3 $utf8::hint_bits = 0x00800000;
8 $^H |= $utf8::hint_bits;
9 $enc{caller()} = $_[1] if $_[1];
13 $^H &= ~$utf8::hint_bits;
17 require "utf8_heavy.pl";
18 goto &$AUTOLOAD if defined &$AUTOLOAD;
19 Carp::croak("Undefined subroutine $AUTOLOAD called");
27 utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
34 $num_octets = utf8::upgrade($string);
35 $success = utf8::downgrade($string[, FAIL_OK]);
37 utf8::encode($string);
38 utf8::decode($string);
40 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
41 $flag = utf8::valid(STRING);
45 The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
46 program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
47 platforms). The C<no utf8> pragma tells Perl to switch back to treating
48 the source text as literal bytes in the current lexical scope.
50 This pragma is primarily a compatibility device. Perl versions
51 earlier than 5.6 allowed arbitrary bytes in source code, whereas
52 in future we would like to standardize on the UTF-8 encoding for
55 B<Do not use this pragma for anything else than telling Perl that your
56 script is written in UTF-8.> The utility functions described below are
57 useful for their own purposes, but they are not really part of the
60 Until UTF-8 becomes the default format for source text, either this
61 pragma or the L</encoding> pragma should be used to recognize UTF-8
62 in the source. When UTF-8 becomes the standard source format, this
63 pragma will effectively become a no-op. For convenience in what
64 follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
65 Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
67 See also the effects of the C<-C> switch and its cousin, the
68 C<$ENV{PERL_UNICODE}>, in L<perlrun>.
70 Enabling the C<utf8> pragma has the following effect:
76 Bytes in the source text that have their high-bit set will be treated
77 as being part of a literal UTF-8 character. This includes most
78 literals such as identifier names, string constants, and constant
79 regular expression patterns.
81 On EBCDIC platforms characters in the Latin 1 character set are
82 treated as being part of a literal UTF-EBCDIC character.
86 Note that if you have bytes with the eighth bit on in your script
87 (for example embedded Latin-1 in your string literals), C<use utf8>
88 will be unhappy since the bytes are most probably not well-formed
89 UTF-8. If you want to have such bytes and use utf8, you can disable
90 utf8 until the end the block (or file, if at top level) by C<no utf8;>.
92 If you want to automatically upgrade your 8-bit legacy bytes to UTF-8,
93 use the L</encoding> pragma instead of this pragma. For example, if
94 you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8
95 as used in e.g. C<chr()> and C<\x{...}>, try this:
97 use encoding "latin-1";
101 In case you are wondering: yes, C<use encoding 'utf8';> works much
102 the same as C<use utf8;>.
104 =head2 Utility functions
106 The following functions are defined in the C<utf8::> package by the
107 Perl core. You do not need to say C<use utf8> to use these and in fact
108 you should not say that unless you really want to have UTF-8 source code.
112 =item * $num_octets = utf8::upgrade($string)
114 Converts (in-place) internal representation of string to Perl's
115 internal I<UTF-X> form. Returns the number of octets necessary to
116 represent the string as I<UTF-X>. Can be used to make sure that the
117 UTF-8 flag is on, so that C<\w> or C<lc()> work as expected on strings
118 containing characters in the range 0x80-0xFF (oon ASCII and
119 derivatives). Note that this should not be used to convert a legacy
120 byte encoding to Unicode: use Encode for that. Affected by the
123 =item * $success = utf8::downgrade($string[, FAIL_OK])
125 Converts (in-place) internal representation of string to be un-encoded
126 bytes. Returns true on success. On failure dies or, if the value of
127 FAIL_OK is true, returns false. Can be used to make sure that the
128 UTF-8 flag is off, e.g. when you want to make sure that the substr()
129 or length() function works with the usually faster byte algorithm.
130 Note that this should not be used to convert Unicode back to a legacy
131 byte encoding: use Encode for that. B<Not> affected by the encoding
134 =item * utf8::encode($string)
136 Converts (in-place) I<$string> from logical characters to octet
137 sequence representing it in Perl's I<UTF-X> encoding. Returns
138 nothing. Same as Encode::encode_utf8(). Note that this should not be
139 used to convert a legacy byte encoding to Unicode: use Encode for
142 =item * utf8::decode($string)
144 Attempts to convert I<$string> in-place from Perl's I<UTF-X> encoding
145 into logical characters. Returns nothing. Same as Encode::decode_utf8().
146 Note that this should not be used to convert Unicode back to a legacy
147 byte encoding: use Encode for that.
149 =item * $flag = utf8::is_utf8(STRING)
151 (Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
152 the same as Encode::is_utf8().
154 =item * $flag = utf8::valid(STRING)
156 [INTERNAL] Test whether STRING is in a consistent state regarding
157 UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
158 on B<or> if string is held as bytes (both these states are 'consistent').
159 Main reason for this routine is to allow Perl's testsuite to check
160 that operations have left strings in a consistent state. You most
161 probably want to use utf8::is_utf8() instead.
165 C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
166 cleared. See L<perlunicode> for more on the UTF8 flag and the C API
167 functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
168 and C<sv_utf8_decode>, which are wrapped by the Perl functions
169 C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
170 C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
171 the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
172 utf8::upgrade, and utf8::downgrade are always available, without a
173 C<require utf8> statement-- this may change in future releases.
177 One can have Unicode in identifier names, but not in package/class or
178 subroutine names. While some limited functionality towards this does
179 exist as of Perl 5.8.0, that is more accidental than designed; use of
180 Unicode for the said purposes is unsupported.
182 One reason of this unfinishedness is its (currently) inherent
183 unportability: since both package names and subroutine names may need
184 to be mapped to file and directory names, the Unicode capability of
185 the filesystem becomes important-- and there unfortunately aren't
190 L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>