This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Localize $! in splainthis() too. (see bug #41717)
[perl5.git] / lib / utf8.pm
CommitLineData
a0ed51b3
LW
1package utf8;
2
d5448623
GS
3$utf8::hint_bits = 0x00800000;
4
e522ce32 5our $VERSION = '1.06';
b75c8c73 6
a0ed51b3 7sub import {
d5448623 8 $^H |= $utf8::hint_bits;
a0ed51b3
LW
9 $enc{caller()} = $_[1] if $_[1];
10}
11
12sub unimport {
d5448623 13 $^H &= ~$utf8::hint_bits;
a0ed51b3
LW
14}
15
16sub AUTOLOAD {
17 require "utf8_heavy.pl";
daf4d4ea 18 goto &$AUTOLOAD if defined &$AUTOLOAD;
bd7017d3 19 require Carp;
daf4d4ea 20 Carp::croak("Undefined subroutine $AUTOLOAD called");
a0ed51b3
LW
21}
22
231;
24__END__
25
26=head1 NAME
27
b3419ed8 28utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
a0ed51b3
LW
29
30=head1 SYNOPSIS
31
32 use utf8;
33 no utf8;
34
2c9359a2 35 # Convert a Perl scalar to/from UTF-8.
973655a8
SB
36 $num_octets = utf8::upgrade($string);
37 $success = utf8::downgrade($string[, FAIL_OK]);
38
2c9359a2 39 # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
973655a8
SB
40 utf8::encode($string);
41 utf8::decode($string);
42
786c9463 43 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
973655a8
SB
44 $flag = utf8::valid(STRING);
45
a0ed51b3
LW
46=head1 DESCRIPTION
47
393fec97 48The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
b3419ed8 49program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
70122e76 50platforms). The C<no utf8> pragma tells Perl to switch back to treating
b3419ed8 51the source text as literal bytes in the current lexical scope.
a0ed51b3 52
393fec97
GS
53This pragma is primarily a compatibility device. Perl versions
54earlier than 5.6 allowed arbitrary bytes in source code, whereas
55in future we would like to standardize on the UTF-8 encoding for
63708e74
JH
56source text.
57
19b49582
JH
58B<Do not use this pragma for anything else than telling Perl that your
59script is written in UTF-8.> The utility functions described below are
60useful for their own purposes, but they are not really part of the
61"pragmatic" effect.
62
63708e74 63Until UTF-8 becomes the default format for source text, either this
0f414b95 64pragma or the L<encoding> pragma should be used to recognize UTF-8
63708e74
JH
65in the source. When UTF-8 becomes the standard source format, this
66pragma will effectively become a no-op. For convenience in what
67follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
68Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
a0ed51b3 69
a74e8b45
JH
70See also the effects of the C<-C> switch and its cousin, the
71C<$ENV{PERL_UNICODE}>, in L<perlrun>.
72
ad0029c4 73Enabling the C<utf8> pragma has the following effect:
a0ed51b3 74
4ac9195f 75=over 4
a0ed51b3
LW
76
77=item *
78
393fec97 79Bytes in the source text that have their high-bit set will be treated
2fa62f66 80as being part of a literal UTF-X sequence. This includes most
c20e2abd 81literals such as identifier names, string constants, and constant
8f8cf39c
JH
82regular expression patterns.
83
84On EBCDIC platforms characters in the Latin 1 character set are
85treated as being part of a literal UTF-EBCDIC character.
a0ed51b3 86
4ac9195f
MS
87=back
88
ae90e350
JH
89Note that if you have bytes with the eighth bit on in your script
90(for example embedded Latin-1 in your string literals), C<use utf8>
91will be unhappy since the bytes are most probably not well-formed
2fa62f66
AT
92UTF-X. If you want to have such bytes under C<use utf8>, you can disable
93this pragma until the end the block (or file, if at top level) by
94C<no utf8;>.
ae90e350 95
2fa62f66 96If you want to automatically upgrade your 8-bit legacy bytes to Unicode,
0f414b95 97use the L<encoding> pragma instead of this pragma. For example, if
2fa62f66 98you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to Unicode
63708e74
JH
99as used in e.g. C<chr()> and C<\x{...}>, try this:
100
101 use encoding "latin-1";
102 my $c = chr(0xc4);
103 my $x = "\x{c5}";
104
2fa62f66
AT
105In case you are wondering: C<use encoding 'utf8';> is mostly the same as
106C<use utf8;>, except that C<use encoding> marks all string literals in the
107source code as Unicode, regardless of whether they contain any high-bit bytes.
108Moreover, C<use encoding> installs IO layers on C<STDIN> and C<STDOUT> to work
109with Unicode strings; see L<encoding> for details.
63708e74 110
1b026014
NIS
111=head2 Utility functions
112
8800c35a
JH
113The following functions are defined in the C<utf8::> package by the
114Perl core. You do not need to say C<use utf8> to use these and in fact
19b49582 115you should not say that unless you really want to have UTF-8 source code.
1b026014
NIS
116
117=over 4
118
973655a8 119=item * $num_octets = utf8::upgrade($string)
1b026014 120
78ea37eb
ST
121Converts in-place the octet sequence in the native encoding
122(Latin-1 or EBCDIC) to the equivalent character sequence in I<UTF-X>.
123I<$string> already encoded as characters does no harm.
124Returns the number of octets necessary to represent the string as I<UTF-X>.
125Can be used to make sure that the UTF-8 flag is on,
126so that C<\w> or C<lc()> work as Unicode on strings
127containing characters in the range 0x80-0xFF (on ASCII and
128derivatives).
129
130B<Note that this function does not handle arbitrary encodings.>
131Therefore I<Encode.pm> is recommended for the general purposes.
132
133Affected by the encoding pragma.
1b026014 134
973655a8 135=item * $success = utf8::downgrade($string[, FAIL_OK])
1b026014 136
78ea37eb
ST
137Converts in-place the character sequence in I<UTF-X>
138to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
139I<$string> already encoded as octets does no harm.
140Returns true on success. On failure dies or, if the value of
141C<FAIL_OK> is true, returns false.
142Can be used to make sure that the UTF-8 flag is off,
143e.g. when you want to make sure that the substr() or length() function
144works with the usually faster byte algorithm.
145
146B<Note that this function does not handle arbitrary encodings.>
147Therefore I<Encode.pm> is recommended for the general purposes.
148
149B<Not> affected by the encoding pragma.
150
151B<NOTE:> this function is experimental and may change
152or be removed without notice.
1b026014
NIS
153
154=item * utf8::encode($string)
155
78ea37eb
ST
156Converts in-place the character sequence to the corresponding octet sequence
157in I<UTF-X>. The UTF-8 flag is turned off. Returns nothing.
158
159B<Note that this function does not handle arbitrary encodings.>
160Therefore I<Encode.pm> is recommended for the general purposes.
094ce63c 161
973655a8 162=item * utf8::decode($string)
1b026014 163
78ea37eb
ST
164Attempts to convert in-place the octet sequence in I<UTF-X>
165to the corresponding character sequence. The UTF-8 flag is turned on
166only if the source string contains multiple-byte I<UTF-X> characters.
167If I<$string> is invalid as I<UTF-X>, returns false; otherwise returns true.
168
169B<Note that this function does not handle arbitrary encodings.>
170Therefore I<Encode.pm> is recommended for the general purposes.
171
172B<NOTE:> this function is experimental and may change
173or be removed without notice.
1b026014 174
8800c35a
JH
175=item * $flag = utf8::is_utf8(STRING)
176
786c9463
JH
177(Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
178the same as Encode::is_utf8().
8800c35a 179
70122e76
JH
180=item * $flag = utf8::valid(STRING)
181
8800c35a
JH
182[INTERNAL] Test whether STRING is in a consistent state regarding
183UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
184on B<or> if string is held as bytes (both these states are 'consistent').
185Main reason for this routine is to allow Perl's testsuite to check
186that operations have left strings in a consistent state. You most
187probably want to use utf8::is_utf8() instead.
70122e76 188
1b026014
NIS
189=back
190
7d865a91
JH
191C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
192cleared. See L<perlunicode> for more on the UTF8 flag and the C API
193functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
094ce63c
AT
194and C<sv_utf8_decode>, which are wrapped by the Perl functions
195C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
786c9463
JH
196C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
197the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
6e37fd2a
JH
198utf8::upgrade, and utf8::downgrade are always available, without a
199C<require utf8> statement-- this may change in future releases.
f1e62f77 200
8f8cf39c
JH
201=head1 BUGS
202
203One can have Unicode in identifier names, but not in package/class or
204subroutine names. While some limited functionality towards this does
205exist as of Perl 5.8.0, that is more accidental than designed; use of
206Unicode for the said purposes is unsupported.
207
208One reason of this unfinishedness is its (currently) inherent
209unportability: since both package names and subroutine names may need
210to be mapped to file and directory names, the Unicode capability of
211the filesystem becomes important-- and there unfortunately aren't
212portable answers.
213
393fec97 214=head1 SEE ALSO
a0ed51b3 215
a74e8b45 216L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>
a0ed51b3
LW
217
218=cut