Powershell : Comparing Variable from one CSV to another CSV and create new variable on based of that

Question

The question to be asked by someone is to edit the post trial method

Answer 1

your csv files aren't properly formatted so I can't be sure if this is exactly what you need, but this should point you in the right direction:

$File1 = Import-Csv .\file1.csv -Delimiter "`t"
$File2 = Import-Csv .\file2.csv -Delimiter "`t"

$NewFile1 = $File1 | % {
    $Obj = [PSCustomObject]$_
    $Obj | Add-Member -Mem NoteProperty -Name Patched -Value ([bool]($_.CommanName -in $File2.CommanName))
    return $Obj
}

$NewFile1

Which will output

Server   HotfixID CommanName      Patched
------   -------- ----------      -------
apdk778  kb3333   apdk778 kb3333     True
apdk778  yn2919   apdk778 yn2919     True
apdk778  lk4898   apdk778 lk4898     True
iijka211 kb3333   iijka211 kb3333   False
iijka211 yn2919   iijka211 yn2919    True
iijka211 lk4898   iijka211 lk4898    True

I replaced the first two sets of spaces with tabs in order to read in the csv files.

Answer 2

ConnorLSW's helpful answer works well, but you can simplify to a single Select-Object call that defines a calculated property, which also performs better:

$file1Objects = Import-Csv .\file1.csv -Delimiter "`t"
$file2Objects = Import-Csv .\file2.csv -Delimiter "`t"

$decoratedFile1Objects = $file1Objects | Select-Object *,
  @{ n='Patched'; e={ ('No', 'Yes')[$file2Objects.CommanName -contains $_.CommanName] } }

Get-Help -Detailed Select-Object briefly explains how calculated properties work; for a more detailed explanation, see this answer of mine.

Note the use of idiom (<choice-A>, <choice-B>)[<Boolean-Test>] for selecting one of two choices based on the outcome of a Boolean test:

• ('No', 'Yes') is a string array with elements No (index 0) and Yes (index 1).
• $file2Objects.CommanName -contains $_.CommanName is a Boolean expression that, when used in the context of an array index ([...]) is coerced to either 0 (if $False) or 1 (if $True).

• In other words:

  • if the Boolean expression returns $False, index 0 is used, resulting in string No.
  • if the Boolean expression returns $True, index 1 is used, resulting in string Yes.

• Note that this approach is a workaround for PowerShell's lack of ternary conditionals that other languages, such as C#, have and that the order in which the branches are specified is reversed:

  • C# pseudo-code: <Boolean-Test> ? "Yes" : "No"
  • PowerShell workaround: ('No', 'Yes')[<Boolean-Test>]
  • Aside from the ordering of branches / choices, there is another important difference: if your array elements are commands/expressions, they are all evaluated, irrespective of which one is chosen (no short-circuiting).
  • There is an outstanding feature request for ternary conditionals.

---

As for what you tried:

Your nested foreach-loop approach:

• doesn't create an output object for un-patched rows
• and, for a patched row, creates a new object whose only property is the new one.

The following code fixes these issues, again relying on Select-Object to add the new property:

$decoratedFile1Objects = foreach ($f1 in $file1) {
  # Add property and default to 'No'
  $f1Decorated = Select-Object -InputObject $f1 *, @{ n='Patched'; e={ 'No' } } 
  foreach($f2 in $file2) {
    if ($f1.CommanName -eq $f2.CommanName) { 
      # Match found: set property to 'Yes' and exit the inner loop
      $f1Decorated.Patched = 'Yes'
      break
    }
  }
  $f1Decorated  # Output the decorated object.
}

However, use of PowerShell's -contains and -in array-membership test operators is not only much more convenient, but also performs better.