Using headers when reading from and editing CSV file with ruby

Question

Let's say I am using code like this to make inline edits of CSV file:

CSV.open(fn, 'r+') do |f|
  old_pos = f.pos
  while r = f.shift
    if r[0] == 'NOT_PROCESSED'
      f.seek(old_pos)
      r[0] = 'PASSED       ' # pay attention to the padding spaces!
      f << r
    end

    old_pos = f.pos
  end
end

Is there a way to somehow use headers with this approach? Like for example r['STATUS']? How should I rewrite code to make this possible?

The idea to edit csv-files in place seem quite dangerous to me. I would either write to a new file, or use some dbm-database when really need to do in-edting of a file. — Meier
– Meier, Commented Mar 3, 2016 at 8:52

Uri Agassi · Accepted Answer · 2016-03-03 08:37:33Z

CSV.open has a third parameter called options, where you can add various options, including :headers:

:headers
If set to :first_row or true, the initial row of the CSV file will be treated as a row of headers. If set to an Array, the contents will be used as the headers. If set to a String, the String is run through a call of ::parse_line with the same :col_sep, :row_sep, and :quote_char as this instance to produce an Array of headers. This setting causes #shift to return rows as CSV::Row objects instead of Arrays and #read to return CSV::Table objects instead of an Array of Arrays.

CSV.open(fn, 'r+', headers: true) do |f|
  old_pos = f.pos
  while r = f.shift
    if r['STATUS'] == 'NOT_PROCESSED'
      f.seek(old_pos)
      r['STATUS'] = 'PASSED       ' # pay attention to the padding spaces!
      f << r
    end

    old_pos = f.pos
  end
end

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