Pipeline
Pipeline syntax
Pipeline element1[ | Pipeline element2][ | Pipeline element3]...
# The [] part is optional.
As you can see from this syntax, actually just one cmdlet is a pipeline.
Example
To be more specific, combine a cmdlet with the pipeline symbol “|” as shown below.
Get-Process | Select-Object Name
ForEach-Object
Use ForEach-Object for the sequential processing of the pipeline.
Alias of ForEach-Object
ForEach-Object has the following aliases.
foreach
%
Example
# Outputs the values from 1 to 3, each doubled.
PS> 1..3 | ForEach-Object {$_ * 2}
PS> 2
PS> 4
PS> 6
Automatic variables $_ and $PSItem
$_ is an automatic variable that indicates the current value being handled by the pipeline.
There is also $PSItem, which means the same as $_.
The three phases
There are three phases in the pipeline sequential processing: Begin, Process, and End.
# Output the sum of the values from 1 to 3.
PS> 1..3 | % {$sum=0} {$sum+=$_} {$sum}
PS> 6
If you just output the sum, you may not understand the three phases we talked about earlier.
Therefore, we will rewrite the code so that we can understand each phase.
# Output the sum of the values from 1 to 3.
PS> 1..3 | % {$sum=0;"Begin $sum $_”} {$sum+=$_;"Process $sum $_"} {"End $sum $_"}
PS> Begin 0
PS> Process 1 1
PS> Process 3 2
PS> Process 6 3
PS> End 6
An abbreviated way of writing ForEach-Object
Example1
PS> Get-Process | ForEach-Object {$_.ProcessName}
↓ Abbreviated way of writing
PS> Get-Process | ForEach-Object ProcessName
Example2
PS> ‘String' | ForEach-Object {$_.ToUpper()}
↓ Abbreviated way of writing
PS> ‘String' | ForEach-Object ToUpper
STRING
PS> ‘String' | ForEach-Object ToLower
string
Where-Object
To Filter an object, use Where-Object.
Alias for Where-Object
There are two aliases for Where-Object.
where
?
Abbreviated way to write in Where-Object.
Get-Process | where {$_.Name -like "*chrome"}
↓ Abbreviated way of writing
Get-Process | where Name -like "*chrome"
Select-Object
To select an object in the pipeline, use Select-Object.
PS> 1..10 | Select-Object -First 3
1
2
3
PS> 1..10 | Select-Object -Last 3
8
9
10
Sort-Object
To align objects in the pipeline, use Sort-Object.
PS> 1..10 | Sort-Object -Descending | Select-Object -First 3
10
9
8
PS> 1..10 | Sort-Object -Descending | Select-Object -Last 3
3
2
1
Measure-Object
To count objects, Measure-Object is useful.
PS> 1..10 | Measure-Object -Sum
Count : 10
Average :
Sum : 55
Maximum :
Minimum :
StandardDeviation :
Property :
To get all the results, specify the AllStats parameter.
PS> 1..10 | Measure-Object -AllStats
Count : 10
Average : 5.5
Sum : 55
Maximum : 10
Minimum : 1
StandardDeviation : 3.02765035409749
Property
YouTube
Click here for a video explanation.