# Basic Set Operations
A set is a collection of items which can be anything. Whatever operator we need to work on these sets are in short the set operators and the operation is also known as set operation. Basic set operation includes Union, Intersection as well as addition, subtraction, etc.
# Filtering: Where-Object / where / ?
Filter an enumeration by using a conditional expression
Synonyms:
Where-Object
where
?
Example:
$names = @( "Aaron", "Albert", "Alphonse","Bernie", "Charlie", "Danny", "Ernie", "Frank")
$names | Where-Object { $_ -like "A*" }
$names | where { $_ -like "A*" }
$names | ? { $_ -like "A*" }
Returns:
Aaron
Albert
Alphonse
# Ordering: Sort-Object / sort
Sort an enumeration in either ascending or descending order
Synonyms:
Sort-Object
sort
Assuming:
$names = @( "Aaron", "Aaron", "Bernie", "Charlie", "Danny" )
Ascending sort is the default:
$names | Sort-Object
$names | sort
Aaron
Aaron
Bernie
Charlie
Danny
To request descending order:
$names | Sort-Object -Descending
$names | sort -Descending
Danny
Charlie
Bernie
Aaron
Aaron
You can sort using an expression.
$names | Sort-Object { $_.length }
Aaron
Aaron
Danny
Bernie
Charlie
# Grouping: Group-Object / group
You can group an enumeration based on an expression.
Synonyms:
Group-Object
group
Examples:
$names = @( "Aaron", "Albert", "Alphonse","Bernie", "Charlie", "Danny", "Ernie", "Frank")
$names | Group-Object -Property Length
$names | group -Property Length
Response:
| Count | Name | Group |
|---|---|---|
| 4 | 5 | {Aaron, Danny, Ernie, Frank} |
| 2 | 6 | {Albert, Bernie} |
| 1 | 8 | {Alphonse} |
| 1 | 7 | {Charlie} |
# Projecting: Select-Object / select
Projecting an enumeration allows you to extract specific members of each object, to extract all the details, or to compute values for each object
Synonyms:
Select-Object
select
Selecting a subset of the properties:
$dir = dir "C:\MyFolder"
$dir | Select-Object Name, FullName, Attributes
$dir | select Name, FullName, Attributes
| Name | FullName | Attributes |
|---|---|---|
| Images | C:\MyFolder\Images | Directory |
| data.txt | C:\MyFolder\data.txt | Archive |
| source.c | C:\MyFolder\source.c | Archive |
Selecting the first element, and show all its properties:
$d | select -first 1 *
| PSPath |
| PSParentPath |
| PSChildName |
| PSDrive |
| PSProvider |
| PSIsContainer |
| BaseName |
| Mode |
| Name |
| Parent |
| Exists |
| Root |
| FullName |
| Extension |
| CreationTime |
| CreationTimeUtc |
| LastAccessTime |
| LastAccessTimeUtc |
| LastWriteTime |
| LastWriteTimeUtc |
| Attributes |