Split csv files with or without header rows, multiline columns with newlines ok.

csv-split.ps1

<#
  Split csv files with or without header rows, multiline columns with newlines ok.
#>

param (
  [string]$in,
  [string]$outdir = [System.IO.Path]::GetDirectoryName($in),
  [int]$count = 1000,
  [string]$delimiter = ',',
  [string[]]$header = @()
)

function createOutPath($in, $outdir, $fileIndex) {
  $name = [System.IO.Path]::GetFileNameWithoutExtension($in)
  $ext = [System.IO.Path]::GetExtension($in)
  # append file index to original file name in outdir
  return join-path $outdir "$name-$fileIndex$ext"
}

# create out dir if it doesn't exist
if (!(test-path $outdir)) {
  mkdir $outdir | Out-Null
}

$fileIndex = 1
$rowIndex = 0
$file = @()

if ($null -ne $header -and $header.count -ne 0) {

  # import with supplied header (file does not have its own header)
  Import-Csv -Path $in -Delimiter $delimiter -Header $header | ForEach-Object {

    $file += $_
    $rowIndex++
    $out = createOutPath $in $outdir $fileIndex

    if ($rowIndex -eq $count) {
      $file | Export-Csv -Path $out -Encoding utf8NoBOM -NoTypeInformation -UseQuotes AsNeeded
      $fileIndex++
      $rowIndex = 0
      $file = @()
      write-host $out
    }
  }

}
else {

  # import and assume first row is header
  Import-Csv -Path $in -Delimiter $delimiter | ForEach-Object {

    $file += $_
    $rowIndex++
    $out = createOutPath $in $outdir $fileIndex

    if ($rowIndex -eq $count) {
      $file | Export-Csv -Path $out -Encoding utf8NoBOM -NoTypeInformation -UseQuotes AsNeeded
      $fileIndex++
      $rowIndex = 0
      $file = @()
      write-host $out
    }
  }

}


if ($file.Count -gt 0) {
  $out = createOutPath $in $outdir $fileIndex
  $file | Export-Csv -Path $out -Encoding utf8NoBOM -NoTypeInformation -UseQuotes AsNeeded
  write-host $out
}