in the largest Chinese, Japanese, and Korean dictionaries are also
encoded. The standards will eventually cover almost all characters in
more than 250 writing systems and thousands of languages.
+Unicode 1.0 was released in October 1991, and 4.0 in April 2003.
A Unicode I<character> is an abstract entity. It is not bound to any
particular integer width, especially not to the C language C<char>.
I<code points>.
The Unicode standard prefers using hexadecimal notation for the code
-points. If numbers like C<0x0041> are unfamiliar to
-you, take a peek at a later section, L</"Hexadecimal Notation">.
-The Unicode standard uses the notation C<U+0041 LATIN CAPITAL LETTER A>,
-to give the hexadecimal code point and the normative name of
-the character.
+points. If numbers like C<0x0041> are unfamiliar to you, take a peek
+at a later section, L</"Hexadecimal Notation">. The Unicode standard
+uses the notation C<U+0041 LATIN CAPITAL LETTER A>, to give the
+hexadecimal code point and the normative name of the character.
Unicode also defines various I<properties> for the characters, like
"uppercase" or "lowercase", "decimal digit", or "punctuation";
A common myth about Unicode is that it would be "16-bit", that is,
Unicode is only represented as C<0x10000> (or 65536) characters from
-C<0x0000> to C<0xFFFF>. B<This is untrue.> Since Unicode 2.0, Unicode
-has been defined all the way up to 21 bits (C<0x10FFFF>), and since
-Unicode 3.1, characters have been defined beyond C<0xFFFF>. The first
-C<0x10000> characters are called the I<Plane 0>, or the I<Basic
-Multilingual Plane> (BMP). With Unicode 3.1, 17 planes in all are
-defined--but nowhere near full of defined characters, yet.
+C<0x0000> to C<0xFFFF>. B<This is untrue.> Since Unicode 2.0 (July
+1996), Unicode has been defined all the way up to 21 bits (C<0x10FFFF>),
+and since Unicode 3.1 (March 2001), characters have been defined
+beyond C<0xFFFF>. The first C<0x10000> characters are called the
+I<Plane 0>, or the I<Basic Multilingual Plane> (BMP). With Unicode
+3.1, 17 (yes, seventeen) planes in all were defined--but they are
+nowhere near full of defined characters, yet.
Another myth is that the 256-character blocks have something to
do with languages--that each block would define the characters used
For further information see L<Unicode::UCD>.
The Unicode code points are just abstract numbers. To input and
-output these abstract numbers, the numbers must be I<encoded> somehow.
-Unicode defines several I<character encoding forms>, of which I<UTF-8>
-is perhaps the most popular. UTF-8 is a variable length encoding that
-encodes Unicode characters as 1 to 6 bytes (only 4 with the currently
-defined characters). Other encodings include UTF-16 and UTF-32 and their
-big- and little-endian variants (UTF-8 is byte-order independent)
-The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms.
+output these abstract numbers, the numbers must be I<encoded> or
+I<serialised> somehow. Unicode defines several I<character encoding
+forms>, of which I<UTF-8> is perhaps the most popular. UTF-8 is a
+variable length encoding that encodes Unicode characters as 1 to 6
+bytes (only 4 with the currently defined characters). Other encodings
+include UTF-16 and UTF-32 and their big- and little-endian variants
+(UTF-8 is byte-order independent) The ISO/IEC 10646 defines the UCS-2
+and UCS-4 encoding forms.
For more information about encodings--for instance, to learn what
I<surrogates> and I<byte order marks> (BOMs) are--see L<perlunicode>.
needed: if your Perl script itself is encoded in UTF-8, you can use
UTF-8 in your identifier names, and in string and regular expression
literals, by saying C<use utf8>. This is not the default because
-scripts with legacy 8-bit data in them would break.
+scripts with legacy 8-bit data in them would break. See L<utf8>.
=head2 Perl's Unicode Model
A user of Perl does not normally need to know nor care how Perl
happens to encode its internal strings, but it becomes relevant when
-outputting Unicode strings to a stream without a discipline--one with
+outputting Unicode strings to a stream without a PerlIO layer -- one with
the "default" encoding. In such a case, the raw bytes used internally
(the native character set or UTF-8, as appropriate for each string)
will be used, and a "Wide character" warning will be issued if those
Wide character in print at ...
-To output UTF-8, use the C<:utf8> output discipline. Prepending
+To output UTF-8, use the C<:utf8> output layer. Prepending
binmode(STDOUT, ":utf8");
to this sample program ensures that the output is completely UTF-8,
and removes the program's warning.
-If your locale environment variables (C<LANGUAGE>, C<LC_ALL>,
-C<LC_CTYPE>, C<LANG>) contain the strings 'UTF-8' or 'UTF8',
-regardless of case, then the default encoding of your STDIN, STDOUT,
-and STDERR and of B<any subsequent file open>, is UTF-8. Note that
-this means that Perl expects other software to work, too: if Perl has
-been led to believe that STDIN should be UTF-8, but then STDIN coming
-in from another command is not UTF-8, Perl will complain about the
-malformed UTF-8.
+You can enable automatic UTF-8-ification of your standard file
+handles, default C<open()> layer, and C<@ARGV> by using either
+the C<-C> command line switch or the C<PERL_UNICODE> environment
+variable, see L<perlrun> for the documentation of the C<-C> switch.
+
+Note that this means that Perl expects other software to work, too:
+if Perl has been led to believe that STDIN should be UTF-8, but then
+STDIN coming in from another command is not UTF-8, Perl will complain
+about the malformed UTF-8.
+
+All features that combine Unicode and I/O also require using the new
+PerlIO feature. Almost all Perl 5.8 platforms do use PerlIO, though:
+you can see whether yours is by running "perl -V" and looking for
+C<useperlio=define>.
=head2 Unicode and EBCDIC
The C<Encode> module knows about many encodings and has interfaces
for doing conversions between those encodings:
- use Encode 'from_to';
- from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8
+ use Encode 'decode';
+ $data = decode("iso-8859-3", $data); # convert from legacy to utf-8
=head2 Unicode I/O
binmode(STDOUT, ":encoding(shift_jis)");
The matching of encoding names is loose: case does not matter, and
-many encodings have several aliases. Note that C<:utf8> discipline
+many encodings have several aliases. Note that the C<:utf8> layer
must always be specified exactly like that; it is I<not> subject to
the loose matching of encoding names.
Reading in a file that you know happens to be encoded in one of the
Unicode or legacy encodings does not magically turn the data into
Unicode in Perl's eyes. To do that, specify the appropriate
-discipline when opening files
+layer when opening files
open(my $fh,'<:utf8', 'anything');
my $line_of_unicode = <$fh>;
open(my $fh,'<:encoding(Big5)', 'anything');
my $line_of_unicode = <$fh>;
-The I/O disciplines can also be specified more flexibly with
+The I/O layers can also be specified more flexibly with
the C<open> pragma. See L<open>, or look at the following example.
- use open ':utf8'; # input and output default discipline will be UTF-8
+ use open ':utf8'; # input and output default layer will be UTF-8
open X, ">file";
print X chr(0x100), "\n";
close X;
printf "%#x\n", ord(<Y>); # this should print 0x100
close Y;
-With the C<open> pragma you can use the C<:locale> discipline
+With the C<open> pragma you can use the C<:locale> layer
- $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R';
+ BEGIN { $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R' }
# the :locale will probe the locale environment variables like LC_ALL
use open OUT => ':locale'; # russki parusski
open(O, ">koi8");
printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
close I;
-or you can also use the C<':encoding(...)'> discipline
+or you can also use the C<':encoding(...)'> layer
open(my $epic,'<:encoding(iso-8859-7)','iliad.greek');
my $line_of_unicode = <$epic>;
stream. The result is always Unicode.
The L<open> pragma affects all the C<open()> calls after the pragma by
-setting default disciplines. If you want to affect only certain
-streams, use explicit disciplines directly in the C<open()> call.
+setting default layers. If you want to affect only certain
+streams, use explicit layers directly in the C<open()> call.
You can switch encodings on an already opened stream by using
C<binmode()>; see L<perlfunc/binmode>.
C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>,
C<binmode()>, and the C<open> pragma.
-Similarly, you may use these I/O disciplines on output streams to
+Similarly, you may use these I/O layers on output streams to
automatically convert Unicode to the specified encoding when it is
written to the stream. For example, the following snippet copies the
contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to
the file "text.utf8", encoded as UTF-8:
- open(my $nihongo, '<:encoding(iso2022-jp)', 'text.jis');
- open(my $unicode, '>:utf8', 'text.utf8');
- while (<$nihongo>) { print $unicode }
+ open(my $nihongo, '<:encoding(iso-2022-jp)', 'text.jis');
+ open(my $unicode, '>:utf8', 'text.utf8');
+ while (<$nihongo>) { print $unicode $_ }
The naming of encodings, both by the C<open()> and by the C<open>
pragma, is similar to the C<encoding> pragma in that it allows for
and C<sysseek()>.
Notice that because of the default behaviour of not doing any
-conversion upon input if there is no default discipline,
+conversion upon input if there is no default layer,
it is easy to mistakenly write code that keeps on expanding a file
by repeatedly encoding the data:
explicitly opening also the F<file> for input as UTF-8.
B<NOTE>: the C<:utf8> and C<:encoding> features work only if your
-Perl has been built with the new "perlio" feature. Almost all
-Perl 5.8 platforms do use "perlio", though: you can see whether
-yours is by running "perl -V" and looking for C<useperlio=define>.
+Perl has been built with the new PerlIO feature (which is the default
+on most systems).
=head2 Displaying Unicode As Text
sprintf("\\x{%04X}", $_) : # \x{...}
chr($_) =~ /[[:cntrl:]]/ ? # else if control character ...
sprintf("\\x%02X", $_) : # \x..
- chr($_) # else as themselves
+ quotemeta(chr($_)) # else quoted or as themselves
} unpack("U*", $_[0])); # unpack Unicode characters
}
nice_string("foo\x{100}bar\n")
-returns:
+returns the string
+
+ 'foo\x{0100}bar\x0A'
- "foo\x{0100}bar\x0A"
+which is ready to be printed.
=head2 Special Cases
Normal users of Perl should never care how Perl encodes any particular
Unicode string (because the normal ways to get at the contents of a
string with Unicode--via input and output--should always be via
-explicitly-defined I/O disciplines). But if you must, there are two
+explicitly-defined I/O layers). But if you must, there are two
ways of looking behind the scenes.
One way of peeking inside the internal encoding of Unicode characters
perl -MDevel::Peek -e 'Dump(chr(0x100))'
-That shows the UTF8 flag in FLAGS and both the UTF-8 bytes
+That shows the C<UTF8> flag in FLAGS and both the UTF-8 bytes
and Unicode characters in C<PV>. See also later in this document
-the discussion about the C<is_utf8> function of the C<Encode> module.
+the discussion about the C<utf8::is_utf8()> function.
=back
Okay, if you insist:
- use Encode 'is_utf8';
- print is_utf8($string) ? 1 : 0, "\n";
+ print utf8::is_utf8($string) ? 1 : 0, "\n";
But note that this doesn't mean that any of the characters in the
string are necessary UTF-8 encoded, or that any of the characters have
as a single byte encoding. If the flag is on, the bytes in the scalar
are interpreted as the (multi-byte, variable-length) UTF-8 encoded code
points of the characters. Bytes added to an UTF-8 encoded string are
-automatically upgraded to UTF-8. If mixed non-UTF8 and UTF-8 scalars
+automatically upgraded to UTF-8. If mixed non-UTF-8 and UTF-8 scalars
are merged (double-quoted interpolation, explicit concatenation, and
printf/sprintf parameter substitution), the result will be UTF-8 encoded
as if copies of the byte strings were upgraded to UTF-8: for example,
$b = "\x{100}";
print "$a = $b\n";
-the output string will be UTF-8-encoded C<ab\x80c\x{100}\n>, but note
-that C<$a> will stay byte-encoded.
+the output string will be UTF-8-encoded C<ab\x80c = \x{100}\n>, but
+C<$a> will stay byte-encoded.
Sometimes you might really need to know the byte length of a string
instead of the character length. For that use either the
How Does Unicode Work With Traditional Locales?
In Perl, not very well. Avoid using locales through the C<locale>
-pragma. Use only one or the other.
+pragma. Use only one or the other. But see L<perlrun> for the
+description of the C<-C> switch and its environment counterpart,
+C<$ENV{PERL_UNICODE}> to see how to enable various Unicode features,
+for example by using locale settings.
=back
Perl front-end C<Convert::Recode> for character conversions.
The following are fast conversions from ISO 8859-1 (Latin-1) bytes
-to UTF-8 bytes, the code works even with older Perl 5 versions.
+to UTF-8 bytes and back, the code works even with older Perl 5 versions.
# ISO 8859-1 to UTF-8
s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg;
=head1 SEE ALSO
L<perlunicode>, L<Encode>, L<encoding>, L<open>, L<utf8>, L<bytes>,
-L<perlretut>, L<Unicode::Collate>, L<Unicode::Normalize>, L<Unicode::UCD>
+L<perlretut>, L<perlrun>, L<Unicode::Collate>, L<Unicode::Normalize>,
+L<Unicode::UCD>
=head1 ACKNOWLEDGMENTS
=head1 AUTHOR, COPYRIGHT, AND LICENSE
-Copyright 2001-2002 Jarkko Hietaniemi <jhi@iki.fi>
+Copyright 2001-2002 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt>
This document may be distributed under the same terms as Perl itself.
projects / p5sagit/p5-mst-13.2.git / blobdiff