Select/map each item of a Powershell array to a new array

Question

I have an array of file names in Powershell, and I would like to prepend a path to each of them and get the result in a new array.

In C# I could do this using Linq...

var files = new string[] { "file1.txt", "file2.txt" };
var path = @"c:\temp\";
var filesWithPath = files.Select(f => path + f).ToArray();

But what is the idiomatic way to do this in Powershell? It looks like there is a foreach syntax I could use, but I figure there must be a more concise, functional way to do it.

Answer 1

An array in Powershell is declared with @() syntax. % is shorthand for foreach-object. Let's declare an array with all the file names and loop through it with foreach. join-path combines a path and a child path into a single path.

$files = @("file1.txt", "file2.txt")
$pFiles = $files | % {join-path "c:\temp" $_ }
$pFiles

Output:

c:\temp\file1.txt
c:\temp\file2.txt

NB: if the input consists of single an element, foreach will not return a collection. If an array is desired, either use explicit type or wrap the results. Like so,

[array]$pFiles = $files | % {join-path "c:\temp" $_ }
$pFiles = @($files | % {join-path "c:\temp" $_ })

Answer 2

Like this:

$a = @("file1.txt","file2.txt")
$b = "c:\temp\"
$c = $a | % { $b + $_ }

I can't figure this w/o a foreach. Sorry

Using the great job from Josh Einstein LINQ for Powershell

you can write this:

$a = @("file1.txt","file2.txt")
$b = "c:\temp\"
$c = $a | Linq-Select -Selector {$b + $_ }

having same results in a LINQ manner but not using a foreach (%).

Answer 3

You could also use the replace operator:

PS> 'file1.txt','file2.txt','file3.txt' -replace '(^.+$)','C:\temp\$1'

C:\temp\file1.txt
C:\temp\file2.txt
C:\temp\file3.txt