PowerShell: How to Filter a Hash Table

You can use the following syntax to filter a hash table in PowerShell:

$keys = @($my_hash.Keys)

$keys | ForEach-Object {
    if ($_ -notmatch 'A000') {
        $my_hash.Remove($_)
    }
}

This particular example filters the hash table named $my_hash to only keep the elements where the key contains the pattern A000.

This syntax works by first creating an array named $keys that contains all of the keys from the hash table named $my_hash.

Then, we use ForEach-Object to loop through each key of the hash table and remove any elements where the key does not contain the pattern A000.

Note: This syntax modifies the hash table in-place.

The following example shows how to use this syntax in practice.

Example: How to Filter a Hash Table in PowerShell

Suppose we create the following hash table named $my_hash:

$my_hash = [ordered]@{
  'A0001' = 24;
  'A0002' = 20;
  'A0003' = 14;
  'B0001' = 31;
  'B0002' = 9;
  'B0003' = 15;
  'A0007' = 22;
} 

We can use the following syntax to filter this hash table to only keep the elements where the key contains the value A000:

$keys = @($my_hash.Keys)

$keys | ForEach-Object {
    if ($_ -notmatch 'A000') {
        $my_hash.Remove($_)
    }
}

The following screenshot shows how to use this syntax in practice:

Notice that the updated hash table only contains the elements where the key contains the value A000.

Feel free to specify any pattern that you’d like following the -notmatch operator to instead filter your hash table based on a different pattern.

Related Tutorials

The following tutorials explain how to perform other common tasks in PowerShell:

PowerShell: How to Check if Hash Table Contains Specific Key
PowerShell: How to Remove Elements from a Hash Table
PowerShell: How to Iterate Over a Hash Table
PowerShell: How to Update Values in Hash Table