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Encode::Guess(3) User Contributed Perl Documentation Encode::Guess(3)
 

Encode::Guess -- Guesses encoding from data

  # if you are sure $data won't contain anything bogus
  use Encode;
  use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
  my $utf8 = decode("Guess", $data);
  my $data = encode("Guess", $utf8);   # this doesn't work!
  # more elaborate way
  use Encode::Guess;
  my $enc = guess_encoding($data, qw/euc-jp shiftjis 7bit-jis/);
  ref($enc) or die "Can't guess: $enc"; # trap error this way
  $utf8 = $enc->decode($data);
  # or
  $utf8 = decode($enc->name, $data)

Encode::Guess enables you to guess in what encoding a given data is encoded, or at least tries to.

By default, it checks only ascii, utf8 and UTF-16/32 with BOM.
  use Encode::Guess; # ascii/utf8/BOMed UTF
To use it more practically, you have to give the names of encodings to check ( suspects as follows). The name of suspects can either be canonical names or aliases.
CAVEAT: Unlike UTF-(16|32), BOM in utf8 is NOT AUTOMATICALLY STRIPPED.
 # tries all major Japanese Encodings as well
  use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
If the $Encode::Guess::NoUTFAutoGuess variable is set to a true value, no heuristics will be applied to UTF8/16/32, and the result will be limited to the suspects and "ascii".
Encode::Guess->set_suspects
You can also change the internal suspects list via "set_suspects" method.
  use Encode::Guess;
  Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/);
    
Encode::Guess->add_suspects
Or you can use "add_suspects" method. The difference is that "set_suspects" flushes the current suspects list while "add_suspects" adds.
  use Encode::Guess;
  Encode::Guess->add_suspects(qw/euc-jp shiftjis 7bit-jis/);
  # now the suspects are euc-jp,shiftjis,7bit-jis, AND
  # euc-kr,euc-cn, and big5-eten
  Encode::Guess->add_suspects(qw/euc-kr euc-cn big5-eten/);
    
Encode::decode("Guess" ...)
When you are content with suspects list, you can now
  my $utf8 = Encode::decode("Guess", $data);
    
Encode::Guess->guess($data)
But it will croak if:
Two or more suspects remain
No suspects left
So you should instead try this;
  my $decoder = Encode::Guess->guess($data);
On success, $decoder is an object that is documented in Encode::Encoding. So you can now do this;
  my $utf8 = $decoder->decode($data);
On failure, $decoder now contains an error message so the whole thing would be as follows;
  my $decoder = Encode::Guess->guess($data);
  die $decoder unless ref($decoder);
  my $utf8 = $decoder->decode($data);
guess_encoding($data, [, list of suspects])
You can also try "guess_encoding" function which is exported by default. It takes $data to check and it also takes the list of suspects by option. The optional suspect list is not reflected to the internal suspects list.
  my $decoder = guess_encoding($data, qw/euc-jp euc-kr euc-cn/);
  die $decoder unless ref($decoder);
  my $utf8 = $decoder->decode($data);
  # check only ascii, utf8 and UTF-(16|32) with BOM
  my $decoder = guess_encoding($data);
    

Because of the algorithm used, ISO-8859 series and other single-byte encodings do not work well unless either one of ISO-8859 is the only one suspect (besides ascii and utf8).
  use Encode::Guess;
  # perhaps ok
  my $decoder = guess_encoding($data, 'latin1');
  # definitely NOT ok
  my $decoder = guess_encoding($data, qw/latin1 greek/);
    
The reason is that Encode::Guess guesses encoding by trial and error. It first splits $data into lines and tries to decode the line for each suspect. It keeps it going until all but one encoding is eliminated out of suspects list. ISO-8859 series is just too successful for most cases (because it fills almost all code points in \x00-\xff).
Do not mix national standard encodings and the corresponding vendor encodings.
  # a very bad idea
  my $decoder
     = guess_encoding($data, qw/shiftjis MacJapanese cp932/);
    
The reason is that vendor encoding is usually a superset of national standard so it becomes too ambiguous for most cases.
On the other hand, mixing various national standard encodings automagically works unless $data is too short to allow for guessing.
 # This is ok if $data is long enough
 my $decoder =  
  guess_encoding($data, qw/euc-cn
                           euc-jp shiftjis 7bit-jis
                           euc-kr
                           big5-eten/);
    
DO NOT PUT TOO MANY SUSPECTS! Don't you try something like this!
  my $decoder = guess_encoding($data, 
                               Encode->encodings(":all"));
    
It is, after all, just a guess. You should alway be explicit when it comes to encodings. But there are some, especially Japanese, environment that guess-coding is a must. Use this module with care.

Encode::Guess does not work on EBCDIC platforms.

Encode, Encode::Encoding
2018-04-22 perl v5.28.1

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