5 perllocale - Perl locale handling (internationalization and localization)
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.
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>).
25 Perl has been extended to support certain types of locales available in
26 the locale system. This is controlled per application by using one
27 pragma, one function call, and several environment variables.
29 Perl supports single-byte locales that are supersets of ASCII, such as
30 the ISO 8859 ones, and one multi-byte-type locale, UTF-8 ones, described
31 in the next paragraph. Perl doesn't support any other multi-byte
32 locales, such as the ones for East Asian languages.
34 Unfortunately, there are quite a few deficiencies with the design (and
35 often, the implementations) of locales. Unicode was invented (see
36 L<perlunitut> for an introduction to that) in part to address these
37 design deficiencies, and nowadays, there is a series of "UTF-8
38 locales", based on Unicode. These are locales whose character set is
39 Unicode, encoded in UTF-8. Starting in v5.20, Perl fully supports
40 UTF-8 locales, except for sorting and string comparisons like C<lt> and
41 C<ge>. Starting in v5.26, Perl can handle these reasonably as well,
42 depending on the platform's implementation. However, for earlier
43 releases or for better control, use L<Unicode::Collate>. There are
44 actually two slightly different types of UTF-8 locales: one for Turkic
45 languages and one for everything else.
47 Starting in Perl v5.30, Perl detects Turkic locales by their
48 behaviour, and seamlessly handles both types; previously only the
49 non-Turkic one was supported. The name of the locale is ignored, if
50 your system has a C<tr_TR.UTF-8> locale and it doesn't behave like a
51 Turkic locale, perl will treat it like a non-Turkic locale.
53 Perl continues to support the old non UTF-8 locales as well. There are
54 currently no UTF-8 locales for EBCDIC platforms.
56 (Unicode is also creating C<CLDR>, the "Common Locale Data Repository",
57 L<http://cldr.unicode.org/> which includes more types of information than
58 are available in the POSIX locale system. At the time of this writing,
59 there was no CPAN module that provides access to this XML-encoded data.
60 However, it is possible to compute the POSIX locale data from them, and
61 earlier CLDR versions had these already extracted for you as UTF-8 locales
62 L<http://unicode.org/Public/cldr/2.0.1/>.)
64 =head1 WHAT IS A LOCALE
66 A locale is a set of data that describes various aspects of how various
67 communities in the world categorize their world. These categories are
68 broken down into the following types (some of which include a brief
73 =item Category C<LC_NUMERIC>: Numeric formatting
75 This indicates how numbers should be formatted for human readability,
76 for example the character used as the decimal point.
78 =item Category C<LC_MONETARY>: Formatting of monetary amounts
82 =item Category C<LC_TIME>: Date/Time formatting
86 =item Category C<LC_MESSAGES>: Error and other messages
88 This is used by Perl itself only for accessing operating system error
89 messages via L<C<$!>|perlvar/$ERRNO> and L<C<$^E>|perlvar/$EXTENDED_OS_ERROR>.
91 =item Category C<LC_COLLATE>: Collation
93 This indicates the ordering of letters for comparison and sorting.
94 In Latin alphabets, for example, "b", generally follows "a".
96 =item Category C<LC_CTYPE>: Character Types
98 This indicates, for example if a character is an uppercase letter.
100 =item Other categories
102 Some platforms have other categories, dealing with such things as
103 measurement units and paper sizes. None of these are used directly by
104 Perl, but outside operations that Perl interacts with may use
105 these. See L</Not within the scope of "use locale"> below.
109 More details on the categories used by Perl are given below in L</LOCALE
112 Together, these categories go a long way towards being able to customize
113 a single program to run in many different locations. But there are
114 deficiencies, so keep reading.
116 =head1 PREPARING TO USE LOCALES
118 Perl itself (outside the L<POSIX> module) will not use locales unless
119 specifically requested to (but
120 again note that Perl may interact with code that does use them). Even
121 if there is such a request, B<all> of the following must be true
122 for it to work properly:
128 B<Your operating system must support the locale system>. If it does,
129 you should find that the C<setlocale()> function is a documented part of
134 B<Definitions for locales that you use must be installed>. You, or
135 your system administrator, must make sure that this is the case. The
136 available locales, the location in which they are kept, and the manner
137 in which they are installed all vary from system to system. Some systems
138 provide only a few, hard-wired locales and do not allow more to be
139 added. Others allow you to add "canned" locales provided by the system
140 supplier. Still others allow you or the system administrator to define
141 and add arbitrary locales. (You may have to ask your supplier to
142 provide canned locales that are not delivered with your operating
143 system.) Read your system documentation for further illumination.
147 B<Perl must believe that the locale system is supported>. If it does,
148 C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is
153 If you want a Perl application to process and present your data
154 according to a particular locale, the application code should include
155 the S<C<use locale>> pragma (see L</The "use locale" pragma>) where
156 appropriate, and B<at least one> of the following must be true:
162 B<The locale-determining environment variables (see L</"ENVIRONMENT">)
163 must be correctly set up> at the time the application is started, either
164 by yourself or by whomever set up your system account; or
168 B<The application must set its own locale> using the method described in
169 L</The setlocale function>.
175 =head2 The C<"use locale"> pragma
177 Starting in Perl 5.28, this pragma may be used in
178 L<multi-threaded|threads> applications on systems that have thread-safe
179 locale ability. Some caveats apply, see L</Multi-threaded> below. On
180 systems without this capability, or in earlier Perls, do NOT use this
181 pragma in scripts that have multiple L<threads|threads> active. The
182 locale in these cases is not local to a single thread. Another thread
183 may change the locale at any time, which could cause at a minimum that a
184 given thread is operating in a locale it isn't expecting to be in. On
185 some platforms, segfaults can also occur. The locale change need not be
186 explicit; some operations cause perl itself to change the locale. You
187 are vulnerable simply by having done a S<C<"use locale">>.
189 By default, Perl itself (outside the L<POSIX> module)
190 ignores the current locale. The S<C<use locale>>
191 pragma tells Perl to use the current locale for some operations.
192 Starting in v5.16, there are optional parameters to this pragma,
193 described below, which restrict which operations are affected by it.
195 The current locale is set at execution time by
196 L<setlocale()|/The setlocale function> described below. If that function
197 hasn't yet been called in the course of the program's execution, the
198 current locale is that which was determined by the L</"ENVIRONMENT"> in
199 effect at the start of the program.
200 If there is no valid environment, the current locale is whatever the
201 system default has been set to. On POSIX systems, it is likely, but
202 not necessarily, the "C" locale. On Windows, the default is set via the
203 computer's S<C<Control Panel-E<gt>Regional and Language Options>> (or its
206 The operations that are affected by locale are:
210 =item B<Not within the scope of C<"use locale">>
212 Only certain operations (all originating outside Perl) should be
213 affected, as follows:
219 The current locale is used when going outside of Perl with
220 operations like L<system()|perlfunc/system LIST> or
221 L<qxE<sol>E<sol>|perlop/qxE<sol>STRINGE<sol>>, if those operations are
226 Also Perl gives access to various C library functions through the
227 L<POSIX> module. Some of those functions are always affected by the
228 current locale. For example, C<POSIX::strftime()> uses C<LC_TIME>;
229 C<POSIX::strtod()> uses C<LC_NUMERIC>; C<POSIX::strcoll()> and
230 C<POSIX::strxfrm()> use C<LC_COLLATE>. All such functions
231 will behave according to the current underlying locale, even if that
232 locale isn't exposed to Perl space.
234 This applies as well to L<I18N::Langinfo>.
238 XS modules for all categories but C<LC_NUMERIC> get the underlying
239 locale, and hence any C library functions they call will use that
240 underlying locale. For more discussion, see L<perlxs/CAVEATS>.
244 Note that all C programs (including the perl interpreter, which is
245 written in C) always have an underlying locale. That locale is the "C"
246 locale unless changed by a call to L<setlocale()|/The setlocale
247 function>. When Perl starts up, it changes the underlying locale to the
248 one which is indicated by the L</ENVIRONMENT>. When using the L<POSIX>
249 module or writing XS code, it is important to keep in mind that the
250 underlying locale may be something other than "C", even if the program
251 hasn't explicitly changed it.
255 =item B<Lingering effects of C<S<use locale>>>
257 Certain Perl operations that are set-up within the scope of a
258 C<use locale> retain that effect even outside the scope.
265 The output format of a L<write()|perlfunc/write> is determined by an
266 earlier format declaration (L<perlfunc/format>), so whether or not the
267 output is affected by locale is determined by if the C<format()> is
268 within the scope of a C<use locale>, not whether the C<write()>
273 Regular expression patterns can be compiled using
274 L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodualn> with actual
275 matching deferred to later. Again, it is whether or not the compilation
276 was done within the scope of C<use locale> that determines the match
277 behavior, not if the matches are done within such a scope or not.
283 =item B<Under C<"use locale";>>
289 All the above operations
293 B<Format declarations> (L<perlfunc/format>) and hence any subsequent
294 C<write()>s use C<LC_NUMERIC>.
298 B<stringification and output> use C<LC_NUMERIC>.
299 These include the results of
308 B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
309 C<LC_COLLATE>. C<sort()> is also affected if used without an
310 explicit comparison function, because it uses C<cmp> by default.
312 B<Note:> C<eq> and C<ne> are unaffected by locale: they always
313 perform a char-by-char comparison of their scalar operands. What's
314 more, if C<cmp> finds that its operands are equal according to the
315 collation sequence specified by the current locale, it goes on to
316 perform a char-by-char comparison, and only returns I<0> (equal) if the
317 operands are char-for-char identical. If you really want to know whether
318 two strings--which C<eq> and C<cmp> may consider different--are equal
319 as far as collation in the locale is concerned, see the discussion in
320 L</Category C<LC_COLLATE>: Collation>.
324 B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
325 C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
329 B<The variables L<C<$!>|perlvar/$ERRNO>> (and its synonyms C<$ERRNO> and
330 C<$OS_ERROR>) B<and> L<C<$^E>|perlvar/$EXTENDED_OS_ERROR>> (and its synonym
331 C<$EXTENDED_OS_ERROR>) when used as strings use C<LC_MESSAGES>.
337 The default behavior is restored with the S<C<no locale>> pragma, or
338 upon reaching the end of the block enclosing C<use locale>.
339 Note that C<use locale> calls may be
340 nested, and that what is in effect within an inner scope will revert to
341 the outer scope's rules at the end of the inner scope.
343 The string result of any operation that uses locale
344 information is tainted, as it is possible for a locale to be
345 untrustworthy. See L</"SECURITY">.
347 Starting in Perl v5.16 in a very limited way, and more generally in
348 v5.22, you can restrict which category or categories are enabled by this
349 particular instance of the pragma by adding parameters to it. For
352 use locale qw(:ctype :numeric);
354 enables locale awareness within its scope of only those operations
355 (listed above) that are affected by C<LC_CTYPE> and C<LC_NUMERIC>.
357 The possible categories are: C<:collate>, C<:ctype>, C<:messages>,
358 C<:monetary>, C<:numeric>, C<:time>, and the pseudo category
359 C<:characters> (described below).
363 use locale ':messages';
365 and only L<C<$!>|perlvar/$ERRNO> and L<C<$^E>|perlvar/$EXTENDED_OS_ERROR>
366 will be locale aware. Everything else is unaffected.
368 Since Perl doesn't currently do anything with the C<LC_MONETARY>
369 category, specifying C<:monetary> does effectively nothing. Some
370 systems have other categories, such as C<LC_PAPER>, but Perl
371 also doesn't do anything with them, and there is no way to specify
372 them in this pragma's arguments.
374 You can also easily say to use all categories but one, by either, for
377 use locale ':!ctype';
378 use locale ':not_ctype';
380 both of which mean to enable locale awareness of all categories but
381 C<LC_CTYPE>. Only one category argument may be specified in a
382 S<C<use locale>> if it is of the negated form.
384 Prior to v5.22 only one form of the pragma with arguments is available:
386 use locale ':not_characters';
388 (and you have to say C<not_>; you can't use the bang C<!> form). This
389 pseudo category is a shorthand for specifying both C<:collate> and
390 C<:ctype>. Hence, in the negated form, it is nearly the same thing as
393 use locale qw(:messages :monetary :numeric :time);
395 We use the term "nearly", because C<:not_characters> also turns on
396 S<C<use feature 'unicode_strings'>> within its scope. This form is
397 less useful in v5.20 and later, and is described fully in
398 L</Unicode and UTF-8>, but briefly, it tells Perl to not use the
399 character portions of the locale definition, that is the C<LC_CTYPE> and
400 C<LC_COLLATE> categories. Instead it will use the native character set
401 (extended by Unicode). When using this parameter, you are responsible
402 for getting the external character set translated into the
403 native/Unicode one (which it already will be if it is one of the
404 increasingly popular UTF-8 locales). There are convenient ways of doing
405 this, as described in L</Unicode and UTF-8>.
407 =head2 The setlocale function
409 WARNING! Prior to Perl 5.28 or on a system that does not support
410 thread-safe locale operations, do NOT use this function in a
411 L<thread|threads>. The locale will change in all other threads at the
412 same time, and should your thread get paused by the operating system,
413 and another started, that thread will not have the locale it is
414 expecting. On some platforms, there can be a race leading to segfaults
415 if two threads call this function nearly simultaneously. This warning
416 does not apply on unthreaded builds, or on perls where
417 C<${^SAFE_LOCALES}> exists and is non-zero; namely Perl 5.28 and later
418 unthreaded or compiled to be locale-thread-safe. On z/OS systems, this
419 function becomes a no-op once any thread is started. Thus, on that
420 system, you can set up the locale before creating any threads, and that
421 locale will be the one in effect for the entire program.
423 Otherwise, you can switch locales as often as you wish at run time with
424 the C<POSIX::setlocale()> function:
426 # Import locale-handling tool set from POSIX module.
427 # This example uses: setlocale -- the function call
428 # LC_CTYPE -- explained below
429 # (Showing the testing for success/failure of operations is
430 # omitted in these examples to avoid distracting from the main
433 use POSIX qw(locale_h);
437 # query and save the old locale
438 $old_locale = setlocale(LC_CTYPE);
440 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
441 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
443 setlocale(LC_CTYPE, "");
444 # LC_CTYPE now reset to the default defined by the
445 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
446 # default. See below for documentation.
448 # restore the old locale
449 setlocale(LC_CTYPE, $old_locale);
451 The first argument of C<setlocale()> gives the B<category>, the second the
452 B<locale>. The category tells in what aspect of data processing you
453 want to apply locale-specific rules. Category names are discussed in
454 L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a
455 collection of customization information corresponding to a particular
456 combination of language, country or territory, and codeset. Read on for
457 hints on the naming of locales: not all systems name locales as in the
460 If no second argument is provided and the category is something other
461 than C<LC_ALL>, the function returns a string naming the current locale
462 for the category. You can use this value as the second argument in a
463 subsequent call to C<setlocale()>, B<but> on some platforms the string
464 is opaque, not something that most people would be able to decipher as
465 to what locale it means.
467 If no second argument is provided and the category is C<LC_ALL>, the
468 result is implementation-dependent. It may be a string of
469 concatenated locale names (separator also implementation-dependent)
470 or a single locale name. Please consult your L<setlocale(3)> man page for
473 If a second argument is given and it corresponds to a valid locale,
474 the locale for the category is set to that value, and the function
475 returns the now-current locale value. You can then use this in yet
476 another call to C<setlocale()>. (In some implementations, the return
477 value may sometimes differ from the value you gave as the second
478 argument--think of it as an alias for the value you gave.)
480 As the example shows, if the second argument is an empty string, the
481 category's locale is returned to the default specified by the
482 corresponding environment variables. Generally, this results in a
483 return to the default that was in force when Perl started up: changes
484 to the environment made by the application after startup may or may not
485 be noticed, depending on your system's C library.
487 Note that when a form of C<use locale> that doesn't include all
488 categories is specified, Perl ignores the excluded categories.
490 If C<setlocale()> fails for some reason (for example, an attempt to set
491 to a locale unknown to the system), the locale for the category is not
492 changed, and the function returns C<undef>.
494 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
495 implement POSIX 2008 thread-safe locale operations, this function
496 doesn't actually call the system C<setlocale>. Instead those
497 thread-safe operations are used to emulate the C<setlocale> function,
498 but in a thread-safe manner.
500 You can force the thread-safe locale operations to always be used (if
501 available) by recompiling perl with
503 -Accflags='-DUSE_THREAD_SAFE_LOCALE'
505 added to your call to F<Configure>.
507 For further information about the categories, consult L<setlocale(3)>.
509 =head2 Multi-threaded operation
511 Beginning in Perl 5.28, multi-threaded locale operation is supported on
512 systems that implement either the POSIX 2008 or Windows-specific
513 thread-safe locale operations. Many modern systems, such as various
514 Unix variants and Darwin do have this.
516 You can tell if using locales is safe on your system by looking at the
517 read-only boolean variable C<${^SAFE_LOCALES}>. The value is 1 if the
518 perl is not threaded, or if it is using thread-safe locale operations.
520 Thread-safe operations are supported in Windows starting in Visual Studio
521 2005, and in systems compatible with POSIX 2008. Some platforms claim
522 to support POSIX 2008, but have buggy implementations, so that the hints
523 files for compiling to run on them turn off attempting to use
524 thread-safety. C<${^SAFE_LOCALES}> will be 0 on them.
526 Be aware that writing a multi-threaded application will not be portable
527 to a platform which lacks the native thread-safe locale support. On
528 systems that do have it, you automatically get this behavior for
529 threaded perls, without having to do anything. If for some reason, you
530 don't want to use this capability (perhaps the POSIX 2008 support is
531 buggy on your system), you can manually compile Perl to use the old
532 non-thread-safe implementation by passing the argument
533 C<-Accflags='-DNO_THREAD_SAFE_LOCALE'> to F<Configure>.
534 Except on Windows, this will continue to use certain of the POSIX 2008
535 functions in some situations. If these are buggy, you can pass the
536 following to F<Configure> instead or additionally:
537 C<-Accflags='-DNO_POSIX_2008_LOCALE'>. This will also keep the code
538 from using thread-safe locales.
539 C<${^SAFE_LOCALES}> will be 0 on systems that turn off the thread-safe
542 Normally on unthreaded builds, the traditional C<setlocale()> is used
543 and not the thread-safe locale functions. You can force the use of these
544 on systems that have them by adding the
545 C<-Accflags='-DUSE_THREAD_SAFE_LOCALE'> to F<Configure>.
547 The initial program is started up using the locale specified from the
548 environment, as currently, described in L</ENVIRONMENT>. All newly
549 created threads start with C<LC_ALL> set to C<"C">. Each thread may
550 use C<POSIX::setlocale()> to query or switch its locale at any time,
551 without affecting any other thread. All locale-dependent operations
552 automatically use their thread's locale.
554 This should be completely transparent to any applications written
555 entirely in Perl (minus a few rarely encountered caveats given in the
556 L</Multi-threaded> section). Information for XS module writers is given
557 in L<perlxs/Locale-aware XS code>.
559 =head2 Finding locales
561 For locales available in your system, consult also L<setlocale(3)> to
562 see whether it leads to the list of available locales (search for the
563 I<SEE ALSO> section). If that fails, try the following command lines:
577 and see whether they list something resembling these
579 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
580 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
583 english german russian
584 english.iso88591 german.iso88591 russian.iso88595
585 english.roman8 russian.koi8r
587 Sadly, even though the calling interface for C<setlocale()> has been
588 standardized, names of locales and the directories where the
589 configuration resides have not been. The basic form of the name is
590 I<language_territory>B<.>I<codeset>, but the latter parts after
591 I<language> are not always present. The I<language> and I<country>
592 are usually from the standards B<ISO 3166> and B<ISO 639>, the
593 two-letter abbreviations for the countries and the languages of the
594 world, respectively. The I<codeset> part often mentions some B<ISO
595 8859> character set, the Latin codesets. For example, C<ISO 8859-1>
596 is the so-called "Western European codeset" that can be used to encode
597 most Western European languages adequately. Again, there are several
598 ways to write even the name of that one standard. Lamentably.
600 Two special locales are worth particular mention: "C" and "POSIX".
601 Currently these are effectively the same locale: the difference is
602 mainly that the first one is defined by the C standard, the second by
603 the POSIX standard. They define the B<default locale> in which
604 every program starts in the absence of locale information in its
605 environment. (The I<default> default locale, if you will.) Its language
606 is (American) English and its character codeset ASCII or, rarely, a
607 superset thereof (such as the "DEC Multinational Character Set
608 (DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
609 may not actually exactly match what the C standard calls for. So
612 B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
613 POSIX-conformant), so use "C" when you need explicitly to specify this
616 =head2 LOCALE PROBLEMS
618 You may encounter the following warning message at Perl startup:
620 perl: warning: Setting locale failed.
621 perl: warning: Please check that your locale settings:
624 are supported and installed on your system.
625 perl: warning: Falling back to the standard locale ("C").
627 This means that your locale settings had C<LC_ALL> set to "En_US" and
628 LANG exists but has no value. Perl tried to believe you but could not.
629 Instead, Perl gave up and fell back to the "C" locale, the default locale
630 that is supposed to work no matter what. (On Windows, it first tries
631 falling back to the system default locale.) This usually means your
632 locale settings were wrong, they mention locales your system has never
633 heard of, or the locale installation in your system has problems (for
634 example, some system files are broken or missing). There are quick and
635 temporary fixes to these problems, as well as more thorough and lasting
638 =head2 Testing for broken locales
640 If you are building Perl from source, the Perl test suite file
641 F<lib/locale.t> can be used to test the locales on your system.
642 Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
643 will cause it to output detailed results. For example, on Linux, you
646 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
648 Besides many other tests, it will test every locale it finds on your
649 system to see if they conform to the POSIX standard. If any have
650 errors, it will include a summary near the end of the output of which
651 locales passed all its tests, and which failed, and why.
653 =head2 Temporarily fixing locale problems
655 The two quickest fixes are either to render Perl silent about any
656 locale inconsistencies or to run Perl under the default locale "C".
658 Perl's moaning about locale problems can be silenced by setting the
659 environment variable C<PERL_BADLANG> to "0" or "".
660 This method really just sweeps the problem under the carpet: you tell
661 Perl to shut up even when Perl sees that something is wrong. Do not
662 be surprised if later something locale-dependent misbehaves.
664 Perl can be run under the "C" locale by setting the environment
665 variable C<LC_ALL> to "C". This method is perhaps a bit more civilized
666 than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or
667 other locale variables) may affect other programs as well, not just
668 Perl. In particular, external programs run from within Perl will see
669 these changes. If you make the new settings permanent (read on), all
670 programs you run see the changes. See L</"ENVIRONMENT"> for
671 the full list of relevant environment variables and L</"USING LOCALES">
672 for their effects in Perl. Effects in other programs are
673 easily deducible. For example, the variable C<LC_COLLATE> may well affect
674 your B<sort> program (or whatever the program that arranges "records"
675 alphabetically in your system is called).
677 You can test out changing these variables temporarily, and if the
678 new settings seem to help, put those settings into your shell startup
679 files. Consult your local documentation for the exact details. For
680 Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
682 LC_ALL=en_US.ISO8859-1
685 This assumes that we saw the locale "en_US.ISO8859-1" using the commands
686 discussed above. We decided to try that instead of the above faulty
687 locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
689 setenv LC_ALL en_US.ISO8859-1
691 or if you have the "env" application you can do (in any shell)
693 env LC_ALL=en_US.ISO8859-1 perl ...
695 If you do not know what shell you have, consult your local
696 helpdesk or the equivalent.
698 =head2 Permanently fixing locale problems
700 The slower but superior fixes are when you may be able to yourself
701 fix the misconfiguration of your own environment variables. The
702 mis(sing)configuration of the whole system's locales usually requires
703 the help of your friendly system administrator.
705 First, see earlier in this document about L</Finding locales>. That tells
706 how to find which locales are really supported--and more importantly,
707 installed--on your system. In our example error message, environment
708 variables affecting the locale are listed in the order of decreasing
709 importance (and unset variables do not matter). Therefore, having
710 LC_ALL set to "En_US" must have been the bad choice, as shown by the
711 error message. First try fixing locale settings listed first.
713 Second, if using the listed commands you see something B<exactly>
714 (prefix matches do not count and case usually counts) like "En_US"
715 without the quotes, then you should be okay because you are using a
716 locale name that should be installed and available in your system.
717 In this case, see L</Permanently fixing your system's locale configuration>.
719 =head2 Permanently fixing your system's locale configuration
721 This is when you see something like:
723 perl: warning: Please check that your locale settings:
726 are supported and installed on your system.
728 but then cannot see that "En_US" listed by the above-mentioned
729 commands. You may see things like "en_US.ISO8859-1", but that isn't
730 the same. In this case, try running under a locale
731 that you can list and which somehow matches what you tried. The
732 rules for matching locale names are a bit vague because
733 standardization is weak in this area. See again the
734 L</Finding locales> about general rules.
736 =head2 Fixing system locale configuration
738 Contact a system administrator (preferably your own) and report the exact
739 error message you get, and ask them to read this same documentation you
740 are now reading. They should be able to check whether there is something
741 wrong with the locale configuration of the system. The L</Finding locales>
742 section is unfortunately a bit vague about the exact commands and places
743 because these things are not that standardized.
745 =head2 The localeconv function
747 The C<POSIX::localeconv()> function allows you to get particulars of the
748 locale-dependent numeric formatting information specified by the current
749 underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of
750 whether called from within the scope of C<S<use locale>> or not). (If
751 you just want the name of
752 the current locale for a particular category, use C<POSIX::setlocale()>
753 with a single parameter--see L</The setlocale function>.)
755 use POSIX qw(locale_h);
757 # Get a reference to a hash of locale-dependent info
758 $locale_values = localeconv();
760 # Output sorted list of the values
761 for (sort keys %$locale_values) {
762 printf "%-20s = %s\n", $_, $locale_values->{$_}
765 C<localeconv()> takes no arguments, and returns B<a reference to> a hash.
766 The keys of this hash are variable names for formatting, such as
767 C<decimal_point> and C<thousands_sep>. The values are the
768 corresponding, er, values. See L<POSIX/localeconv> for a longer
769 example listing the categories an implementation might be expected to
770 provide; some provide more and others fewer. You don't need an
771 explicit C<use locale>, because C<localeconv()> always observes the
774 Here's a simple-minded example program that rewrites its command-line
775 parameters as integers correctly formatted in the current locale:
777 use POSIX qw(locale_h);
779 # Get some of locale's numeric formatting parameters
780 my ($thousands_sep, $grouping) =
781 @{localeconv()}{'thousands_sep', 'grouping'};
783 # Apply defaults if values are missing
784 $thousands_sep = ',' unless $thousands_sep;
786 # grouping and mon_grouping are packed lists
787 # of small integers (characters) telling the
788 # grouping (thousand_seps and mon_thousand_seps
789 # being the group dividers) of numbers and
790 # monetary quantities. The integers' meanings:
791 # 255 means no more grouping, 0 means repeat
792 # the previous grouping, 1-254 means use that
793 # as the current grouping. Grouping goes from
794 # right to left (low to high digits). In the
795 # below we cheat slightly by never using anything
796 # else than the first grouping (whatever that is).
798 @grouping = unpack("C*", $grouping);
803 # Format command line params for current locale
805 $_ = int; # Chop non-integer part
807 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
812 Note that if the platform doesn't have C<LC_NUMERIC> and/or
813 C<LC_MONETARY> available or enabled, the corresponding elements of the
814 hash will be missing.
816 =head2 I18N::Langinfo
818 Another interface for querying locale-dependent information is the
819 C<I18N::Langinfo::langinfo()> function.
821 The following example will import the C<langinfo()> function itself and
822 three constants to be used as arguments to C<langinfo()>: a constant for
823 the abbreviated first day of the week (the numbering starts from
824 Sunday = 1) and two more constants for the affirmative and negative
825 answers for a yes/no question in the current locale.
827 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
829 my ($abday_1, $yesstr, $nostr)
830 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
832 print "$abday_1? [$yesstr/$nostr] ";
834 In other words, in the "C" (or English) locale the above will probably
835 print something like:
839 See L<I18N::Langinfo> for more information.
841 =head1 LOCALE CATEGORIES
843 The following subsections describe basic locale categories. Beyond these,
844 some combination categories allow manipulation of more than one
845 basic category at a time. See L</"ENVIRONMENT"> for a discussion of these.
847 =head2 Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting
849 In the scope of a S<C<use locale>> form that includes collation, Perl
850 looks to the C<LC_COLLATE>
851 environment variable to determine the application's notions on collation
852 (ordering) of characters. For example, "b" follows "a" in Latin
853 alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
854 "color" follows "chocolate" in English, what about in traditional Spanish?
856 The following collations all make sense and you may meet any of them
857 if you C<"use locale">.
864 Here is a code snippet to tell what "word"
865 characters are in the current locale, in that locale's order:
868 print +(sort grep /\w/, map { chr } 0..255), "\n";
870 Compare this with the characters that you see and their order if you
871 state explicitly that the locale should be ignored:
874 print +(sort grep /\w/, map { chr } 0..255), "\n";
876 This machine-native collation (which is what you get unless S<C<use
877 locale>> has appeared earlier in the same block) must be used for
878 sorting raw binary data, whereas the locale-dependent collation of the
879 first example is useful for natural text.
881 As noted in L</USING LOCALES>, C<cmp> compares according to the current
882 collation locale when C<use locale> is in effect, but falls back to a
883 char-by-char comparison for strings that the locale says are equal. You
884 can use C<POSIX::strcoll()> if you don't want this fall-back:
886 use POSIX qw(strcoll);
888 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
890 C<$equal_in_locale> will be true if the collation locale specifies a
891 dictionary-like ordering that ignores space characters completely and
894 Perl uses the platform's C library collation functions C<strcoll()> and
895 C<strxfrm()>. That means you get whatever they give. On some
896 platforms, these functions work well on UTF-8 locales, giving
897 a reasonable default collation for the code points that are important in
898 that locale. (And if they aren't working well, the problem may only be
899 that the locale definition is deficient, so can be fixed by using a
900 better definition file. Unicode's definitions (see L</Freely available
901 locale definitions>) provide reasonable UTF-8 locale collation
902 definitions.) Starting in Perl v5.26, Perl's use of these functions has
903 been made more seamless. This may be sufficient for your needs. For
904 more control, and to make sure strings containing any code point (not
905 just the ones important in the locale) collate properly, the
906 L<Unicode::Collate> module is suggested.
908 In non-UTF-8 locales (hence single byte), code points above 0xFF are
909 technically invalid. But if present, again starting in v5.26, they will
910 collate to the same position as the highest valid code point does. This
911 generally gives good results, but the collation order may be skewed if
912 the valid code point gets special treatment when it forms particular
913 sequences with other characters as defined by the locale.
914 When two strings collate identically, the code point order is used as a
917 If Perl detects that there are problems with the locale collation order,
918 it reverts to using non-locale collation rules for that locale.
920 If you have a single string that you want to check for "equality in
921 locale" against several others, you might think you could gain a little
922 efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
924 use POSIX qw(strxfrm);
925 $xfrm_string = strxfrm("Mixed-case string");
926 print "locale collation ignores spaces\n"
927 if $xfrm_string eq strxfrm("Mixed-casestring");
928 print "locale collation ignores hyphens\n"
929 if $xfrm_string eq strxfrm("Mixedcase string");
930 print "locale collation ignores case\n"
931 if $xfrm_string eq strxfrm("mixed-case string");
933 C<strxfrm()> takes a string and maps it into a transformed string for use
934 in char-by-char comparisons against other transformed strings during
935 collation. "Under the hood", locale-affected Perl comparison operators
936 call C<strxfrm()> for both operands, then do a char-by-char
937 comparison of the transformed strings. By calling C<strxfrm()> explicitly
938 and using a non locale-affected comparison, the example attempts to save
939 a couple of transformations. But in fact, it doesn't save anything: Perl
940 magic (see L<perlguts/Magic Variables>) creates the transformed version of a
941 string the first time it's needed in a comparison, then keeps this version around
942 in case it's needed again. An example rewritten the easy way with
943 C<cmp> runs just about as fast. It also copes with null characters
944 embedded in strings; if you call C<strxfrm()> directly, it treats the first
945 null it finds as a terminator. Don't expect the transformed strings
946 it produces to be portable across systems--or even from one revision
947 of your operating system to the next. In short, don't call C<strxfrm()>
948 directly: let Perl do it for you.
950 Note: C<use locale> isn't shown in some of these examples because it isn't
951 needed: C<strcoll()> and C<strxfrm()> are POSIX functions
952 which use the standard system-supplied C<libc> functions that
953 always obey the current C<LC_COLLATE> locale.
955 =head2 Category C<LC_CTYPE>: Character Types
957 In the scope of a S<C<use locale>> form that includes C<LC_CTYPE>, Perl
958 obeys the C<LC_CTYPE> locale
959 setting. This controls the application's notion of which characters are
960 alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
961 regular expression metanotation,
962 which stands for alphanumeric characters--that is, alphabetic,
963 numeric, and the platform's native underscore.
964 (Consult L<perlre> for more information about
965 regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
966 setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
967 "E<oslash>" may be understood as C<\w> characters.
968 It also affects things like C<\s>, C<\D>, and the POSIX character
969 classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
970 information on all these.)
972 The C<LC_CTYPE> locale also provides the map used in transliterating
973 characters between lower and uppercase. This affects the case-mapping
974 functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>;
976 interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
977 strings and C<s///> substitutions; and case-insensitive regular expression
978 pattern matching using the C<i> modifier.
980 Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
981 otherwise Perl only supports single-byte locales, such as the ISO 8859
982 series. This means that wide character locales, for example for Asian
983 languages, are not well-supported. Use of these locales may cause core
984 dumps. If the platform has the capability for Perl to detect such a
985 locale, starting in Perl v5.22, L<Perl will warn, default
986 enabled|warnings/Category Hierarchy>, using the C<locale> warning
987 category, whenever such a locale is switched into. The UTF-8 locale
988 support is actually a
989 superset of POSIX locales, because it is really full Unicode behavior
990 as if no C<LC_CTYPE> locale were in effect at all (except for tainting;
991 see L</SECURITY>). POSIX locales, even UTF-8 ones,
992 are lacking certain concepts in Unicode, such as the idea that changing
993 the case of a character could expand to be more than one character.
994 Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
995 Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
996 with some restrictions, and on other platforms more like the "C" locale.
997 For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
998 used as a workaround for this (see L</Unicode and UTF-8>).
1000 Note that there are quite a few things that are unaffected by the
1001 current locale. Any literal character is the native character for the
1002 given platform. Hence 'A' means the character at code point 65 on ASCII
1003 platforms, and 193 on EBCDIC. That may or may not be an 'A' in the
1004 current locale, if that locale even has an 'A'.
1005 Similarly, all the escape sequences for particular characters,
1006 C<\n> for example, always mean the platform's native one. This means,
1007 for example, that C<\N> in regular expressions (every character
1008 but new-line) works on the platform character set.
1010 Starting in v5.22, Perl will by default warn when switching into a
1011 locale that redefines any ASCII printable character (plus C<\t> and
1012 C<\n>) into a different class than expected. This is likely to
1013 happen on modern locales only on EBCDIC platforms, where, for example,
1014 a CCSID 0037 locale on a CCSID 1047 machine moves C<"[">, but it can
1015 happen on ASCII platforms with the ISO 646 and other
1016 7-bit locales that are essentially obsolete. Things may still work,
1017 depending on what features of Perl are used by the program. For
1018 example, in the example from above where C<"|"> becomes a C<\w>, and
1019 there are no regular expressions where this matters, the program may
1020 still work properly. The warning lists all the characters that
1021 it can determine could be adversely affected.
1023 B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
1024 in clearly ineligible characters being considered to be alphanumeric by
1025 your application. For strict matching of (mundane) ASCII letters and
1026 digits--for example, in command strings--locale-aware applications
1027 should use C<\w> with the C</a> regular expression modifier. See L</"SECURITY">.
1029 =head2 Category C<LC_NUMERIC>: Numeric Formatting
1031 After a proper C<POSIX::setlocale()> call, and within the scope
1032 of a C<use locale> form that includes numerics, Perl obeys the
1033 C<LC_NUMERIC> locale information, which controls an application's idea
1034 of how numbers should be formatted for human readability.
1035 In most implementations the only effect is to
1036 change the character used for the decimal point--perhaps from "." to ",".
1037 The functions aren't aware of such niceties as thousands separation and
1038 so on. (See L</The localeconv function> if you care about these things.)
1040 use POSIX qw(strtod setlocale LC_NUMERIC);
1043 setlocale LC_NUMERIC, "";
1045 $n = 5/2; # Assign numeric 2.5 to $n
1047 $a = " $n"; # Locale-dependent conversion to string
1049 print "half five is $n\n"; # Locale-dependent output
1051 printf "half five is %g\n", $n; # Locale-dependent output
1053 print "DECIMAL POINT IS COMMA\n"
1054 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
1056 See also L<I18N::Langinfo> and C<RADIXCHAR>.
1058 =head2 Category C<LC_MONETARY>: Formatting of monetary amounts
1060 The C standard defines the C<LC_MONETARY> category, but not a function
1061 that is affected by its contents. (Those with experience of standards
1062 committees will recognize that the working group decided to punt on the
1063 issue.) Consequently, Perl essentially takes no notice of it. If you
1064 really want to use C<LC_MONETARY>, you can query its contents--see
1065 L</The localeconv function>--and use the information that it returns in your
1066 application's own formatting of currency amounts. However, you may well
1067 find that the information, voluminous and complex though it may be, still
1068 does not quite meet your requirements: currency formatting is a hard nut
1071 See also L<I18N::Langinfo> and C<CRNCYSTR>.
1073 =head2 Category C<LC_TIME>: Respresentation of time
1075 Output produced by C<POSIX::strftime()>, which builds a formatted
1076 human-readable date/time string, is affected by the current C<LC_TIME>
1077 locale. Thus, in a French locale, the output produced by the C<%B>
1078 format element (full month name) for the first month of the year would
1079 be "janvier". Here's how to get a list of long month names in the
1082 use POSIX qw(strftime);
1084 $long_month_name[$_] =
1085 strftime("%B", 0, 0, 0, 1, $_, 96);
1088 Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
1089 function which uses the standard system-supplied C<libc> function that
1090 always obeys the current C<LC_TIME> locale.
1092 See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
1093 C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
1095 =head2 Other categories
1097 The remaining locale categories are not currently used by Perl itself.
1098 But again note that things Perl interacts with may use these, including
1099 extensions outside the standard Perl distribution, and by the
1100 operating system and its utilities. Note especially that the string
1101 value of C<$!> and the error messages given by external utilities may
1102 be changed by C<LC_MESSAGES>. If you want to have portable error
1103 codes, use C<%!>. See L<Errno>.
1107 Although the main discussion of Perl security issues can be found in
1108 L<perlsec>, a discussion of Perl's locale handling would be incomplete
1109 if it did not draw your attention to locale-dependent security issues.
1110 Locales--particularly on systems that allow unprivileged users to
1111 build their own locales--are untrustworthy. A malicious (or just plain
1112 broken) locale can make a locale-aware application give unexpected
1113 results. Here are a few possibilities:
1119 Regular expression checks for safe file names or mail addresses using
1120 C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
1121 characters such as C<"E<gt>"> and C<"|"> are alphanumeric.
1125 String interpolation with case-mapping, as in, say, C<$dest =
1126 "C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE>
1127 case-mapping table is in effect.
1131 A sneaky C<LC_COLLATE> locale could result in the names of students with
1132 "D" grades appearing ahead of those with "A"s.
1136 An application that takes the trouble to use information in
1137 C<LC_MONETARY> may format debits as if they were credits and vice versa
1138 if that locale has been subverted. Or it might make payments in US
1139 dollars instead of Hong Kong dollars.
1143 The date and day names in dates formatted by C<strftime()> could be
1144 manipulated to advantage by a malicious user able to subvert the
1145 C<LC_DATE> locale. ("Look--it says I wasn't in the building on
1150 Such dangers are not peculiar to the locale system: any aspect of an
1151 application's environment which may be modified maliciously presents
1152 similar challenges. Similarly, they are not specific to Perl: any
1153 programming language that allows you to write programs that take
1154 account of their environment exposes you to these issues.
1156 Perl cannot protect you from all possibilities shown in the
1157 examples--there is no substitute for your own vigilance--but, when
1158 C<use locale> is in effect, Perl uses the tainting mechanism (see
1159 L<perlsec>) to mark string results that become locale-dependent, and
1160 which may be untrustworthy in consequence. Here is a summary of the
1161 tainting behavior of operators and functions that may be affected by
1168 B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
1170 Scalar true/false (or less/equal/greater) result is never tainted.
1174 B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
1176 The result string containing interpolated material is tainted if
1177 a C<use locale> form that includes C<LC_CTYPE> is in effect.
1181 B<Matching operator> (C<m//>):
1183 Scalar true/false result never tainted.
1185 All subpatterns, either delivered as a list-context result or as C<$1>
1186 I<etc>., are tainted if a C<use locale> form that includes
1187 C<LC_CTYPE> is in effect, and the subpattern
1188 regular expression contains a locale-dependent construct. These
1189 constructs include C<\w> (to match an alphanumeric character), C<\W>
1190 (non-alphanumeric character), C<\b> and C<\B> (word-boundary and
1191 non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
1192 (whitespace character), C<\S> (non whitespace character), C<\d> and
1193 C<\D> (digits and non-digits), and the POSIX character classes, such as
1194 C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
1196 Tainting is also likely if the pattern is to be matched
1197 case-insensitively (via C</i>). The exception is if all the code points
1198 to be matched this way are above 255 and do not have folds under Unicode
1199 rules to below 256. Tainting is not done for these because Perl
1200 only uses Unicode rules for such code points, and those rules are the
1201 same no matter what the current locale.
1203 The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
1204 (post-match), and C<$+> (last match) also are tainted.
1208 B<Substitution operator> (C<s///>):
1210 Has the same behavior as the match operator. Also, the left
1211 operand of C<=~> becomes tainted when a C<use locale>
1212 form that includes C<LC_CTYPE> is in effect, if modified as
1213 a result of a substitution based on a regular
1214 expression match involving any of the things mentioned in the previous
1215 item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
1219 B<Output formatting functions> (C<printf()> and C<write()>):
1221 Results are never tainted because otherwise even output from print,
1222 for example C<print(1/7)>, should be tainted if C<use locale> is in
1227 B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
1229 Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is
1234 B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
1235 C<strftime()>, C<strxfrm()>):
1237 Results are never tainted.
1241 Three examples illustrate locale-dependent tainting.
1242 The first program, which ignores its locale, won't run: a value taken
1243 directly from the command line may not be used to name an output file
1244 when taint checks are enabled.
1246 #/usr/local/bin/perl -T
1247 # Run with taint checking
1249 # Command line sanity check omitted...
1250 $tainted_output_file = shift;
1252 open(F, ">$tainted_output_file")
1253 or warn "Open of $tainted_output_file failed: $!\n";
1255 The program can be made to run by "laundering" the tainted value through
1256 a regular expression: the second example--which still ignores locale
1257 information--runs, creating the file named on its command line
1260 #/usr/local/bin/perl -T
1262 $tainted_output_file = shift;
1263 $tainted_output_file =~ m%[\w/]+%;
1264 $untainted_output_file = $&;
1266 open(F, ">$untainted_output_file")
1267 or warn "Open of $untainted_output_file failed: $!\n";
1269 Compare this with a similar but locale-aware program:
1271 #/usr/local/bin/perl -T
1273 $tainted_output_file = shift;
1275 $tainted_output_file =~ m%[\w/]+%;
1276 $localized_output_file = $&;
1278 open(F, ">$localized_output_file")
1279 or warn "Open of $localized_output_file failed: $!\n";
1281 This third program fails to run because C<$&> is tainted: it is the result
1282 of a match involving C<\w> while C<use locale> is in effect.
1288 =item PERL_SKIP_LOCALE_INIT
1290 This environment variable, available starting in Perl v5.20, if set
1291 (to any value), tells Perl to not use the rest of the
1292 environment variables to initialize with. Instead, Perl uses whatever
1293 the current locale settings are. This is particularly useful in
1294 embedded environments, see
1295 L<perlembed/Using embedded Perl with POSIX locales>.
1299 A string that can suppress Perl's warning about failed locale settings
1300 at startup. Failure can occur if the locale support in the operating
1301 system is lacking (broken) in some way--or if you mistyped the name of
1302 a locale when you set up your environment. If this environment
1303 variable is absent, or has a value other than "0" or "", Perl will
1304 complain about locale setting failures.
1306 B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message.
1307 The message tells about some problem in your system's locale support,
1308 and you should investigate what the problem is.
1312 The following environment variables are not specific to Perl: They are
1313 part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
1314 for controlling an application's opinion on data. Windows is non-POSIX,
1315 but Perl arranges for the following to work as described anyway.
1316 If the locale given by an environment variable is not valid, Perl tries
1317 the next lower one in priority. If none are valid, on Windows, the
1318 system default locale is then tried. If all else fails, the C<"C">
1319 locale is used. If even that doesn't work, something is badly broken,
1320 but Perl tries to forge ahead with whatever the locale settings might
1327 C<LC_ALL> is the "override-all" locale environment variable. If
1328 set, it overrides all the rest of the locale environment variables.
1332 B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
1333 are using the GNU libc. This is the case if you are using e.g. Linux.
1334 If you are using "commercial" Unixes you are most probably I<not>
1335 using GNU libc and you can ignore C<LANGUAGE>.
1337 However, in the case you are using C<LANGUAGE>: it affects the
1338 language of informational, warning, and error messages output by
1339 commands (in other words, it's like C<LC_MESSAGES>) but it has higher
1340 priority than C<LC_ALL>. Moreover, it's not a single value but
1341 instead a "path" (":"-separated list) of I<languages> (not locales).
1342 See the GNU C<gettext> library documentation for more information.
1346 In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
1347 locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
1348 chooses the character type locale.
1352 In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
1353 (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
1354 C<LANG> chooses the collation locale.
1356 =item C<LC_MONETARY>
1358 In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
1359 formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
1360 C<LANG> chooses the monetary formatting locale.
1364 In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
1365 locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
1366 chooses the numeric format.
1370 In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
1371 formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
1372 C<LANG> chooses the date and time formatting locale.
1376 C<LANG> is the "catch-all" locale environment variable. If it is set, it
1377 is used as the last resort after the overall C<LC_ALL> and the
1378 category-specific C<LC_I<foo>>.
1384 The C<LC_NUMERIC> controls the numeric output:
1387 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1388 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1389 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1391 and also how strings are parsed by C<POSIX::strtod()> as numbers:
1394 use POSIX qw(locale_h strtod);
1395 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1396 my $x = strtod("2,34") + 5;
1397 print $x, "\n"; # Probably shows 7,34.
1401 =head2 String C<eval> and C<LC_NUMERIC>
1403 A string L<eval|perlfunc/eval EXPR> parses its expression as standard
1404 Perl. It is therefore expecting the decimal point to be a dot. If
1405 C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
1406 be confused, perhaps silently.
1409 use POSIX qw(locale_h);
1410 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1412 print eval "$a + 1.5";
1415 prints C<13,5>. This is because in that locale, the comma is the
1416 decimal point character. The C<eval> thus expands to:
1420 and the result is not what you likely expected. No warnings are
1421 generated. If you do string C<eval>'s within the scope of
1422 S<C<use locale>>, you should instead change the C<eval> line to do
1425 print eval "no locale; $a + 1.5";
1429 You could also exclude C<LC_NUMERIC>, if you don't need it, by
1431 use locale ':!numeric';
1433 =head2 Backward compatibility
1435 Versions of Perl prior to 5.004 B<mostly> ignored locale information,
1436 generally behaving as if something similar to the C<"C"> locale were
1437 always in force, even if the program environment suggested otherwise
1438 (see L</The setlocale function>). By default, Perl still behaves this
1439 way for backward compatibility. If you want a Perl application to pay
1440 attention to locale information, you B<must> use the S<C<use locale>>
1441 pragma (see L</The "use locale" pragma>) or, in the unlikely event
1442 that you want to do so for just pattern matching, the
1443 C</l> regular expression modifier (see L<perlre/Character set
1444 modifiers>) to instruct it to do so.
1446 Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
1447 information if available; that is, C<\w> did understand what
1448 were the letters according to the locale environment variables.
1449 The problem was that the user had no control over the feature:
1450 if the C library supported locales, Perl used them.
1452 =head2 I18N:Collate obsolete
1454 In versions of Perl prior to 5.004, per-locale collation was possible
1455 using the C<I18N::Collate> library module. This module is now mildly
1456 obsolete and should be avoided in new applications. The C<LC_COLLATE>
1457 functionality is now integrated into the Perl core language: One can
1458 use locale-specific scalar data completely normally with C<use locale>,
1459 so there is no longer any need to juggle with the scalar references of
1462 =head2 Sort speed and memory use impacts
1464 Comparing and sorting by locale is usually slower than the default
1465 sorting; slow-downs of two to four times have been observed. It will
1466 also consume more memory: once a Perl scalar variable has participated
1467 in any string comparison or sorting operation obeying the locale
1468 collation rules, it will take 3-15 times more memory than before. (The
1469 exact multiplier depends on the string's contents, the operating system
1470 and the locale.) These downsides are dictated more by the operating
1471 system's implementation of the locale system than by Perl.
1473 =head2 Freely available locale definitions
1475 The Unicode CLDR project extracts the POSIX portion of many of its
1476 locales, available at
1478 https://unicode.org/Public/cldr/2.0.1/
1480 (Newer versions of CLDR require you to compute the POSIX data yourself.
1481 See L<http://unicode.org/Public/cldr/latest/>.)
1483 There is a large collection of locale definitions at:
1485 http://std.dkuug.dk/i18n/WG15-collection/locales/
1487 You should be aware that it is
1488 unsupported, and is not claimed to be fit for any purpose. If your
1489 system allows installation of arbitrary locales, you may find the
1490 definitions useful as they are, or as a basis for the development of
1493 =head2 I18n and l10n
1495 "Internationalization" is often abbreviated as B<i18n> because its first
1496 and last letters are separated by eighteen others. (You may guess why
1497 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1498 the same way, "localization" is often abbreviated to B<l10n>.
1500 =head2 An imperfect standard
1502 Internationalization, as defined in the C and POSIX standards, can be
1503 criticized as incomplete and ungainly. They also have a tendency, like
1504 standards groups, to divide the world into nations, when we all know
1505 that the world can equally well be divided into bankers, bikers, gamers,
1508 =head1 Unicode and UTF-8
1510 The support of Unicode is new starting from Perl version v5.6, and more fully
1511 implemented in versions v5.8 and later. See L<perluniintro>.
1513 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1514 C<LC_COLLATE> is only partially supported; collation support is improved
1515 in Perl v5.26 to a level that may be sufficient for your needs
1516 (see L</Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting>).
1518 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1520 use locale ':not_characters';
1522 When this form of the pragma is used, only the non-character portions of
1523 locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
1524 you have translated all the characters it is to operate on into Unicode
1525 (actually the platform's native character set (ASCII or EBCDIC) plus
1526 Unicode). For data in files, this can conveniently be done by also
1531 This pragma arranges for all inputs from files to be translated into
1532 Unicode from the current locale as specified in the environment (see
1533 L</ENVIRONMENT>), and all outputs to files to be translated back
1534 into the locale. (See L<open>). On a per-filehandle basis, you can
1535 instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
1536 module, both available from CPAN. The latter module also has methods to
1537 ease the handling of C<ARGV> and environment variables, and can be used
1538 on individual strings. If you know that all your locales will be
1539 UTF-8, as many are these days, you can use the
1540 L<B<-C>|perlrun/-C [numberE<sol>list]> command line switch.
1542 This form of the pragma allows essentially seamless handling of locales
1543 with Unicode. The collation order will be by Unicode code point order.
1544 L<Unicode::Collate> can be used to get Unicode rules collation.
1546 All the modules and switches just described can be used in v5.20 with
1547 just plain C<use locale>, and, should the input locales not be UTF-8,
1548 you'll get the less than ideal behavior, described below, that you get
1549 with pre-v5.16 Perls, or when you use the locale pragma without the
1550 C<:not_characters> parameter in v5.16 and v5.18. If you are using
1551 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1552 does not apply to you.
1554 There are two cases, multi-byte and single-byte locales. First
1557 The only multi-byte (or wide character) locale that Perl is ever likely
1558 to support is UTF-8. This is due to the difficulty of implementation,
1559 the fact that high quality UTF-8 locales are now published for every
1560 area of the world (L<https://unicode.org/Public/cldr/2.0.1/> for
1561 ones that are already set-up, but from an earlier version;
1562 L<https://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1563 you have to extract the POSIX information yourself), and
1564 failing all that, you can use the L<Encode> module to translate to/from
1565 your locale. So, you'll have to do one of those things if you're using
1566 one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1567 Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1568 work reasonably well (depending on your C library implementation)
1570 they and Perl store characters that take up multiple bytes the same way.
1571 However, some, if not most, C library implementations may not process
1572 the characters in the upper half of the Latin-1 range (128 - 255)
1573 properly under C<LC_CTYPE>. To see if a character is a particular type
1574 under a locale, Perl uses the functions like C<isalnum()>. Your C
1575 library may not work for UTF-8 locales with those functions, instead
1576 only working under the newer wide library functions like C<iswalnum()>,
1577 which Perl does not use.
1578 These multi-byte locales are treated like single-byte locales, and will
1579 have the restrictions described below. Starting in Perl v5.22 a warning
1580 message is raised when Perl detects a multi-byte locale that it doesn't
1583 For single-byte locales,
1584 Perl generally takes the tack to use locale rules on code points that can fit
1585 in a single byte, and Unicode rules for those that can't (though this
1586 isn't uniformly applied, see the note at the end of this section). This
1587 prevents many problems in locales that aren't UTF-8. Suppose the locale
1588 is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
1589 in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
1590 regular expression character class C<[[:alpha:]]> will magically match
1591 0xD7 in the Greek locale but not in the Latin one.
1593 However, there are places where this breaks down. Certain Perl constructs are
1594 for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
1595 Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
1596 subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
1597 Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
1598 issue occurs with C<\N{...}>. Prior to v5.20, it is therefore a bad
1599 idea to use C<\p{}> or
1600 C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
1601 locale will be ISO8859-1. Use POSIX character classes instead.
1603 Another problem with this approach is that operations that cross the
1604 single byte/multiple byte boundary are not well-defined, and so are
1605 disallowed. (This boundary is between the codepoints at 255/256.)
1606 For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1607 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1608 Greek locale, for example, there is no character at 0xFF, and Perl
1609 has no way of knowing what the character at 0xFF is really supposed to
1610 represent. Thus it disallows the operation. In this mode, the
1611 lowercase of U+0178 is itself.
1613 The same problems ensue if you enable automatic UTF-8-ification of your
1614 standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
1615 non-UTF-8 locales (by using either the B<-C> command line switch or the
1616 C<PERL_UNICODE> environment variable; see
1617 L<perlrun|perlrun/-C [numberE<sol>list]>).
1618 Things are read in as UTF-8, which would normally imply a Unicode
1619 interpretation, but the presence of a locale causes them to be interpreted
1620 in that locale instead. For example, a 0xD7 code point in the Unicode
1621 input, which should mean the multiplication sign, won't be interpreted by
1622 Perl that way under the Greek locale. This is not a problem
1623 I<provided> you make certain that all locales will always and only be either
1624 an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
1626 Still another problem is that this approach can lead to two code
1627 points meaning the same character. Thus in a Greek locale, both U+03A7
1628 and U+00D7 are GREEK CAPITAL LETTER CHI.
1630 Because of all these problems, starting in v5.22, Perl will raise a
1631 warning if a multi-byte (hence Unicode) code point is used when a
1632 single-byte locale is in effect. (Although it doesn't check for this if
1633 doing so would unreasonably slow execution down.)
1635 Vendor locales are notoriously buggy, and it is difficult for Perl to test
1636 its locale-handling code because this interacts with code that Perl has no
1637 control over; therefore the locale-handling code in Perl may be buggy as
1638 well. (However, the Unicode-supplied locales should be better, and
1639 there is a feed back mechanism to correct any problems. See
1640 L</Freely available locale definitions>.)
1642 If you have Perl v5.16, the problems mentioned above go away if you use
1643 the C<:not_characters> parameter to the locale pragma (except for vendor
1644 bugs in the non-character portions). If you don't have v5.16, and you
1645 I<do> have locales that work, using them may be worthwhile for certain
1646 specific purposes, as long as you keep in mind the gotchas already
1647 mentioned. For example, if the collation for your locales works, it
1648 runs faster under locales than under L<Unicode::Collate>; and you gain
1649 access to such things as the local currency symbol and the names of the
1650 months and days of the week. (But to hammer home the point, in v5.16,
1651 you get this access without the downsides of locales by using the
1652 C<:not_characters> form of the pragma.)
1654 Note: The policy of using locale rules for code points that can fit in a
1655 byte, and Unicode rules for those that can't is not uniformly applied.
1656 Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
1657 consistently to regular expression matching except for bracketed
1658 character classes; in v5.14 it was extended to all regex matches; and in
1659 v5.16 to the casing operations such as C<\L> and C<uc()>. For
1660 collation, in all releases so far, the system's C<strxfrm()> function is
1661 called, and whatever it does is what you get. Starting in v5.26, various
1662 bugs are fixed with the way perl uses this function.
1666 =head2 Collation of strings containing embedded C<NUL> characters
1668 C<NUL> characters will sort the same as the lowest collating control
1669 character does, or to C<"\001"> in the unlikely event that there are no
1670 control characters at all in the locale. In cases where the strings
1671 don't contain this non-C<NUL> control, the results will be correct, and
1672 in many locales, this control, whatever it might be, will rarely be
1673 encountered. But there are cases where a C<NUL> should sort before this
1674 control, but doesn't. If two strings do collate identically, the one
1675 containing the C<NUL> will sort to earlier. Prior to 5.26, there were
1678 =head2 Multi-threaded
1680 XS code or C-language libraries called from it that use the system
1681 L<C<setlocale(3)>> function (except on Windows) likely will not work
1682 from a multi-threaded application without changes. See
1683 L<perlxs/Locale-aware XS code>.
1685 An XS module that is locale-dependent could have been written under the
1686 assumption that it will never be called in a multi-threaded environment,
1687 and so uses other non-locale constructs that aren't multi-thread-safe.
1688 See L<perlxs/Thread-aware system interfaces>.
1690 POSIX does not define a way to get the name of the current per-thread
1691 locale. Some systems, such as Darwin and NetBSD do implement a
1692 function, L<querylocale(3)> to do this. On non-Windows systems without
1693 it, such as Linux, there are some additional caveats:
1699 An embedded perl needs to be started up while the global locale is in
1700 effect. See L<perlembed/Using embedded Perl with POSIX locales>.
1704 It becomes more important for perl to know about all the possible
1705 locale categories on the platform, even if they aren't apparently used
1706 in your program. Perl knows all of the Linux ones. If your platform
1707 has others, you can submit an issue at
1708 L<https://github.com/Perl/perl5/issues> for
1709 inclusion of it in the next release. In the meantime, it is possible to
1710 edit the Perl source to teach it about the category, and then recompile.
1711 Search for instances of, say, C<LC_PAPER> in the source, and use that as
1712 a template to add the omitted one.
1716 It is possible, though hard to do, to call C<POSIX::setlocale> with a
1717 locale that it doesn't recognize as syntactically legal, but actually is
1718 legal on that system. This should happen only with embedded perls, or
1719 if you hand-craft a locale name yourself.
1723 =head2 Broken systems
1725 In certain systems, the operating system's locale support
1726 is broken and cannot be fixed or used by Perl. Such deficiencies can
1727 and will result in mysterious hangs and/or Perl core dumps when
1728 C<use locale> is in effect. When confronted with such a system,
1729 please report in excruciating detail to
1730 <L<https://github.com/Perl/perl5/issues>>, and
1731 also contact your vendor: bug fixes may exist for these problems
1732 in your operating system. Sometimes such bug fixes are called an
1733 operating system upgrade. If you have the source for Perl, include in
1734 the bug report the output of the test described above in L</Testing
1735 for broken locales>.
1739 L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
1740 L<POSIX/localeconv>,
1741 L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
1742 L<POSIX/strtod>, L<POSIX/strxfrm>.
1744 For special considerations when Perl is embedded in a C program,
1745 see L<perlembed/Using embedded Perl with POSIX locales>.
1749 Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
1750 Dunlop, assisted by the perl5-porters. Prose worked over a bit by
1751 Tom Christiansen, and now maintained by Perl 5 porters.