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