1utf8(3pm) Perl Programmers Reference Guide utf8(3pm)
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6 utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source
7 code
8
10 use utf8;
11 no utf8;
12 # Convert the internal representation of a Perl scalar to/from UTF-8.
14 $num_octets = utf8::upgrade($string);
16 $success = utf8::downgrade($string[, $fail_ok]);
17 # Change each character of a Perl scalar to/from a series of
19 # characters that represent the UTF-8 bytes of each original character.
20 utf8::encode($string); # "\x{100}" becomes "\xc4\x80"
22 utf8::decode($string); # "\xc4\x80" becomes "\x{100}"
23 # Convert a code point from the platform native character set to
25 # Unicode, and vice-versa.
26 $unicode = utf8::native_to_unicode(ord('A')); # returns 65 on both
27 # ASCII and EBCDIC
28 # platforms
29 $native = utf8::unicode_to_native(65); # returns 65 on ASCII
30 # platforms; 193 on
31 # EBCDIC
32 $flag = utf8::is_utf8($string); # since Perl 5.8.1
34 $flag = utf8::valid($string);
35
37 The "use utf8" pragma tells the Perl parser to allow UTF-8 in the
38 program text in the current lexical scope. The "no utf8" pragma tells
39 Perl to switch back to treating the source text as literal bytes in the
40 current lexical scope. (On EBCDIC platforms, technically it is
41 allowing UTF-EBCDIC, and not UTF-8, but this distinction is academic,
42 so in this document the term UTF-8 is used to mean both).
43 Do not use this pragma for anything else than telling Perl that your
45 script is written in UTF-8. The utility functions described below are
46 directly usable without "use utf8;".
47 Because it is not possible to reliably tell UTF-8 from native 8 bit
49 encodings, you need either a Byte Order Mark at the beginning of your
50 source code, or "use utf8;", to instruct perl.
51 When UTF-8 becomes the standard source format, this pragma will
53 effectively become a no-op.
54 See also the effects of the "-C" switch and its cousin, the
56 "PERL_UNICODE" environment variable, in perlrun.
57 Enabling the "utf8" pragma has the following effect:
59 · Bytes in the source text that are not in the ASCII character set
61 will be treated as being part of a literal UTF-8 sequence. This
62 includes most literals such as identifier names, string constants,
63 and constant regular expression patterns.
64 Note that if you have non-ASCII, non-UTF-8 bytes in your script (for
66 example embedded Latin-1 in your string literals), "use utf8" will be
67 unhappy. If you want to have such bytes under "use utf8", you can
68 disable this pragma until the end the block (or file, if at top level)
69 by "no utf8;".
70 Utility functions
72 The following functions are defined in the "utf8::" package by the Perl
73 core. You do not need to say "use utf8" to use these and in fact you
74 should not say that unless you really want to have UTF-8 source code.
75 · "$num_octets = utf8::upgrade($string)"
77 (Since Perl v5.8.0) Converts in-place the internal representation
79 of the string from an octet sequence in the native encoding
80 (Latin-1 or EBCDIC) to UTF-8. The logical character sequence itself
81 is unchanged. If $string is already stored as UTF-8, then this is
82 a no-op. Returns the number of octets necessary to represent the
83 string as UTF-8. Can be used to make sure that the UTF-8 flag is
84 on, so that "\w" or "lc()" work as Unicode on strings containing
85 non-ASCII characters whose code points are below 256.
86 Note that this function does not handle arbitrary encodings; use
88 Encode instead.
89 · "$success = utf8::downgrade($string[, $fail_ok])"
91 (Since Perl v5.8.0) Converts in-place the internal representation
93 of the string from UTF-8 to the equivalent octet sequence in the
94 native encoding (Latin-1 or EBCDIC). The logical character sequence
95 itself is unchanged. If $string is already stored as native 8 bit,
96 then this is a no-op. Can be used to make sure that the UTF-8 flag
97 is off, e.g. when you want to make sure that the substr() or
98 length() function works with the usually faster byte algorithm.
99 Fails if the original UTF-8 sequence cannot be represented in the
101 native 8 bit encoding. On failure dies or, if the value of $fail_ok
102 is true, returns false.
103 Returns true on success.
105 Note that this function does not handle arbitrary encodings; use
107 Encode instead.
108 · "utf8::encode($string)"
110 (Since Perl v5.8.0) Converts in-place the character sequence to the
112 corresponding octet sequence in UTF-8. That is, every (possibly
113 wide) character gets replaced with a sequence of one or more
114 characters that represent the individual UTF-8 bytes of the
115 character. The UTF8 flag is turned off. Returns nothing.
116 my $a = "\x{100}"; # $a contains one character, with ord 0x100
118 utf8::encode($a); # $a contains two characters, with ords (on
119 # ASCII platforms) 0xc4 and 0x80. On EBCDIC
120 # 1047, this would instead be 0x8C and 0x41.
121 Note that this function does not handle arbitrary encodings; use
123 Encode instead.
124 · "$success = utf8::decode($string)"
126 (Since Perl v5.8.0) Attempts to convert in-place the octet sequence
128 encoded as UTF-8 to the corresponding character sequence. That is,
129 it replaces each sequence of characters in the string whose ords
130 represent a valid UTF-8 byte sequence, with the corresponding
131 single character. The UTF-8 flag is turned on only if the source
132 string contains multiple-byte UTF-8 characters. If $string is
133 invalid as UTF-8, returns false; otherwise returns true.
134 my $a = "\xc4\x80"; # $a contains two characters, with ords
136 # 0xc4 and 0x80
137 utf8::decode($a); # On ASCII platforms, $a contains one char,
138 # with ord 0x100. Since these bytes aren't
139 # legal UTF-EBCDIC, on EBCDIC platforms, $a is
140 # unchanged and the function returns FALSE.
141 Note that this function does not handle arbitrary encodings; use
143 Encode instead.
144 · "$unicode = utf8::native_to_unicode($code_point)"
146 (Since Perl v5.8.0) This takes an unsigned integer (which
148 represents the ordinal number of a character (or a code point) on
149 the platform the program is being run on) and returns its Unicode
150 equivalent value. Since ASCII platforms natively use the Unicode
151 code points, this function returns its input on them. On EBCDIC
152 platforms it converts from EBCDIC to Unicode.
153 A meaningless value will currently be returned if the input is not
155 an unsigned integer.
156 Since Perl v5.22.0, calls to this function are optimized out on
158 ASCII platforms, so there is no performance hit in using it there.
159 · "$native = utf8::unicode_to_native($code_point)"
161 (Since Perl v5.8.0) This is the inverse of
163 "utf8::native_to_unicode()", converting the other direction.
164 Again, on ASCII platforms, this returns its input, but on EBCDIC
165 platforms it will find the native platform code point, given any
166 Unicode one.
167 A meaningless value will currently be returned if the input is not
169 an unsigned integer.
170 Since Perl v5.22.0, calls to this function are optimized out on
172 ASCII platforms, so there is no performance hit in using it there.
173 · "$flag = utf8::is_utf8($string)"
175 (Since Perl 5.8.1) Test whether $string is marked internally as
177 encoded in UTF-8. Functionally the same as "Encode::is_utf8()".
178 · "$flag = utf8::valid($string)"
180 [INTERNAL] Test whether $string is in a consistent state regarding
182 UTF-8. Will return true if it is well-formed UTF-8 and has the
183 UTF-8 flag on or if $string is held as bytes (both these states are
184 'consistent'). Main reason for this routine is to allow Perl's
185 test suite to check that operations have left strings in a
186 consistent state. You most probably want to use "utf8::is_utf8()"
187 instead.
188 "utf8::encode" is like "utf8::upgrade", but the UTF8 flag is cleared.
190 See perlunicode, and the C API functions "sv_utf8_upgrade",
191 ""sv_utf8_downgrade" in perlapi", ""sv_utf8_encode" in perlapi", and
192 ""sv_utf8_decode" in perlapi", which are wrapped by the Perl functions
193 "utf8::upgrade", "utf8::downgrade", "utf8::encode" and "utf8::decode".
194 Also, the functions "utf8::is_utf8", "utf8::valid", "utf8::encode",
195 "utf8::decode", "utf8::upgrade", and "utf8::downgrade" are actually
196 internal, and thus always available, without a "require utf8"
197 statement.
198
200 Some filesystems may not support UTF-8 file names, or they may be
201 supported incompatibly with Perl. Therefore UTF-8 names that are
202 visible to the filesystem, such as module names may not work.
203
205 perlunitut, perluniintro, perlrun, bytes, perlunicode
206perl v5.26.3 2018-03-01 utf8(3pm)