From: dblack@...
Date: 2006-04-24T00:42:15+09:00
Subject: Re: how to ensure no blank lines in DATA statements

Hi --

On Mon, 24 Apr 2006, Joseph Paish wrote:

> On Mon, 24 Apr 2006 00:20:46 +0900
> dblack@wobblini.net wrote:
>
>> Hi --
>>
>> On Mon, 24 Apr 2006, Joseph Paish wrote:
>>
>>> suppose i have the following piece of code to read some data (input by
>>> the user) following __END__
>>>
>>> while line = DATA.gets
>>>  one_record = line.chomp!.split
>>>  # do stuff
>>>  end
>>>
>>>
>>>
>>> __END__
>>>
>>> bought 2 widgets 17.99
>>> sold 12 widgets 22.49
>>>
>>> bought 11 things 12.99
>>>
>>> sold 5 things 10.49
>>>
>>>
>>> as you can see, there is a blank line ahead of the first line of data (i
>>> don't want that), and there may be one or more blank lines or lines
>>> containing spaces after the data or even between the lines of data.
>>>
>>> i can't control what the user will do here, but i need to take it into
>>> account.  any suggestions on how to ensure that any line i read contains
>>> the 4 desired fields and doesn't contain anything else (even 4 blank
>>> spaces like between the last bought and sold records)?
>>
>> Here's a nice way to avoid worrying about the spaces, though it may
>> run aground if you have lines that have non-spaces and are malformed:
>>
>> require 'scanf'
>>
>> DATA.scanf("%s%d%s%f") do |action, num, item, price|
>>    puts "#{action} #{num} #{item} at $#{price}, total $#{price * num}"
>> end
>>
>> Output (with your sample):
>>
>> bought 2 widgets at $17.99, total $35.98
>> sold 12 widgets at $22.49, total $269.88
>> bought 11 things at $12.99, total $142.89
>> sold 5 things at $10.49, total $52.45
>>
>>
>> David
>>
>
>
> this is exactly what i needed.
>
> thank you
>
> joe

Do be careful, though, if there's a chance of a malformed line.  scanf
will just stop.  But if the data are as they should be it will work
nicely.


David

-- 
David A. Black (dblack@wobblini.net)
Ruby Power and Light, LLC (http://www.rubypowerandlight.com)

"Ruby for Rails" PDF now on sale!  http://www.manning.com/black
Paper version coming in early May!