From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-04-21T05:15:05+09:00
Subject: Re: Finding non-printable characters using Regular Expressions

Alex Young wrote:
> Michael W. Ryder wrote:
>> As part of a method I am playing with while learning Ruby I need to be 
>> able to determine which characters in a string are non-printable.  
>> What is the "best" method for determining if a character is printable, 
>> such as an "A", or unprintable, such as a tab?
>> While I could create a list of printable characters using ranges is 
>> this the best way to do this?
>>
> The POSIX character classes are for exactly this:
> 
> irb(main):001:0> "A \n B \t C".gsub(/[[:graph:]]/, '')
> => " \n  \t "
> irb(main):002:0> "A \n B \t C".gsub(/[[:print:]]/, '')
> => "\n\t"
> 

This is very close to what I am looking for.  If I use
"A \n B \t C".gsub(/[^[:graph:]]/, '')
it returns "ABC", but I need to keep the spaces and have not been able 
to figure out how to include them in the output so that it shows "A B C".
Thank you for your assistance, it has given me a starting point and I 
will have to spend some time experimenting and researching to reach the 
final step.