. Figure 3 - Script with Sleep statement and Clear-Host ADDING A FOR LOOP A For loop can be used when you would like to loop a specific number of times. For example, if you have 25 users in your organization and you would like to update some property for all users then a For Loop could work. In this step, we are going to use a For Loop to loop through an array of computers and perform a simple hardware inventory. To add a For Loop to your script, perform the following steps:

4 1. Open or verify that the Get-Inventory2.ps1 script is open and add the following code to the Initialization section: $computers = DC1, W7-Client, W8-Client 2. In the Main Body of the script, remove the line in the script block for the A option Write-Host This code is not yet implemented 3. In place of the line you just removed, insert the following code: for ($i=0; $i -lt $computers.length; $i++) { $computers[$i] Get-WmiObject Win32_ComputerSystemProduct -ComputerName $computers[$i] } Read-Host -Prompt "Press Enter to Continue..." 4. The code in the Main Body section should look like the code below. Figure 4 - Code to view installed software 5. Correct any errors in your code and save the script. 6. Run the script and test that it works properly. You should see output similar to the screen below when you choose option A. Figure 5 - Script Output showing installed software

5 ADDING A FOREACH LOOP The Foreach Loop is used to loop through a collection of objects assigning each one to a variable that is used in a script block. In this step, we will use the $computers array in Foreach Loop to perform a WMI query on each of the computers. To add a Foreach Loop perform the following steps: 1. Verify that the Get-Inventory2.ps1 script is open in the PowerShell ISE. 2. In the Main Body of the script, remove the line in the script block for the B option Write-Host This code is not yet implemented 3. In place of the line you just removed, insert the following code: foreach ($computer in $computers) { Get-WmiObject -Class Win32_Processor -ComputerName $computer Get-WmiObject -Class Win32_PhysicalMemory -ComputerName $computer Get-WmiObject -Class Win32_LogicalDisk -ComputerName $computer } Read-Host -Prompt "Press Enter to Continue..." 4. Your Switch statement should now look like the figure below. Figure 6 - Switch Statement

6 5. Correct any errors and save your script. 6. Test and verify your script. This script s output is rather verbose and formatted poorly. We will address this in a future lab.