Introduction to PowerShell’s Examples of -Like and -NotLike
On this page I will explain how to filter data with PowerShell’s -Like comparator.
One day I wanted to create a WMI script using the network adapter, but even using PowerShell I could not find the right properties, so I went back to basics and listed all the cmdlets containing ‘Adapter’.
Topics for PowerShell -Like Operator
- Differences Between -Like and -Match
- Example 1: PowerShell’s -Like Comparator
- Example 2: Double Wildcards -Match *Adapter*
- Example 3: The -Match Comparator Instead of -Like
- Example 4: PowerShell -NotLike
Differences Between -Like and -Match
In a nutshell, if you are thinking, ‘I am probably going to need a wildcard to find this item’, then start with -Like. However, if you are pretty sure of most of the letters in the word that you are looking for, then you are better off experimenting with -Match.
Here is a more technical distinction: -Match is a regular expression, whereas -Like is just a wildcard comparison, a subset of -Match.
Example 1: PowerShell’s -Like Comparator
This example only lists those cmdlets that end with the letters ‘adapter’.
# PowerShell -Like Operator
# Author: Guy Thomas
# Version September 2011 tested on PowerShell v 2.0
Clear-Host
Get-WmiObject -List | Where-Object {$_.name -Like "*Adapter"}
Learning Points
Note 1: Observe how Get-WmiObject uses the -List parameter.
Note 2: Most comparator scripts are introduced with Where-Object, followed by the pipeline construction: $_.
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Example 2: Double Wildcards -Match *Adapter*
The problem with Example 1 is that I suspect there are more cmdlets containing the word Adapter, for instance ‘adapter’ maybe in the middle of the WMI class name.
# PowerShell example to demonstrate -Like
# Author: Guy Thomas
# Version September 2011 tested on PowerShell v 2.0
Clear-Host
Get-WmiObject -List | Where-Object {$_.name -Like "*Adapter*"}
Learning Points
Note 3: Once again, realise the importance of the construction $_. Dollar, underscore. The dot means ‘in this data stream’.
Note 4: Thanks to the second *, Example 2 should returns more cmdlets.
See more PowerShell -Match examples.
Example 3: The -Match Comparator Instead of -Like
I like to be flexible with PowerShell’s comparators, if the results are not as I anticipated then I may try an alternative such as -Match or -Contains.
# PowerShell example to check with -Match
# Author: Guy Thomas
# Version September 2011 tested on PowerShell v 2.0
Clear-Host
Get-WmiObject -List | Where-Object {$_.name -Match "Adapter"}
Learning Points
Note 5: Actually this example should list the same WMI classes as Example 2, but in other scripts you may getter better results using -Match instead of -Like.
See also PowerShell’s -Match »
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Example 4: More Comparators -NotLike
Time for a recap: The simplest comparator is ‘equals’, and the way you code this in PowerShell with -eq (not =). However, in these examples, -eq would not be effective, because realistically you would have to know the answer before you could ask the question!
I would like to take this opportunity to examine other comparators. It is surprising how often the negative -NotLike operator produces a neat solution to a scripting problem. For instance, there are several WmiObjects beginning with CIM, one way of excluding them would be to Not Like “CIM*”.
Furthermore, by using multiple criteria in the filter, you can fine tune the output, to achieve my goal I have added ‘-And’. If for any reason -And fails remember this, when appending a second comparator the secret is to add another instance of the comparator ($_.name) after the -And.
# PowerShell example to list demonstrate -NotLike with -And
# Author: Guy Thomas
# Version September tested on PowerShell v 2
Clear-Host
$WMI = Get-WmiObject -List `
| where-Object {$_.name -NotLike "CIM*" -And $_.name -NotLike "__*"}
$WMI
Write-Host `n $WMI.count "WMI objects not contain CIM or __"
Learning Points
Note 6: My mission is always to get you started. Now it’s over to you; experiment with different filters, substitute your ideas for “CIM”, and “__”. Perhaps best of all would be to combine -NotLike and -Like.
Note 7: I appended code to count the number of WMI classes, this helps to see which variation of my script returns the most items.
Follow-up
As usual with my scripts, the mission is to get you started. If you want to know more about -Match, -Like and their relatives, then start with PowerShell’s own help thus:
Get-Help about_comparison_operators. (Or try Get-Help about*)
These help files introduce a whole world of specific terms, for example, ‘regular expression comparisons’ and ‘wildcard comparison’. Once you need and understand such extra information, then I have succeeded in my mission of introducing you to -Match and -Like.
See more about PowerShell Comparison Operators »
Summary of PowerShell -Like Operator
So often we suffer from information overload. Working with PowerShell is no different, however it does supply three conditional operators to filter your information: -Match, -Like and -Contains. Each operator has different properties; with research, you can get just the filter you need, and thus filter the desired stream of information into your script’s output.
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See more Windows PowerShell flow control examples
• PowerShell Switch Statement • PowerShell Real-life Techniques • Free Permissions Analyzer
• Differences between For, ForEach and ForEach-Object • PowerShell Loops • PowerShell Home
• Conditional Operators • Do While Loop • PowerShell If Statement • PowerShell Brackets
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.
