Question

How to check whether the character set is in utf-8 encoding,through ruby|ror ?

Answer 1

There’s no definite way to do this, in Ruby nor anywhere else:

str = 'foo' # start with a simple string
# => "foo" 
str.encoding
# => #<Encoding:UTF-8> # which is UTF-8 encoded
str.bytes.to_a
# => [102, 111, 111] # as you can see, it consists of three bytes 102, 111 and 111
str.encode!('us-ascii') # now we will recode the string to 8-bit us-ascii encoding
# => "foo" 
str.encoding
# => #<Encoding:US-ASCII> 
str.bytes.to_a
# => [102, 111, 111] # see, same three bytes
str.encode!('windows-1251') # let us try some cyrillic
# => "foo" 
str.encoding
# => #<Encoding:Windows-1251> 
str.bytes.to_a
# => [102, 111, 111] # see, the same three again!

Of course, you can employ some statistical analysis on the text, and eliminate encodings which the text is not valid for, but theoretically, this is not solvable problem.