Run command, extract a field, run a resultant command - powershell

Question

Apologies if this is an insanely simple question, but I'm at something at a loss.
What I'm trying to do is take a command output - in this case from NetApp DFM:
dfm event list
ID Source Name Severity Timestamp
------- ------- ------------- ----------- ------------
1 332 volume-online Normal 20 Apr 10:16
2 443 volume-online Normal 20 Apr 10:17
3 3222 volume-online Normal 20 Apr 10:18
I have about 17,000 events - I want to delete them all by ID, by running:
dfm event delete <ID>
I know exactly how I'd do this on Unix (and used to, when this was our platform):
for i in `dfm event list | awk '{print $1}'`
do
dfm event delete $i
done
For bonus points - a 'grep' type criteria? I apologise in advance for the basic nature of the question - I've tried looking on Google for a suitable example, but haven't found anything.
I've made a start by:
dfm event list > dfmevent.txt
foreach ( $line in get-content dfmevent.txt ) {
echo $line
}
But I thought I would ask if there's a better way.

Answer 1

I don't have access to your environment to test but if you are just trying to get access to that first element which is the ID then that should be straight forward.
dfm event list | ForEach-Object{$_.Split(" ",2)[0]} | Where-Object{$_ -match '^\d+$'} | ForEach-Object{
#For Testing
Write-Host "Id: $_ will be deleted"
# Then do something
# dfm event delete $_
}
I'm sure the output is already delimited with new line so sending to file might be redundant.
We take each line and try and split it on the first space. Then pass the first element from that array. Next we ensure that element is indeed a number with a simple regex check. This will ensure that we only get numbers. I had thought about skipping the first two lines but this should work for other occurrences of text as well.
The last loop is for processing that ID. I left a Write-Host there for testing. Assuming you get the id's you are looking for you should just be able to uncomment out that last line with dfm event delete $_

Answer 2

Capturing the output of a DOS command into Powershell is a challenge.
Using a native snapin or module from NetApp would be easier.
might be worth checking out if that link helps
Otherwise, your method of writing to a text file and reading it back in is actually quite a good idea, this is one way of reading it back and pushing the data into the command you need.
$a = get-content dfmevent.txt
foreach ($i in $a) { if ($i.ReadCount -gt 2) { dfm event delete ($i.Substring(0,$i.IndexOf(" "))) } }
This will assign to the variable $result only
$a = get-content dfmevent.txt
$result = #()
foreach ($i in $a) { if ($i.ReadCount -gt 2) { $result += $i.Substring(0,$i.IndexOf(" "))} }
And if you did not want to write to a text file, you could use the .NET method of capturing the output directly
$ProcessInfo = New-Object System.Diagnostics.ProcessStartInfo
$ProcessInfo.FileName = "dfm"
$ProcessInfo.RedirectStandardOutput = $true
$ProcessInfo.UseShellExecute = $false
$ProcessInfo.Arguments = "event list"
$Process = New-Object System.Diagnostics.Process
$Process.StartInfo = $ProcessInfo
$Process.Start() | Out-Null
$Process.WaitForExit()
$output = $Process.StandardOutput.ReadToEnd()