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129 | .\" ======================================================================== | |
130 | .\" | |
131 | .IX Title "utf8 3" | |
132 | .TH utf8 3 "2001-09-21" "perl v5.8.8" "Perl Programmers Reference Guide" | |
133 | .SH "NAME" | |
134 | utf8 \- Perl pragma to enable/disable UTF\-8 (or UTF\-EBCDIC) in source code | |
135 | .SH "SYNOPSIS" | |
136 | .IX Header "SYNOPSIS" | |
137 | .Vb 2 | |
138 | \& use utf8; | |
139 | \& no utf8; | |
140 | .Ve | |
141 | .PP | |
142 | .Vb 3 | |
143 | \& # Convert a Perl scalar to/from UTF-8. | |
144 | \& $num_octets = utf8::upgrade($string); | |
145 | \& $success = utf8::downgrade($string[, FAIL_OK]); | |
146 | .Ve | |
147 | .PP | |
148 | .Vb 3 | |
149 | \& # Change the native bytes of a Perl scalar to/from UTF-8 bytes. | |
150 | \& utf8::encode($string); | |
151 | \& utf8::decode($string); | |
152 | .Ve | |
153 | .PP | |
154 | .Vb 2 | |
155 | \& $flag = utf8::is_utf8(STRING); # since Perl 5.8.1 | |
156 | \& $flag = utf8::valid(STRING); | |
157 | .Ve | |
158 | .SH "DESCRIPTION" | |
159 | .IX Header "DESCRIPTION" | |
160 | The \f(CW\*(C`use utf8\*(C'\fR pragma tells the Perl parser to allow \s-1UTF\-8\s0 in the | |
161 | program text in the current lexical scope (allow UTF-EBCDIC on \s-1EBCDIC\s0 based | |
162 | platforms). The \f(CW\*(C`no utf8\*(C'\fR pragma tells Perl to switch back to treating | |
163 | the source text as literal bytes in the current lexical scope. | |
164 | .PP | |
165 | This pragma is primarily a compatibility device. Perl versions | |
166 | earlier than 5.6 allowed arbitrary bytes in source code, whereas | |
167 | in future we would like to standardize on the \s-1UTF\-8\s0 encoding for | |
168 | source text. | |
169 | .PP | |
170 | \&\fBDo not use this pragma for anything else than telling Perl that your | |
171 | script is written in \s-1UTF\-8\s0.\fR The utility functions described below are | |
172 | useful for their own purposes, but they are not really part of the | |
173 | \&\*(L"pragmatic\*(R" effect. | |
174 | .PP | |
175 | Until \s-1UTF\-8\s0 becomes the default format for source text, either this | |
176 | pragma or the encoding pragma should be used to recognize \s-1UTF\-8\s0 | |
177 | in the source. When \s-1UTF\-8\s0 becomes the standard source format, this | |
178 | pragma will effectively become a no\-op. For convenience in what | |
179 | follows the term \fIUTF-X\fR is used to refer to \s-1UTF\-8\s0 on \s-1ASCII\s0 and \s-1ISO\s0 | |
180 | Latin based platforms and UTF-EBCDIC on \s-1EBCDIC\s0 based platforms. | |
181 | .PP | |
182 | See also the effects of the \f(CW\*(C`\-C\*(C'\fR switch and its cousin, the | |
183 | \&\f(CW$ENV{PERL_UNICODE}\fR, in perlrun. | |
184 | .PP | |
185 | Enabling the \f(CW\*(C`utf8\*(C'\fR pragma has the following effect: | |
186 | .IP "\(bu" 4 | |
187 | Bytes in the source text that have their high-bit set will be treated | |
188 | as being part of a literal \s-1UTF\-8\s0 character. This includes most | |
189 | literals such as identifier names, string constants, and constant | |
190 | regular expression patterns. | |
191 | .Sp | |
192 | On \s-1EBCDIC\s0 platforms characters in the Latin 1 character set are | |
193 | treated as being part of a literal UTF-EBCDIC character. | |
194 | .PP | |
195 | Note that if you have bytes with the eighth bit on in your script | |
196 | (for example embedded Latin\-1 in your string literals), \f(CW\*(C`use utf8\*(C'\fR | |
197 | will be unhappy since the bytes are most probably not well-formed | |
198 | \&\s-1UTF\-8\s0. If you want to have such bytes and use utf8, you can disable | |
199 | utf8 until the end the block (or file, if at top level) by \f(CW\*(C`no utf8;\*(C'\fR. | |
200 | .PP | |
201 | If you want to automatically upgrade your 8\-bit legacy bytes to \s-1UTF\-8\s0, | |
202 | use the encoding pragma instead of this pragma. For example, if | |
203 | you want to implicitly upgrade your \s-1ISO\s0 8859\-1 (Latin\-1) bytes to \s-1UTF\-8\s0 | |
204 | as used in e.g. \f(CW\*(C`chr()\*(C'\fR and \f(CW\*(C`\ex{...}\*(C'\fR, try this: | |
205 | .PP | |
206 | .Vb 3 | |
207 | \& use encoding "latin-1"; | |
208 | \& my $c = chr(0xc4); | |
209 | \& my $x = "\ex{c5}"; | |
210 | .Ve | |
211 | .PP | |
212 | In case you are wondering: yes, \f(CW\*(C`use encoding 'utf8';\*(C'\fR works much | |
213 | the same as \f(CW\*(C`use utf8;\*(C'\fR. | |
214 | .Sh "Utility functions" | |
215 | .IX Subsection "Utility functions" | |
216 | The following functions are defined in the \f(CW\*(C`utf8::\*(C'\fR package by the | |
217 | Perl core. You do not need to say \f(CW\*(C`use utf8\*(C'\fR to use these and in fact | |
218 | you should not say that unless you really want to have \s-1UTF\-8\s0 source code. | |
219 | .ie n .IP "* $num_octets = utf8::upgrade($string)" 4 | |
220 | .el .IP "* \f(CW$num_octets\fR = utf8::upgrade($string)" 4 | |
221 | .IX Item "$num_octets = utf8::upgrade($string)" | |
222 | Converts in-place the octet sequence in the native encoding | |
223 | (Latin\-1 or \s-1EBCDIC\s0) to the equivalent character sequence in \fIUTF-X\fR. | |
224 | \&\fI$string\fR already encoded as characters does no harm. | |
225 | Returns the number of octets necessary to represent the string as \fIUTF-X\fR. | |
226 | Can be used to make sure that the \s-1UTF\-8\s0 flag is on, | |
227 | so that \f(CW\*(C`\ew\*(C'\fR or \f(CW\*(C`lc()\*(C'\fR work as Unicode on strings | |
228 | containing characters in the range 0x80\-0xFF (on \s-1ASCII\s0 and | |
229 | derivatives). | |
230 | .Sp | |
231 | \&\fBNote that this function does not handle arbitrary encodings.\fR | |
232 | Therefore \fIEncode.pm\fR is recommended for the general purposes. | |
233 | .Sp | |
234 | Affected by the encoding pragma. | |
235 | .ie n .IP "* $success = utf8::downgrade($string[, \s-1FAIL_OK\s0])" 4 | |
236 | .el .IP "* \f(CW$success\fR = utf8::downgrade($string[, \s-1FAIL_OK\s0])" 4 | |
237 | .IX Item "$success = utf8::downgrade($string[, FAIL_OK])" | |
238 | Converts in-place the character sequence in \fIUTF-X\fR | |
239 | to the equivalent octet sequence in the native encoding (Latin\-1 or \s-1EBCDIC\s0). | |
240 | \&\fI$string\fR already encoded as octets does no harm. | |
241 | Returns true on success. On failure dies or, if the value of | |
242 | \&\f(CW\*(C`FAIL_OK\*(C'\fR is true, returns false. | |
243 | Can be used to make sure that the \s-1UTF\-8\s0 flag is off, | |
244 | e.g. when you want to make sure that the \fIsubstr()\fR or \fIlength()\fR function | |
245 | works with the usually faster byte algorithm. | |
246 | .Sp | |
247 | \&\fBNote that this function does not handle arbitrary encodings.\fR | |
248 | Therefore \fIEncode.pm\fR is recommended for the general purposes. | |
249 | .Sp | |
250 | \&\fBNot\fR affected by the encoding pragma. | |
251 | .Sp | |
252 | \&\fB\s-1NOTE:\s0\fR this function is experimental and may change | |
253 | or be removed without notice. | |
254 | .IP "* utf8::encode($string)" 4 | |
255 | .IX Item "utf8::encode($string)" | |
256 | Converts in-place the character sequence to the corresponding octet sequence | |
257 | in \fIUTF-X\fR. The \s-1UTF\-8\s0 flag is turned off. Returns nothing. | |
258 | .Sp | |
259 | \&\fBNote that this function does not handle arbitrary encodings.\fR | |
260 | Therefore \fIEncode.pm\fR is recommended for the general purposes. | |
261 | .IP "* utf8::decode($string)" 4 | |
262 | .IX Item "utf8::decode($string)" | |
263 | Attempts to convert in-place the octet sequence in \fIUTF-X\fR | |
264 | to the corresponding character sequence. The \s-1UTF\-8\s0 flag is turned on | |
265 | only if the source string contains multiple-byte \fIUTF-X\fR characters. | |
266 | If \fI$string\fR is invalid as \fIUTF-X\fR, returns false; otherwise returns true. | |
267 | .Sp | |
268 | \&\fBNote that this function does not handle arbitrary encodings.\fR | |
269 | Therefore \fIEncode.pm\fR is recommended for the general purposes. | |
270 | .Sp | |
271 | \&\fB\s-1NOTE:\s0\fR this function is experimental and may change | |
272 | or be removed without notice. | |
273 | .ie n .IP "* $flag = utf8::is_utf8(\s-1STRING\s0)" 4 | |
274 | .el .IP "* \f(CW$flag\fR = utf8::is_utf8(\s-1STRING\s0)" 4 | |
275 | .IX Item "$flag = utf8::is_utf8(STRING)" | |
276 | (Since Perl 5.8.1) Test whether \s-1STRING\s0 is in \s-1UTF\-8\s0. Functionally | |
277 | the same as \fIEncode::is_utf8()\fR. | |
278 | .ie n .IP "* $flag = utf8::valid(\s-1STRING\s0)" 4 | |
279 | .el .IP "* \f(CW$flag\fR = utf8::valid(\s-1STRING\s0)" 4 | |
280 | .IX Item "$flag = utf8::valid(STRING)" | |
281 | [\s-1INTERNAL\s0] Test whether \s-1STRING\s0 is in a consistent state regarding | |
282 | \&\s-1UTF\-8\s0. Will return true is well-formed \s-1UTF\-8\s0 and has the \s-1UTF\-8\s0 flag | |
283 | on \fBor\fR if string is held as bytes (both these states are 'consistent'). | |
284 | Main reason for this routine is to allow Perl's testsuite to check | |
285 | that operations have left strings in a consistent state. You most | |
286 | probably want to use \fIutf8::is_utf8()\fR instead. | |
287 | .PP | |
288 | \&\f(CW\*(C`utf8::encode\*(C'\fR is like \f(CW\*(C`utf8::upgrade\*(C'\fR, but the \s-1UTF8\s0 flag is | |
289 | cleared. See perlunicode for more on the \s-1UTF8\s0 flag and the C \s-1API\s0 | |
290 | functions \f(CW\*(C`sv_utf8_upgrade\*(C'\fR, \f(CW\*(C`sv_utf8_downgrade\*(C'\fR, \f(CW\*(C`sv_utf8_encode\*(C'\fR, | |
291 | and \f(CW\*(C`sv_utf8_decode\*(C'\fR, which are wrapped by the Perl functions | |
292 | \&\f(CW\*(C`utf8::upgrade\*(C'\fR, \f(CW\*(C`utf8::downgrade\*(C'\fR, \f(CW\*(C`utf8::encode\*(C'\fR and | |
293 | \&\f(CW\*(C`utf8::decode\*(C'\fR. Note that in the Perl 5.8.0 and 5.8.1 implementation | |
294 | the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode, | |
295 | utf8::upgrade, and utf8::downgrade are always available, without a | |
296 | \&\f(CW\*(C`require utf8\*(C'\fR statement\*(-- this may change in future releases. | |
297 | .SH "BUGS" | |
298 | .IX Header "BUGS" | |
299 | One can have Unicode in identifier names, but not in package/class or | |
300 | subroutine names. While some limited functionality towards this does | |
301 | exist as of Perl 5.8.0, that is more accidental than designed; use of | |
302 | Unicode for the said purposes is unsupported. | |
303 | .PP | |
304 | One reason of this unfinishedness is its (currently) inherent | |
305 | unportability: since both package names and subroutine names may need | |
306 | to be mapped to file and directory names, the Unicode capability of | |
307 | the filesystem becomes important\*(-- and there unfortunately aren't | |
308 | portable answers. | |
309 | .SH "SEE ALSO" | |
310 | .IX Header "SEE ALSO" | |
311 | perluniintro, encoding, perlrun, bytes, perlunicode |