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1 | =head1 NAME |
2 | ||
3 | perllocale - Perl locale handling (internationalization and localization) | |
4 | ||
5 | =head1 DESCRIPTION | |
6 | ||
7 | Perl supports language-specific notions of data such as "is this | |
8 | a letter", "what is the uppercase equivalent of this letter", and | |
9 | "which of these letters comes first". These are important issues, | |
10 | especially for languages other than English--but also for English: it | |
11 | would be naE<iuml>ve to imagine that C<A-Za-z> defines all the "letters" | |
12 | needed to write in English. Perl is also aware that some character other | |
13 | than '.' may be preferred as a decimal point, and that output date | |
14 | representations may be language-specific. The process of making an | |
15 | application take account of its users' preferences in such matters is | |
16 | called B<internationalization> (often abbreviated as B<i18n>); telling | |
17 | such an application about a particular set of preferences is known as | |
18 | B<localization> (B<l10n>). | |
19 | ||
20 | Perl can understand language-specific data via the standardized (ISO C, | |
21 | XPG4, POSIX 1.c) method called "the locale system". The locale system is | |
22 | controlled per application using one pragma, one function call, and | |
23 | several environment variables. | |
24 | ||
25 | B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an | |
26 | application specifically requests it--see L<Backward compatibility>. | |
27 | The one exception is that write() now B<always> uses the current locale | |
28 | - see L<"NOTES">. | |
29 | ||
30 | =head1 PREPARING TO USE LOCALES | |
31 | ||
32 | If Perl applications are to understand and present your data | |
33 | correctly according a locale of your choice, B<all> of the following | |
34 | must be true: | |
35 | ||
36 | =over 4 | |
37 | ||
38 | =item * | |
39 | ||
40 | B<Your operating system must support the locale system>. If it does, | |
41 | you should find that the setlocale() function is a documented part of | |
42 | its C library. | |
43 | ||
44 | =item * | |
45 | ||
46 | B<Definitions for locales that you use must be installed>. You, or | |
47 | your system administrator, must make sure that this is the case. The | |
48 | available locales, the location in which they are kept, and the manner | |
49 | in which they are installed all vary from system to system. Some systems | |
50 | provide only a few, hard-wired locales and do not allow more to be | |
51 | added. Others allow you to add "canned" locales provided by the system | |
52 | supplier. Still others allow you or the system administrator to define | |
53 | and add arbitrary locales. (You may have to ask your supplier to | |
54 | provide canned locales that are not delivered with your operating | |
55 | system.) Read your system documentation for further illumination. | |
56 | ||
57 | =item * | |
58 | ||
59 | B<Perl must believe that the locale system is supported>. If it does, | |
60 | C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is | |
61 | C<define>. | |
62 | ||
63 | =back | |
64 | ||
65 | If you want a Perl application to process and present your data | |
66 | according to a particular locale, the application code should include | |
67 | the S<C<use locale>> pragma (see L<The use locale pragma>) where | |
68 | appropriate, and B<at least one> of the following must be true: | |
69 | ||
70 | =over 4 | |
71 | ||
72 | =item * | |
73 | ||
74 | B<The locale-determining environment variables (see L<"ENVIRONMENT">) | |
75 | must be correctly set up> at the time the application is started, either | |
76 | by yourself or by whoever set up your system account. | |
77 | ||
78 | =item * | |
79 | ||
80 | B<The application must set its own locale> using the method described in | |
81 | L<The setlocale function>. | |
82 | ||
83 | =back | |
84 | ||
85 | =head1 USING LOCALES | |
86 | ||
87 | =head2 The use locale pragma | |
88 | ||
89 | By default, Perl ignores the current locale. The S<C<use locale>> | |
90 | pragma tells Perl to use the current locale for some operations: | |
91 | ||
92 | =over 4 | |
93 | ||
94 | =item * | |
95 | ||
96 | B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) and | |
97 | the POSIX string collation functions strcoll() and strxfrm() use | |
98 | C<LC_COLLATE>. sort() is also affected if used without an | |
99 | explicit comparison function, because it uses C<cmp> by default. | |
100 | ||
101 | B<Note:> C<eq> and C<ne> are unaffected by locale: they always | |
102 | perform a char-by-char comparison of their scalar operands. What's | |
103 | more, if C<cmp> finds that its operands are equal according to the | |
104 | collation sequence specified by the current locale, it goes on to | |
105 | perform a char-by-char comparison, and only returns I<0> (equal) if the | |
106 | operands are char-for-char identical. If you really want to know whether | |
107 | two strings--which C<eq> and C<cmp> may consider different--are equal | |
108 | as far as collation in the locale is concerned, see the discussion in | |
109 | L<Category LC_COLLATE: Collation>. | |
110 | ||
111 | =item * | |
112 | ||
113 | B<Regular expressions and case-modification functions> (uc(), lc(), | |
114 | ucfirst(), and lcfirst()) use C<LC_CTYPE> | |
115 | ||
116 | =item * | |
117 | ||
118 | B<The formatting functions> (printf(), sprintf() and write()) use | |
119 | C<LC_NUMERIC> | |
120 | ||
121 | =item * | |
122 | ||
123 | B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>. | |
124 | ||
125 | =back | |
126 | ||
127 | C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in | |
128 | L<LOCALE CATEGORIES>. | |
129 | ||
130 | The default behavior is restored with the S<C<no locale>> pragma, or | |
131 | upon reaching the end of block enclosing C<use locale>. | |
132 | ||
133 | The string result of any operation that uses locale | |
134 | information is tainted, as it is possible for a locale to be | |
135 | untrustworthy. See L<"SECURITY">. | |
136 | ||
137 | =head2 The setlocale function | |
138 | ||
139 | You can switch locales as often as you wish at run time with the | |
140 | POSIX::setlocale() function: | |
141 | ||
142 | # This functionality not usable prior to Perl 5.004 | |
143 | require 5.004; | |
144 | ||
145 | # Import locale-handling tool set from POSIX module. | |
146 | # This example uses: setlocale -- the function call | |
147 | # LC_CTYPE -- explained below | |
148 | use POSIX qw(locale_h); | |
149 | ||
150 | # query and save the old locale | |
151 | $old_locale = setlocale(LC_CTYPE); | |
152 | ||
153 | setlocale(LC_CTYPE, "fr_CA.ISO8859-1"); | |
154 | # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1" | |
155 | ||
156 | setlocale(LC_CTYPE, ""); | |
157 | # LC_CTYPE now reset to default defined by LC_ALL/LC_CTYPE/LANG | |
158 | # environment variables. See below for documentation. | |
159 | ||
160 | # restore the old locale | |
161 | setlocale(LC_CTYPE, $old_locale); | |
162 | ||
163 | The first argument of setlocale() gives the B<category>, the second the | |
164 | B<locale>. The category tells in what aspect of data processing you | |
165 | want to apply locale-specific rules. Category names are discussed in | |
166 | L<LOCALE CATEGORIES> and L<"ENVIRONMENT">. The locale is the name of a | |
167 | collection of customization information corresponding to a particular | |
168 | combination of language, country or territory, and codeset. Read on for | |
169 | hints on the naming of locales: not all systems name locales as in the | |
170 | example. | |
171 | ||
172 | If no second argument is provided and the category is something else | |
173 | than LC_ALL, the function returns a string naming the current locale | |
174 | for the category. You can use this value as the second argument in a | |
175 | subsequent call to setlocale(). | |
176 | ||
177 | If no second argument is provided and the category is LC_ALL, the | |
178 | result is implementation-dependent. It may be a string of | |
179 | concatenated locales names (separator also implementation-dependent) | |
180 | or a single locale name. Please consult your L<setlocale(3)> for | |
181 | details. | |
182 | ||
183 | If a second argument is given and it corresponds to a valid locale, | |
184 | the locale for the category is set to that value, and the function | |
185 | returns the now-current locale value. You can then use this in yet | |
186 | another call to setlocale(). (In some implementations, the return | |
187 | value may sometimes differ from the value you gave as the second | |
188 | argument--think of it as an alias for the value you gave.) | |
189 | ||
190 | As the example shows, if the second argument is an empty string, the | |
191 | category's locale is returned to the default specified by the | |
192 | corresponding environment variables. Generally, this results in a | |
193 | return to the default that was in force when Perl started up: changes | |
194 | to the environment made by the application after startup may or may not | |
195 | be noticed, depending on your system's C library. | |
196 | ||
197 | If the second argument does not correspond to a valid locale, the locale | |
198 | for the category is not changed, and the function returns I<undef>. | |
199 | ||
200 | For further information about the categories, consult L<setlocale(3)>. | |
201 | ||
202 | =head2 Finding locales | |
203 | ||
204 | For locales available in your system, consult also L<setlocale(3)> to | |
205 | see whether it leads to the list of available locales (search for the | |
206 | I<SEE ALSO> section). If that fails, try the following command lines: | |
207 | ||
208 | locale -a | |
209 | ||
210 | nlsinfo | |
211 | ||
212 | ls /usr/lib/nls/loc | |
213 | ||
214 | ls /usr/lib/locale | |
215 | ||
216 | ls /usr/lib/nls | |
217 | ||
218 | ls /usr/share/locale | |
219 | ||
220 | and see whether they list something resembling these | |
221 | ||
222 | en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5 | |
223 | en_US.iso88591 de_DE.iso88591 ru_RU.iso88595 | |
224 | en_US de_DE ru_RU | |
225 | en de ru | |
226 | english german russian | |
227 | english.iso88591 german.iso88591 russian.iso88595 | |
228 | english.roman8 russian.koi8r | |
229 | ||
230 | Sadly, even though the calling interface for setlocale() has been | |
231 | standardized, names of locales and the directories where the | |
232 | configuration resides have not been. The basic form of the name is | |
233 | I<language_territory>B<.>I<codeset>, but the latter parts after | |
234 | I<language> are not always present. The I<language> and I<country> | |
235 | are usually from the standards B<ISO 3166> and B<ISO 639>, the | |
236 | two-letter abbreviations for the countries and the languages of the | |
237 | world, respectively. The I<codeset> part often mentions some B<ISO | |
238 | 8859> character set, the Latin codesets. For example, C<ISO 8859-1> | |
239 | is the so-called "Western European codeset" that can be used to encode | |
240 | most Western European languages adequately. Again, there are several | |
241 | ways to write even the name of that one standard. Lamentably. | |
242 | ||
243 | Two special locales are worth particular mention: "C" and "POSIX". | |
244 | Currently these are effectively the same locale: the difference is | |
245 | mainly that the first one is defined by the C standard, the second by | |
246 | the POSIX standard. They define the B<default locale> in which | |
247 | every program starts in the absence of locale information in its | |
248 | environment. (The I<default> default locale, if you will.) Its language | |
249 | is (American) English and its character codeset ASCII. | |
250 | ||
251 | B<NOTE>: Not all systems have the "POSIX" locale (not all systems are | |
252 | POSIX-conformant), so use "C" when you need explicitly to specify this | |
253 | default locale. | |
254 | ||
255 | =head2 LOCALE PROBLEMS | |
256 | ||
257 | You may encounter the following warning message at Perl startup: | |
258 | ||
259 | perl: warning: Setting locale failed. | |
260 | perl: warning: Please check that your locale settings: | |
261 | LC_ALL = "En_US", | |
262 | LANG = (unset) | |
263 | are supported and installed on your system. | |
264 | perl: warning: Falling back to the standard locale ("C"). | |
265 | ||
266 | This means that your locale settings had LC_ALL set to "En_US" and | |
267 | LANG exists but has no value. Perl tried to believe you but could not. | |
268 | Instead, Perl gave up and fell back to the "C" locale, the default locale | |
269 | that is supposed to work no matter what. This usually means your locale | |
270 | settings were wrong, they mention locales your system has never heard | |
271 | of, or the locale installation in your system has problems (for example, | |
272 | some system files are broken or missing). There are quick and temporary | |
273 | fixes to these problems, as well as more thorough and lasting fixes. | |
274 | ||
275 | =head2 Temporarily fixing locale problems | |
276 | ||
277 | The two quickest fixes are either to render Perl silent about any | |
278 | locale inconsistencies or to run Perl under the default locale "C". | |
279 | ||
280 | Perl's moaning about locale problems can be silenced by setting the | |
281 | environment variable PERL_BADLANG to a zero value, for example "0". | |
282 | This method really just sweeps the problem under the carpet: you tell | |
283 | Perl to shut up even when Perl sees that something is wrong. Do not | |
284 | be surprised if later something locale-dependent misbehaves. | |
285 | ||
286 | Perl can be run under the "C" locale by setting the environment | |
287 | variable LC_ALL to "C". This method is perhaps a bit more civilized | |
288 | than the PERL_BADLANG approach, but setting LC_ALL (or | |
289 | other locale variables) may affect other programs as well, not just | |
290 | Perl. In particular, external programs run from within Perl will see | |
291 | these changes. If you make the new settings permanent (read on), all | |
292 | programs you run see the changes. See L<ENVIRONMENT> for | |
293 | the full list of relevant environment variables and L<USING LOCALES> | |
294 | for their effects in Perl. Effects in other programs are | |
295 | easily deducible. For example, the variable LC_COLLATE may well affect | |
296 | your B<sort> program (or whatever the program that arranges "records" | |
297 | alphabetically in your system is called). | |
298 | ||
299 | You can test out changing these variables temporarily, and if the | |
300 | new settings seem to help, put those settings into your shell startup | |
301 | files. Consult your local documentation for the exact details. For in | |
302 | Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>): | |
303 | ||
304 | LC_ALL=en_US.ISO8859-1 | |
305 | export LC_ALL | |
306 | ||
307 | This assumes that we saw the locale "en_US.ISO8859-1" using the commands | |
308 | discussed above. We decided to try that instead of the above faulty | |
309 | locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>) | |
310 | ||
311 | setenv LC_ALL en_US.ISO8859-1 | |
312 | ||
313 | or if you have the "env" application you can do in any shell | |
314 | ||
315 | env LC_ALL=en_US.ISO8859-1 perl ... | |
316 | ||
317 | If you do not know what shell you have, consult your local | |
318 | helpdesk or the equivalent. | |
319 | ||
320 | =head2 Permanently fixing locale problems | |
321 | ||
322 | The slower but superior fixes are when you may be able to yourself | |
323 | fix the misconfiguration of your own environment variables. The | |
324 | mis(sing)configuration of the whole system's locales usually requires | |
325 | the help of your friendly system administrator. | |
326 | ||
327 | First, see earlier in this document about L<Finding locales>. That tells | |
328 | how to find which locales are really supported--and more importantly, | |
329 | installed--on your system. In our example error message, environment | |
330 | variables affecting the locale are listed in the order of decreasing | |
331 | importance (and unset variables do not matter). Therefore, having | |
332 | LC_ALL set to "En_US" must have been the bad choice, as shown by the | |
333 | error message. First try fixing locale settings listed first. | |
334 | ||
335 | Second, if using the listed commands you see something B<exactly> | |
336 | (prefix matches do not count and case usually counts) like "En_US" | |
337 | without the quotes, then you should be okay because you are using a | |
338 | locale name that should be installed and available in your system. | |
339 | In this case, see L<Permanently fixing your system's locale configuration>. | |
340 | ||
341 | =head2 Permanently fixing your system's locale configuration | |
342 | ||
343 | This is when you see something like: | |
344 | ||
345 | perl: warning: Please check that your locale settings: | |
346 | LC_ALL = "En_US", | |
347 | LANG = (unset) | |
348 | are supported and installed on your system. | |
349 | ||
350 | but then cannot see that "En_US" listed by the above-mentioned | |
351 | commands. You may see things like "en_US.ISO8859-1", but that isn't | |
352 | the same. In this case, try running under a locale | |
353 | that you can list and which somehow matches what you tried. The | |
354 | rules for matching locale names are a bit vague because | |
355 | standardization is weak in this area. See again the | |
356 | L<Finding locales> about general rules. | |
357 | ||
358 | =head2 Fixing system locale configuration | |
359 | ||
360 | Contact a system administrator (preferably your own) and report the exact | |
361 | error message you get, and ask them to read this same documentation you | |
362 | are now reading. They should be able to check whether there is something | |
363 | wrong with the locale configuration of the system. The L<Finding locales> | |
364 | section is unfortunately a bit vague about the exact commands and places | |
365 | because these things are not that standardized. | |
366 | ||
367 | =head2 The localeconv function | |
368 | ||
369 | The POSIX::localeconv() function allows you to get particulars of the | |
370 | locale-dependent numeric formatting information specified by the current | |
371 | C<LC_NUMERIC> and C<LC_MONETARY> locales. (If you just want the name of | |
372 | the current locale for a particular category, use POSIX::setlocale() | |
373 | with a single parameter--see L<The setlocale function>.) | |
374 | ||
375 | use POSIX qw(locale_h); | |
376 | ||
377 | # Get a reference to a hash of locale-dependent info | |
378 | $locale_values = localeconv(); | |
379 | ||
380 | # Output sorted list of the values | |
381 | for (sort keys %$locale_values) { | |
382 | printf "%-20s = %s\n", $_, $locale_values->{$_} | |
383 | } | |
384 | ||
385 | localeconv() takes no arguments, and returns B<a reference to> a hash. | |
386 | The keys of this hash are variable names for formatting, such as | |
387 | C<decimal_point> and C<thousands_sep>. The values are the | |
388 | corresponding, er, values. See L<POSIX/localeconv> for a longer | |
389 | example listing the categories an implementation might be expected to | |
390 | provide; some provide more and others fewer. You don't need an | |
391 | explicit C<use locale>, because localeconv() always observes the | |
392 | current locale. | |
393 | ||
394 | Here's a simple-minded example program that rewrites its command-line | |
395 | parameters as integers correctly formatted in the current locale: | |
396 | ||
397 | # See comments in previous example | |
398 | require 5.004; | |
399 | use POSIX qw(locale_h); | |
400 | ||
401 | # Get some of locale's numeric formatting parameters | |
402 | my ($thousands_sep, $grouping) = | |
403 | @{localeconv()}{'thousands_sep', 'grouping'}; | |
404 | ||
405 | # Apply defaults if values are missing | |
406 | $thousands_sep = ',' unless $thousands_sep; | |
407 | ||
408 | # grouping and mon_grouping are packed lists | |
409 | # of small integers (characters) telling the | |
410 | # grouping (thousand_seps and mon_thousand_seps | |
411 | # being the group dividers) of numbers and | |
412 | # monetary quantities. The integers' meanings: | |
413 | # 255 means no more grouping, 0 means repeat | |
414 | # the previous grouping, 1-254 means use that | |
415 | # as the current grouping. Grouping goes from | |
416 | # right to left (low to high digits). In the | |
417 | # below we cheat slightly by never using anything | |
418 | # else than the first grouping (whatever that is). | |
419 | if ($grouping) { | |
420 | @grouping = unpack("C*", $grouping); | |
421 | } else { | |
422 | @grouping = (3); | |
423 | } | |
424 | ||
425 | # Format command line params for current locale | |
426 | for (@ARGV) { | |
427 | $_ = int; # Chop non-integer part | |
428 | 1 while | |
429 | s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/; | |
430 | print "$_"; | |
431 | } | |
432 | print "\n"; | |
433 | ||
434 | =head2 I18N::Langinfo | |
435 | ||
436 | Another interface for querying locale-dependent information is the | |
437 | I18N::Langinfo::langinfo() function, available at least in UNIX-like | |
438 | systems and VMS. | |
439 | ||
440 | The following example will import the langinfo() function itself and | |
441 | three constants to be used as arguments to langinfo(): a constant for | |
442 | the abbreviated first day of the week (the numbering starts from | |
443 | Sunday = 1) and two more constants for the affirmative and negative | |
444 | answers for a yes/no question in the current locale. | |
445 | ||
446 | use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR); | |
447 | ||
448 | my ($abday_1, $yesstr, $nostr) = map { langinfo } qw(ABDAY_1 YESSTR NOSTR); | |
449 | ||
450 | print "$abday_1? [$yesstr/$nostr] "; | |
451 | ||
452 | In other words, in the "C" (or English) locale the above will probably | |
453 | print something like: | |
454 | ||
455 | Sun? [yes/no] | |
456 | ||
457 | See L<I18N::Langinfo> for more information. | |
458 | ||
459 | =head1 LOCALE CATEGORIES | |
460 | ||
461 | The following subsections describe basic locale categories. Beyond these, | |
462 | some combination categories allow manipulation of more than one | |
463 | basic category at a time. See L<"ENVIRONMENT"> for a discussion of these. | |
464 | ||
465 | =head2 Category LC_COLLATE: Collation | |
466 | ||
467 | In the scope of S<C<use locale>>, Perl looks to the C<LC_COLLATE> | |
468 | environment variable to determine the application's notions on collation | |
469 | (ordering) of characters. For example, 'b' follows 'a' in Latin | |
470 | alphabets, but where do 'E<aacute>' and 'E<aring>' belong? And while | |
471 | 'color' follows 'chocolate' in English, what about in Spanish? | |
472 | ||
473 | The following collations all make sense and you may meet any of them | |
474 | if you "use locale". | |
475 | ||
476 | A B C D E a b c d e | |
477 | A a B b C c D d E e | |
478 | a A b B c C d D e E | |
479 | a b c d e A B C D E | |
480 | ||
481 | Here is a code snippet to tell what "word" | |
482 | characters are in the current locale, in that locale's order: | |
483 | ||
484 | use locale; | |
485 | print +(sort grep /\w/, map { chr } 0..255), "\n"; | |
486 | ||
487 | Compare this with the characters that you see and their order if you | |
488 | state explicitly that the locale should be ignored: | |
489 | ||
490 | no locale; | |
491 | print +(sort grep /\w/, map { chr } 0..255), "\n"; | |
492 | ||
493 | This machine-native collation (which is what you get unless S<C<use | |
494 | locale>> has appeared earlier in the same block) must be used for | |
495 | sorting raw binary data, whereas the locale-dependent collation of the | |
496 | first example is useful for natural text. | |
497 | ||
498 | As noted in L<USING LOCALES>, C<cmp> compares according to the current | |
499 | collation locale when C<use locale> is in effect, but falls back to a | |
500 | char-by-char comparison for strings that the locale says are equal. You | |
501 | can use POSIX::strcoll() if you don't want this fall-back: | |
502 | ||
503 | use POSIX qw(strcoll); | |
504 | $equal_in_locale = | |
505 | !strcoll("space and case ignored", "SpaceAndCaseIgnored"); | |
506 | ||
507 | $equal_in_locale will be true if the collation locale specifies a | |
508 | dictionary-like ordering that ignores space characters completely and | |
509 | which folds case. | |
510 | ||
511 | If you have a single string that you want to check for "equality in | |
512 | locale" against several others, you might think you could gain a little | |
513 | efficiency by using POSIX::strxfrm() in conjunction with C<eq>: | |
514 | ||
515 | use POSIX qw(strxfrm); | |
516 | $xfrm_string = strxfrm("Mixed-case string"); | |
517 | print "locale collation ignores spaces\n" | |
518 | if $xfrm_string eq strxfrm("Mixed-casestring"); | |
519 | print "locale collation ignores hyphens\n" | |
520 | if $xfrm_string eq strxfrm("Mixedcase string"); | |
521 | print "locale collation ignores case\n" | |
522 | if $xfrm_string eq strxfrm("mixed-case string"); | |
523 | ||
524 | strxfrm() takes a string and maps it into a transformed string for use | |
525 | in char-by-char comparisons against other transformed strings during | |
526 | collation. "Under the hood", locale-affected Perl comparison operators | |
527 | call strxfrm() for both operands, then do a char-by-char | |
528 | comparison of the transformed strings. By calling strxfrm() explicitly | |
529 | and using a non locale-affected comparison, the example attempts to save | |
530 | a couple of transformations. But in fact, it doesn't save anything: Perl | |
531 | magic (see L<perlguts/Magic Variables>) creates the transformed version of a | |
532 | string the first time it's needed in a comparison, then keeps this version around | |
533 | in case it's needed again. An example rewritten the easy way with | |
534 | C<cmp> runs just about as fast. It also copes with null characters | |
535 | embedded in strings; if you call strxfrm() directly, it treats the first | |
536 | null it finds as a terminator. don't expect the transformed strings | |
537 | it produces to be portable across systems--or even from one revision | |
538 | of your operating system to the next. In short, don't call strxfrm() | |
539 | directly: let Perl do it for you. | |
540 | ||
541 | Note: C<use locale> isn't shown in some of these examples because it isn't | |
542 | needed: strcoll() and strxfrm() exist only to generate locale-dependent | |
543 | results, and so always obey the current C<LC_COLLATE> locale. | |
544 | ||
545 | =head2 Category LC_CTYPE: Character Types | |
546 | ||
547 | In the scope of S<C<use locale>>, Perl obeys the C<LC_CTYPE> locale | |
548 | setting. This controls the application's notion of which characters are | |
549 | alphabetic. This affects Perl's C<\w> regular expression metanotation, | |
550 | which stands for alphanumeric characters--that is, alphabetic, | |
551 | numeric, and including other special characters such as the underscore or | |
552 | hyphen. (Consult L<perlre> for more information about | |
553 | regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale | |
554 | setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and | |
555 | 'E<oslash>' may be understood as C<\w> characters. | |
556 | ||
557 | The C<LC_CTYPE> locale also provides the map used in transliterating | |
558 | characters between lower and uppercase. This affects the case-mapping | |
559 | functions--lc(), lcfirst, uc(), and ucfirst(); case-mapping | |
560 | interpolation with C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted strings | |
561 | and C<s///> substitutions; and case-independent regular expression | |
562 | pattern matching using the C<i> modifier. | |
563 | ||
564 | Finally, C<LC_CTYPE> affects the POSIX character-class test | |
565 | functions--isalpha(), islower(), and so on. For example, if you move | |
566 | from the "C" locale to a 7-bit Scandinavian one, you may find--possibly | |
567 | to your surprise--that "|" moves from the ispunct() class to isalpha(). | |
568 | ||
569 | B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result | |
570 | in clearly ineligible characters being considered to be alphanumeric by | |
571 | your application. For strict matching of (mundane) letters and | |
572 | digits--for example, in command strings--locale-aware applications | |
573 | should use C<\w> inside a C<no locale> block. See L<"SECURITY">. | |
574 | ||
575 | =head2 Category LC_NUMERIC: Numeric Formatting | |
576 | ||
577 | In the scope of S<C<use locale>>, Perl obeys the C<LC_NUMERIC> locale | |
578 | information, which controls an application's idea of how numbers should | |
579 | be formatted for human readability by the printf(), sprintf(), and | |
580 | write() functions. String-to-numeric conversion by the POSIX::strtod() | |
581 | function is also affected. In most implementations the only effect is to | |
582 | change the character used for the decimal point--perhaps from '.' to ','. | |
583 | These functions aren't aware of such niceties as thousands separation and | |
584 | so on. (See L<The localeconv function> if you care about these things.) | |
585 | ||
586 | Output produced by print() is also affected by the current locale: it | |
587 | depends on whether C<use locale> or C<no locale> is in effect, and | |
588 | corresponds to what you'd get from printf() in the "C" locale. The | |
589 | same is true for Perl's internal conversions between numeric and | |
590 | string formats: | |
591 | ||
592 | use POSIX qw(strtod); | |
593 | use locale; | |
594 | ||
595 | $n = 5/2; # Assign numeric 2.5 to $n | |
596 | ||
597 | $a = " $n"; # Locale-dependent conversion to string | |
598 | ||
599 | print "half five is $n\n"; # Locale-dependent output | |
600 | ||
601 | printf "half five is %g\n", $n; # Locale-dependent output | |
602 | ||
603 | print "DECIMAL POINT IS COMMA\n" | |
604 | if $n == (strtod("2,5"))[0]; # Locale-dependent conversion | |
605 | ||
606 | See also L<I18N::Langinfo> and C<RADIXCHAR>. | |
607 | ||
608 | =head2 Category LC_MONETARY: Formatting of monetary amounts | |
609 | ||
610 | The C standard defines the C<LC_MONETARY> category, but no function | |
611 | that is affected by its contents. (Those with experience of standards | |
612 | committees will recognize that the working group decided to punt on the | |
613 | issue.) Consequently, Perl takes no notice of it. If you really want | |
614 | to use C<LC_MONETARY>, you can query its contents--see | |
615 | L<The localeconv function>--and use the information that it returns in your | |
616 | application's own formatting of currency amounts. However, you may well | |
617 | find that the information, voluminous and complex though it may be, still | |
618 | does not quite meet your requirements: currency formatting is a hard nut | |
619 | to crack. | |
620 | ||
621 | See also L<I18N::Langinfo> and C<CRNCYSTR>. | |
622 | ||
623 | =head2 LC_TIME | |
624 | ||
625 | Output produced by POSIX::strftime(), which builds a formatted | |
626 | human-readable date/time string, is affected by the current C<LC_TIME> | |
627 | locale. Thus, in a French locale, the output produced by the C<%B> | |
628 | format element (full month name) for the first month of the year would | |
629 | be "janvier". Here's how to get a list of long month names in the | |
630 | current locale: | |
631 | ||
632 | use POSIX qw(strftime); | |
633 | for (0..11) { | |
634 | $long_month_name[$_] = | |
635 | strftime("%B", 0, 0, 0, 1, $_, 96); | |
636 | } | |
637 | ||
638 | Note: C<use locale> isn't needed in this example: as a function that | |
639 | exists only to generate locale-dependent results, strftime() always | |
640 | obeys the current C<LC_TIME> locale. | |
641 | ||
642 | See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>, | |
643 | C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>. | |
644 | ||
645 | =head2 Other categories | |
646 | ||
647 | The remaining locale category, C<LC_MESSAGES> (possibly supplemented | |
648 | by others in particular implementations) is not currently used by | |
649 | Perl--except possibly to affect the behavior of library functions | |
650 | called by extensions outside the standard Perl distribution and by the | |
651 | operating system and its utilities. Note especially that the string | |
652 | value of C<$!> and the error messages given by external utilities may | |
653 | be changed by C<LC_MESSAGES>. If you want to have portable error | |
654 | codes, use C<%!>. See L<Errno>. | |
655 | ||
656 | =head1 SECURITY | |
657 | ||
658 | Although the main discussion of Perl security issues can be found in | |
659 | L<perlsec>, a discussion of Perl's locale handling would be incomplete | |
660 | if it did not draw your attention to locale-dependent security issues. | |
661 | Locales--particularly on systems that allow unprivileged users to | |
662 | build their own locales--are untrustworthy. A malicious (or just plain | |
663 | broken) locale can make a locale-aware application give unexpected | |
664 | results. Here are a few possibilities: | |
665 | ||
666 | =over 4 | |
667 | ||
668 | =item * | |
669 | ||
670 | Regular expression checks for safe file names or mail addresses using | |
671 | C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that | |
672 | characters such as "E<gt>" and "|" are alphanumeric. | |
673 | ||
674 | =item * | |
675 | ||
676 | String interpolation with case-mapping, as in, say, C<$dest = | |
677 | "C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE | |
678 | case-mapping table is in effect. | |
679 | ||
680 | =item * | |
681 | ||
682 | A sneaky C<LC_COLLATE> locale could result in the names of students with | |
683 | "D" grades appearing ahead of those with "A"s. | |
684 | ||
685 | =item * | |
686 | ||
687 | An application that takes the trouble to use information in | |
688 | C<LC_MONETARY> may format debits as if they were credits and vice versa | |
689 | if that locale has been subverted. Or it might make payments in US | |
690 | dollars instead of Hong Kong dollars. | |
691 | ||
692 | =item * | |
693 | ||
694 | The date and day names in dates formatted by strftime() could be | |
695 | manipulated to advantage by a malicious user able to subvert the | |
696 | C<LC_DATE> locale. ("Look--it says I wasn't in the building on | |
697 | Sunday.") | |
698 | ||
699 | =back | |
700 | ||
701 | Such dangers are not peculiar to the locale system: any aspect of an | |
702 | application's environment which may be modified maliciously presents | |
703 | similar challenges. Similarly, they are not specific to Perl: any | |
704 | programming language that allows you to write programs that take | |
705 | account of their environment exposes you to these issues. | |
706 | ||
707 | Perl cannot protect you from all possibilities shown in the | |
708 | examples--there is no substitute for your own vigilance--but, when | |
709 | C<use locale> is in effect, Perl uses the tainting mechanism (see | |
710 | L<perlsec>) to mark string results that become locale-dependent, and | |
711 | which may be untrustworthy in consequence. Here is a summary of the | |
712 | tainting behavior of operators and functions that may be affected by | |
713 | the locale: | |
714 | ||
715 | =over 4 | |
716 | ||
717 | =item * | |
718 | ||
719 | B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>): | |
720 | ||
721 | Scalar true/false (or less/equal/greater) result is never tainted. | |
722 | ||
723 | =item * | |
724 | ||
725 | B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>) | |
726 | ||
727 | Result string containing interpolated material is tainted if | |
728 | C<use locale> is in effect. | |
729 | ||
730 | =item * | |
731 | ||
732 | B<Matching operator> (C<m//>): | |
733 | ||
734 | Scalar true/false result never tainted. | |
735 | ||
736 | Subpatterns, either delivered as a list-context result or as $1 etc. | |
737 | are tainted if C<use locale> is in effect, and the subpattern regular | |
738 | expression contains C<\w> (to match an alphanumeric character), C<\W> | |
739 | (non-alphanumeric character), C<\s> (whitespace character), or C<\S> | |
740 | (non whitespace character). The matched-pattern variable, $&, $` | |
741 | (pre-match), $' (post-match), and $+ (last match) are also tainted if | |
742 | C<use locale> is in effect and the regular expression contains C<\w>, | |
743 | C<\W>, C<\s>, or C<\S>. | |
744 | ||
745 | =item * | |
746 | ||
747 | B<Substitution operator> (C<s///>): | |
748 | ||
749 | Has the same behavior as the match operator. Also, the left | |
750 | operand of C<=~> becomes tainted when C<use locale> in effect | |
751 | if modified as a result of a substitution based on a regular | |
752 | expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of | |
753 | case-mapping with C<\l>, C<\L>,C<\u> or C<\U>. | |
754 | ||
755 | =item * | |
756 | ||
757 | B<Output formatting functions> (printf() and write()): | |
758 | ||
759 | Results are never tainted because otherwise even output from print, | |
760 | for example C<print(1/7)>, should be tainted if C<use locale> is in | |
761 | effect. | |
762 | ||
763 | =item * | |
764 | ||
765 | B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()): | |
766 | ||
767 | Results are tainted if C<use locale> is in effect. | |
768 | ||
769 | =item * | |
770 | ||
771 | B<POSIX locale-dependent functions> (localeconv(), strcoll(), | |
772 | strftime(), strxfrm()): | |
773 | ||
774 | Results are never tainted. | |
775 | ||
776 | =item * | |
777 | ||
778 | B<POSIX character class tests> (isalnum(), isalpha(), isdigit(), | |
779 | isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), | |
780 | isxdigit()): | |
781 | ||
782 | True/false results are never tainted. | |
783 | ||
784 | =back | |
785 | ||
786 | Three examples illustrate locale-dependent tainting. | |
787 | The first program, which ignores its locale, won't run: a value taken | |
788 | directly from the command line may not be used to name an output file | |
789 | when taint checks are enabled. | |
790 | ||
791 | #/usr/local/bin/perl -T | |
792 | # Run with taint checking | |
793 | ||
794 | # Command line sanity check omitted... | |
795 | $tainted_output_file = shift; | |
796 | ||
797 | open(F, ">$tainted_output_file") | |
798 | or warn "Open of $untainted_output_file failed: $!\n"; | |
799 | ||
800 | The program can be made to run by "laundering" the tainted value through | |
801 | a regular expression: the second example--which still ignores locale | |
802 | information--runs, creating the file named on its command line | |
803 | if it can. | |
804 | ||
805 | #/usr/local/bin/perl -T | |
806 | ||
807 | $tainted_output_file = shift; | |
808 | $tainted_output_file =~ m%[\w/]+%; | |
809 | $untainted_output_file = $&; | |
810 | ||
811 | open(F, ">$untainted_output_file") | |
812 | or warn "Open of $untainted_output_file failed: $!\n"; | |
813 | ||
814 | Compare this with a similar but locale-aware program: | |
815 | ||
816 | #/usr/local/bin/perl -T | |
817 | ||
818 | $tainted_output_file = shift; | |
819 | use locale; | |
820 | $tainted_output_file =~ m%[\w/]+%; | |
821 | $localized_output_file = $&; | |
822 | ||
823 | open(F, ">$localized_output_file") | |
824 | or warn "Open of $localized_output_file failed: $!\n"; | |
825 | ||
826 | This third program fails to run because $& is tainted: it is the result | |
827 | of a match involving C<\w> while C<use locale> is in effect. | |
828 | ||
829 | =head1 ENVIRONMENT | |
830 | ||
831 | =over 12 | |
832 | ||
833 | =item PERL_BADLANG | |
834 | ||
835 | A string that can suppress Perl's warning about failed locale settings | |
836 | at startup. Failure can occur if the locale support in the operating | |
837 | system is lacking (broken) in some way--or if you mistyped the name of | |
838 | a locale when you set up your environment. If this environment | |
839 | variable is absent, or has a value that does not evaluate to integer | |
840 | zero--that is, "0" or ""-- Perl will complain about locale setting | |
841 | failures. | |
842 | ||
843 | B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message. | |
844 | The message tells about some problem in your system's locale support, | |
845 | and you should investigate what the problem is. | |
846 | ||
847 | =back | |
848 | ||
849 | The following environment variables are not specific to Perl: They are | |
850 | part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method | |
851 | for controlling an application's opinion on data. | |
852 | ||
853 | =over 12 | |
854 | ||
855 | =item LC_ALL | |
856 | ||
857 | C<LC_ALL> is the "override-all" locale environment variable. If | |
858 | set, it overrides all the rest of the locale environment variables. | |
859 | ||
860 | =item LANGUAGE | |
861 | ||
862 | B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you | |
863 | are using the GNU libc. This is the case if you are using e.g. Linux. | |
864 | If you are using "commercial" UNIXes you are most probably I<not> | |
865 | using GNU libc and you can ignore C<LANGUAGE>. | |
866 | ||
867 | However, in the case you are using C<LANGUAGE>: it affects the | |
868 | language of informational, warning, and error messages output by | |
869 | commands (in other words, it's like C<LC_MESSAGES>) but it has higher | |
870 | priority than L<LC_ALL>. Moreover, it's not a single value but | |
871 | instead a "path" (":"-separated list) of I<languages> (not locales). | |
872 | See the GNU C<gettext> library documentation for more information. | |
873 | ||
874 | =item LC_CTYPE | |
875 | ||
876 | In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type | |
877 | locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG> | |
878 | chooses the character type locale. | |
879 | ||
880 | =item LC_COLLATE | |
881 | ||
882 | In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation | |
883 | (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>, | |
884 | C<LANG> chooses the collation locale. | |
885 | ||
886 | =item LC_MONETARY | |
887 | ||
888 | In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary | |
889 | formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>, | |
890 | C<LANG> chooses the monetary formatting locale. | |
891 | ||
892 | =item LC_NUMERIC | |
893 | ||
894 | In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format | |
895 | locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG> | |
896 | chooses the numeric format. | |
897 | ||
898 | =item LC_TIME | |
899 | ||
900 | In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time | |
901 | formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>, | |
902 | C<LANG> chooses the date and time formatting locale. | |
903 | ||
904 | =item LANG | |
905 | ||
906 | C<LANG> is the "catch-all" locale environment variable. If it is set, it | |
907 | is used as the last resort after the overall C<LC_ALL> and the | |
908 | category-specific C<LC_...>. | |
909 | ||
910 | =back | |
911 | ||
912 | =head1 NOTES | |
913 | ||
914 | =head2 Backward compatibility | |
915 | ||
916 | Versions of Perl prior to 5.004 B<mostly> ignored locale information, | |
917 | generally behaving as if something similar to the C<"C"> locale were | |
918 | always in force, even if the program environment suggested otherwise | |
919 | (see L<The setlocale function>). By default, Perl still behaves this | |
920 | way for backward compatibility. If you want a Perl application to pay | |
921 | attention to locale information, you B<must> use the S<C<use locale>> | |
922 | pragma (see L<The use locale pragma>) to instruct it to do so. | |
923 | ||
924 | Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE> | |
925 | information if available; that is, C<\w> did understand what | |
926 | were the letters according to the locale environment variables. | |
927 | The problem was that the user had no control over the feature: | |
928 | if the C library supported locales, Perl used them. | |
929 | ||
930 | =head2 I18N:Collate obsolete | |
931 | ||
932 | In versions of Perl prior to 5.004, per-locale collation was possible | |
933 | using the C<I18N::Collate> library module. This module is now mildly | |
934 | obsolete and should be avoided in new applications. The C<LC_COLLATE> | |
935 | functionality is now integrated into the Perl core language: One can | |
936 | use locale-specific scalar data completely normally with C<use locale>, | |
937 | so there is no longer any need to juggle with the scalar references of | |
938 | C<I18N::Collate>. | |
939 | ||
940 | =head2 Sort speed and memory use impacts | |
941 | ||
942 | Comparing and sorting by locale is usually slower than the default | |
943 | sorting; slow-downs of two to four times have been observed. It will | |
944 | also consume more memory: once a Perl scalar variable has participated | |
945 | in any string comparison or sorting operation obeying the locale | |
946 | collation rules, it will take 3-15 times more memory than before. (The | |
947 | exact multiplier depends on the string's contents, the operating system | |
948 | and the locale.) These downsides are dictated more by the operating | |
949 | system's implementation of the locale system than by Perl. | |
950 | ||
951 | =head2 write() and LC_NUMERIC | |
952 | ||
953 | Formats are the only part of Perl that unconditionally use information | |
954 | from a program's locale; if a program's environment specifies an | |
955 | LC_NUMERIC locale, it is always used to specify the decimal point | |
956 | character in formatted output. Formatted output cannot be controlled by | |
957 | C<use locale> because the pragma is tied to the block structure of the | |
958 | program, and, for historical reasons, formats exist outside that block | |
959 | structure. | |
960 | ||
961 | =head2 Freely available locale definitions | |
962 | ||
963 | There is a large collection of locale definitions at | |
964 | ftp://dkuug.dk/i18n/WG15-collection . You should be aware that it is | |
965 | unsupported, and is not claimed to be fit for any purpose. If your | |
966 | system allows installation of arbitrary locales, you may find the | |
967 | definitions useful as they are, or as a basis for the development of | |
968 | your own locales. | |
969 | ||
970 | =head2 I18n and l10n | |
971 | ||
972 | "Internationalization" is often abbreviated as B<i18n> because its first | |
973 | and last letters are separated by eighteen others. (You may guess why | |
974 | the internalin ... internaliti ... i18n tends to get abbreviated.) In | |
975 | the same way, "localization" is often abbreviated to B<l10n>. | |
976 | ||
977 | =head2 An imperfect standard | |
978 | ||
979 | Internationalization, as defined in the C and POSIX standards, can be | |
980 | criticized as incomplete, ungainly, and having too large a granularity. | |
981 | (Locales apply to a whole process, when it would arguably be more useful | |
982 | to have them apply to a single thread, window group, or whatever.) They | |
983 | also have a tendency, like standards groups, to divide the world into | |
984 | nations, when we all know that the world can equally well be divided | |
985 | into bankers, bikers, gamers, and so on. But, for now, it's the only | |
986 | standard we've got. This may be construed as a bug. | |
987 | ||
988 | =head1 Unicode and UTF-8 | |
989 | ||
990 | The support of Unicode is new starting from Perl version 5.6, and | |
991 | more fully implemented in the version 5.8. See L<perluniintro> and | |
992 | L<perlunicode> for more details. | |
993 | ||
994 | Usually locale settings and Unicode do not affect each other, but | |
995 | there are exceptions, see L<perlunicode/Locales> for examples. | |
996 | ||
997 | =head1 BUGS | |
998 | ||
999 | =head2 Broken systems | |
1000 | ||
1001 | In certain systems, the operating system's locale support | |
1002 | is broken and cannot be fixed or used by Perl. Such deficiencies can | |
1003 | and will result in mysterious hangs and/or Perl core dumps when the | |
1004 | C<use locale> is in effect. When confronted with such a system, | |
1005 | please report in excruciating detail to <F<perlbug@perl.org>>, and | |
1006 | complain to your vendor: bug fixes may exist for these problems | |
1007 | in your operating system. Sometimes such bug fixes are called an | |
1008 | operating system upgrade. | |
1009 | ||
1010 | =head1 SEE ALSO | |
1011 | ||
1012 | L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>, | |
1013 | L<POSIX/isalnum>, L<POSIX/isalpha>, | |
1014 | L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>, | |
1015 | L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>, | |
1016 | L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>, | |
1017 | L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>, | |
1018 | L<POSIX/strtod>, L<POSIX/strxfrm>. | |
1019 | ||
1020 | =head1 HISTORY | |
1021 | ||
1022 | Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic | |
1023 | Dunlop, assisted by the perl5-porters. Prose worked over a bit by | |
1024 | Tom Christiansen. | |
1025 | ||
1026 | Last update: Thu Jun 11 08:44:13 MDT 1998 |