Sorting & Filtering

As previously mentioned, PowerShell is based on objects, rather than strings. Where this really shines is in the case where you need to select specific elements of what is returned, and sort them for easier consumption.

Filtering

Filtering in PowerShell is achieved in two ways:

When you have an array of objects, choosing which objects you wish to keep
When you have an array of objects, choosing which properties of those objects you wish to keep

Where-Object

Where-object (alias where or ?) is the command used to filter objects based on a condition. For example, let's say you have a list of CPS enrollments.

$Enrollments = Get-CPSEnrollment

Now, we only want those enrollments which are Domain Validation. You can achieve this with a simple filter:

$Enrollments | Where-Object validationType -eq 'DV'

See the Conditional Operators page for a full list of operators you can use in your filters.

When filtering an array of objects based on a single property you can use this shorthand syntax. However, if you need to filter based on multiple properties, or a child property of your objects, you will need to use the full syntax:

$Enrollments | Where-Object { $_.validationType -eq 'DV' -and $_.csr.cn -eq 'www.example.com' }

Remember that the $_ variable represents the current object being processed in the pipeline, so you can access any property of that object to use in your filter.

Select-Object

Select-Object (alias select) is the command used to select specific properties of an object. For example, let's say you have a list of CPS enrollments.

$Enrollments | Select-Object id, validationType
 
    id validationType
    -- --------------
 11111 dv
 22222 dv
 33333 dv
 44444 third-party
 55555 dv

This can be a great tool to cherry-pick the data you are interested in, which can be read from the shell, or even piped to Export-CSV and written to a CSV file.

This approach works well when you are selecting top-level properties, but there are many occasions where you may wish to select something in a child object. To continue our CPS example, you might well want to know the Common Name, and the acceptable TLS versions. In this case you have can use Select-Object, but with a hashtable for the selected parameter. This hashtable must have two elements: label (alias l) and expression (alias e).

You can combine the simple and complex filter terms in a single Select-Object command

$Enrollments | Select-Object id, @{ label ='CommonName'; expression = {$_.csr.cn} }, @{ l='DisallowedTLSVersions';e={$_.networkConfiguration.disallowedTlsVersions -Join ','}}
 
    id  CommonName               DisallowedTLSVersions
    --  ----------               ---------------------
 11111  a.example.com            TLSv1,TLSv1_3
 22222  b.example.com            TLSv1,TLSv1_1
 33333  c.example.com
 44444  d.example.com            TLSv1,TLSv1_1
 55555  e.example.com            None

Sorting

Sorting objects is another essential element in getting your PowerShell data into the desired format. Sort-Object (alias sort) can sort both arrays of simple objects, like strings or integers, and arrays of complex objects.

Simple Sorting

1,3,5,2,4 | Sort-Object
 
1
2
3
4
5

'apple','banana','cherry','date' | Sort-Object -Descending
 
date
cherry
banana
apple

Sorting by Property

You can sort objects by a given property, and even sort by multiple properties. For example, let's say you have a list of CPS enrollments.

$Enrollments | Sort-Object -property id

Then let's say you want to sort by validation type, and then by ID. You can do this by passing an array of properties to the -property parameter.

$Enrollments | Sort-Object -property validationType, id

Sorting by Expression

You can also use Sort-Object in the same advanced format as you would use Select-Object, except you don't need the label element. For example, let's say you wanted to sort CPS enrollments by Common Name.

$Enrollments | Sort-Object -property @{ expression = {$_.csr.cn} }

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