Calculating percentage: Attempted to divide by zero error

Question

I can't work out why the script is calculating the disk freespace storage correctly but issues the "Attempted to divide by zero" error on execution. Can anyone shed light on this? I know that there are other more efficient ways to get the percentage but I'm determined to crack this one!

Get-WmiObject Win32_LogicalDisk -ComputerName "*servername*" |
ForEach-Object {
'Disk {0} has {1:0.0} GB space available out of {2:0.0} GB   {3:p0} Freespace' -f $_.Caption, ($_.FreeSpace / 1GB), ($_.Size / 1GB), ($_.Freespace / $_.Size)
}

Disk C: has 30.9 GB space available out of 79.7 GB 39%

Disk E: has 18.8 GB space available out of 20.0 GB 94%

Disk L: has 332.2 GB space available out of 377.0 GB 88%

Attempted to divide by zero.

At line:3 char:1

'Disk {0} has {1:0.0} GB space available out of {2:0.0} GB {3:p0} '

CategoryInfo : NotSpecified: (:) [], RuntimeException FullyQualifiedErrorId : RuntimeException

A disk that contains no partitions (including removable drives with no disks in them) may well report a size of 0, and then `$_.Freespace / $_.Size` is invalid. Test for this first (`if ($_.Size -ne 0) { ... }`. — Jeroen Mostert, Aug 20 '21 at 17:38
As an aside: The CIM cmdlets (e.g., `Get-CimInstance`) superseded the WMI cmdlets (e.g., `Get-WmiObject`) in PowerShell v3 (released in September 2012). Therefore, the WMI cmdlets should be avoided, not least because PowerShell (Core) (v6+), where all future effort will go, doesn't even _have_ them anymore. Note that WMI still _underlies_ the CIM cmdlets, however. For more information, see [this answer](https://stackoverflow.com/a/54508009/45375). — mklement0, Aug 20 '21 at 18:53

codewario · Answer 1 · 2021-08-23T15:36:51.480

One of your disks has a Size of 0. This is (to my knowledge) only possible in one of three scenarios:

Your partition table is corrupted
Your disk is visible but is failing
Removable storage that doesn't have any storage (e.g. SD card reader with no card inserted)

If the issue is one of the former two, you can attempt to fix partition or disk issues with chkdisk, diskpart or PowerShell's Storage Module, but back the data up first since it's very easy to nuke data with these tools. To get your script working as intended in any of the scenarios, read on.

In your code you can attempt to detect this with an if statement and act accordingly:

Get-WmiObject Win32_LogicalDisk -ComputerName "*servername*" | ForEach-Object {
  if( $_.Size -ne 0 ) {
    'Disk {0} has {1:0.0} GB space available out of {2:0.0} GB   {3:p0} Freespace' -f $_.Caption, ($_.FreeSpace / 1GB), ($_.Size / 1GB), ($_.Freespace / $_.Size)
  } else {
    # Disk is 0 bytes case
  }
}

Another approach you could take is to filter out any disks with a size of 0 using Where-Object:

Get-WmiObject Win32_LogicalDisk -ComputerName "*servername*" | Where-Object {
  $_.Size -ne 0
} | Foreach-Object {
'Disk {0} has {1:0.0} GB space available out of {2:0.0} GB   {3:p0} Freespace' -f $_.Caption, ($_.FreeSpace / 1GB), ($_.Size / 1GB), ($_.Freespace / $_.Size)
}

Calculating percentage: Attempted to divide by zero error

1 Answers1