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.
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 65536) characters from C<0x0000> to C<0xFFFF> would be
-needed. This soon proved to be false, and since Unicode 2.0 (July
+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 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
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 principal, and so the C<Script>
+"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
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
problems of the initial Unicode implementation, but for example
regular expressions still do not work with Unicode in 5.6.1.
Perl v5.14.0 is the first release where Unicode support is
-(almost) seamlessly integrable without some gotchas (the exception being
-some differences in L<quotemeta|perlfunc/quotemeta>, which is fixed
-starting in Perl 5.16.0). To enable this
+(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
=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);
+
+since 0x5d0 is above 255.
+
+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.
-You can invoke characters
-by name in double-quoted strings:
+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 $arabic_alef = "\N{ARABIC LETTER ALEF}";
+See L</"Further Resources"> for how to find all these names and numeric
+codes.
-And, as mentioned above, you can also C<pack()> numbers into Unicode
-characters:
+=head3 Earlier releases caveats
- my $georgian_an = pack("U", 0x10a0);
+On EBCDIC platforms, prior to v5.22, using C<\N{U+...}> doesn't work
+properly.
-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()>.
+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>>.
-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:
+Prior to v5.14, there were some bugs in C<\N{...}> with a character name
+(as opposed to a C<U+...> code point).
- my $chars = pack("U0W*", 0x80, 0x42);
+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:
-Likewise, you can stop such UTF-8 interpretation by using the special
-C<"C0"> prefix.
+ use charnames ();
+ my $hebrew_alef_from_name
+ = pack("U", charnames::vianame("HEBREW LETTER ALEF"));
=head2 Handling Unicode
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;
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
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.
+
+=item *
-The bit complement operator C<~> may produce surprising results if
+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 *
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 *
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?
-If your locale is a UTF-8 locale, starting in Perl v5.20, Perl works
-well for all categories except C<LC_COLLATE> dealing with sorting and
-the C<cmp> operator.
+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
=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