1Encode::Guess(3) User Contributed Perl Documentation Encode::Guess(3)
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6 Encode::Guess -- Guesses encoding from data
7
9 # if you are sure $data won't contain anything bogus
10 use Encode;
12 use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
13 my $utf8 = decode("Guess", $data);
14 my $data = encode("Guess", $utf8); # this doesn't work!
15 # more elaborate way
17 use Encode::Guess;
18 my $enc = guess_encoding($data, qw/euc-jp shiftjis 7bit-jis/);
19 ref($enc) or die "Can't guess: $enc"; # trap error this way
20 $utf8 = $enc->decode($data);
21 # or
22 $utf8 = decode($enc->name, $data)
23
25 Encode::Guess enables you to guess in what encoding a given data is
26 encoded, or at least tries to.
27
29 By default, it checks only ascii, utf8 and UTF-16/32 with BOM.
30 use Encode::Guess; # ascii/utf8/BOMed UTF
32 To use it more practically, you have to give the names of encodings to
34 check (suspects as follows). The name of suspects can either be
35 canonical names or aliases.
36 CAVEAT: Unlike UTF-(16|32), BOM in utf8 is NOT AUTOMATICALLY STRIPPED.
38 # tries all major Japanese Encodings as well
40 use Encode::Guess qw/euc-jp shiftjis 7bit-jis/;
41 If the $Encode::Guess::NoUTFAutoGuess variable is set to a true value,
43 no heuristics will be applied to UTF8/16/32, and the result will be
44 limited to the suspects and "ascii".
45 Encode::Guess->set_suspects
47 You can also change the internal suspects list via "set_suspects"
48 method.
49 use Encode::Guess;
51 Encode::Guess->set_suspects(qw/euc-jp shiftjis 7bit-jis/);
52 Encode::Guess->add_suspects
54 Or you can use "add_suspects" method. The difference is that
55 "set_suspects" flushes the current suspects list while
56 "add_suspects" adds.
57 use Encode::Guess;
59 Encode::Guess->add_suspects(qw/euc-jp shiftjis 7bit-jis/);
60 # now the suspects are euc-jp,shiftjis,7bit-jis, AND
61 # euc-kr,euc-cn, and big5-eten
62 Encode::Guess->add_suspects(qw/euc-kr euc-cn big5-eten/);
63 Encode::decode("Guess" ...)
65 When you are content with suspects list, you can now
66 my $utf8 = Encode::decode("Guess", $data);
68 Encode::Guess->guess($data)
70 But it will croak if:
71 • Two or more suspects remain
73 • No suspects left
75 So you should instead try this;
77 my $decoder = Encode::Guess->guess($data);
79 On success, $decoder is an object that is documented in
81 Encode::Encoding. So you can now do this;
82 my $utf8 = $decoder->decode($data);
84 On failure, $decoder now contains an error message so the whole
86 thing would be as follows;
87 my $decoder = Encode::Guess->guess($data);
89 die $decoder unless ref($decoder);
90 my $utf8 = $decoder->decode($data);
91 guess_encoding($data, [, list of suspects])
93 You can also try "guess_encoding" function which is exported by
94 default. It takes $data to check and it also takes the list of
95 suspects by option. The optional suspect list is not reflected to
96 the internal suspects list.
97 my $decoder = guess_encoding($data, qw/euc-jp euc-kr euc-cn/);
99 die $decoder unless ref($decoder);
100 my $utf8 = $decoder->decode($data);
101 # check only ascii, utf8 and UTF-(16|32) with BOM
102 my $decoder = guess_encoding($data);
103
105 • Because of the algorithm used, ISO-8859 series and other single-
106 byte encodings do not work well unless either one of ISO-8859 is
107 the only one suspect (besides ascii and utf8).
108 use Encode::Guess;
110 # perhaps ok
111 my $decoder = guess_encoding($data, 'latin1');
112 # definitely NOT ok
113 my $decoder = guess_encoding($data, qw/latin1 greek/);
114 The reason is that Encode::Guess guesses encoding by trial and
116 error. It first splits $data into lines and tries to decode the
117 line for each suspect. It keeps it going until all but one
118 encoding is eliminated out of suspects list. ISO-8859 series is
119 just too successful for most cases (because it fills almost all
120 code points in \x00-\xff).
121 • Do not mix national standard encodings and the corresponding vendor
123 encodings.
124 # a very bad idea
126 my $decoder
127 = guess_encoding($data, qw/shiftjis MacJapanese cp932/);
128 The reason is that vendor encoding is usually a superset of
130 national standard so it becomes too ambiguous for most cases.
131 • On the other hand, mixing various national standard encodings
133 automagically works unless $data is too short to allow for
134 guessing.
135 # This is ok if $data is long enough
137 my $decoder =
138 guess_encoding($data, qw/euc-cn
139 euc-jp shiftjis 7bit-jis
140 euc-kr
141 big5-eten/);
142 • DO NOT PUT TOO MANY SUSPECTS! Don't you try something like this!
144 my $decoder = guess_encoding($data,
146 Encode->encodings(":all"));
147 It is, after all, just a guess. You should alway be explicit when it
149 comes to encodings. But there are some, especially Japanese,
150 environment that guess-coding is a must. Use this module with care.
151
153 Encode::Guess does not work on EBCDIC platforms.
154
156 Encode, Encode::Encoding
157perl v5.34.0 2021-10-10 Encode::Guess(3)