Returning a value from within a ForEach in Powershell

Question

This seems really basic, but I can't see how or why it behaves this way:

function ReturnStuff{
    $a=1,2,3,4,5
    $a.ForEach{
        return $_
    }
}

ReturnStuff

Why does this give me: 1 2 3 4 5 instead of just 1?

Solution

It looks like you are calling ForEach (a function in [System.Array]) with a parameter which is a scriptblock. Essentially, you are defining and returning { Return $_ } every iteration of the loop.

This means ReturnStuff will capture output each time, and because this function does nothing with the output of this line, all the output is returned:

$a.ForEach{ return $_ }

This behavior is similar to $a | Foreach-Object { return $_ }

So what to do?

1. Use a ForEach loop instead (not to be confused with Foreach-Object):

   ForEach ($item In $a) { return $item }
   

2. Select the first value returned from all the scriptblocks:

   $a.ForEach{ return $_ } | Select -First 1
   

Comments

[Ben Power]

Wow, that's one hell of a trap for newbies! Thanks!

[mhenry1384]

Doesn't make any sense to me why they work differently. Isn't the ForEach loop (option #1) also being called with a parameter which is a scriptblock?