Can Powershell Loop Through a Collection N objects at a time? - loops

Question

I am wondering how one would tackle looping through a collection of objects, processing the elements of that collection in groups instead of singularly, as is the case in normal Foreach loops. For example, instead of this:
$items = get-vm
foreach ($item in $items) { do something }
I would like to do this:
$items = get-vm
foreach ((5)$item in $items) {do something}
Essentially, this statement intends to say foreach 5 items in items do some work.....
Can anyone show me the proper constructs required to accomplish this?

Answer 1

I've got this:
$array = 1..100
$group = 10
$i = 0
do {
$array[$i..(($i+= $group) - 1)]
'*****'
}
until ($i -ge $array.count -1)

Answer 2

Here's a function that will collection items into chunks of a specified size:
function ChunkBy($items,[int]$size) {
$list = new-object System.Collections.ArrayList
$tmpList = new-object System.Collections.ArrayList
foreach($item in $items) {
$tmpList.Add($item) | out-null
if ($tmpList.Count -ge $size) {
$list.Add($tmpList.ToArray()) | out-null
$tmpList.Clear()
}
}
if ($tmpList.Count -gt 0) {
$list.Add($tmpList.ToArray()) | out-null
}
return $list.ToArray()
}
The usage would be something like:
ChunkBy (get-process) 10 | foreach { $_.Count }

Answer 3

You guys definitely gave me some great ideas for this functionality. I ended up going with the following:
#create base collection
$group = get-vm
$i = 0
do {
new-variable -Name "subgroup$i" -value $group[0..4]
++$i
$group = $group[5..$group.length]
}
while ($group.length -gt 0)
This code results in a number of subgroups, which is based on how many times the base collection is divisible by 5, which is the desired subgroup quantity in this case......

Answer 4

Change to Do...Until, increment counter by 5 each time.
$items = get-vm
$i = 0
do {
#STUFF
$i = $i + 5
} until ($i -ge $items.count)
(Untested, but should give you an idea)
EDIT:
Fully tested:
$items = #()
foreach ($item in (get-alias)) {
$items += $item
}
$i = 0
do {
write-host $i
$i = $i + 5
} until ($i -ge $items.count)
Output:
0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
115 120 125 130 135
EDIT 2:
$items = #()
for($i=1; $i -le 75; $i++) {
$items += $i
}
[int]$i = 0
$outarray = #()
do {
$outarray += $items[$i]
if ((($i+1)%5) -eq 0) {
write-host $outarray
write-host ---------
$outarray = #()
}
$i = $i + 1
} until ($i -gt $items.count)