From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-04-21T07:55:04+09:00
Subject: Re: Finding non-printable characters using Regular Expressions

Alex Young wrote:
> Michael W. Ryder wrote:
>> 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.
> 
> You're nearly there.  Look a little closer at my suggestion, 
> particularly the second regex.
> 

Thank you very much for your assistance using "A \n B \t 
C".gsub(/[^[:print:]]/, '') gives me "A B C" which is what I was looking 
for.
Can you recommend a good reference on regular expressions so I can learn 
more?