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66cbab2c KW |
1 | =encoding utf8 |
2 | ||
5f05dabc | 3 | =head1 NAME |
4 | ||
b0c42ed9 | 5 | perllocale - Perl locale handling (internationalization and localization) |
5f05dabc | 6 | |
7 | =head1 DESCRIPTION | |
8 | ||
66cbab2c KW |
9 | In the beginning there was ASCII, the "American Standard Code for |
10 | Information Interchange", which works quite well for Americans with | |
11 | their English alphabet and dollar-denominated currency. But it doesn't | |
12 | work so well even for other English speakers, who may use different | |
13 | currencies, such as the pound sterling (as the symbol for that currency | |
14 | is not in ASCII); and it's hopelessly inadequate for many of the | |
15 | thousands of the world's other languages. | |
16 | ||
17 | To address these deficiencies, the concept of locales was invented | |
18 | (formally the ISO C, XPG4, POSIX 1.c "locale system"). And applications | |
19 | were and are being written that use the locale mechanism. The process of | |
20 | making such an application take account of its users' preferences in | |
21 | these kinds of matters is called B<internationalization> (often | |
22 | abbreviated as B<i18n>); telling such an application about a particular | |
23 | set of preferences is known as B<localization> (B<l10n>). | |
24 | ||
39332f68 | 25 | Perl has been extended to support the locale system. This |
66cbab2c KW |
26 | is controlled per application by using one pragma, one function call, |
27 | and several environment variables. | |
28 | ||
29 | Unfortunately, there are quite a few deficiencies with the design (and | |
31f05a37 KW |
30 | often, the implementations) of locales. Unicode was invented (see |
31 | L<perlunitut> for an introduction to that) in part to address these | |
32 | design deficiencies, and nowadays, there is a series of "UTF-8 | |
33 | locales", based on Unicode. These are locales whose character set is | |
34 | Unicode, encoded in UTF-8. Starting in v5.20, Perl fully supports | |
35 | UTF-8 locales, except for sorting and string comparisions. (Use | |
36 | L<Unicode::Collate> for these.) Perl continues to support the old | |
37 | non UTF-8 locales as well. | |
38 | ||
66cbab2c KW |
39 | (Unicode is also creating C<CLDR>, the "Common Locale Data Repository", |
40 | L<http://cldr.unicode.org/> which includes more types of information than | |
41 | are available in the POSIX locale system. At the time of this writing, | |
42 | there was no CPAN module that provides access to this XML-encoded data. | |
43 | However, many of its locales have the POSIX-only data extracted, and are | |
31f05a37 KW |
44 | available as UTF-8 locales at |
45 | L<http://unicode.org/Public/cldr/latest/>.) | |
66cbab2c KW |
46 | |
47 | =head1 WHAT IS A LOCALE | |
48 | ||
49 | A locale is a set of data that describes various aspects of how various | |
50 | communities in the world categorize their world. These categories are | |
51 | broken down into the following types (some of which include a brief | |
52 | note here): | |
53 | ||
54 | =over | |
55 | ||
cb88b78e | 56 | =item Category C<LC_NUMERIC>: Numeric formatting |
66cbab2c KW |
57 | |
58 | This indicates how numbers should be formatted for human readability, | |
59 | for example the character used as the decimal point. | |
60 | ||
cb88b78e | 61 | =item Category C<LC_MONETARY>: Formatting of monetary amounts |
66cbab2c KW |
62 | |
63 | =for comment | |
ebc3223b | 64 | The nbsp below makes this look better (though not great) |
66cbab2c KW |
65 | |
66 | E<160> | |
67 | ||
cb88b78e | 68 | =item Category C<LC_TIME>: Date/Time formatting |
66cbab2c KW |
69 | |
70 | =for comment | |
ebc3223b | 71 | The nbsp below makes this look better (though not great) |
66cbab2c KW |
72 | |
73 | E<160> | |
74 | ||
cb88b78e | 75 | =item Category C<LC_MESSAGES>: Error and other messages |
66cbab2c | 76 | |
2619d284 | 77 | This is used by Perl itself only for accessing operating system error |
03c702c5 | 78 | messages via L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>. |
66cbab2c | 79 | |
cb88b78e | 80 | =item Category C<LC_COLLATE>: Collation |
66cbab2c | 81 | |
76073c88 | 82 | This indicates the ordering of letters for comparison and sorting. |
66cbab2c KW |
83 | In Latin alphabets, for example, "b", generally follows "a". |
84 | ||
cb88b78e | 85 | =item Category C<LC_CTYPE>: Character Types |
66cbab2c KW |
86 | |
87 | This indicates, for example if a character is an uppercase letter. | |
88 | ||
2619d284 KW |
89 | =item Other categories |
90 | ||
91 | Some platforms have other categories, dealing with such things as | |
92 | measurement units and paper sizes. None of these are used directly by | |
93 | Perl, but outside operations that Perl interacts with may use | |
d6ded950 | 94 | these. See L</Not within the scope of "use locale"> below. |
2619d284 | 95 | |
66cbab2c KW |
96 | =back |
97 | ||
2619d284 KW |
98 | More details on the categories used by Perl are given below in L</LOCALE |
99 | CATEGORIES>. | |
66cbab2c KW |
100 | |
101 | Together, these categories go a long way towards being able to customize | |
102 | a single program to run in many different locations. But there are | |
103 | deficiencies, so keep reading. | |
5f05dabc | 104 | |
105 | =head1 PREPARING TO USE LOCALES | |
106 | ||
2619d284 KW |
107 | Perl itself will not use locales unless specifically requested to (but |
108 | again note that Perl may interact with code that does use them). Even | |
109 | if there is such a request, B<all> of the following must be true | |
b960a36e | 110 | for it to work properly: |
5f05dabc | 111 | |
112 | =over 4 | |
113 | ||
114 | =item * | |
115 | ||
116 | B<Your operating system must support the locale system>. If it does, | |
39332f68 | 117 | you should find that the C<setlocale()> function is a documented part of |
5f05dabc | 118 | its C library. |
119 | ||
120 | =item * | |
121 | ||
5a964f20 | 122 | B<Definitions for locales that you use must be installed>. You, or |
14280422 DD |
123 | your system administrator, must make sure that this is the case. The |
124 | available locales, the location in which they are kept, and the manner | |
5a964f20 TC |
125 | in which they are installed all vary from system to system. Some systems |
126 | provide only a few, hard-wired locales and do not allow more to be | |
127 | added. Others allow you to add "canned" locales provided by the system | |
128 | supplier. Still others allow you or the system administrator to define | |
14280422 | 129 | and add arbitrary locales. (You may have to ask your supplier to |
5a964f20 | 130 | provide canned locales that are not delivered with your operating |
14280422 | 131 | system.) Read your system documentation for further illumination. |
5f05dabc | 132 | |
133 | =item * | |
134 | ||
135 | B<Perl must believe that the locale system is supported>. If it does, | |
136 | C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is | |
137 | C<define>. | |
138 | ||
139 | =back | |
140 | ||
141 | If you want a Perl application to process and present your data | |
142 | according to a particular locale, the application code should include | |
d6ded950 | 143 | the S<C<use locale>> pragma (see L<The "use locale" pragma>) where |
5f05dabc | 144 | appropriate, and B<at least one> of the following must be true: |
145 | ||
146 | =over 4 | |
147 | ||
c052850d | 148 | =item 1 |
5f05dabc | 149 | |
66cbab2c | 150 | B<The locale-determining environment variables (see L</"ENVIRONMENT">) |
5a964f20 | 151 | must be correctly set up> at the time the application is started, either |
ef3087ec | 152 | by yourself or by whomever set up your system account; or |
5f05dabc | 153 | |
c052850d | 154 | =item 2 |
5f05dabc | 155 | |
14280422 DD |
156 | B<The application must set its own locale> using the method described in |
157 | L<The setlocale function>. | |
5f05dabc | 158 | |
159 | =back | |
160 | ||
161 | =head1 USING LOCALES | |
162 | ||
d6ded950 | 163 | =head2 The C<"use locale"> pragma |
5f05dabc | 164 | |
2619d284 | 165 | By default, Perl itself ignores the current locale. The S<C<use locale>> |
66cbab2c | 166 | pragma tells Perl to use the current locale for some operations. |
d6ded950 KW |
167 | Starting in v5.16, there are optional parameters to this pragma, |
168 | described below, which restrict which operations are affected by it. | |
c052850d KW |
169 | |
170 | The current locale is set at execution time by | |
171 | L<setlocale()|/The setlocale function> described below. If that function | |
172 | hasn't yet been called in the course of the program's execution, the | |
66cbab2c | 173 | current locale is that which was determined by the L</"ENVIRONMENT"> in |
ebc3223b | 174 | effect at the start of the program. |
dfcc8045 | 175 | If there is no valid environment, the current locale is whatever the |
65ebb059 KW |
176 | system default has been set to. On POSIX systems, it is likely, but |
177 | not necessarily, the "C" locale. On Windows, the default is set via the | |
178 | computer's S<C<Control Panel-E<gt>Regional and Language Options>> (or its | |
179 | current equivalent). | |
c052850d KW |
180 | |
181 | The operations that are affected by locale are: | |
5f05dabc | 182 | |
183 | =over 4 | |
184 | ||
d6ded950 | 185 | =item B<Not within the scope of C<"use locale">> |
b960a36e | 186 | |
d6ded950 KW |
187 | Only certain operations originating outside Perl should be affected, as |
188 | follows: | |
1d2ab946 KW |
189 | |
190 | =over 4 | |
191 | ||
192 | =item * | |
2619d284 | 193 | |
2619d284 KW |
194 | The current locale is also used when going outside of Perl with |
195 | operations like L<system()|perlfunc/system LIST> or | |
196 | L<qxE<sol>E<sol>|perlop/qxE<sol>STRINGE<sol>>, if those operations are | |
197 | locale-sensitive. | |
198 | ||
1d2ab946 KW |
199 | =item * |
200 | ||
2619d284 KW |
201 | Also Perl gives access to various C library functions through the |
202 | L<POSIX> module. Some of those functions are always affected by the | |
203 | current locale. For example, C<POSIX::strftime()> uses C<LC_TIME>; | |
204 | C<POSIX::strtod()> uses C<LC_NUMERIC>; C<POSIX::strcoll()> and | |
205 | C<POSIX::strxfrm()> use C<LC_COLLATE>; and character classification | |
206 | functions like C<POSIX::isalnum()> use C<LC_CTYPE>. All such functions | |
207 | will behave according to the current underlying locale, even if that | |
1d2ab946 | 208 | locale isn't exposed to Perl space. |
2619d284 | 209 | |
1d2ab946 KW |
210 | =item * |
211 | ||
52686f2a KW |
212 | XS modules for all categories but C<LC_NUMERIC> get the underlying |
213 | locale, and hence any C library functions they call will use that | |
8a384d3a | 214 | underlying locale. For more discussion, see L<perlxs/CAVEATS>. |
1d2ab946 KW |
215 | |
216 | =back | |
217 | ||
ebc3223b KW |
218 | =for comment |
219 | The nbsp below makes this look better (though not great) | |
220 | ||
221 | E<160> | |
222 | ||
223 | =item B<Lingering effects of C<S<use locale>>> | |
1d2ab946 KW |
224 | |
225 | Certain Perl operations that are set-up within the scope of a | |
d6ded950 | 226 | C<use locale> retain that effect even outside the scope. |
b960a36e KW |
227 | These include: |
228 | ||
229 | =over 4 | |
230 | ||
231 | =item * | |
232 | ||
233 | The output format of a L<write()|perlfunc/write> is determined by an | |
234 | earlier format declaration (L<perlfunc/format>), so whether or not the | |
235 | output is affected by locale is determined by if the C<format()> is | |
d6ded950 | 236 | within the scope of a C<use locale>, not whether the C<write()> |
b960a36e KW |
237 | is. |
238 | ||
239 | =item * | |
240 | ||
241 | Regular expression patterns can be compiled using | |
242 | L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodual> with actual | |
243 | matching deferred to later. Again, it is whether or not the compilation | |
244 | was done within the scope of C<use locale> that determines the match | |
245 | behavior, not if the matches are done within such a scope or not. | |
246 | ||
247 | =back | |
248 | ||
ebc3223b KW |
249 | =for comment |
250 | The nbsp below makes this look better (though not great) | |
251 | ||
d6ded950 | 252 | |
ebc3223b KW |
253 | E<160> |
254 | ||
d6ded950 | 255 | =item B<Under C<"use locale";>> |
66cbab2c KW |
256 | |
257 | =over 4 | |
258 | ||
259 | =item * | |
260 | ||
d6ded950 | 261 | All the above operations |
b960a36e KW |
262 | |
263 | =item * | |
264 | ||
265 | B<Format declarations> (L<perlfunc/format>) and hence any subsequent | |
266 | C<write()>s use C<LC_NUMERIC>. | |
66cbab2c KW |
267 | |
268 | =item * | |
269 | ||
b960a36e KW |
270 | B<stringification and output> use C<LC_NUMERIC>. |
271 | These include the results of | |
272 | C<print()>, | |
273 | C<printf()>, | |
274 | C<say()>, | |
275 | and | |
276 | C<sprintf()>. | |
66cbab2c | 277 | |
b960a36e KW |
278 | =item * |
279 | ||
280 | B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use | |
39332f68 | 281 | C<LC_COLLATE>. C<sort()> is also affected if used without an |
5a964f20 | 282 | explicit comparison function, because it uses C<cmp> by default. |
14280422 | 283 | |
5a964f20 | 284 | B<Note:> C<eq> and C<ne> are unaffected by locale: they always |
de108802 | 285 | perform a char-by-char comparison of their scalar operands. What's |
14280422 DD |
286 | more, if C<cmp> finds that its operands are equal according to the |
287 | collation sequence specified by the current locale, it goes on to | |
de108802 RGS |
288 | perform a char-by-char comparison, and only returns I<0> (equal) if the |
289 | operands are char-for-char identical. If you really want to know whether | |
5a964f20 | 290 | two strings--which C<eq> and C<cmp> may consider different--are equal |
14280422 | 291 | as far as collation in the locale is concerned, see the discussion in |
cb88b78e | 292 | L<Category C<LC_COLLATE>: Collation>. |
5f05dabc | 293 | |
294 | =item * | |
295 | ||
39332f68 KW |
296 | B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>, |
297 | C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE> | |
5f05dabc | 298 | |
2c6ee1a7 KW |
299 | =item * |
300 | ||
301 | The variables L<$!|perlvar/$ERRNO> (and its synonyms C<$ERRNO> and | |
302 | C<$OS_ERROR>) and L<$^E|perlvar/$EXTENDED_OS_ERROR> (and its synonym | |
303 | C<$EXTENDED_OS_ERROR>) when used as strings use C<LC_MESSAGES>. | |
304 | ||
5f05dabc | 305 | =back |
306 | ||
66cbab2c | 307 | =back |
5f05dabc | 308 | |
5a964f20 | 309 | The default behavior is restored with the S<C<no locale>> pragma, or |
ef3087ec | 310 | upon reaching the end of the block enclosing C<use locale>. |
66cbab2c KW |
311 | Note that C<use locale> and C<use locale ':not_characters'> may be |
312 | nested, and that what is in effect within an inner scope will revert to | |
313 | the outer scope's rules at the end of the inner scope. | |
5f05dabc | 314 | |
5a964f20 | 315 | The string result of any operation that uses locale |
14280422 DD |
316 | information is tainted, as it is possible for a locale to be |
317 | untrustworthy. See L<"SECURITY">. | |
5f05dabc | 318 | |
d6ded950 KW |
319 | Starting in Perl v5.16 in a very limited way, and more generally in |
320 | v5.22, you can restrict which category or categories are enabled by this | |
321 | particular instance of the pragma by adding parameters to it. For | |
322 | example, | |
323 | ||
324 | use locale qw(:ctype :numeric); | |
325 | ||
326 | enables locale awareness within its scope of only those operations | |
327 | (listed above) that are affected by C<LC_CTYPE> and C<LC_NUMERIC>. | |
328 | ||
329 | The possible categories are: C<:collate>, C<:ctype>, C<:messages>, | |
330 | C<:monetary>, C<:numeric>, C<:time>, and the pseudo category | |
331 | C<:characters> (described below). | |
332 | ||
333 | Thus you can say | |
334 | ||
335 | use locale ':messages'; | |
336 | ||
337 | and only L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR> | |
338 | will be locale aware. Everything else is unaffected. | |
339 | ||
340 | Since Perl doesn't currently do anything with the C<LC_MONETARY> | |
341 | category, specifying C<:monetary> does effectively nothing. Some | |
342 | systems have other categories, such as C<LC_PAPER_SIZE>, but Perl | |
343 | also doesn't know anything about them, and there is no way to specify | |
344 | them in this pragma's arguments. | |
345 | ||
346 | You can also easily say to use all categories but one, by either, for | |
347 | example, | |
348 | ||
349 | use locale ':!ctype'; | |
350 | use locale ':not_ctype'; | |
351 | ||
352 | both of which mean to enable locale awarness of all categories but | |
353 | C<LC_CTYPE>. Only one category argument may be specified in a | |
354 | S<C<use locale>> if it is of the negated form. | |
355 | ||
356 | Prior to v5.22 only one form of the pragma with arguments is available: | |
357 | ||
358 | use locale ':not_characters'; | |
359 | ||
360 | (and you have to say C<not_>; you can't use the bang C<!> form). This | |
361 | pseudo category is a shorthand for specifying both C<:collate> and | |
362 | C<:ctype>. Hence, in the negated form, it is nearly the same thing as | |
363 | saying | |
364 | ||
365 | use locale qw(:messages :monetary :numeric :time); | |
366 | ||
367 | We use the term "nearly", because C<:not_characters> also turns on | |
368 | S<C<use feature 'unicode_strings'>> within its scope. This form is | |
369 | less useful in v5.20 and later, and is described fully in | |
370 | L</Unicode and UTF-8>, but briefly, it tells Perl to not use the | |
371 | character portions of the locale definition, that is the C<LC_CTYPE> and | |
372 | C<LC_COLLATE> categories. Instead it will use the native character set | |
373 | (extended by Unicode). When using this parameter, you are responsible | |
374 | for getting the external character set translated into the | |
375 | native/Unicode one (which it already will be if it is one of the | |
376 | increasingly popular UTF-8 locales). There are convenient ways of doing | |
377 | this, as described in L</Unicode and UTF-8>. | |
378 | ||
5f05dabc | 379 | =head2 The setlocale function |
380 | ||
14280422 | 381 | You can switch locales as often as you wish at run time with the |
39332f68 | 382 | C<POSIX::setlocale()> function: |
5f05dabc | 383 | |
5f05dabc | 384 | # Import locale-handling tool set from POSIX module. |
385 | # This example uses: setlocale -- the function call | |
386 | # LC_CTYPE -- explained below | |
2619d284 KW |
387 | # (Showing the testing for success/failure of operations is |
388 | # omitted in these examples to avoid distracting from the main | |
ebc3223b | 389 | # point) |
6ea81ccf | 390 | |
5f05dabc | 391 | use POSIX qw(locale_h); |
dfcc8045 KW |
392 | use locale; |
393 | my $old_locale; | |
5f05dabc | 394 | |
14280422 | 395 | # query and save the old locale |
5f05dabc | 396 | $old_locale = setlocale(LC_CTYPE); |
397 | ||
398 | setlocale(LC_CTYPE, "fr_CA.ISO8859-1"); | |
399 | # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1" | |
400 | ||
401 | setlocale(LC_CTYPE, ""); | |
65ebb059 KW |
402 | # LC_CTYPE now reset to the default defined by the |
403 | # LC_ALL/LC_CTYPE/LANG environment variables, or to the system | |
404 | # default. See below for documentation. | |
5f05dabc | 405 | |
406 | # restore the old locale | |
407 | setlocale(LC_CTYPE, $old_locale); | |
408 | ||
39332f68 | 409 | The first argument of C<setlocale()> gives the B<category>, the second the |
14280422 DD |
410 | B<locale>. The category tells in what aspect of data processing you |
411 | want to apply locale-specific rules. Category names are discussed in | |
66cbab2c | 412 | L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a |
14280422 DD |
413 | collection of customization information corresponding to a particular |
414 | combination of language, country or territory, and codeset. Read on for | |
415 | hints on the naming of locales: not all systems name locales as in the | |
416 | example. | |
417 | ||
39332f68 | 418 | If no second argument is provided and the category is something other |
cb88b78e | 419 | than C<LC_ALL>, the function returns a string naming the current locale |
502a173a | 420 | for the category. You can use this value as the second argument in a |
f170b852 KW |
421 | subsequent call to C<setlocale()>, B<but> on some platforms the string |
422 | is opaque, not something that most people would be able to decipher as | |
423 | to what locale it means. | |
502a173a | 424 | |
cb88b78e | 425 | If no second argument is provided and the category is C<LC_ALL>, the |
502a173a | 426 | result is implementation-dependent. It may be a string of |
c052850d | 427 | concatenated locale names (separator also implementation-dependent) |
39332f68 | 428 | or a single locale name. Please consult your L<setlocale(3)> man page for |
502a173a JH |
429 | details. |
430 | ||
431 | If a second argument is given and it corresponds to a valid locale, | |
432 | the locale for the category is set to that value, and the function | |
433 | returns the now-current locale value. You can then use this in yet | |
39332f68 | 434 | another call to C<setlocale()>. (In some implementations, the return |
502a173a JH |
435 | value may sometimes differ from the value you gave as the second |
436 | argument--think of it as an alias for the value you gave.) | |
5f05dabc | 437 | |
438 | As the example shows, if the second argument is an empty string, the | |
439 | category's locale is returned to the default specified by the | |
440 | corresponding environment variables. Generally, this results in a | |
5a964f20 | 441 | return to the default that was in force when Perl started up: changes |
54310121 | 442 | to the environment made by the application after startup may or may not |
5a964f20 | 443 | be noticed, depending on your system's C library. |
5f05dabc | 444 | |
d6ded950 KW |
445 | Note that when a form of C<use locale> that doesn't include all |
446 | categories is specified, Perl ignores the excluded categories. | |
66cbab2c | 447 | |
f170b852 | 448 | If C<set_locale()> fails for some reason (for example, an attempt to set |
dfcc8045 KW |
449 | to a locale unknown to the system), the locale for the category is not |
450 | changed, and the function returns C<undef>. | |
451 | ||
2619d284 | 452 | |
39332f68 | 453 | For further information about the categories, consult L<setlocale(3)>. |
3e6e419a JH |
454 | |
455 | =head2 Finding locales | |
456 | ||
39332f68 | 457 | For locales available in your system, consult also L<setlocale(3)> to |
5a964f20 TC |
458 | see whether it leads to the list of available locales (search for the |
459 | I<SEE ALSO> section). If that fails, try the following command lines: | |
5f05dabc | 460 | |
461 | locale -a | |
462 | ||
463 | nlsinfo | |
464 | ||
465 | ls /usr/lib/nls/loc | |
466 | ||
467 | ls /usr/lib/locale | |
468 | ||
469 | ls /usr/lib/nls | |
470 | ||
b478f28d JH |
471 | ls /usr/share/locale |
472 | ||
5f05dabc | 473 | and see whether they list something resembling these |
474 | ||
2bdf8add | 475 | en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5 |
502a173a | 476 | en_US.iso88591 de_DE.iso88591 ru_RU.iso88595 |
2bdf8add | 477 | en_US de_DE ru_RU |
14280422 | 478 | en de ru |
2bdf8add JH |
479 | english german russian |
480 | english.iso88591 german.iso88591 russian.iso88595 | |
502a173a | 481 | english.roman8 russian.koi8r |
5f05dabc | 482 | |
39332f68 | 483 | Sadly, even though the calling interface for C<setlocale()> has been |
528d65ad | 484 | standardized, names of locales and the directories where the |
5a964f20 | 485 | configuration resides have not been. The basic form of the name is |
528d65ad JH |
486 | I<language_territory>B<.>I<codeset>, but the latter parts after |
487 | I<language> are not always present. The I<language> and I<country> | |
488 | are usually from the standards B<ISO 3166> and B<ISO 639>, the | |
489 | two-letter abbreviations for the countries and the languages of the | |
490 | world, respectively. The I<codeset> part often mentions some B<ISO | |
491 | 8859> character set, the Latin codesets. For example, C<ISO 8859-1> | |
492 | is the so-called "Western European codeset" that can be used to encode | |
493 | most Western European languages adequately. Again, there are several | |
494 | ways to write even the name of that one standard. Lamentably. | |
5f05dabc | 495 | |
14280422 DD |
496 | Two special locales are worth particular mention: "C" and "POSIX". |
497 | Currently these are effectively the same locale: the difference is | |
5a964f20 TC |
498 | mainly that the first one is defined by the C standard, the second by |
499 | the POSIX standard. They define the B<default locale> in which | |
14280422 | 500 | every program starts in the absence of locale information in its |
5a964f20 | 501 | environment. (The I<default> default locale, if you will.) Its language |
39332f68 KW |
502 | is (American) English and its character codeset ASCII or, rarely, a |
503 | superset thereof (such as the "DEC Multinational Character Set | |
504 | (DEC-MCS)"). B<Warning>. The C locale delivered by some vendors | |
505 | may not actually exactly match what the C standard calls for. So | |
506 | beware. | |
5f05dabc | 507 | |
14280422 DD |
508 | B<NOTE>: Not all systems have the "POSIX" locale (not all systems are |
509 | POSIX-conformant), so use "C" when you need explicitly to specify this | |
510 | default locale. | |
5f05dabc | 511 | |
3e6e419a JH |
512 | =head2 LOCALE PROBLEMS |
513 | ||
5a964f20 | 514 | You may encounter the following warning message at Perl startup: |
3e6e419a JH |
515 | |
516 | perl: warning: Setting locale failed. | |
517 | perl: warning: Please check that your locale settings: | |
518 | LC_ALL = "En_US", | |
519 | LANG = (unset) | |
520 | are supported and installed on your system. | |
521 | perl: warning: Falling back to the standard locale ("C"). | |
522 | ||
cb88b78e | 523 | This means that your locale settings had C<LC_ALL> set to "En_US" and |
5a964f20 TC |
524 | LANG exists but has no value. Perl tried to believe you but could not. |
525 | Instead, Perl gave up and fell back to the "C" locale, the default locale | |
65ebb059 KW |
526 | that is supposed to work no matter what. (On Windows, it first tries |
527 | falling back to the system default locale.) This usually means your | |
528 | locale settings were wrong, they mention locales your system has never | |
529 | heard of, or the locale installation in your system has problems (for | |
530 | example, some system files are broken or missing). There are quick and | |
531 | temporary fixes to these problems, as well as more thorough and lasting | |
532 | fixes. | |
3e6e419a | 533 | |
83fb1bf0 KW |
534 | =head2 Testing for broken locales |
535 | ||
536 | If you are building Perl from source, the Perl test suite file | |
537 | F<lib/locale.t> can be used to test the locales on your system. | |
538 | Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1 | |
539 | will cause it to output detailed results. For example, on Linux, you | |
540 | could say | |
541 | ||
1d2ab946 | 542 | PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1 |
83fb1bf0 KW |
543 | |
544 | Besides many other tests, it will test every locale it finds on your | |
545 | system to see if they conform to the POSIX standard. If any have | |
546 | errors, it will include a summary near the end of the output of which | |
547 | locales passed all its tests, and which failed, and why. | |
548 | ||
3e6e419a JH |
549 | =head2 Temporarily fixing locale problems |
550 | ||
5a964f20 | 551 | The two quickest fixes are either to render Perl silent about any |
3e6e419a JH |
552 | locale inconsistencies or to run Perl under the default locale "C". |
553 | ||
554 | Perl's moaning about locale problems can be silenced by setting the | |
cb88b78e | 555 | environment variable C<PERL_BADLANG> to a zero value, for example "0". |
900bd440 JH |
556 | This method really just sweeps the problem under the carpet: you tell |
557 | Perl to shut up even when Perl sees that something is wrong. Do not | |
558 | be surprised if later something locale-dependent misbehaves. | |
3e6e419a JH |
559 | |
560 | Perl can be run under the "C" locale by setting the environment | |
cb88b78e KW |
561 | variable C<LC_ALL> to "C". This method is perhaps a bit more civilized |
562 | than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or | |
5a964f20 TC |
563 | other locale variables) may affect other programs as well, not just |
564 | Perl. In particular, external programs run from within Perl will see | |
3e6e419a | 565 | these changes. If you make the new settings permanent (read on), all |
f979aebc | 566 | programs you run see the changes. See L<"ENVIRONMENT"> for |
5a964f20 | 567 | the full list of relevant environment variables and L<USING LOCALES> |
e05ffc7d | 568 | for their effects in Perl. Effects in other programs are |
cb88b78e | 569 | easily deducible. For example, the variable C<LC_COLLATE> may well affect |
b432a672 | 570 | your B<sort> program (or whatever the program that arranges "records" |
3e6e419a JH |
571 | alphabetically in your system is called). |
572 | ||
5a964f20 TC |
573 | You can test out changing these variables temporarily, and if the |
574 | new settings seem to help, put those settings into your shell startup | |
575 | files. Consult your local documentation for the exact details. For in | |
576 | Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>): | |
3e6e419a JH |
577 | |
578 | LC_ALL=en_US.ISO8859-1 | |
579 | export LC_ALL | |
580 | ||
5a964f20 TC |
581 | This assumes that we saw the locale "en_US.ISO8859-1" using the commands |
582 | discussed above. We decided to try that instead of the above faulty | |
583 | locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>) | |
3e6e419a JH |
584 | |
585 | setenv LC_ALL en_US.ISO8859-1 | |
c47ff5f1 | 586 | |
c406981e JH |
587 | or if you have the "env" application you can do in any shell |
588 | ||
589 | env LC_ALL=en_US.ISO8859-1 perl ... | |
590 | ||
5a964f20 | 591 | If you do not know what shell you have, consult your local |
3e6e419a JH |
592 | helpdesk or the equivalent. |
593 | ||
594 | =head2 Permanently fixing locale problems | |
595 | ||
5a964f20 TC |
596 | The slower but superior fixes are when you may be able to yourself |
597 | fix the misconfiguration of your own environment variables. The | |
3e6e419a JH |
598 | mis(sing)configuration of the whole system's locales usually requires |
599 | the help of your friendly system administrator. | |
600 | ||
5a964f20 TC |
601 | First, see earlier in this document about L<Finding locales>. That tells |
602 | how to find which locales are really supported--and more importantly, | |
603 | installed--on your system. In our example error message, environment | |
604 | variables affecting the locale are listed in the order of decreasing | |
605 | importance (and unset variables do not matter). Therefore, having | |
606 | LC_ALL set to "En_US" must have been the bad choice, as shown by the | |
607 | error message. First try fixing locale settings listed first. | |
3e6e419a | 608 | |
5a964f20 TC |
609 | Second, if using the listed commands you see something B<exactly> |
610 | (prefix matches do not count and case usually counts) like "En_US" | |
611 | without the quotes, then you should be okay because you are using a | |
612 | locale name that should be installed and available in your system. | |
4a4eefd0 | 613 | In this case, see L<Permanently fixing your system's locale configuration>. |
3e6e419a | 614 | |
4a4eefd0 | 615 | =head2 Permanently fixing your system's locale configuration |
3e6e419a | 616 | |
5a964f20 | 617 | This is when you see something like: |
3e6e419a JH |
618 | |
619 | perl: warning: Please check that your locale settings: | |
620 | LC_ALL = "En_US", | |
621 | LANG = (unset) | |
622 | are supported and installed on your system. | |
623 | ||
624 | but then cannot see that "En_US" listed by the above-mentioned | |
5a964f20 TC |
625 | commands. You may see things like "en_US.ISO8859-1", but that isn't |
626 | the same. In this case, try running under a locale | |
627 | that you can list and which somehow matches what you tried. The | |
3e6e419a | 628 | rules for matching locale names are a bit vague because |
e05ffc7d | 629 | standardization is weak in this area. See again the |
13a2d996 | 630 | L<Finding locales> about general rules. |
3e6e419a | 631 | |
b687b08b | 632 | =head2 Fixing system locale configuration |
3e6e419a | 633 | |
5a964f20 TC |
634 | Contact a system administrator (preferably your own) and report the exact |
635 | error message you get, and ask them to read this same documentation you | |
636 | are now reading. They should be able to check whether there is something | |
637 | wrong with the locale configuration of the system. The L<Finding locales> | |
638 | section is unfortunately a bit vague about the exact commands and places | |
639 | because these things are not that standardized. | |
3e6e419a | 640 | |
5f05dabc | 641 | =head2 The localeconv function |
642 | ||
39332f68 | 643 | The C<POSIX::localeconv()> function allows you to get particulars of the |
14280422 | 644 | locale-dependent numeric formatting information specified by the current |
a835cd47 KW |
645 | underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of |
646 | whether called from within the scope of C<S<use locale>> or not). (If | |
647 | you just want the name of | |
39332f68 | 648 | the current locale for a particular category, use C<POSIX::setlocale()> |
5a964f20 | 649 | with a single parameter--see L<The setlocale function>.) |
5f05dabc | 650 | |
651 | use POSIX qw(locale_h); | |
5f05dabc | 652 | |
653 | # Get a reference to a hash of locale-dependent info | |
654 | $locale_values = localeconv(); | |
655 | ||
656 | # Output sorted list of the values | |
657 | for (sort keys %$locale_values) { | |
14280422 | 658 | printf "%-20s = %s\n", $_, $locale_values->{$_} |
5f05dabc | 659 | } |
660 | ||
39332f68 | 661 | C<localeconv()> takes no arguments, and returns B<a reference to> a hash. |
5a964f20 | 662 | The keys of this hash are variable names for formatting, such as |
502a173a | 663 | C<decimal_point> and C<thousands_sep>. The values are the |
cea6626f | 664 | corresponding, er, values. See L<POSIX/localeconv> for a longer |
502a173a JH |
665 | example listing the categories an implementation might be expected to |
666 | provide; some provide more and others fewer. You don't need an | |
39332f68 | 667 | explicit C<use locale>, because C<localeconv()> always observes the |
502a173a | 668 | current locale. |
5f05dabc | 669 | |
5a964f20 TC |
670 | Here's a simple-minded example program that rewrites its command-line |
671 | parameters as integers correctly formatted in the current locale: | |
5f05dabc | 672 | |
ef3087ec KW |
673 | use POSIX qw(locale_h); |
674 | ||
675 | # Get some of locale's numeric formatting parameters | |
676 | my ($thousands_sep, $grouping) = | |
677 | @{localeconv()}{'thousands_sep', 'grouping'}; | |
678 | ||
679 | # Apply defaults if values are missing | |
680 | $thousands_sep = ',' unless $thousands_sep; | |
681 | ||
682 | # grouping and mon_grouping are packed lists | |
683 | # of small integers (characters) telling the | |
684 | # grouping (thousand_seps and mon_thousand_seps | |
685 | # being the group dividers) of numbers and | |
686 | # monetary quantities. The integers' meanings: | |
687 | # 255 means no more grouping, 0 means repeat | |
688 | # the previous grouping, 1-254 means use that | |
689 | # as the current grouping. Grouping goes from | |
690 | # right to left (low to high digits). In the | |
691 | # below we cheat slightly by never using anything | |
692 | # else than the first grouping (whatever that is). | |
693 | if ($grouping) { | |
694 | @grouping = unpack("C*", $grouping); | |
695 | } else { | |
696 | @grouping = (3); | |
697 | } | |
698 | ||
699 | # Format command line params for current locale | |
700 | for (@ARGV) { | |
701 | $_ = int; # Chop non-integer part | |
702 | 1 while | |
703 | s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/; | |
704 | print "$_"; | |
705 | } | |
706 | print "\n"; | |
5f05dabc | 707 | |
03ceeedf KW |
708 | Note that if the platform doesn't have C<LC_NUMERIC> and/or |
709 | C<LC_MONETARY> available or enabled, the corresponding elements of the | |
710 | hash will be missing. | |
711 | ||
74c76037 | 712 | =head2 I18N::Langinfo |
4bbcc6e8 JH |
713 | |
714 | Another interface for querying locale-dependent information is the | |
39332f68 | 715 | C<I18N::Langinfo::langinfo()> function, available at least in Unix-like |
4bbcc6e8 JH |
716 | systems and VMS. |
717 | ||
39332f68 KW |
718 | The following example will import the C<langinfo()> function itself and |
719 | three constants to be used as arguments to C<langinfo()>: a constant for | |
74c76037 JH |
720 | the abbreviated first day of the week (the numbering starts from |
721 | Sunday = 1) and two more constants for the affirmative and negative | |
722 | answers for a yes/no question in the current locale. | |
4bbcc6e8 | 723 | |
74c76037 | 724 | use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR); |
4bbcc6e8 | 725 | |
ef3087ec KW |
726 | my ($abday_1, $yesstr, $nostr) |
727 | = map { langinfo } qw(ABDAY_1 YESSTR NOSTR); | |
4bbcc6e8 | 728 | |
74c76037 | 729 | print "$abday_1? [$yesstr/$nostr] "; |
4bbcc6e8 | 730 | |
74c76037 JH |
731 | In other words, in the "C" (or English) locale the above will probably |
732 | print something like: | |
733 | ||
e05ffc7d | 734 | Sun? [yes/no] |
4bbcc6e8 JH |
735 | |
736 | See L<I18N::Langinfo> for more information. | |
737 | ||
5f05dabc | 738 | =head1 LOCALE CATEGORIES |
739 | ||
5a964f20 TC |
740 | The following subsections describe basic locale categories. Beyond these, |
741 | some combination categories allow manipulation of more than one | |
742 | basic category at a time. See L<"ENVIRONMENT"> for a discussion of these. | |
5f05dabc | 743 | |
cb88b78e | 744 | =head2 Category C<LC_COLLATE>: Collation |
5f05dabc | 745 | |
d6ded950 KW |
746 | In the scope of a S<C<use locale>> form that includes collation, Perl |
747 | looks to the C<LC_COLLATE> | |
5a964f20 | 748 | environment variable to determine the application's notions on collation |
b4ffc3db TC |
749 | (ordering) of characters. For example, "b" follows "a" in Latin |
750 | alphabets, but where do "E<aacute>" and "E<aring>" belong? And while | |
f87fa335 | 751 | "color" follows "chocolate" in English, what about in traditional Spanish? |
5f05dabc | 752 | |
60f0fa02 JH |
753 | The following collations all make sense and you may meet any of them |
754 | if you "use locale". | |
755 | ||
756 | A B C D E a b c d e | |
35316ca3 | 757 | A a B b C c D d E e |
60f0fa02 JH |
758 | a A b B c C d D e E |
759 | a b c d e A B C D E | |
760 | ||
f1cbbd6e | 761 | Here is a code snippet to tell what "word" |
5a964f20 | 762 | characters are in the current locale, in that locale's order: |
5f05dabc | 763 | |
764 | use locale; | |
35316ca3 | 765 | print +(sort grep /\w/, map { chr } 0..255), "\n"; |
5f05dabc | 766 | |
14280422 DD |
767 | Compare this with the characters that you see and their order if you |
768 | state explicitly that the locale should be ignored: | |
5f05dabc | 769 | |
770 | no locale; | |
35316ca3 | 771 | print +(sort grep /\w/, map { chr } 0..255), "\n"; |
5f05dabc | 772 | |
773 | This machine-native collation (which is what you get unless S<C<use | |
774 | locale>> has appeared earlier in the same block) must be used for | |
775 | sorting raw binary data, whereas the locale-dependent collation of the | |
b0c42ed9 | 776 | first example is useful for natural text. |
5f05dabc | 777 | |
14280422 DD |
778 | As noted in L<USING LOCALES>, C<cmp> compares according to the current |
779 | collation locale when C<use locale> is in effect, but falls back to a | |
de108802 | 780 | char-by-char comparison for strings that the locale says are equal. You |
39332f68 | 781 | can use C<POSIX::strcoll()> if you don't want this fall-back: |
14280422 DD |
782 | |
783 | use POSIX qw(strcoll); | |
784 | $equal_in_locale = | |
785 | !strcoll("space and case ignored", "SpaceAndCaseIgnored"); | |
786 | ||
39332f68 | 787 | C<$equal_in_locale> will be true if the collation locale specifies a |
5a964f20 | 788 | dictionary-like ordering that ignores space characters completely and |
9e3a2af8 | 789 | which folds case. |
14280422 | 790 | |
31f05a37 KW |
791 | Perl only supports single-byte locales for C<LC_COLLATE>. This means |
792 | that a UTF-8 locale likely will just give you machine-native ordering. | |
793 | Use L<Unicode::Collate> for the full implementation of the Unicode | |
794 | Collation Algorithm. | |
795 | ||
5a964f20 | 796 | If you have a single string that you want to check for "equality in |
14280422 | 797 | locale" against several others, you might think you could gain a little |
39332f68 | 798 | efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>: |
14280422 DD |
799 | |
800 | use POSIX qw(strxfrm); | |
801 | $xfrm_string = strxfrm("Mixed-case string"); | |
802 | print "locale collation ignores spaces\n" | |
803 | if $xfrm_string eq strxfrm("Mixed-casestring"); | |
804 | print "locale collation ignores hyphens\n" | |
805 | if $xfrm_string eq strxfrm("Mixedcase string"); | |
806 | print "locale collation ignores case\n" | |
807 | if $xfrm_string eq strxfrm("mixed-case string"); | |
808 | ||
39332f68 | 809 | C<strxfrm()> takes a string and maps it into a transformed string for use |
de108802 | 810 | in char-by-char comparisons against other transformed strings during |
14280422 | 811 | collation. "Under the hood", locale-affected Perl comparison operators |
39332f68 KW |
812 | call C<strxfrm()> for both operands, then do a char-by-char |
813 | comparison of the transformed strings. By calling C<strxfrm()> explicitly | |
14280422 | 814 | and using a non locale-affected comparison, the example attempts to save |
5a964f20 | 815 | a couple of transformations. But in fact, it doesn't save anything: Perl |
2ae324a7 | 816 | magic (see L<perlguts/Magic Variables>) creates the transformed version of a |
5a964f20 | 817 | string the first time it's needed in a comparison, then keeps this version around |
14280422 | 818 | in case it's needed again. An example rewritten the easy way with |
e38874e2 | 819 | C<cmp> runs just about as fast. It also copes with null characters |
39332f68 | 820 | embedded in strings; if you call C<strxfrm()> directly, it treats the first |
5a964f20 TC |
821 | null it finds as a terminator. don't expect the transformed strings |
822 | it produces to be portable across systems--or even from one revision | |
39332f68 | 823 | of your operating system to the next. In short, don't call C<strxfrm()> |
e38874e2 | 824 | directly: let Perl do it for you. |
14280422 | 825 | |
5a964f20 | 826 | Note: C<use locale> isn't shown in some of these examples because it isn't |
dfcc8045 KW |
827 | needed: C<strcoll()> and C<strxfrm()> are POSIX functions |
828 | which use the standard system-supplied C<libc> functions that | |
829 | always obey the current C<LC_COLLATE> locale. | |
5f05dabc | 830 | |
cb88b78e | 831 | =head2 Category C<LC_CTYPE>: Character Types |
5f05dabc | 832 | |
d6ded950 KW |
833 | In the scope of a S<C<use locale>> form that includes C<LC_CTYPE>, Perl |
834 | obeys the C<LC_CTYPE> locale | |
14280422 | 835 | setting. This controls the application's notion of which characters are |
ebc3223b KW |
836 | alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w> |
837 | regular expression metanotation, | |
f1cbbd6e | 838 | which stands for alphanumeric characters--that is, alphabetic, |
ebc3223b KW |
839 | numeric, and the platform's native underscore. |
840 | (Consult L<perlre> for more information about | |
14280422 | 841 | regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale |
b4ffc3db TC |
842 | setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and |
843 | "E<oslash>" may be understood as C<\w> characters. | |
ebc3223b KW |
844 | It also affects things like C<\s>, C<\D>, and the POSIX character |
845 | classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more | |
846 | information on all these.) | |
5f05dabc | 847 | |
2c268ad5 | 848 | The C<LC_CTYPE> locale also provides the map used in transliterating |
68dc0745 | 849 | characters between lower and uppercase. This affects the case-mapping |
39332f68 | 850 | functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>; case-mapping |
b9cc4f69 KW |
851 | interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted |
852 | strings and C<s///> substitutions; and case-independent regular expression | |
e38874e2 DD |
853 | pattern matching using the C<i> modifier. |
854 | ||
2da736a2 | 855 | Finally, C<LC_CTYPE> affects the (deprecated) POSIX character-class test |
1d2ab946 KW |
856 | functions--C<POSIX::isalpha()>, C<POSIX::islower()>, and so on. For |
857 | example, if you move from the "C" locale to a 7-bit Scandinavian one, | |
858 | you may find--possibly to your surprise--that "|" moves from the | |
859 | C<POSIX::ispunct()> class to C<POSIX::isalpha()>. | |
ef3087ec KW |
860 | Unfortunately, this creates big problems for regular expressions. "|" still |
861 | means alternation even though it matches C<\w>. | |
5f05dabc | 862 | |
31f05a37 KW |
863 | Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but |
864 | otherwise Perl only supports single-byte locales, such as the ISO 8859 | |
865 | series. This means that wide character locales, for example for Asian | |
866 | languages, are not supported. The UTF-8 locale support is actually a | |
867 | superset of POSIX locales, because it is really full Unicode behavior | |
868 | as if no locale were in effect at all (except for tainting; see | |
869 | L</SECURITY>). POSIX locales, even UTF-8 ones, | |
870 | are lacking certain concepts in Unicode, such as the idea that changing | |
871 | the case of a character could expand to be more than one character. | |
872 | Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20, | |
873 | Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one, | |
874 | with some restrictions, and on other platforms more like the "C" locale. | |
875 | For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be | |
876 | used as a workaround for this (see L</Unicode and UTF-8>). | |
877 | ||
5d63e270 KW |
878 | Note that there are quite a few things that are unaffected by the |
879 | current locale. All the escape sequences for particular characters, | |
880 | C<\n> for example, always mean the platform's native one. This means, | |
881 | for example, that C<\N> in regular expressions (every character | |
1d2ab946 | 882 | but new-line) works on the platform character set. |
5d63e270 | 883 | |
14280422 DD |
884 | B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result |
885 | in clearly ineligible characters being considered to be alphanumeric by | |
e199995e | 886 | your application. For strict matching of (mundane) ASCII letters and |
5a964f20 | 887 | digits--for example, in command strings--locale-aware applications |
e199995e | 888 | should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">. |
5f05dabc | 889 | |
fee33030 | 890 | =head2 Category C<LC_NUMERIC>: Numeric Formatting |
5f05dabc | 891 | |
d6ded950 KW |
892 | After a proper C<POSIX::setlocale()> call, and within the scope of |
893 | of a C<use locale> form that includes numerics, Perl obeys the | |
894 | C<LC_NUMERIC> locale information, which controls an application's idea | |
895 | of how numbers should be formatted for human readability. | |
b960a36e | 896 | In most implementations the only effect is to |
b4ffc3db | 897 | change the character used for the decimal point--perhaps from "." to ",". |
b960a36e | 898 | The functions aren't aware of such niceties as thousands separation and |
2095dafa | 899 | so on. (See L<The localeconv function> if you care about these things.) |
5a964f20 | 900 | |
b960a36e KW |
901 | use POSIX qw(strtod setlocale LC_NUMERIC); |
902 | use locale; | |
5f05dabc | 903 | |
b960a36e | 904 | setlocale LC_NUMERIC, ""; |
14280422 | 905 | |
b960a36e | 906 | $n = 5/2; # Assign numeric 2.5 to $n |
5f05dabc | 907 | |
b960a36e | 908 | $a = " $n"; # Locale-dependent conversion to string |
5f05dabc | 909 | |
b960a36e | 910 | print "half five is $n\n"; # Locale-dependent output |
5f05dabc | 911 | |
b960a36e | 912 | printf "half five is %g\n", $n; # Locale-dependent output |
5f05dabc | 913 | |
b960a36e KW |
914 | print "DECIMAL POINT IS COMMA\n" |
915 | if $n == (strtod("2,5"))[0]; # Locale-dependent conversion | |
5f05dabc | 916 | |
4bbcc6e8 JH |
917 | See also L<I18N::Langinfo> and C<RADIXCHAR>. |
918 | ||
cb88b78e | 919 | =head2 Category C<LC_MONETARY>: Formatting of monetary amounts |
5f05dabc | 920 | |
e199995e | 921 | The C standard defines the C<LC_MONETARY> category, but not a function |
5a964f20 | 922 | that is affected by its contents. (Those with experience of standards |
b0c42ed9 | 923 | committees will recognize that the working group decided to punt on the |
fa9b773e KW |
924 | issue.) Consequently, Perl essentially takes no notice of it. If you |
925 | really want to use C<LC_MONETARY>, you can query its contents--see | |
e05ffc7d KW |
926 | L<The localeconv function>--and use the information that it returns in your |
927 | application's own formatting of currency amounts. However, you may well | |
928 | find that the information, voluminous and complex though it may be, still | |
929 | does not quite meet your requirements: currency formatting is a hard nut | |
13a2d996 | 930 | to crack. |
5f05dabc | 931 | |
4bbcc6e8 JH |
932 | See also L<I18N::Langinfo> and C<CRNCYSTR>. |
933 | ||
cb88b78e | 934 | =head2 C<LC_TIME> |
5f05dabc | 935 | |
39332f68 | 936 | Output produced by C<POSIX::strftime()>, which builds a formatted |
5f05dabc | 937 | human-readable date/time string, is affected by the current C<LC_TIME> |
938 | locale. Thus, in a French locale, the output produced by the C<%B> | |
939 | format element (full month name) for the first month of the year would | |
5a964f20 | 940 | be "janvier". Here's how to get a list of long month names in the |
5f05dabc | 941 | current locale: |
942 | ||
943 | use POSIX qw(strftime); | |
14280422 DD |
944 | for (0..11) { |
945 | $long_month_name[$_] = | |
946 | strftime("%B", 0, 0, 0, 1, $_, 96); | |
5f05dabc | 947 | } |
948 | ||
2619d284 KW |
949 | Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX |
950 | function which uses the standard system-supplied C<libc> function that | |
951 | always obeys the current C<LC_TIME> locale. | |
5f05dabc | 952 | |
4bbcc6e8 | 953 | See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>, |
2a2bf5f4 | 954 | C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>. |
4bbcc6e8 | 955 | |
5f05dabc | 956 | =head2 Other categories |
957 | ||
2619d284 KW |
958 | The remaining locale categories are not currently used by Perl itself. |
959 | But again note that things Perl interacts with may use these, including | |
960 | extensions outside the standard Perl distribution, and by the | |
98a6f11e | 961 | operating system and its utilities. Note especially that the string |
962 | value of C<$!> and the error messages given by external utilities may | |
963 | be changed by C<LC_MESSAGES>. If you want to have portable error | |
265f5c4a | 964 | codes, use C<%!>. See L<Errno>. |
14280422 DD |
965 | |
966 | =head1 SECURITY | |
967 | ||
5a964f20 | 968 | Although the main discussion of Perl security issues can be found in |
14280422 DD |
969 | L<perlsec>, a discussion of Perl's locale handling would be incomplete |
970 | if it did not draw your attention to locale-dependent security issues. | |
5a964f20 TC |
971 | Locales--particularly on systems that allow unprivileged users to |
972 | build their own locales--are untrustworthy. A malicious (or just plain | |
14280422 DD |
973 | broken) locale can make a locale-aware application give unexpected |
974 | results. Here are a few possibilities: | |
975 | ||
976 | =over 4 | |
977 | ||
978 | =item * | |
979 | ||
980 | Regular expression checks for safe file names or mail addresses using | |
5a964f20 | 981 | C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that |
14280422 DD |
982 | characters such as "E<gt>" and "|" are alphanumeric. |
983 | ||
984 | =item * | |
985 | ||
e38874e2 | 986 | String interpolation with case-mapping, as in, say, C<$dest = |
cb88b78e | 987 | "C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE> |
e38874e2 DD |
988 | case-mapping table is in effect. |
989 | ||
990 | =item * | |
991 | ||
14280422 DD |
992 | A sneaky C<LC_COLLATE> locale could result in the names of students with |
993 | "D" grades appearing ahead of those with "A"s. | |
994 | ||
995 | =item * | |
996 | ||
5a964f20 | 997 | An application that takes the trouble to use information in |
14280422 | 998 | C<LC_MONETARY> may format debits as if they were credits and vice versa |
5a964f20 | 999 | if that locale has been subverted. Or it might make payments in US |
14280422 DD |
1000 | dollars instead of Hong Kong dollars. |
1001 | ||
1002 | =item * | |
1003 | ||
39332f68 | 1004 | The date and day names in dates formatted by C<strftime()> could be |
14280422 | 1005 | manipulated to advantage by a malicious user able to subvert the |
5a964f20 | 1006 | C<LC_DATE> locale. ("Look--it says I wasn't in the building on |
14280422 DD |
1007 | Sunday.") |
1008 | ||
1009 | =back | |
1010 | ||
1011 | Such dangers are not peculiar to the locale system: any aspect of an | |
5a964f20 | 1012 | application's environment which may be modified maliciously presents |
14280422 | 1013 | similar challenges. Similarly, they are not specific to Perl: any |
5a964f20 | 1014 | programming language that allows you to write programs that take |
14280422 DD |
1015 | account of their environment exposes you to these issues. |
1016 | ||
5a964f20 TC |
1017 | Perl cannot protect you from all possibilities shown in the |
1018 | examples--there is no substitute for your own vigilance--but, when | |
14280422 | 1019 | C<use locale> is in effect, Perl uses the tainting mechanism (see |
5a964f20 | 1020 | L<perlsec>) to mark string results that become locale-dependent, and |
14280422 | 1021 | which may be untrustworthy in consequence. Here is a summary of the |
5a964f20 | 1022 | tainting behavior of operators and functions that may be affected by |
14280422 DD |
1023 | the locale: |
1024 | ||
1025 | =over 4 | |
1026 | ||
551e1d92 RB |
1027 | =item * |
1028 | ||
1029 | B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>): | |
14280422 DD |
1030 | |
1031 | Scalar true/false (or less/equal/greater) result is never tainted. | |
1032 | ||
551e1d92 RB |
1033 | =item * |
1034 | ||
1d2ab946 | 1035 | B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>) |
e38874e2 | 1036 | |
d6ded950 KW |
1037 | The result string containing interpolated material is tainted if |
1038 | a C<use locale> form that includes C<LC_CTYPE> is in effect. | |
e38874e2 | 1039 | |
551e1d92 RB |
1040 | =item * |
1041 | ||
1042 | B<Matching operator> (C<m//>): | |
14280422 DD |
1043 | |
1044 | Scalar true/false result never tainted. | |
1045 | ||
1d2ab946 | 1046 | All subpatterns, either delivered as a list-context result or as C<$1> |
d6ded950 KW |
1047 | I<etc>., are tainted if a C<use locale> form that includes |
1048 | C<LC_CTYPE> is in effect, and the subpattern | |
63baef57 KW |
1049 | regular expression contains a locale-dependent construct. These |
1050 | constructs include C<\w> (to match an alphanumeric character), C<\W> | |
1051 | (non-alphanumeric character), C<\b> and C<\B> (word-boundary and | |
1052 | non-boundardy, which depend on what C<\w> and C<\W> match), C<\s> | |
1053 | (whitespace character), C<\S> (non whitespace character), C<\d> and | |
1054 | C<\D> (digits and non-digits), and the POSIX character classes, such as | |
1055 | C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>). | |
1056 | ||
1057 | Tainting is also likely if the pattern is to be matched | |
1058 | case-insensitively (via C</i>). The exception is if all the code points | |
1059 | to be matched this way are above 255 and do not have folds under Unicode | |
1060 | rules to below 256. Tainting is not done for these because Perl | |
1061 | only uses Unicode rules for such code points, and those rules are the | |
1062 | same no matter what the current locale. | |
1063 | ||
1d2ab946 KW |
1064 | The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'> |
1065 | (post-match), and C<$+> (last match) also are tainted. | |
14280422 | 1066 | |
551e1d92 RB |
1067 | =item * |
1068 | ||
1069 | B<Substitution operator> (C<s///>): | |
14280422 | 1070 | |
e38874e2 | 1071 | Has the same behavior as the match operator. Also, the left |
d6ded950 KW |
1072 | operand of C<=~> becomes tainted when a C<use locale> |
1073 | form that includes C<LC_CTYPE> is in effect, if modified as | |
66cbab2c | 1074 | a result of a substitution based on a regular |
1d2ab946 KW |
1075 | expression match involving any of the things mentioned in the previous |
1076 | item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>. | |
14280422 | 1077 | |
551e1d92 RB |
1078 | =item * |
1079 | ||
39332f68 | 1080 | B<Output formatting functions> (C<printf()> and C<write()>): |
14280422 | 1081 | |
3cf03d68 JH |
1082 | Results are never tainted because otherwise even output from print, |
1083 | for example C<print(1/7)>, should be tainted if C<use locale> is in | |
1084 | effect. | |
14280422 | 1085 | |
551e1d92 RB |
1086 | =item * |
1087 | ||
39332f68 | 1088 | B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>): |
14280422 | 1089 | |
d6ded950 KW |
1090 | Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is |
1091 | in effect. | |
14280422 | 1092 | |
551e1d92 RB |
1093 | =item * |
1094 | ||
39332f68 KW |
1095 | B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>, |
1096 | C<strftime()>, C<strxfrm()>): | |
14280422 DD |
1097 | |
1098 | Results are never tainted. | |
1099 | ||
551e1d92 RB |
1100 | =item * |
1101 | ||
1d2ab946 KW |
1102 | B<POSIX character class tests> (C<POSIX::isalnum()>, |
1103 | C<POSIX::isalpha()>, C<POSIX::isdigit()>, C<POSIX::isgraph()>, | |
1104 | C<POSIX::islower()>, C<POSIX::isprint()>, C<POSIX::ispunct()>, | |
1105 | C<POSIX::isspace()>, C<POSIX::isupper()>, C<POSIX::isxdigit()>): | |
14280422 DD |
1106 | |
1107 | True/false results are never tainted. | |
1108 | ||
1109 | =back | |
1110 | ||
1111 | Three examples illustrate locale-dependent tainting. | |
1112 | The first program, which ignores its locale, won't run: a value taken | |
54310121 | 1113 | directly from the command line may not be used to name an output file |
14280422 DD |
1114 | when taint checks are enabled. |
1115 | ||
1116 | #/usr/local/bin/perl -T | |
1117 | # Run with taint checking | |
1118 | ||
54310121 | 1119 | # Command line sanity check omitted... |
14280422 DD |
1120 | $tainted_output_file = shift; |
1121 | ||
1122 | open(F, ">$tainted_output_file") | |
3183d96c | 1123 | or warn "Open of $tainted_output_file failed: $!\n"; |
14280422 DD |
1124 | |
1125 | The program can be made to run by "laundering" the tainted value through | |
5a964f20 TC |
1126 | a regular expression: the second example--which still ignores locale |
1127 | information--runs, creating the file named on its command line | |
14280422 DD |
1128 | if it can. |
1129 | ||
1130 | #/usr/local/bin/perl -T | |
1131 | ||
1132 | $tainted_output_file = shift; | |
1133 | $tainted_output_file =~ m%[\w/]+%; | |
1134 | $untainted_output_file = $&; | |
1135 | ||
1136 | open(F, ">$untainted_output_file") | |
1137 | or warn "Open of $untainted_output_file failed: $!\n"; | |
1138 | ||
5a964f20 | 1139 | Compare this with a similar but locale-aware program: |
14280422 DD |
1140 | |
1141 | #/usr/local/bin/perl -T | |
1142 | ||
1143 | $tainted_output_file = shift; | |
1144 | use locale; | |
1145 | $tainted_output_file =~ m%[\w/]+%; | |
1146 | $localized_output_file = $&; | |
1147 | ||
1148 | open(F, ">$localized_output_file") | |
1149 | or warn "Open of $localized_output_file failed: $!\n"; | |
1150 | ||
1d2ab946 | 1151 | This third program fails to run because C<$&> is tainted: it is the result |
5a964f20 | 1152 | of a match involving C<\w> while C<use locale> is in effect. |
5f05dabc | 1153 | |
1154 | =head1 ENVIRONMENT | |
1155 | ||
1156 | =over 12 | |
1157 | ||
ee1ec05f KW |
1158 | =item PERL_SKIP_LOCALE_INIT |
1159 | ||
1160 | This environment variable, available starting in Perl v5.20, and if it | |
1161 | evaluates to a TRUE value, tells Perl to not use the rest of the | |
1162 | environment variables to initialize with. Instead, Perl uses whatever | |
1163 | the current locale settings are. This is particularly useful in | |
1164 | embedded environments, see | |
1165 | L<perlembed/Using embedded Perl with POSIX locales>. | |
1166 | ||
5f05dabc | 1167 | =item PERL_BADLANG |
1168 | ||
14280422 | 1169 | A string that can suppress Perl's warning about failed locale settings |
54310121 | 1170 | at startup. Failure can occur if the locale support in the operating |
5a964f20 | 1171 | system is lacking (broken) in some way--or if you mistyped the name of |
900bd440 JH |
1172 | a locale when you set up your environment. If this environment |
1173 | variable is absent, or has a value that does not evaluate to integer | |
1174 | zero--that is, "0" or ""-- Perl will complain about locale setting | |
1175 | failures. | |
5f05dabc | 1176 | |
cb88b78e | 1177 | B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message. |
14280422 DD |
1178 | The message tells about some problem in your system's locale support, |
1179 | and you should investigate what the problem is. | |
5f05dabc | 1180 | |
1181 | =back | |
1182 | ||
1183 | The following environment variables are not specific to Perl: They are | |
39332f68 | 1184 | part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method |
b385bb4d KW |
1185 | for controlling an application's opinion on data. Windows is non-POSIX, |
1186 | but Perl arranges for the following to work as described anyway. | |
65ebb059 KW |
1187 | If the locale given by an environment variable is not valid, Perl tries |
1188 | the next lower one in priority. If none are valid, on Windows, the | |
1189 | system default locale is then tried. If all else fails, the C<"C"> | |
1190 | locale is used. If even that doesn't work, something is badly broken, | |
c5e9a8e7 | 1191 | but Perl tries to forge ahead with whatever the locale settings might |
65ebb059 | 1192 | be. |
5f05dabc | 1193 | |
1194 | =over 12 | |
1195 | ||
cb88b78e | 1196 | =item C<LC_ALL> |
5f05dabc | 1197 | |
5a964f20 | 1198 | C<LC_ALL> is the "override-all" locale environment variable. If |
5f05dabc | 1199 | set, it overrides all the rest of the locale environment variables. |
1200 | ||
cb88b78e | 1201 | =item C<LANGUAGE> |
528d65ad JH |
1202 | |
1203 | B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you | |
1204 | are using the GNU libc. This is the case if you are using e.g. Linux. | |
e1020413 | 1205 | If you are using "commercial" Unixes you are most probably I<not> |
22b6f60d JH |
1206 | using GNU libc and you can ignore C<LANGUAGE>. |
1207 | ||
1208 | However, in the case you are using C<LANGUAGE>: it affects the | |
1209 | language of informational, warning, and error messages output by | |
1210 | commands (in other words, it's like C<LC_MESSAGES>) but it has higher | |
96090e4f | 1211 | priority than C<LC_ALL>. Moreover, it's not a single value but |
22b6f60d JH |
1212 | instead a "path" (":"-separated list) of I<languages> (not locales). |
1213 | See the GNU C<gettext> library documentation for more information. | |
528d65ad | 1214 | |
cb88b78e | 1215 | =item C<LC_CTYPE>. |
5f05dabc | 1216 | |
1217 | In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type | |
1218 | locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG> | |
1219 | chooses the character type locale. | |
1220 | ||
cb88b78e | 1221 | =item C<LC_COLLATE> |
5f05dabc | 1222 | |
14280422 DD |
1223 | In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation |
1224 | (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>, | |
1225 | C<LANG> chooses the collation locale. | |
5f05dabc | 1226 | |
cb88b78e | 1227 | =item C<LC_MONETARY> |
5f05dabc | 1228 | |
14280422 DD |
1229 | In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary |
1230 | formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>, | |
1231 | C<LANG> chooses the monetary formatting locale. | |
5f05dabc | 1232 | |
cb88b78e | 1233 | =item C<LC_NUMERIC> |
5f05dabc | 1234 | |
1235 | In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format | |
1236 | locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG> | |
1237 | chooses the numeric format. | |
1238 | ||
cb88b78e | 1239 | =item C<LC_TIME> |
5f05dabc | 1240 | |
14280422 DD |
1241 | In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time |
1242 | formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>, | |
1243 | C<LANG> chooses the date and time formatting locale. | |
5f05dabc | 1244 | |
cb88b78e | 1245 | =item C<LANG> |
5f05dabc | 1246 | |
14280422 DD |
1247 | C<LANG> is the "catch-all" locale environment variable. If it is set, it |
1248 | is used as the last resort after the overall C<LC_ALL> and the | |
cb88b78e | 1249 | category-specific C<LC_I<foo>> |
5f05dabc | 1250 | |
1251 | =back | |
1252 | ||
7e4353e9 RGS |
1253 | =head2 Examples |
1254 | ||
cb88b78e | 1255 | The C<LC_NUMERIC> controls the numeric output: |
7e4353e9 | 1256 | |
ef3087ec KW |
1257 | use locale; |
1258 | use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants. | |
1259 | setlocale(LC_NUMERIC, "fr_FR") or die "Pardon"; | |
1260 | printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23. | |
7e4353e9 | 1261 | |
39332f68 | 1262 | and also how strings are parsed by C<POSIX::strtod()> as numbers: |
7e4353e9 | 1263 | |
ef3087ec KW |
1264 | use locale; |
1265 | use POSIX qw(locale_h strtod); | |
1266 | setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung"; | |
1267 | my $x = strtod("2,34") + 5; | |
1268 | print $x, "\n"; # Probably shows 7,34. | |
7e4353e9 | 1269 | |
5f05dabc | 1270 | =head1 NOTES |
1271 | ||
b960a36e KW |
1272 | =head2 String C<eval> and C<LC_NUMERIC> |
1273 | ||
1274 | A string L<eval|perlfunc/eval EXPR> parses its expression as standard | |
1275 | Perl. It is therefore expecting the decimal point to be a dot. If | |
1276 | C<LC_NUMERIC> is set to have this be a comma instead, the parsing will | |
1277 | be confused, perhaps silently. | |
1278 | ||
1279 | use locale; | |
1280 | use POSIX qw(locale_h); | |
1281 | setlocale(LC_NUMERIC, "fr_FR") or die "Pardon"; | |
1282 | my $a = 1.2; | |
1283 | print eval "$a + 1.5"; | |
1284 | print "\n"; | |
1285 | ||
1286 | prints C<13,5>. This is because in that locale, the comma is the | |
1287 | decimal point character. The C<eval> thus expands to: | |
1288 | ||
1289 | eval "1,2 + 1.5" | |
1290 | ||
1291 | and the result is not what you likely expected. No warnings are | |
1292 | generated. If you do string C<eval>'s within the scope of | |
1293 | S<C<use locale>>, you should instead change the C<eval> line to do | |
1294 | something like: | |
1295 | ||
1296 | print eval "no locale; $a + 1.5"; | |
1297 | ||
1298 | This prints C<2.7>. | |
1299 | ||
d6ded950 KW |
1300 | You could also exclude C<LC_NUMERIC>, if you don't need it, by |
1301 | ||
1302 | use locale ':!numeric'; | |
1303 | ||
5f05dabc | 1304 | =head2 Backward compatibility |
1305 | ||
b0c42ed9 | 1306 | Versions of Perl prior to 5.004 B<mostly> ignored locale information, |
5a964f20 TC |
1307 | generally behaving as if something similar to the C<"C"> locale were |
1308 | always in force, even if the program environment suggested otherwise | |
1309 | (see L<The setlocale function>). By default, Perl still behaves this | |
1310 | way for backward compatibility. If you want a Perl application to pay | |
1311 | attention to locale information, you B<must> use the S<C<use locale>> | |
d6ded950 | 1312 | pragma (see L<The "use locale" pragma>) or, in the unlikely event |
062ca197 | 1313 | that you want to do so for just pattern matching, the |
70709c68 KW |
1314 | C</l> regular expression modifier (see L<perlre/Character set |
1315 | modifiers>) to instruct it to do so. | |
b0c42ed9 JH |
1316 | |
1317 | Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE> | |
5a964f20 TC |
1318 | information if available; that is, C<\w> did understand what |
1319 | were the letters according to the locale environment variables. | |
b0c42ed9 JH |
1320 | The problem was that the user had no control over the feature: |
1321 | if the C library supported locales, Perl used them. | |
1322 | ||
1323 | =head2 I18N:Collate obsolete | |
1324 | ||
5a964f20 | 1325 | In versions of Perl prior to 5.004, per-locale collation was possible |
b0c42ed9 JH |
1326 | using the C<I18N::Collate> library module. This module is now mildly |
1327 | obsolete and should be avoided in new applications. The C<LC_COLLATE> | |
1328 | functionality is now integrated into the Perl core language: One can | |
1329 | use locale-specific scalar data completely normally with C<use locale>, | |
1330 | so there is no longer any need to juggle with the scalar references of | |
1331 | C<I18N::Collate>. | |
5f05dabc | 1332 | |
14280422 | 1333 | =head2 Sort speed and memory use impacts |
5f05dabc | 1334 | |
1335 | Comparing and sorting by locale is usually slower than the default | |
14280422 DD |
1336 | sorting; slow-downs of two to four times have been observed. It will |
1337 | also consume more memory: once a Perl scalar variable has participated | |
1338 | in any string comparison or sorting operation obeying the locale | |
1339 | collation rules, it will take 3-15 times more memory than before. (The | |
1340 | exact multiplier depends on the string's contents, the operating system | |
1341 | and the locale.) These downsides are dictated more by the operating | |
1342 | system's implementation of the locale system than by Perl. | |
5f05dabc | 1343 | |
5f05dabc | 1344 | =head2 Freely available locale definitions |
1345 | ||
66cbab2c KW |
1346 | The Unicode CLDR project extracts the POSIX portion of many of its |
1347 | locales, available at | |
1348 | ||
1349 | http://unicode.org/Public/cldr/latest/ | |
1350 | ||
08d7a6b2 LB |
1351 | There is a large collection of locale definitions at: |
1352 | ||
1353 | http://std.dkuug.dk/i18n/WG15-collection/locales/ | |
1354 | ||
1355 | You should be aware that it is | |
14280422 | 1356 | unsupported, and is not claimed to be fit for any purpose. If your |
5a964f20 | 1357 | system allows installation of arbitrary locales, you may find the |
14280422 DD |
1358 | definitions useful as they are, or as a basis for the development of |
1359 | your own locales. | |
5f05dabc | 1360 | |
14280422 | 1361 | =head2 I18n and l10n |
5f05dabc | 1362 | |
b0c42ed9 JH |
1363 | "Internationalization" is often abbreviated as B<i18n> because its first |
1364 | and last letters are separated by eighteen others. (You may guess why | |
1365 | the internalin ... internaliti ... i18n tends to get abbreviated.) In | |
1366 | the same way, "localization" is often abbreviated to B<l10n>. | |
14280422 DD |
1367 | |
1368 | =head2 An imperfect standard | |
1369 | ||
1370 | Internationalization, as defined in the C and POSIX standards, can be | |
1371 | criticized as incomplete, ungainly, and having too large a granularity. | |
1372 | (Locales apply to a whole process, when it would arguably be more useful | |
1373 | to have them apply to a single thread, window group, or whatever.) They | |
1374 | also have a tendency, like standards groups, to divide the world into | |
1375 | nations, when we all know that the world can equally well be divided | |
e199995e | 1376 | into bankers, bikers, gamers, and so on. |
5f05dabc | 1377 | |
b310b053 JH |
1378 | =head1 Unicode and UTF-8 |
1379 | ||
7ee2ae1e | 1380 | The support of Unicode is new starting from Perl version v5.6, and more fully |
31f05a37 KW |
1381 | implemented in versions v5.8 and later. See L<perluniintro>. |
1382 | ||
1383 | Starting in Perl v5.20, UTF-8 locales are supported in Perl, except for | |
1384 | C<LC_COLLATE> (use L<Unicode::Collate> instead). If you have Perl v5.16 | |
1385 | or v5.18 and can't upgrade, you can use | |
66cbab2c KW |
1386 | |
1387 | use locale ':not_characters'; | |
1388 | ||
1389 | When this form of the pragma is used, only the non-character portions of | |
1390 | locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that | |
1391 | you have translated all the characters it is to operate on into Unicode | |
1392 | (actually the platform's native character set (ASCII or EBCDIC) plus | |
1393 | Unicode). For data in files, this can conveniently be done by also | |
1394 | specifying | |
1395 | ||
1396 | use open ':locale'; | |
1397 | ||
1398 | This pragma arranges for all inputs from files to be translated into | |
1399 | Unicode from the current locale as specified in the environment (see | |
1400 | L</ENVIRONMENT>), and all outputs to files to be translated back | |
1401 | into the locale. (See L<open>). On a per-filehandle basis, you can | |
1402 | instead use the L<PerlIO::locale> module, or the L<Encode::Locale> | |
1403 | module, both available from CPAN. The latter module also has methods to | |
1404 | ease the handling of C<ARGV> and environment variables, and can be used | |
31f05a37 | 1405 | on individual strings. If you know that all your locales will be |
66cbab2c KW |
1406 | UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C> |
1407 | command line switch. | |
1408 | ||
1409 | This form of the pragma allows essentially seamless handling of locales | |
31f05a37 KW |
1410 | with Unicode. The collation order will be by Unicode code point order. |
1411 | It is strongly | |
66cbab2c KW |
1412 | recommended that when you need to order and sort strings that you use |
1413 | the standard module L<Unicode::Collate> which gives much better results | |
1414 | in many instances than you can get with the old-style locale handling. | |
1415 | ||
31f05a37 KW |
1416 | All the modules and switches just described can be used in v5.20 with |
1417 | just plain C<use locale>, and, should the input locales not be UTF-8, | |
1418 | you'll get the less than ideal behavior, described below, that you get | |
1419 | with pre-v5.16 Perls, or when you use the locale pragma without the | |
1420 | C<:not_characters> parameter in v5.16 and v5.18. If you are using | |
1421 | exclusively UTF-8 locales in v5.20 and higher, the rest of this section | |
1422 | does not apply to you. | |
1423 | ||
1424 | There are two cases, multi-byte and single-byte locales. First | |
1425 | multi-byte: | |
1426 | ||
1427 | The only multi-byte (or wide character) locale that Perl is ever likely | |
1428 | to support is UTF-8. This is due to the difficulty of implementation, | |
1429 | the fact that high quality UTF-8 locales are now published for every | |
1430 | area of the world (L<http://unicode.org/Public/cldr/latest/>), and that | |
1431 | failing all that you can use the L<Encode> module to translate to/from | |
1432 | your locale. So, you'll have to do one of those things if you're using | |
1433 | one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in | |
1434 | Perls (pre v5.20) that don't have full UTF-8 locale support, they may | |
1435 | work reasonably well (depending on your C library implementation) | |
1436 | simply because both | |
dc4bfc4b KW |
1437 | they and Perl store characters that take up multiple bytes the same way. |
1438 | However, some, if not most, C library implementations may not process | |
1439 | the characters in the upper half of the Latin-1 range (128 - 255) | |
cb88b78e | 1440 | properly under C<LC_CTYPE>. To see if a character is a particular type |
dc4bfc4b KW |
1441 | under a locale, Perl uses the functions like C<isalnum()>. Your C |
1442 | library may not work for UTF-8 locales with those functions, instead | |
1443 | only working under the newer wide library functions like C<iswalnum()>. | |
31f05a37 KW |
1444 | However, they are treated like single-byte locales, and will have the |
1445 | restrictions described below. | |
e199995e | 1446 | |
31f05a37 | 1447 | For single-byte locales, |
e199995e | 1448 | Perl generally takes the tack to use locale rules on code points that can fit |
66cbab2c KW |
1449 | in a single byte, and Unicode rules for those that can't (though this |
1450 | isn't uniformly applied, see the note at the end of this section). This | |
1451 | prevents many problems in locales that aren't UTF-8. Suppose the locale | |
1452 | is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But | |
1453 | in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX | |
1454 | regular expression character class C<[[:alpha:]]> will magically match | |
1455 | 0xD7 in the Greek locale but not in the Latin one. | |
e199995e | 1456 | |
1d2ab946 | 1457 | However, there are places where this breaks down. Certain Perl constructs are |
b4ffc3db TC |
1458 | for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its |
1459 | Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a | |
1460 | subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and | |
1461 | Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar | |
31f05a37 KW |
1462 | issue occurs with C<\N{...}>. Prior to v5.20, It is therefore a bad |
1463 | idea to use C<\p{}> or | |
66cbab2c KW |
1464 | C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the |
1465 | locale will be a ISO8859-1. Use POSIX character classes instead. | |
1466 | ||
1467 | Another problem with this approach is that operations that cross the | |
1468 | single byte/multiple byte boundary are not well-defined, and so are | |
4a70680a | 1469 | disallowed. (This boundary is between the codepoints at 255/256.) |
66cbab2c KW |
1470 | For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178) |
1471 | should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the | |
1472 | Greek locale, for example, there is no character at 0xFF, and Perl | |
1473 | has no way of knowing what the character at 0xFF is really supposed to | |
1474 | represent. Thus it disallows the operation. In this mode, the | |
1475 | lowercase of U+0178 is itself. | |
1476 | ||
1477 | The same problems ensue if you enable automatic UTF-8-ification of your | |
e199995e | 1478 | standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1, |
b4ffc3db TC |
1479 | non-UTF-8 locales (by using either the B<-C> command line switch or the |
1480 | C<PERL_UNICODE> environment variable; see L<perlrun>). | |
1481 | Things are read in as UTF-8, which would normally imply a Unicode | |
1482 | interpretation, but the presence of a locale causes them to be interpreted | |
1483 | in that locale instead. For example, a 0xD7 code point in the Unicode | |
1484 | input, which should mean the multiplication sign, won't be interpreted by | |
66cbab2c | 1485 | Perl that way under the Greek locale. This is not a problem |
b4ffc3db | 1486 | I<provided> you make certain that all locales will always and only be either |
66cbab2c | 1487 | an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale. |
b4ffc3db | 1488 | |
1d2ab946 KW |
1489 | Still another problem is that this approach can lead to two code |
1490 | points meaning the same character. Thus in a Greek locale, both U+03A7 | |
1491 | and U+00D7 are GREEK CAPITAL LETTER CHI. | |
1492 | ||
b4ffc3db TC |
1493 | Vendor locales are notoriously buggy, and it is difficult for Perl to test |
1494 | its locale-handling code because this interacts with code that Perl has no | |
1495 | control over; therefore the locale-handling code in Perl may be buggy as | |
66cbab2c KW |
1496 | well. (However, the Unicode-supplied locales should be better, and |
1497 | there is a feed back mechanism to correct any problems. See | |
1498 | L</Freely available locale definitions>.) | |
1499 | ||
7ee2ae1e | 1500 | If you have Perl v5.16, the problems mentioned above go away if you use |
66cbab2c | 1501 | the C<:not_characters> parameter to the locale pragma (except for vendor |
7ee2ae1e | 1502 | bugs in the non-character portions). If you don't have v5.16, and you |
66cbab2c KW |
1503 | I<do> have locales that work, using them may be worthwhile for certain |
1504 | specific purposes, as long as you keep in mind the gotchas already | |
1505 | mentioned. For example, if the collation for your locales works, it | |
1506 | runs faster under locales than under L<Unicode::Collate>; and you gain | |
1507 | access to such things as the local currency symbol and the names of the | |
7ee2ae1e | 1508 | months and days of the week. (But to hammer home the point, in v5.16, |
66cbab2c KW |
1509 | you get this access without the downsides of locales by using the |
1510 | C<:not_characters> form of the pragma.) | |
1511 | ||
1512 | Note: The policy of using locale rules for code points that can fit in a | |
1513 | byte, and Unicode rules for those that can't is not uniformly applied. | |
7ee2ae1e | 1514 | Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly |
66cbab2c | 1515 | consistently to regular expression matching except for bracketed |
7ee2ae1e KW |
1516 | character classes; in v5.14 it was extended to all regex matches; and in |
1517 | v5.16 to the casing operations such as C<"\L"> and C<uc()>. For | |
66cbab2c KW |
1518 | collation, in all releases, the system's C<strxfrm()> function is called, |
1519 | and whatever it does is what you get. | |
b310b053 | 1520 | |
5f05dabc | 1521 | =head1 BUGS |
1522 | ||
1523 | =head2 Broken systems | |
1524 | ||
5a964f20 | 1525 | In certain systems, the operating system's locale support |
2bdf8add | 1526 | is broken and cannot be fixed or used by Perl. Such deficiencies can |
b4ffc3db | 1527 | and will result in mysterious hangs and/or Perl core dumps when |
2bdf8add | 1528 | C<use locale> is in effect. When confronted with such a system, |
7f2de2d2 | 1529 | please report in excruciating detail to <F<perlbug@perl.org>>, and |
b4ffc3db | 1530 | also contact your vendor: bug fixes may exist for these problems |
2bdf8add | 1531 | in your operating system. Sometimes such bug fixes are called an |
83fb1bf0 KW |
1532 | operating system upgrade. If you have the source for Perl, include in |
1533 | the perlbug email the output of the test described above in L</Testing | |
1534 | for broken locales>. | |
5f05dabc | 1535 | |
1536 | =head1 SEE ALSO | |
1537 | ||
b310b053 JH |
1538 | L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>, |
1539 | L<POSIX/isalnum>, L<POSIX/isalpha>, | |
4bbcc6e8 JH |
1540 | L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>, |
1541 | L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>, | |
1542 | L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>, | |
1543 | L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>, | |
1544 | L<POSIX/strtod>, L<POSIX/strxfrm>. | |
5f05dabc | 1545 | |
ccd65d51 KW |
1546 | For special considerations when Perl is embedded in a C program, |
1547 | see L<perlembed/Using embedded Perl with POSIX locales>. | |
1548 | ||
5f05dabc | 1549 | =head1 HISTORY |
1550 | ||
b0c42ed9 | 1551 | Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic |
5a964f20 | 1552 | Dunlop, assisted by the perl5-porters. Prose worked over a bit by |
c052850d | 1553 | Tom Christiansen, and updated by Perl 5 porters. |