Powershell. Trying to loop using Import-csv - powershell

Question

I am converting code that currently parse a large csv file once for each agency. Below is what one line looks like:
Import-Csv $HostList | Where-Object {$_."IP Address" -Match "^192.168.532.*" -or $_Domain -eq "MYDOMAIN"`
-and (get-date $_.discovery_timestamp) -gt $PreviousDays} | select-object Hostname","Domain","IP Address","discovery_timestamp","some_version" | `
Export-Csv -NoTypeInformation -Path $out_data"\OBS_"$Days"_days.txt"
write-host "OBS_DONE"
I have about 30 of these.
I want to parse the csv file once, possibly using foreach and import.csv.
I thought I could do something like:
$HostFile = Import-csv .\HostList.csv
foreach ($line in $HostFile)
{
Where-Object {$_."IP Address" -Match "^172.31.52.*"}
write-host $line
#| Export-Csv -NoTypeInformation -Path H:\Case_Scripts\test.csv
I've tried many permutations of the above, and it never is matching on the "Where-Object" like it does on the example functioning script above.
Any guidance and learning opportunities are appreciated.

Answer 1

My good man, you need to be introduced to the Switch cmdlet. This will sort for all of your companies at once.
$CompanyA = #()
$CompanyB = #()
$CompanyD = #()
$Unknown = #()
Switch(Import-CSV .\HostList.csv){
{(($_."IP Address" -match "^192.168.532.*") -or ($_Domain -eq "CompanyA.com")) -and ((get-date $_.discovery_timestamp) -gt $PreviousDays)} {$CompanyA += $_; Continue}
{(($_."IP Address" -match "^192.26.19.*") -or ($_Domain -eq "CompanyB.net")) -and ((get-date $_.discovery_timestamp) -gt $PreviousDays)} {$CompanyB += $_; Continue}
{(($_."IP Address" -match "^94.8.222.*") -or ($_Domain -eq "CompanyC.org")) -and ((get-date $_.discovery_timestamp) -gt $PreviousDays)} {$CompanyC += $_; Continue}
default {$Unknown += $_}
}
$CompanyA | Export-Csv $out_data"\CompanyA"$Days"_days.txt" -NoType
$CompanyB | Export-Csv $out_data"\CompanyB"$Days"_days.txt" -NoType
$CompanyC | Export-Csv $out_data"\CompanyC"$Days"_days.txt" -NoType
If($Unknown.count -gt 0){Write-Host $Unknown.count + " Entries Did Not Match Any Company" -Fore Red
$Unknown}
That will import the CSV, and for each entry try to match it against the criteria for each of the three lines. If it matches the criteria in the first ScriptBlock, it will perform the action in the second ScriptBlock (add that entry to one of the three arrays I created first). Then it outputs each array to it's own text file in CSV format as you had done in your script. The ;Continue just makes it so it stops trying to match once it finds a valid match, and continue's to the next record. If it can't match any of them it will default to adding it to the Unknown array, and at the end it checks if there are any in there it warns the host and lists the unmatched entries.
Edit: Switch's -RegEx argument... Ok, so the purpose of that is if you want a simple regex match such as:
Switch -regex ($ArrayOfData){
".*#.+?\..{2,5}" {"It's an email address"}
"\d{3}(?:\)|\.|-)\d{3}(?:\.|-)\d{4}" {"It's a phone number"}
"\d{3}-\d{2}-\d{4}" {"Probably a social security number"}
}
What this doesn't allow for is -and, or -or statements. If you use a scriptblock to match against (like I did in my top example) you can use the -match operator, which performs a regex match by default, so you can still use regex without having to use the -regex argument for Switch.

Answer 2

Where-Object should have a collection of objects passed to it. In your second script block this isn't happening, so in the filter the $_ variable will be empty.
There are a couple of ways to fix this - the first one that comes to mind is to replace Where-Object with an 'if' statement. For example
if ($line."IP Address" -Match "^172.31.52.*") { write-output $line }