powershell - Create objects with custom properties containing derived filesystem path information and export them to a CSV - calculated properties

Question

<sup>Editor's note:
The gist of this question is:
* How do I add custom properties to objects output by Get-ChildItem that contain derived path information, namely the parent folder path (as Folder and name (as Foldername)?
* How do I export the resulting objects to a CSV file?</sup>

Currently have a script running that I took from StackOverflow and modified for my own use. The purpose of the script is to look at a directory, grab file names, then export them to a directory as a .csv file.

I was able to modify the script to pull through just the file name as originally it only pulled through the path, user etc. Was able to do this by adding ,Name. For some reason I can't get the script to pull through the parent folder it's in, also wanting the parents parent folder.

I believe this part of the code is what I am having most trouble with. Upon the select I was able to add ,Name but adding ,folder or ,foldername after the select doesn't pull through properly.

ForEach-Object {$_ | Add-Member -Name "Owner" -MemberType NoteProperty -Value (Get-Acl $_.FullName).Owner -PassThru} | 
 Sort-Object fullname | 
  Select FullName,CreationTime,LastWriteTime,Owner,Name,Folder,Foldername

Answer 1

The [System.IO.FileInfo] instances returned by Get-ChildItem for files do not have Folder or FolderName properties.

Get-ChildItem -File $HOMEDesktop | Get-Member, for instance, will show you the available properties, and will show you that the desired information can be derived from the PSPath and PSParentPath properties.

Select-Object allows hashtable-based property definitions, so-called calculated properties, which allow you to rename and/or transform properties and/or add custom properties derived from other property values by way of a script block.

Note: You can also use calculated properties with the Format-Table and Format-List cmdlets for creating output for display only (as well as with other cmdlets - see the linked help topic).

A simplified example of what you're looking for (includes output to a CSV file):

Get-ChildItem $HOMEDesktop | Select-Object Name,
  @{ Name = 'Folder'; Expression = { Convert-Path $_.PSParentPath } },
  @{ Name = 'Foldername'; Expression = { ($_.PSPath -split '\')[-2] } } |
    Export-Csv Out.csv -Encoding Utf8 -NoTypeInformation

^{Note that, alternatively, you could add Folder and FolderName properties to the input objects via Add-Member, as you did with the Owner property in your question.}

Explanation:

^{Note that you can get more detailed information about any of the commands mentioned by running Get-Help <command-name> -Full; add -online to view the help topic in a browser; to learn more about the -split operator, run Get-Help about_split; to learn about PowerShell's help system in general, run Get-Help Get-Help -online.}

• Each @{ ... } construct passed to Select-Object is a hash table that defines a property to attach to each output object:

  • The hash table must have two entries:
    • Name or Label, which defines the property's name; for brevity, you may use a (case-insensitive) prefix of the key name, such as just n or l.
    • Expression, which defines the property's value; again, a (case-insensitive) prefix of the key name works too, such as just e.
      • The expression can be a mere property name (a string), in case you simply want to rename an input property, but is more typically a script block ({ ... }), which is a piece of code that gets executed for each input object, and whose output becomes the value of the property being defined; inside that script block, automatic variable $_ (or $PSItem) refers to the input object at hand.

• Definition of the Folder property: Convert-Path $_.PSParentPath converts the fully qualified PowerShell path that the PSParentPath property contains - which includes a prefix identifying the drive provider - to a regular filesystem path; e.g., Microsoft.PowerShell.CoreFileSystem::C:UsersjdoeDesktop -> C:UsersjdoeDesktop.

• Definition of the Foldername property: ($_.PSPath -split '\')[-2] splits the full path into components by path separator , and then accesses the next-to-last component (-2), which is the parent folder name; e.g., C:UsersjdoeDesktopfile.txt -> Desktop

  • '\' must be used to represent , because -split's 1st RHS operand is a regular expression, where has special meaning and must therefore be doubled to be taken as a literal.
  • If you wanted to support / as the path separator as well for cross-platform support, you'd use ($_.PSPath -split '[\/]')[-2].

• Export-Csv exports the objects output by Select-Object to CSV Out.csv, where the input objects' property names become the header row, and the property values the data rows.

  • -Encoding Utf8, required in Windows PowerShell only (PowerShell (Core) 7+ now fortunately consistently uses BOM-less UTF-8), ensures that non-ASCII characters are properly encoded; by default, Export-Csv uses ASCII encoding and simply replaces non-ASCII characters, such as foreign letters, with verbatim ? characters, resulting in loss of information; note that -Encoding Utf8 in Windows PowerShell invariably creates UTF-8 files with a BOM.

  • -NoTypeInformation, again required in Windows PowerShell only, suppresses a line that Export-Csv by defaults adds as the first line of the output file, which contains the full type name (class name) of the input objects (e.g., #TYPE System.Management.Automation.PSCustomObject; this is meant to facilitate later reconversion into objects).