PowerShell cmdLet Where-Object

Ways to construct a where-object command

There are two methods to construct a where-object command:

Comparison statement
Script block

Example

The get-command cmdLet allows to find cmdLets whose verb is format with is -verb argument:

PS C:\> get-command -verb format

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Function        Format-Hex                                         3.1.0.0    Microsoft.PowerShell.Utility
Function        Format-Volume                                      2.0.0.0    Storage
Cmdlet          Format-Custom                                      3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-List                                        3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-SecureBootUEFI                              2.0.0.0    SecureBoot
Cmdlet          Format-Table                                       3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-Wide                                        3.1.0.0    Microsoft.PowerShell.Utility

However, I also get the commands whose commandType is Function which I don't want to see. I can exclude them by pipelining them into the where-object:

PS C:\> get-command -verb format | where-object commandType -eq cmdLet

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Cmdlet          Format-Custom                                      3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-List                                        3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-SecureBootUEFI                              2.0.0.0    SecureBoot
Cmdlet          Format-Table                                       3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-Wide                                        3.1.0.0    Microsoft.PowerShell.Utility

I am much happier now with the result. But still, I want to get rid of the format-secureBootUEFI cmdLet because it does not fit in the list. So I need to add a second criteria.

It seems that PowerShell is not capable of specifying multiple criterias without script block. So, I use a script block for the second criteria.

PS C:\> get-command -verb format | where-object { $_.commandType -eq 'cmdLet' -and $_.source -match 'PowerShell' }

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Cmdlet          Format-Custom                                      3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-List                                        3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-Table                                       3.1.0.0    Microsoft.PowerShell.Utility
Cmdlet          Format-Wide                                        3.1.0.0    Microsoft.PowerShell.Utility

Note: when using script blocks, the object on which the criterias are performed needs to be referenced by the automatic variable $_.

Removing elements from an array

The following example removes elements from an array that contains numbers. Elements that contain numbers are matched by the regular expression \d whose meaning is reversed with the -notMatch operator.

'foo','bar', 'hello world', 'the number is 42.', 'baz' | where-object {$_  -notMatch '\d' }

Abbreviation with the question mark

where-object can also be abbreviated with a question mark:

get-service | ? name -match xbox

PowerShell cmdLet Where-Object

Ways to construct a where-object command

Example

Removing elements from an array

Abbreviation with the question mark

See also