How to convert CSV to Excel?

For those seeing this currently, the syntax changed a bit in these eight years. The following worked perfectly for me, based on the previous answer (recopied here for the sake of your copy-and-paste habits):

def convert_csv_to_xlsx
  book = Spreadsheet::Workbook.new
  sheet1 = book.create_worksheet

  header_format = Spreadsheet::Format.new(
    weight: :bold,
    horizontal_align: :center,
    bottom: :medium,
    locked: true
  )

  sheet1.row(0).default_format = header_format

  CSV.open(input_path, 'r') do |csv|
    csv.each_with_index do |row, i|
      sheet1.row(i).replace(row)
    end
  end

  book.write(output_path)
end

I.E.: FasterCSV is now just CSV and true for :bottom is deprecated

If you don't found any gem for convert CSV to EXCEL then you can try to find two gems separately

1. Read/Write CSV(For reading CSV file) e.g. FasterCSV
2. Read/Write EXCEL(For write EXCEL file) e.g. SpreadSheet

According to this post, the spreadsheet gem is a possibility. It looks like this is a very popular gem. Check it out. Example:

book = Spreadsheet::Workbook.new
sheet1 = book.create_worksheet

header_format = Spreadsheet::Format.new(
  :weight => :bold,
  :horizontal_align => :center,
  :bottom => true,
  :locked => true
)

sheet1.row(0).default_format = header_format

FasterCSV.open(input_path, 'r') do |csv|
  csv.each_with_index do |row, i|
    sheet1.row(i).replace(row)
  end
end

book.write(output_path)

According to this post, write_xlsx is a possibility.

I've used the Apache POI library with JRuby to export xls files. Here's a quick example.

require 'java'
require 'poi.jar'
# require 'poi-ooxml.jar'
require 'rubygems'
require 'fastercsv'

java_import org.apache.poi.hssf.usermodel.HSSFWorkbook;

wb = HSSFWorkbook.new # OR XSSFWorkbook, for xlsx
sheet = wb.create_sheet('Sheet 1')

FasterCSV.open(ARGV.first) do |csv|
  csv.each_with_index do |csv_row, line_no|
    row = sheet.createRow(line_no)
    csv_row.each_with_index do |csv_value, col_no|
      cell = row.createCell(col_no)
      cell.setCellValue(csv_value) unless csv_value.nil? # can't pass nil.
    end
  end
end


f = java.io.FileOutputStream.new("workbook.xls")
wb.write(f)
f.close

Some useful methods for formatting POI spreadsheets are

• sheet.createFreezePane(0,1,0,1)
• wb.setRepeatingRowsAndColumns(0, -1, -1, 0, 1)
• sheet.setColumnWidth(i, 100 *256)
• sheet.autoSizeColumn(i), but beware, if you're running in headless mode, you have to call java.lang.System.setProperty("java.awt.headless", "true")

You can also use Win32ole on Windows, if you have Excel installed

require 'win32ole'
require 'rubygems'
require 'fastercsv'

xl = WIN32OLE.new('Excel.Application')
xl.Visible = 0
wb = xl.Workbooks.Add
ws = wb.Worksheets(1)

FasterCSV.open(ARGV.first) do |csv|
  csv.each_with_index do |csv_row, line_no|
    csv_row.each_with_index do |value, col|
      ws.Cells(line_no + 1, col + 1).Value = value
    end
  end
end

wb.SaveAs("workbook.xls", 56) # 56 = xlExcel8 aka Excel 97-2003. i.e. xls
wb.SaveAs("workbook.xlsx", 51) # 51 = xlOpenXMLWorkbook
wb.SaveAs("workbook.xlsb", 50) # 50 = xlExcel12

wb.Close(2) #xlDoNotSaveChanges
xl.Quit

Some useful methods for formatting with Excel are

• xl.Rows(1).Font.Bold = true
• ws.Cells.EntireColumn.AutoFit

Yet another option is to write directly to Microsoft's XML Spreadsheet format, as Ryan Bates at Railscasts.com does at the end of his Exporting CSV and Excel episode.

<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
  xmlns:o="urn:schemas-microsoft-com:office:office"
  xmlns:x="urn:schemas-microsoft-com:office:excel"
  xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
  xmlns:html="http://www.w3.org/TR/REC-html40">
  <Worksheet ss:Name="Sheet1">
    <Table>
      <Row>
        <Cell><Data ss:Type="String">ID</Data></Cell>
        <Cell><Data ss:Type="String">Name</Data></Cell>
        <Cell><Data ss:Type="String">Release Date</Data></Cell>
        <Cell><Data ss:Type="String">Price</Data></Cell>
      </Row>
    <% @products.each do |product| %>
      <Row>
        <Cell><Data ss:Type="Number"><%= product.id %></Data></Cell>
        <Cell><Data ss:Type="String"><%= product.name %></Data></Cell>
        <Cell><Data ss:Type="String"><%= product.released_on %></Data></Cell>
        <Cell><Data ss:Type="Number"><%= product.price %></Data></Cell>
      </Row>
    <% end %>
    </Table>
  </Worksheet>
</Workbook>

This gem looks promising, too.