Introduction to PowerShell’s Else If Logic
PowerShell’s ‘ElseIf’ statement comes under the umbrella of flow control. Once you master the basic ‘If’ construction then you can increase the scope of your script by adding extra ‘ElseIf’ statements to the logic control.
Topics for PowerShell’s ElseIf Statement
- Begin With The Plain ‘If’ Statement
- Example 1: Plain PowerShell If
- Example 2: PowerShell ElseIf
- Example 3: PowerShell ElseIf and Plain Else
- Example 4: Check If a Service is Installed and Working
- Example 5: PowerShell ElseIf Help File
- PowerShell If -or
- Summary of PowerShell’s ElseIf Construction
Begin With The Plain ‘If’ Statement
Let us get started by mastering PowerShell’s basic ‘If’ construction. All that you need here is a condition or test, followed by the block command payload.
Note in passing that PowerShell employs different types of bracket for each component, the (parenthesis style of bracket are for the first part, namely the condition), while {braces are for the block command}.
If (condition) {Block Command}
Here is a different explanation of the same ‘If’ construction:
If (test) { execute when true }
Summary: The PowerShell ‘If’ conditionally executes what’s inside the {curly brackets}, depending on the truth of the test expression.
Example 1: Plain PowerShell ‘If’
# Trivial PowerShell If Example
$Number = 10
if ($Number -gt 0) {"$Number is greater than zero"}
Learning Points
Note 1: Separate the If statement into two components: if (test) and {what to do}, then study each component of the PowerShell construction.
Note 2: Avoid over-think; remember that there is no ‘Then’ in a PowerShell ‘If’ statement. Incidentally, for those familiar with VBScript there is no endif in PowerShell.
Example 2: PowerShell ElseIf
Let us extend my trivial ‘If’ example by introducing an ‘ElseIf’ statement. Incidentally, while ElseIf is not case sensitive, it does highlight the two words ‘Else’ and ‘if’.
# Simple PowerShell ElseIf Example
$Number = -10
If ($Number -gt 0) {"$Number is bigger than zero"}
ElseIf ($Number -lt 0) {"$Number is negative"}
Note 3: Do check the logic of each line, -gt is PowerShell’s way of saying ‘Greater than’, and -lt means ‘Less than’.
PowerShell’s Else If
In this example I cannot get Else If, to work; what I find is that when there is a space between the Else and If, PowerShell generates an error. What happens is I get message from PowerShell saying: ‘Missing block statement’.
Guy Recommends: Free WMI Monitor for PowerShell (FREE TOOL)
Windows Management Instrumentation (WMI) is one of the hidden treasures of Microsoft’s operating systems. Fortunately, SolarWinds have created a Free WMI Monitor for PowerShell so that you can discover these gems of performance information, and thus improve your PowerShell scripts.
Take the guesswork out of which WMI counters to use when scripting the operating system, Active Directory, or Exchange Server. Give this WMI monitor a try – it’s free.
Example 3: PowerShell ElseIf and Plain Else
It’s good practice to add a final Else statement. This catch-all will check for anything that slips through your ElseIf logic. For example, what if the value of $Number was precisely zero?
# Simple PowerShell ElseIf Example
$Number = -10 +10
if ($Number -gt 0) {
"$Number is bigger than zero"
}
ElseIf ($Number -lt 0) {
"$Number is negative"
}
Else {
"This number appears to be zero"
}
Example 4: Check If a Service is Installed and Working
Here is a real-life example of PowerShell ElseIf script, it uses the ‘Display’ property of the Windows spooler service.
# PowerShell script to check whether the spooler service is working
Clear-Host
$SrvName = "Print Spooler"
$Service = Get-Service -display $SrvName -ErrorAction SilentlyContinue
if (-Not $Service) {$SrvName + " is not installed on this computer."}
ElseIf ($Service.Status -eq "Running") {$SrvName + " is working." }
ElseIf ($Service.Status -eq "Stopped") {$SrvName + " is not working." }
Else {"Guy is baffled "}
Note 4: In addition to that final ‘Else’, this example uses multiple ElseIf conditional tests, however, for scripts that need even more complex logic I prefer ‘PowerShell’s Switch parameter‘.
Note 5: See more on -ErrorAction SilentlyContinue
Researching PowerShell’s Else If Logic
For more information on using this logical construction refer to PowerShell’s built-in About_IF file
Get-Help About_If
For example, the About_If file reminds us that when a test is true, then after executing the {Statement}, PowerShell exits. However, should the test be false then PowerShell continues to the next test.
Get more help on PowerShell’s About files »
Guy Recommends: Network Performance Monitor (FREE TRIAL)
SolarWinds Network Performance Monitor (NPM) will help you discover what’s happening on your network. This utility will also guide you through troubleshooting; the dashboard will indicate whether the root cause is a broken link, faulty equipment or resource overload.
What I like best is the way NPM suggests solutions to network problems. Its also has the ability to monitor the health of individual VMware virtual machines. If you are interested in troubleshooting, and creating network maps, then I recommend that you try NPM on a 30-day free trial.
Example 5: PowerShell ElseIf Checks Help File
This example has an important task, and that is to check that we have the name of an actual file. Remember that second (test statement) followed by a second {Block Script}.
# Help on PowerShell's ElseIf statements
Clear-Host
$File = Get-Help About_scope
If ($File -Match "The if Statement") {"We have the correct help file"}
ElseIf ($File.Length -lt 1) {"Check the file name and its location"}
Else {"File exists, but does not contain info about the 'If statement'"}
Learning Points
Note 6: The advantage of ElseIf over plain Else, is that we can introduce multiple tests. In the above example we use ElseIf to check if the length of the file is less than 1. To activate the ‘ElseIf’ block, set $File to a non-existent file for example
$File = Get-Help about_ifxx.
Note 7: To trigger the final ‘Else’, try changing:
$File = Get-Help About_If
to
$File = Get-Help about_scope
Note 8: Alternatively, see more about the PowerShell ElseIf statement at Microsoft’s site.
Guy Recommends: SolarWinds Admin Bundle for Active Directory (FREE TOOL)
Import users from a spreadsheet. Just provide a list of the users with their fields in the top row, and save as .csv file. Then launch this FREE utility and match your fields with AD’s attributes, click and import the users.
Optionally, you can provide the name of the OU where the new accounts will be born. Download your FREE bulk import tool.
If you need more comprehensive application analysis software, Download a free trial of SAM (Server & Application Monitor)
PowerShell’s Else Construction
PowerShell’s ‘Else’ acts as a safety net for flow logic. Following on from the ‘If’ command you often you have multiple ElseIf statements, with a final plain ‘else’ statement.
See more on PowerShell’s plain ‘Else’ statement »
Summary of PowerShell’s ElseIf Construction
One of the oldest, and one of the best, statements for filtering data is the ‘If’ clause. Nevertheless it’s always worth a refresher on the basic ‘If’ statement, before progressing to the more versatile ‘ElseIf’. The secret of understanding PowerShell’s implementation of If and ElseIf is to pay close attention to the style bracket. ElseIf (parenthesis for the test) and {braces for the action}.
If you like this page then please share it with your friends
See more Windows PowerShell flow control examples
• PowerShell Continue Statement • PowerShell If Statement • PowerShell ElseIf • PowerShell Else
• PowerShell Comparison Operators • PowerShell If -And • PowerShell If -Or • PowerShell If -Not
• Conditional Operators • Where Filter • PowerShell Real-life Techniques • PowerShell Home
Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.
