For some combinations of base character and modifiers, there are
I<precomposed> characters. There is a single character equivalent, for
-example, to the sequence C<LATIN CAPITAL LETTER A> followed by
+example, for the sequence C<LATIN CAPITAL LETTER A> followed by
C<COMBINING ACUTE ACCENT>. It is called C<LATIN CAPITAL LETTER A WITH
ACUTE>. These precomposed characters are, however, only available for
some combinations, and are mainly meant to support round-trip
number for every character" idea breaks down a bit: instead, there is
"at least one number for every character". The same character could
be represented differently in several legacy encodings. The
-converse is not also true: some code points do not have an assigned
+converse is not true: some code points do not have an assigned
character. Firstly, there are unallocated code points within
otherwise used blocks. Secondly, there are special Unicode control
characters that do not represent true characters.
-A common myth about Unicode is that it is "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 (July
+When Unicode was first conceived, it was thought that all the world's
+characters could be represented using a 16-bit word; that is a maximum of
+C<0x10000> (or 65,536) characters would be needed, from C<0x0000> to
+C<0xFFFF>. This soon proved to be wrong, and 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 about Unicode blocks--that they have something to
-do with languages--that each block would define the characters used
-by a language or a set of languages. B<This is also untrue.>
+and Unicode 3.1 (March 2001) defined the first characters above 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.
+
+When a new language is being encoded, Unicode generally will choose a
+C<block> of consecutive unallocated code points for its characters. So
+far, the number of code points in these blocks has always been evenly
+divisible by 16. Extras in a block, not currently needed, are left
+unallocated, for future growth. But there have been occasions when
+a later release needed more code points than the available extras, and a
+new block had to allocated somewhere else, not contiguous to the initial
+one, to handle the overflow. Thus, it became apparent early on that
+"block" wasn't an adequate organizing principle, and so the C<Script>
+property was created. (Later an improved script property was added as
+well, the C<Script_Extensions> property.) Those code points that are in
+overflow blocks can still
+have the same script as the original ones. The script concept fits more
+closely with natural language: there is C<Latin> script, C<Greek>
+script, and so on; and there are several artificial scripts, like
+C<Common> for characters that are used in multiple scripts, such as
+mathematical symbols. Scripts usually span varied parts of several
+blocks. For more information about scripts, see L<perlunicode/Scripts>.
The division into blocks exists, but it is almost completely
-accidental--an artifact of how the characters have been and
-still are allocated. Instead, there is a concept called I<scripts>, which is
-more useful: there is C<Latin> script, C<Greek> script, and so on. Scripts
-usually span varied parts of several blocks. For more information about
-scripts, see L<perlunicode/Scripts>.
+accidental--an artifact of how the characters have been and still are
+allocated. (Note that this paragraph has oversimplified things for the
+sake of this being an introduction. Unicode doesn't really encode
+languages, but the writing systems for them--their scripts; and one
+script can be used by many languages. Unicode also encodes things that
+aren't really about languages, such as symbols like C<BAGGAGE CLAIM>.)
The Unicode code points are just abstract numbers. To input and
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
+forms>, of which I<UTF-8> is the most popular. UTF-8 is a
+variable length encoding that encodes Unicode characters as 1 to 4
bytes. 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
+(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
=head2 Perl's Unicode Support
-Starting from Perl 5.6.0, Perl has had the capacity to handle Unicode
-natively. Perl 5.8.0, however, is the first recommended release for
+Starting from Perl v5.6.0, Perl has had the capacity to handle Unicode
+natively. Perl v5.8.0, however, is the first recommended release for
serious Unicode work. The maintenance release 5.6.1 fixed many of the
problems of the initial Unicode implementation, but for example
regular expressions still do not work with Unicode in 5.6.1.
-Perl 5.14.0 is the first release where Unicode support is
-(almost) seamlessly integrable without some gotchas (the exception being
-some differences in L<quotemeta|perlfunc/quotemeta>). To enable this
+Perl v5.14.0 is the first release where Unicode support is
+(almost) seamlessly integrable without some gotchas. (There are a few
+exceptions. Firstly, some differences in L<quotemeta|perlfunc/quotemeta>
+were fixed starting in Perl 5.16.0. Secondly, some differences in
+L<the range operator|perlop/Range Operators> were fixed starting in
+Perl 5.26.0. Thirdly, some differences in L<split|perlfunc/split> were fixed
+started in Perl 5.28.0.)
+
+To enable this
seamless support, you should C<use feature 'unicode_strings'> (which is
automatically selected if you C<use 5.012> or higher). See L<feature>.
(5.14 also fixes a number of bugs and departures from the Unicode
standard.)
-Before Perl 5.8.0, the use of C<use utf8> was used to declare
+Before Perl v5.8.0, the use of C<use utf8> was used to declare
that operations in the current block or file would be Unicode-aware.
This model was found to be wrong, or at least clumsy: the "Unicodeness"
is now carried with the data, instead of being attached to the
operations.
-Starting with Perl 5.8.0, only one case remains where an explicit C<use
+Starting with Perl v5.8.0, only one case remains where an explicit C<use
utf8> is 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
strings of Unicode characters. The general principle is that Perl tries
to keep its data as eight-bit bytes for as long as possible, but as soon
as Unicodeness cannot be avoided, the data is transparently upgraded
-to Unicode. Prior to Perl 5.14, the upgrade was not completely
+to Unicode. Prior to Perl v5.14.0, the upgrade was not completely
transparent (see L<perlunicode/The "Unicode Bug">), and for backwards
compatibility, full transparency is not gained unless C<use feature
'unicode_strings'> (see L<feature>) or C<use 5.012> (or higher) is
=head2 Unicode and EBCDIC
-Perl 5.8.0 also supports Unicode on EBCDIC platforms. There,
-Unicode support is somewhat more complex to implement since
-additional conversions are needed at every step.
-
-Later Perl releases have added code that will not work on EBCDIC platforms, and
-no one has complained, so the divergence has continued. If you want to run
-Perl on an EBCDIC platform, send email to perlbug@perl.org
+Perl 5.8.0 added support for Unicode on EBCDIC platforms. This support
+was allowed to lapse in later releases, but was revived in 5.22.
+Unicode support is somewhat more complex to implement since additional
+conversions are needed. See L<perlebcdic> for more information.
On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC
instead of UTF-8. The difference is that as UTF-8 is "ASCII-safe" in
that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is
-"EBCDIC-safe".
+"EBCDIC-safe", in that all the basic characters (which includes all
+those that have ASCII equivalents (like C<"A">, C<"0">, C<"%">, I<etc.>)
+are the same in both EBCDIC and UTF-EBCDIC. Often, documentation
+will use the term "UTF-8" to mean UTF-EBCDIC as well. This is the case
+in this document.
=head2 Creating Unicode
-To create Unicode characters in literals for code points above C<0xFF>,
-use the C<\x{...}> notation in double-quoted strings:
+This section applies fully to Perls starting with v5.22. Various
+caveats for earlier releases are in the L</Earlier releases caveats>
+subsection below.
- my $smiley = "\x{263a}";
+To create Unicode characters in literals,
+use the C<\N{...}> notation in double-quoted strings:
-Similarly, it can be used in regular expression literals
+ my $smiley_from_name = "\N{WHITE SMILING FACE}";
+ my $smiley_from_code_point = "\N{U+263a}";
- $smiley =~ /\x{263a}/;
+Similarly, they can be used in regular expression literals
-At run-time you can use C<chr()>:
+ $smiley =~ /\N{WHITE SMILING FACE}/;
+ $smiley =~ /\N{U+263a}/;
- my $hebrew_alef = chr(0x05d0);
+At run-time you can use:
-See L</"Further Resources"> for how to find all these numeric codes.
+ use charnames ();
+ my $hebrew_alef_from_name
+ = charnames::string_vianame("HEBREW LETTER ALEF");
+ my $hebrew_alef_from_code_point = charnames::string_vianame("U+05D0");
Naturally, C<ord()> will do the reverse: it turns a character into
a code point.
-Note that C<\x..> (no C<{}> and only two hexadecimal digits), C<\x{...}>,
-and C<chr(...)> for arguments less than C<0x100> (decimal 256)
-generate an eight-bit character for backward compatibility with older
-Perls. For arguments of C<0x100> or more, Unicode characters are
-always produced. If you want to force the production of Unicode
-characters regardless of the numeric value, use C<pack("U", ...)>
-instead of C<\x..>, C<\x{...}>, or C<chr()>.
+There are other runtime options as well. You can use C<pack()>:
+
+ my $hebrew_alef_from_code_point = pack("U", 0x05d0);
+
+Or you can use C<chr()>, though it is less convenient in the general
+case:
+
+ $hebrew_alef_from_code_point = chr(utf8::unicode_to_native(0x05d0));
+ utf8::upgrade($hebrew_alef_from_code_point);
+
+The C<utf8::unicode_to_native()> and C<utf8::upgrade()> aren't needed if
+the argument is above 0xFF, so the above could have been written as
+
+ $hebrew_alef_from_code_point = chr(0x05d0);
-You can also use the C<charnames> pragma to invoke characters
-by name in double-quoted strings:
+since 0x5d0 is above 255.
- use charnames ':full';
- my $arabic_alef = "\N{ARABIC LETTER ALEF}";
+C<\x{}> and C<\o{}> can also be used to specify code points at compile
+time in double-quotish strings, but, for backward compatibility with
+older Perls, the same rules apply as with C<chr()> for code points less
+than 256.
-And, as mentioned above, you can also C<pack()> numbers into Unicode
-characters:
+C<utf8::unicode_to_native()> is used so that the Perl code is portable
+to EBCDIC platforms. You can omit it if you're I<really> sure no one
+will ever want to use your code on a non-ASCII platform. Starting in
+Perl v5.22, calls to it on ASCII platforms are optimized out, so there's
+no performance penalty at all in adding it. Or you can simply use the
+other constructs that don't require it.
- my $georgian_an = pack("U", 0x10a0);
+See L</"Further Resources"> for how to find all these names and numeric
+codes.
-Note that both C<\x{...}> and C<\N{...}> are compile-time string
-constants: you cannot use variables in them. if you want similar
-run-time functionality, use C<chr()> and C<charnames::string_vianame()>.
+=head3 Earlier releases caveats
-If you want to force the result to Unicode characters, use the special
-C<"U0"> prefix. It consumes no arguments but causes the following bytes
-to be interpreted as the UTF-8 encoding of Unicode characters:
+On EBCDIC platforms, prior to v5.22, using C<\N{U+...}> doesn't work
+properly.
- my $chars = pack("U0W*", 0x80, 0x42);
+Prior to v5.16, using C<\N{...}> with a character name (as opposed to a
+C<U+...> code point) required a S<C<use charnames :full>>.
-Likewise, you can stop such UTF-8 interpretation by using the special
-C<"C0"> prefix.
+Prior to v5.14, there were some bugs in C<\N{...}> with a character name
+(as opposed to a C<U+...> code point).
+
+C<charnames::string_vianame()> was introduced in v5.14. Prior to that,
+C<charnames::vianame()> should work, but only if the argument is of the
+form C<"U+...">. Your best bet there for runtime Unicode by character
+name is probably:
+
+ use charnames ();
+ my $hebrew_alef_from_name
+ = pack("U", charnames::vianame("HEBREW LETTER ALEF"));
=head2 Handling Unicode
Note that Perl considers grapheme clusters to be separate characters, so for
example
- use charnames ':full';
- print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n";
+ print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"),
+ "\n";
will print 2, not 1. The only exception is that regular expressions
have C<\X> for matching an extended grapheme cluster. (Thus C<\X> in a
for doing conversions between those encodings:
use Encode 'decode';
- $data = decode("iso-8859-3", $data); # convert from legacy to utf-8
+ $data = decode("iso-8859-3", $data); # convert from legacy
=head2 Unicode I/O
must always be specified exactly like that; it is I<not> subject to
the loose matching of encoding names. Also note that currently C<:utf8> is unsafe for
input, because it accepts the data without validating that it is indeed valid
-UTF-8; you should instead use C<:encoding(utf-8)> (with or without a
+UTF-8; you should instead use C<:encoding(UTF-8)> (with or without a
hyphen).
See L<PerlIO> for the C<:utf8> layer, L<PerlIO::encoding> and
Unicode in Perl's eyes. To do that, specify the appropriate
layer when opening files
- open(my $fh,'<:encoding(utf8)', 'anything');
+ open(my $fh,'<:encoding(UTF-8)', 'anything');
my $line_of_unicode = <$fh>;
open(my $fh,'<:encoding(Big5)', 'anything');
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 ':encoding(utf8)'; # input/output default encoding will be
- # UTF-8
+ use open ':encoding(UTF-8)'; # input/output default encoding will be
+ # UTF-8
open X, ">file";
print X chr(0x100), "\n";
close X;
You can switch encodings on an already opened stream by using
C<binmode()>; see L<perlfunc/binmode>.
-The C<:locale> does not currently (as of Perl 5.8.0) work with
+The C<:locale> does not currently work with
C<open()> and C<binmode()>, only with the C<open> pragma. The
C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>,
C<binmode()>, and the C<open> pragma.
list see L<Encode::Supported>.
C<read()> reads characters and returns the number of characters.
-C<seek()> and C<tell()> operate on byte counts, as do C<sysread()>
-and C<sysseek()>.
+C<seek()> and C<tell()> operate on byte counts, as does C<sysseek()>.
+
+C<sysread()> and C<syswrite()> should not be used on file handles with
+character encoding layers, they behave badly, and that behaviour has
+been deprecated since perl 5.24.
Notice that because of the default behaviour of not doing any
conversion upon input if there is no default layer,
local $/; ## read in the whole file of 8-bit characters
$t = <F>;
close F;
- open F, ">:encoding(utf8)", "file";
+ open F, ">:encoding(UTF-8)", "file";
print F $t; ## convert to UTF-8 on output
close F;
If you run this code twice, the contents of the F<file> will be twice
-UTF-8 encoded. A C<use open ':encoding(utf8)'> would have avoided the
+UTF-8 encoded. A C<use open ':encoding(UTF-8)'> would have avoided the
bug, or 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 (which is the default
-on most systems).
+Perl has been built with L<PerlIO>, which is the default
+on most systems.
=head2 Displaying Unicode As Text
displayed as C<\x..>, and the rest of the characters as themselves:
sub nice_string {
- join("",
- map { $_ > 255 ? # if wide character...
- sprintf("\\x{%04X}", $_) : # \x{...}
- chr($_) =~ /[[:cntrl:]]/ ? # else if control character ...
- sprintf("\\x%02X", $_) : # \x..
- quotemeta(chr($_)) # else quoted or as themselves
- } unpack("W*", $_[0])); # unpack Unicode characters
+ join("",
+ map { $_ > 255 # if wide character...
+ ? sprintf("\\x{%04X}", $_) # \x{...}
+ : chr($_) =~ /[[:cntrl:]]/ # else if control character...
+ ? sprintf("\\x%02X", $_) # \x..
+ : quotemeta(chr($_)) # else quoted or as themselves
+ } unpack("W*", $_[0])); # unpack Unicode characters
}
For example,
which is ready to be printed.
+(C<\\x{}> is used here instead of C<\\N{}>, since it's most likely that
+you want to see what the native values are.)
+
=head2 Special Cases
=over 4
=item *
-Bit Complement Operator ~ And vec()
+Starting in Perl 5.28, it is illegal for bit operators, like C<~>, to
+operate on strings containing code points above 255.
-The bit complement operator C<~> may produce surprising results if
+=item *
+
+The vec() function may produce surprising results if
used on strings containing characters with ordinal values above
255. In such a case, the results are consistent with the internal
encoding of the characters, but not with much else. So don't do
-that. Similarly for C<vec()>: you will be operating on the
-internally-encoded bit patterns of the Unicode characters, not on
-the code point values, which is very probably not what you want.
+that, and starting in Perl 5.28, a deprecation message is issued if you
+do so, becoming illegal in Perl 5.32.
=item *
sections on case mapping in the L<Unicode Standard|http://www.unicode.org>.
As of Perl 5.8.0, the "Full" case-folding of I<Case
-Mappings/SpecialCasing> is implemented, but bugs remain in C<qr//i> with them.
+Mappings/SpecialCasing> is implemented, but bugs remain in C<qr//i> with them,
+mostly fixed by 5.14, and essentially entirely by 5.18.
=item *
character classes that are Unicode-aware. There are dozens of them, see
L<perluniprops>.
-You can use Unicode code points as the end points of character ranges, and the
-range will include all Unicode code points that lie between those end points.
+Starting in v5.22, you can use Unicode code points as the end points of
+regular expression pattern character ranges, and the range will include
+all Unicode code points that lie between those end points, inclusive.
+
+ qr/ [ \N{U+03} - \N{U+20} ] /xx
+
+includes the code points
+C<\N{U+03}>, C<\N{U+04}>, ..., C<\N{U+20}>.
+
+This also works for ranges in C<tr///> starting in Perl v5.24.
=item *
Unicode does define several other decimal--and numeric--characters
besides the familiar 0 to 9, such as the Arabic and Indic digits.
Perl does not support string-to-number conversion for digits other
-than ASCII 0 to 9 (and ASCII a to f for hexadecimal).
+than ASCII C<0> to C<9> (and ASCII C<a> to C<f> for hexadecimal).
To get safe conversions from any Unicode string, use
L<Unicode::UCD/num()>.
You shouldn't have to care. But you may if your Perl is before 5.14.0
or you haven't specified C<use feature 'unicode_strings'> or C<use
-5.012> (or higher) because otherwise the semantics of the code points
+5.012> (or higher) because otherwise the rules for the code points
in the range 128 to 255 are different depending on
whether the string they are contained within is in Unicode or not.
(See L<perlunicode/When Unicode Does Not Happen>.)
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
-C<Encode::encode_utf8()> function or the C<bytes> pragma
+instead of the character length. For that use the C<bytes> pragma
and the C<length()> function:
my $unicode = chr(0x100);
print length($unicode), "\n"; # will print 1
- require Encode;
- print length(Encode::encode_utf8($unicode)), "\n"; # will print 2
use bytes;
- print length($unicode), "\n"; # will also print 2
+ print length($unicode), "\n"; # will print 2
# (the 0xC4 0x80 of the UTF-8)
no bytes;
Use the C<Encode> package to try converting it.
For example,
- use Encode 'decode_utf8';
+ use Encode 'decode';
- if (eval { decode_utf8($string, Encode::FB_CROAK); 1 }) {
- # $string is valid utf8
+ if (eval { decode('UTF-8', $string, Encode::FB_CROAK); 1 }) {
+ # $string is valid UTF-8
} else {
- # $string is not valid utf8
+ # $string is not valid UTF-8
}
Or use C<unpack> to try decoding it:
interpreted via a particular encoding, you can use C<Encode>:
use Encode 'from_to';
- from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8
+ from_to($data, "iso-8859-1", "UTF-8"); # from latin-1 to UTF-8
The call to C<from_to()> changes the bytes in C<$data>, but nothing
material about the nature of the string has changed as far as Perl is
If you have a sequence of bytes you B<know> is valid UTF-8,
but Perl doesn't know it yet, you can make Perl a believer, too:
- use Encode 'decode_utf8';
- $Unicode = decode_utf8($bytes);
+ $Unicode = $bytes;
+ utf8::decode($Unicode);
or:
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. 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.
+If your locale is a UTF-8 locale, starting in Perl v5.26, Perl works
+well for all categories; before this, starting with Perl v5.20, it works
+for all categories but C<LC_COLLATE>, which deals with
+sorting and the C<cmp> operator. But note that the standard
+C<L<Unicode::Collate>> and C<L<Unicode::Collate::Locale>> modules offer
+much more powerful solutions to collation issues, and work on earlier
+releases.
+
+For other locales, starting in Perl 5.16, you can specify
+
+ use locale ':not_characters';
+
+to get Perl to work well with them. The catch is that you
+have to translate from the locale character set to/from Unicode
+yourself. See L</Unicode IE<sol>O> above for how to
+
+ use open ':locale';
+
+to accomplish this, but full details are in L<perllocale/Unicode and
+UTF-8>, including gotchas that happen if you don't specify
+C<:not_characters>.
=back
=head1 AUTHOR, COPYRIGHT, AND LICENSE
-Copyright 2001-2011 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt>
+Copyright 2001-2011 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt>.
+Now maintained by Perl 5 Porters.
This document may be distributed under the same terms as Perl itself.
https://perl5.git.perl.org / perl5.git / blobdiff