Understanding Export-CSV

Description:

Reddit post:

So I’m working on sds and trying to upload CSV’s and I ran into something I cannot figure out: Why does this work?

   Import-Csv 'C:\scripts\section.csv' | Select-Object * | Export-Csv -Path "c:/scripts/section3.csv" -NoTypeInformation

But this doesn’t?

   $sectionCsv = Import-Csv 'C:\scripts\section.csv'
   $tempCSV = $sectionCsv | 
      Select-Object -Property "SIS ID","School SIS ID","Section Name","Section Number","Term SIS ID","Term Name","Term StartDate","Term EndDate","Course SIS ID","Course Name","Course Number","Course Description","Status"
   Export-Csv -InputObject $tempCSV -Path "c:/scripts/section2.csv" -NoTypeInformation

When I say it doesn’t, I mean that it is giving me a 1kb file:

   "Count","Length","LongLength","Rank","SyncRoot","IsReadOnly","IsFixedSize","IsSynchronized"
   "25169","25169","25169","1","System.Object[]","False","True","False"

I tried googling and found a few examples like this but I still cannot understand. In vscode, if I type tempCSV, I get a list of all the records like one would expect. Why cannot export-csv this object which is of type Selected.System.Management.Automation.PSCustomObject ? Does it have to just be a PSCustomObject?

To be clear I’m only trying to learn as the one liner solves the issue but trying to see why I cannot grasp such a simple concept. Another thing I have tried is:

   $csvPath = Get-Childitem 'C:/scripts'
   foreach ( $csv in $csvPath)
   {
      $tempCsv = Import-Csv $($csv.fullname)
      $columnNames = $tempcsv | get-member -MemberType "NoteProperty"

      $list = @()
      foreach ( $column in $($columnNames.Name))
      {
         $list += $column
      }
      $export = $tempCSV | Select-Object -Property $list
      
      $params = @{
         "InputObject"       = $export
         "Path"              = ( "c:/scripts/" + $($csv.name) )
         "Encoding"          = "ascii"
         "NoTypeInformation" = $True
      }
      Export-Csv @params
   }

Again, this exports the 1kb file instead the whole CSV. If I check $export in debug, it lists the 5,000 records I would expect to see in the final CSV. Lastly, the reason I’m doing this is because I have a series of CSVs I have built manually and they work fine, but I want a ‘clean’ CSV with quotes around each row so I’m doing this. The one liner produces this, but it irks me because I’m not a huge fan of piping because I want to understand. Ideally the solution will import-csv, get all the columns that are not built in (NoteProperties and not regular properties or methods), and export it to a new CSV. Thanks!

To Resolve:

1. Answer per u/Jantu01

   • Perfect! one.csv and three.csv are the same, thank you much!

   $a = Get-Process | Select-Object -first 5 -Property "name"
   $a | Export-CSV -Path 'c:\scripts\one.csv' -NoTypeInformation
   
   New-Item -Itemtype "file" -Path 'c:\scripts\three.csv' -Value 'something' -Force | Out-Null
   #$a = Get-Process | Select-Object -first 5
   # System.Diagnostics.Process
   
   #get-member -InputObject $a
   # System.Object[]
   
   # Works!
   $a | ForEach-Object -Begin { 
      Clear-Content 'c:\scripts\three.csv' 
   } -Process {
      Export-CSV -InputObject $_ -Path 'c:\scripts\three.csv' -Append -NoTypeInformation
   }
   

   • And:

   $a = Get-Process | Select-Object -first 5 -Property "name"
   $a | Export-CSV -Path 'c:\scripts\one.csv' -NoTypeInformation
   
   New-Item -Itemtype "file" -Path 'c:\scripts\three.csv' -Value 'something' -Force | Out-Null
   #$a = Get-Process | Select-Object -first 5
   # System.Diagnostics.Process
   
   #get-member -InputObject $a
   # System.Object[]
   
   # Works!
   $a | ForEach-Object -Begin { 
      Clear-Content 'c:\scripts\three.csv' 
   } -Process {
      Export-CSV -InputObject $_ -Path 'c:\scripts\three.csv' -Append -NoTypeInformation
   }
   

2. Another good answer from u/MadWithPowerShell:

   Export-CSV is specifically designed as a pipeline command. Parameter -InputObject is not intended to be used explicitly, and not with the entire array of objects at one time. It is designed to get the items in the array one at a time, through the pipeline.
   
   This:
   
   $TempCSV | Export-CSV
   
   NOT this:
   
   Export-CSV -InputObject $TempCSV
   
   Sort-Object, Where-Object, Whatever-Object, etc., are similarly pipeline commands. They all have the -InputObject parameter, but they are all designed to only work as expected when input objects are passed to them through the pipeline, not explicitly.