From: Greg Willits <lists@...>
Date: 2008-06-10T07:55:07+09:00
Subject: Re: Parsing a comma-separated file

> name, age, gender
> Bob, 32, M
> Stacy, 14, F
> ...
> How do I parse 'Bob', knowing it's the first element on the line, '32'
> is the second, 'M' is the last...I've been reading about regular
> expressions. Is this the best way to solve this problem? And how exactly
> do you use them?

This doesn't handle all CSV specs, but if you know you have pure data 
like you show above, these are the rudimentary steps without the 
one-liner tricks, so it should be pretty straight forward to understand 
each step. Arranging them as methods to a class would be good.


# read the file into a var

  if FileTest::exist?(file_name)
    file_lines = IO.readlines(file_name)
  end

# normalize line endings so it doesn't matter what they are

  file_lines.strip!
  file_lines.gsub!(/\r\n/,'\n')
  file_lines.gsub!(/\r/,'\n')

# normalize comma delimiters so it doesn't matter
# if you have one, two or one,two or one , two etc...

   file_lines.gsub!(/\s*,\s*/, ',')

# split lines into a single array of lines

  lines_array = file_lines.split('\n')

# split each line into an array

  final_data = []

  lines_array.each do |this_line|
    final_data << this_line.split(',')
  end

# final_data is now an array of arrays that looks like this:

  [
    ['name', 'age', 'gender'],
    ['Bob', '32', 'M'],
    ['Stacy', '14', 'F']
  ]

So, to get Bob, you'd have to know his line number, and index into the 
record array:

  final_data[1][0]    # Bob
  final_data[2][3]    # F


-- greg willits

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