Select columns from a CSV file. See csv and RIO::Doc::INTRO.

Puts a Rio in CSV mode and sets the field and record separators. In csv mode selecting with Rio#records will cause each line read to be parsed into a line with the CSV standard library. Specifying using Rio#lines to select will return unparsed strings as normal.

 # copy a csv file, changing the field separator
 rio('afile.csv').csv > rio('afile_semicolons.csv').csv(';')

CSV mode also adds two methods columns and skipcolumns which allows selecting columns by column index using Fixnums or Ranges in a way similar to how lines are selected.

 # iterate through every line but only get the first three columns
 rio("afile.csv").csv.columns(0..2) { |array_of_fields| ... }

 # iterate through every line but skip the columns 2 and 3 through 5
 rio("afile.csv").csv.skipcolumns(2,3..5) { |array_of_fields| ... }

 # an array containg all but the first line returning columns 5,6 and 7
 rio("afile.csv").csv.columns(5..7).skiplines[0]

See RIO::Doc::INTRO for complete documentation on csv mode.

Reject columns from a CSV file. See csv and RIO::Doc::INTRO.