Windows PowerShell -Like

Introduction to PowerShell's Examples of -Like

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

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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 w

ay 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 ยป

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.

 

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