Using a function with ForEach-Object

Question

When using the ForEach-Object function, is there a way to provide a function instead of a code block.

This would enable me to simplify this:

@(1, 2, 3, 4) | % { Add-One $_ }

to this, or similar:

@(1, 2, 3, 4) | % Add-One

For completeness here is the current definition of the Add-One function

function Add-One($Number) {
    return $Number + 1
}

It's easy to write a function with process to do something similar, like so:

@(1, 2, 3, 4) | Add-One

However, this means that you have to re-implement the loop and ValueFromPipeline for each function instead of reusing what ForEach-Object already provides. So in short is there a way to use a scalar function with ForEach-Object that avoids wrapping it in a Code Block?

Keith Hill · Accepted Answer · 2014-05-28 05:53:28Z

10

Sure, you can use a scriptblock like so:

PS> $sb = { process { $_ + 1 }}
PS> 1..4 | % $sb
2
3
4
5

But perhaps a more straightforward approach is to create a filter:

filter Add-One { $_ + 1 }
1..4 | Add-One

You can also use a function e.g.:

function Add-One {process {$_ + 1}}
1..4 | Add-One

Filter is basically a function with an implied process block. The advanced function approach looks like this:

function Add-One {
    [CmdletBinding()]
    param(
        [Parameter(ValueFromPipeline)]
        [int[]]
        $Number
    )
    process {
        foreach ($n in $Number) {$n + 1}
    }
 }
1..4 | Add-One
Add-One (1..4)

edited May 28, 2014 at 5:53

answered May 28, 2014 at 4:20

Keith Hill

204k44 gold badges370 silver badges377 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

bouvierr Over a year ago

For those like me who are searching for the filter documentation, it's in about_Functions: "A filter is a type of function that runs on each object in the pipeline. A filter resembles a function with all its statements in a Process block. The syntax of a filter is as follows: filter [<scope:>]<name> {<statement list>}"

Collectives™ on Stack Overflow

Using a function with ForEach-Object

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related