From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-04-21T09:35:05+09:00
Subject: Re: Finding non-printable characters using Regular Expressions

John Joyce wrote:
> THE book on RegEx is "Mastering Regular Expressions" from OReilly.
> It is a bit Perl focused in the examples, but the book itself is all 
> about regular expressions in use.
> 

I will get a copy of the book as trying to find the information on the 
web is very time consuming and hit or miss.  Thank you for the suggestion.


> On Apr 21, 2007, at 7:55 AM, Michael W. Ryder wrote:
> 
>> 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?
>>
> 
>