How to remove non-printable/invisible characters in ruby?

Question

Sometimes I have evil non-printable characters in the middle of a string. These strings are user input, so I must make my program receive it well instead of try to change the source of the problem.

For example, they can have zero width no-break space in the middle of the string. For example, while parsing a .po file, one problematic part was the string "he is a man of god" in the middle of the file. While it everything seems correct, inspecting it with irb shows:

 "he is a man of god".codepoints
 => [104, 101, 32, 105, 115, 32, 97, 32, 65279, 109, 97, 110, 32, 111, 102, 32, 103, 111, 100] 

I believe that I know what a BOM is, and I even handle it nicely. However sometimes I have such characters on the middle of the file, so it is not a BOM.

My current approach is to remove all characters that I found evil in a really smelly fashion:

text = (text.codepoints - CODEPOINTS_BlACKLIST).pack("U*")

The most close I got was following this post which leaded me to :print: option on regexps. However it was no good for me:

"m".scan(/[[:print:]]/).join.codepoints
 => [65279, 109] 

so the question is: How can I remove all non-printable characters from a string in ruby?

Answer 1

try this:

>>"aaa\f\d\x00abcd".gsub(/[^[:print:]]/,'.')
=>"aaa.d.abcd"