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>. Perl continues to
44 support the old non UTF-8 locales as well. There are currently no UTF-8
45 locales for EBCDIC platforms.
47 (Unicode is also creating C<CLDR>, the "Common Locale Data Repository",
48 L<http://cldr.unicode.org/> which includes more types of information than
49 are available in the POSIX locale system. At the time of this writing,
50 there was no CPAN module that provides access to this XML-encoded data.
51 However, it is possible to compute the POSIX locale data from them, and
52 earlier CLDR versions had these already extracted for you as UTF-8 locales
53 L<http://unicode.org/Public/cldr/2.0.1/>.)
55 =head1 WHAT IS A LOCALE
57 A locale is a set of data that describes various aspects of how various
58 communities in the world categorize their world. These categories are
59 broken down into the following types (some of which include a brief
64 =item Category C<LC_NUMERIC>: Numeric formatting
66 This indicates how numbers should be formatted for human readability,
67 for example the character used as the decimal point.
69 =item Category C<LC_MONETARY>: Formatting of monetary amounts
73 =item Category C<LC_TIME>: Date/Time formatting
77 =item Category C<LC_MESSAGES>: Error and other messages
79 This is used by Perl itself only for accessing operating system error
80 messages via L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>.
82 =item Category C<LC_COLLATE>: Collation
84 This indicates the ordering of letters for comparison and sorting.
85 In Latin alphabets, for example, "b", generally follows "a".
87 =item Category C<LC_CTYPE>: Character Types
89 This indicates, for example if a character is an uppercase letter.
91 =item Other categories
93 Some platforms have other categories, dealing with such things as
94 measurement units and paper sizes. None of these are used directly by
95 Perl, but outside operations that Perl interacts with may use
96 these. See L</Not within the scope of "use locale"> below.
100 More details on the categories used by Perl are given below in L</LOCALE
103 Together, these categories go a long way towards being able to customize
104 a single program to run in many different locations. But there are
105 deficiencies, so keep reading.
107 =head1 PREPARING TO USE LOCALES
109 Perl itself (outside the L<POSIX> module) will not use locales unless
110 specifically requested to (but
111 again note that Perl may interact with code that does use them). Even
112 if there is such a request, B<all> of the following must be true
113 for it to work properly:
119 B<Your operating system must support the locale system>. If it does,
120 you should find that the C<setlocale()> function is a documented part of
125 B<Definitions for locales that you use must be installed>. You, or
126 your system administrator, must make sure that this is the case. The
127 available locales, the location in which they are kept, and the manner
128 in which they are installed all vary from system to system. Some systems
129 provide only a few, hard-wired locales and do not allow more to be
130 added. Others allow you to add "canned" locales provided by the system
131 supplier. Still others allow you or the system administrator to define
132 and add arbitrary locales. (You may have to ask your supplier to
133 provide canned locales that are not delivered with your operating
134 system.) Read your system documentation for further illumination.
138 B<Perl must believe that the locale system is supported>. If it does,
139 C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is
144 If you want a Perl application to process and present your data
145 according to a particular locale, the application code should include
146 the S<C<use locale>> pragma (see L</The "use locale" pragma>) where
147 appropriate, and B<at least one> of the following must be true:
153 B<The locale-determining environment variables (see L</"ENVIRONMENT">)
154 must be correctly set up> at the time the application is started, either
155 by yourself or by whomever set up your system account; or
159 B<The application must set its own locale> using the method described in
160 L</The setlocale function>.
166 =head2 The C<"use locale"> pragma
168 Starting in Perl 5.28, this pragma may be used in
169 L<multi-threaded|threads> applications on systems that have thread-safe
170 locale ability. Some caveats apply, see L</Multi-threaded> below. On
171 systems without this capability, or in earlier Perls, do NOT use this
172 pragma in scripts that have multiple L<threads|threads> active. The
173 locale in these cases is not local to a single thread. Another thread
174 may change the locale at any time, which could cause at a minimum that a
175 given thread is operating in a locale it isn't expecting to be in. On
176 some platforms, segfaults can also occur. The locale change need not be
177 explicit; some operations cause perl to change the locale itself. You
178 are vulnerable simply by having done a S<C<"use locale">>.
180 By default, Perl itself (outside the L<POSIX> module)
181 ignores the current locale. The S<C<use locale>>
182 pragma tells Perl to use the current locale for some operations.
183 Starting in v5.16, there are optional parameters to this pragma,
184 described below, which restrict which operations are affected by it.
186 The current locale is set at execution time by
187 L<setlocale()|/The setlocale function> described below. If that function
188 hasn't yet been called in the course of the program's execution, the
189 current locale is that which was determined by the L</"ENVIRONMENT"> in
190 effect at the start of the program.
191 If there is no valid environment, the current locale is whatever the
192 system default has been set to. On POSIX systems, it is likely, but
193 not necessarily, the "C" locale. On Windows, the default is set via the
194 computer's S<C<Control Panel-E<gt>Regional and Language Options>> (or its
197 The operations that are affected by locale are:
201 =item B<Not within the scope of C<"use locale">>
203 Only certain operations (all originating outside Perl) should be
204 affected, as follows:
210 The current locale is used when going outside of Perl with
211 operations like L<system()|perlfunc/system LIST> or
212 L<qxE<sol>E<sol>|perlop/qxE<sol>STRINGE<sol>>, if those operations are
217 Also Perl gives access to various C library functions through the
218 L<POSIX> module. Some of those functions are always affected by the
219 current locale. For example, C<POSIX::strftime()> uses C<LC_TIME>;
220 C<POSIX::strtod()> uses C<LC_NUMERIC>; C<POSIX::strcoll()> and
221 C<POSIX::strxfrm()> use C<LC_COLLATE>. All such functions
222 will behave according to the current underlying locale, even if that
223 locale isn't exposed to Perl space.
225 This applies as well to L<I18N::Langinfo>.
229 XS modules for all categories but C<LC_NUMERIC> get the underlying
230 locale, and hence any C library functions they call will use that
231 underlying locale. For more discussion, see L<perlxs/CAVEATS>.
235 Note that all C programs (including the perl interpreter, which is
236 written in C) always have an underlying locale. That locale is the "C"
237 locale unless changed by a call to L<setlocale()|/The setlocale
238 function>. When Perl starts up, it changes the underlying locale to the
239 one which is indicated by the L</ENVIRONMENT>. When using the L<POSIX>
240 module or writing XS code, it is important to keep in mind that the
241 underlying locale may be something other than "C", even if the program
242 hasn't explicitly changed it.
246 =item B<Lingering effects of C<S<use locale>>>
248 Certain Perl operations that are set-up within the scope of a
249 C<use locale> retain that effect even outside the scope.
256 The output format of a L<write()|perlfunc/write> is determined by an
257 earlier format declaration (L<perlfunc/format>), so whether or not the
258 output is affected by locale is determined by if the C<format()> is
259 within the scope of a C<use locale>, not whether the C<write()>
264 Regular expression patterns can be compiled using
265 L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodualn> with actual
266 matching deferred to later. Again, it is whether or not the compilation
267 was done within the scope of C<use locale> that determines the match
268 behavior, not if the matches are done within such a scope or not.
274 =item B<Under C<"use locale";>>
280 All the above operations
284 B<Format declarations> (L<perlfunc/format>) and hence any subsequent
285 C<write()>s use C<LC_NUMERIC>.
289 B<stringification and output> use C<LC_NUMERIC>.
290 These include the results of
299 B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
300 C<LC_COLLATE>. C<sort()> is also affected if used without an
301 explicit comparison function, because it uses C<cmp> by default.
303 B<Note:> C<eq> and C<ne> are unaffected by locale: they always
304 perform a char-by-char comparison of their scalar operands. What's
305 more, if C<cmp> finds that its operands are equal according to the
306 collation sequence specified by the current locale, it goes on to
307 perform a char-by-char comparison, and only returns I<0> (equal) if the
308 operands are char-for-char identical. If you really want to know whether
309 two strings--which C<eq> and C<cmp> may consider different--are equal
310 as far as collation in the locale is concerned, see the discussion in
311 L<Category C<LC_COLLATE>: Collation>.
315 B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
316 C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
320 B<The variables L<$!|perlvar/$ERRNO>> (and its synonyms C<$ERRNO> and
321 C<$OS_ERROR>) B<and L<$^E|perlvar/$EXTENDED_OS_ERROR>> (and its synonym
322 C<$EXTENDED_OS_ERROR>) when used as strings use C<LC_MESSAGES>.
328 The default behavior is restored with the S<C<no locale>> pragma, or
329 upon reaching the end of the block enclosing C<use locale>.
330 Note that C<use locale> calls may be
331 nested, and that what is in effect within an inner scope will revert to
332 the outer scope's rules at the end of the inner scope.
334 The string result of any operation that uses locale
335 information is tainted, as it is possible for a locale to be
336 untrustworthy. See L</"SECURITY">.
338 Starting in Perl v5.16 in a very limited way, and more generally in
339 v5.22, you can restrict which category or categories are enabled by this
340 particular instance of the pragma by adding parameters to it. For
343 use locale qw(:ctype :numeric);
345 enables locale awareness within its scope of only those operations
346 (listed above) that are affected by C<LC_CTYPE> and C<LC_NUMERIC>.
348 The possible categories are: C<:collate>, C<:ctype>, C<:messages>,
349 C<:monetary>, C<:numeric>, C<:time>, and the pseudo category
350 C<:characters> (described below).
354 use locale ':messages';
356 and only L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>
357 will be locale aware. Everything else is unaffected.
359 Since Perl doesn't currently do anything with the C<LC_MONETARY>
360 category, specifying C<:monetary> does effectively nothing. Some
361 systems have other categories, such as C<LC_PAPER>, but Perl
362 also doesn't do anything with them, and there is no way to specify
363 them in this pragma's arguments.
365 You can also easily say to use all categories but one, by either, for
368 use locale ':!ctype';
369 use locale ':not_ctype';
371 both of which mean to enable locale awarness of all categories but
372 C<LC_CTYPE>. Only one category argument may be specified in a
373 S<C<use locale>> if it is of the negated form.
375 Prior to v5.22 only one form of the pragma with arguments is available:
377 use locale ':not_characters';
379 (and you have to say C<not_>; you can't use the bang C<!> form). This
380 pseudo category is a shorthand for specifying both C<:collate> and
381 C<:ctype>. Hence, in the negated form, it is nearly the same thing as
384 use locale qw(:messages :monetary :numeric :time);
386 We use the term "nearly", because C<:not_characters> also turns on
387 S<C<use feature 'unicode_strings'>> within its scope. This form is
388 less useful in v5.20 and later, and is described fully in
389 L</Unicode and UTF-8>, but briefly, it tells Perl to not use the
390 character portions of the locale definition, that is the C<LC_CTYPE> and
391 C<LC_COLLATE> categories. Instead it will use the native character set
392 (extended by Unicode). When using this parameter, you are responsible
393 for getting the external character set translated into the
394 native/Unicode one (which it already will be if it is one of the
395 increasingly popular UTF-8 locales). There are convenient ways of doing
396 this, as described in L</Unicode and UTF-8>.
398 =head2 The setlocale function
400 WARNING! Prior to Perl 5.28 or on a system that does not support
401 thread-safe locale operations, do NOT use this function in a
402 L<thread|threads>. The locale will change in all other threads at the
403 same time, and should your thread get paused by the operating system,
404 and another started, that thread will not have the locale it is
405 expecting. On some platforms, there can be a race leading to segfaults
406 if two threads call this function nearly simultaneously.
408 You can switch locales as often as you wish at run time with the
409 C<POSIX::setlocale()> function:
411 # Import locale-handling tool set from POSIX module.
412 # This example uses: setlocale -- the function call
413 # LC_CTYPE -- explained below
414 # (Showing the testing for success/failure of operations is
415 # omitted in these examples to avoid distracting from the main
418 use POSIX qw(locale_h);
422 # query and save the old locale
423 $old_locale = setlocale(LC_CTYPE);
425 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
426 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
428 setlocale(LC_CTYPE, "");
429 # LC_CTYPE now reset to the default defined by the
430 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
431 # default. See below for documentation.
433 # restore the old locale
434 setlocale(LC_CTYPE, $old_locale);
436 The first argument of C<setlocale()> gives the B<category>, the second the
437 B<locale>. The category tells in what aspect of data processing you
438 want to apply locale-specific rules. Category names are discussed in
439 L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a
440 collection of customization information corresponding to a particular
441 combination of language, country or territory, and codeset. Read on for
442 hints on the naming of locales: not all systems name locales as in the
445 If no second argument is provided and the category is something other
446 than C<LC_ALL>, the function returns a string naming the current locale
447 for the category. You can use this value as the second argument in a
448 subsequent call to C<setlocale()>, B<but> on some platforms the string
449 is opaque, not something that most people would be able to decipher as
450 to what locale it means.
452 If no second argument is provided and the category is C<LC_ALL>, the
453 result is implementation-dependent. It may be a string of
454 concatenated locale names (separator also implementation-dependent)
455 or a single locale name. Please consult your L<setlocale(3)> man page for
458 If a second argument is given and it corresponds to a valid locale,
459 the locale for the category is set to that value, and the function
460 returns the now-current locale value. You can then use this in yet
461 another call to C<setlocale()>. (In some implementations, the return
462 value may sometimes differ from the value you gave as the second
463 argument--think of it as an alias for the value you gave.)
465 As the example shows, if the second argument is an empty string, the
466 category's locale is returned to the default specified by the
467 corresponding environment variables. Generally, this results in a
468 return to the default that was in force when Perl started up: changes
469 to the environment made by the application after startup may or may not
470 be noticed, depending on your system's C library.
472 Note that when a form of C<use locale> that doesn't include all
473 categories is specified, Perl ignores the excluded categories.
475 If C<set_locale()> fails for some reason (for example, an attempt to set
476 to a locale unknown to the system), the locale for the category is not
477 changed, and the function returns C<undef>.
479 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
480 implement POSIX 2008 thread-safe locale operations, this function
481 doesn't actually call the system C<setlocale>. Instead those
482 thread-safe operations are used to emulate the C<setlocale> function,
483 but in a thread-safe manner.
485 For further information about the categories, consult L<setlocale(3)>.
487 =head2 Multi-threaded operation
489 Beginning in Perl 5.28, multi-threaded locale operation is supported on
490 systems that implement either the POSIX 2008 or Windows-specific
491 thread-safe locale operations. Many modern systems, such as various
492 Unix variants and Darwin do have this.
494 You can tell if using locales is safe on your system by looking at the
495 read-only boolean variable C<${^SAFE_LOCALES}>. The value is 1 if the
496 perl is not threaded, or if it is using thread-safe locale operations.
498 Thread-safe operations are supported in Windows starting in Visual Studio
499 2005, and in systems compatible with POSIX 2008. Some platforms claim
500 to support POSIX 2008, but have buggy implementations, so that the hints
501 files for compiling to run on them turn off attempting to use
502 thread-safety. C<${^SAFE_LOCALES}> will be 0 on them.
504 Be aware that writing a multi-threaded application will not be portable
505 to a platform which lacks the native thread-safe locale support. On
506 systems that do have it, you automatically get this behavior for
507 threaded perls, without having to do anything. If for some reason, you
508 don't want to use this capability (perhaps the POSIX 2008 support is
509 buggy on your system), you can manually compile Perl to use the old
510 non-thread-safe implementation by passing the argument
511 C<-Accflags='-DNO_THREAD_SAFE_LOCALE'> to F<Configure>.
512 Except on Windows, this will continue to use certain of the POSIX 2008
513 functions in some situations. If these are buggy, you can pass the
514 following to F<Configure> instead or additionally:
515 C<-Accflags='-DNO_POSIX_2008_LOCALE'>. This will also keep the code
516 from using thread-safe locales.
517 C<${^SAFE_LOCALES}> will be 0 on systems that turn off the thread-safe
520 The initial program is started up using the locale specified from the
521 environment, as currently, described in L</ENVIRONMENT>. All newly
522 created threads start with C<LC_ALL> set to C<"C">>. Each thread may
523 use C<POSIX::setlocale()> to query or switch its locale at any time,
524 without affecting any other thread. All locale-dependent operations
525 automatically use their thread's locale.
527 This should be completely transparent to any applications written
528 entirely in Perl (minus a few rarely encountered caveats given in the
529 L</Multi-threaded> section). Information for XS module writers is given
530 in L<perlxs/Locale-aware XS code>.
532 =head2 Finding locales
534 For locales available in your system, consult also L<setlocale(3)> to
535 see whether it leads to the list of available locales (search for the
536 I<SEE ALSO> section). If that fails, try the following command lines:
550 and see whether they list something resembling these
552 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
553 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
556 english german russian
557 english.iso88591 german.iso88591 russian.iso88595
558 english.roman8 russian.koi8r
560 Sadly, even though the calling interface for C<setlocale()> has been
561 standardized, names of locales and the directories where the
562 configuration resides have not been. The basic form of the name is
563 I<language_territory>B<.>I<codeset>, but the latter parts after
564 I<language> are not always present. The I<language> and I<country>
565 are usually from the standards B<ISO 3166> and B<ISO 639>, the
566 two-letter abbreviations for the countries and the languages of the
567 world, respectively. The I<codeset> part often mentions some B<ISO
568 8859> character set, the Latin codesets. For example, C<ISO 8859-1>
569 is the so-called "Western European codeset" that can be used to encode
570 most Western European languages adequately. Again, there are several
571 ways to write even the name of that one standard. Lamentably.
573 Two special locales are worth particular mention: "C" and "POSIX".
574 Currently these are effectively the same locale: the difference is
575 mainly that the first one is defined by the C standard, the second by
576 the POSIX standard. They define the B<default locale> in which
577 every program starts in the absence of locale information in its
578 environment. (The I<default> default locale, if you will.) Its language
579 is (American) English and its character codeset ASCII or, rarely, a
580 superset thereof (such as the "DEC Multinational Character Set
581 (DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
582 may not actually exactly match what the C standard calls for. So
585 B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
586 POSIX-conformant), so use "C" when you need explicitly to specify this
589 =head2 LOCALE PROBLEMS
591 You may encounter the following warning message at Perl startup:
593 perl: warning: Setting locale failed.
594 perl: warning: Please check that your locale settings:
597 are supported and installed on your system.
598 perl: warning: Falling back to the standard locale ("C").
600 This means that your locale settings had C<LC_ALL> set to "En_US" and
601 LANG exists but has no value. Perl tried to believe you but could not.
602 Instead, Perl gave up and fell back to the "C" locale, the default locale
603 that is supposed to work no matter what. (On Windows, it first tries
604 falling back to the system default locale.) This usually means your
605 locale settings were wrong, they mention locales your system has never
606 heard of, or the locale installation in your system has problems (for
607 example, some system files are broken or missing). There are quick and
608 temporary fixes to these problems, as well as more thorough and lasting
611 =head2 Testing for broken locales
613 If you are building Perl from source, the Perl test suite file
614 F<lib/locale.t> can be used to test the locales on your system.
615 Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
616 will cause it to output detailed results. For example, on Linux, you
619 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
621 Besides many other tests, it will test every locale it finds on your
622 system to see if they conform to the POSIX standard. If any have
623 errors, it will include a summary near the end of the output of which
624 locales passed all its tests, and which failed, and why.
626 =head2 Temporarily fixing locale problems
628 The two quickest fixes are either to render Perl silent about any
629 locale inconsistencies or to run Perl under the default locale "C".
631 Perl's moaning about locale problems can be silenced by setting the
632 environment variable C<PERL_BADLANG> to "0" or "".
633 This method really just sweeps the problem under the carpet: you tell
634 Perl to shut up even when Perl sees that something is wrong. Do not
635 be surprised if later something locale-dependent misbehaves.
637 Perl can be run under the "C" locale by setting the environment
638 variable C<LC_ALL> to "C". This method is perhaps a bit more civilized
639 than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or
640 other locale variables) may affect other programs as well, not just
641 Perl. In particular, external programs run from within Perl will see
642 these changes. If you make the new settings permanent (read on), all
643 programs you run see the changes. See L</"ENVIRONMENT"> for
644 the full list of relevant environment variables and L</"USING LOCALES">
645 for their effects in Perl. Effects in other programs are
646 easily deducible. For example, the variable C<LC_COLLATE> may well affect
647 your B<sort> program (or whatever the program that arranges "records"
648 alphabetically in your system is called).
650 You can test out changing these variables temporarily, and if the
651 new settings seem to help, put those settings into your shell startup
652 files. Consult your local documentation for the exact details. For
653 Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
655 LC_ALL=en_US.ISO8859-1
658 This assumes that we saw the locale "en_US.ISO8859-1" using the commands
659 discussed above. We decided to try that instead of the above faulty
660 locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
662 setenv LC_ALL en_US.ISO8859-1
664 or if you have the "env" application you can do (in any shell)
666 env LC_ALL=en_US.ISO8859-1 perl ...
668 If you do not know what shell you have, consult your local
669 helpdesk or the equivalent.
671 =head2 Permanently fixing locale problems
673 The slower but superior fixes are when you may be able to yourself
674 fix the misconfiguration of your own environment variables. The
675 mis(sing)configuration of the whole system's locales usually requires
676 the help of your friendly system administrator.
678 First, see earlier in this document about L</Finding locales>. That tells
679 how to find which locales are really supported--and more importantly,
680 installed--on your system. In our example error message, environment
681 variables affecting the locale are listed in the order of decreasing
682 importance (and unset variables do not matter). Therefore, having
683 LC_ALL set to "En_US" must have been the bad choice, as shown by the
684 error message. First try fixing locale settings listed first.
686 Second, if using the listed commands you see something B<exactly>
687 (prefix matches do not count and case usually counts) like "En_US"
688 without the quotes, then you should be okay because you are using a
689 locale name that should be installed and available in your system.
690 In this case, see L</Permanently fixing your system's locale configuration>.
692 =head2 Permanently fixing your system's locale configuration
694 This is when you see something like:
696 perl: warning: Please check that your locale settings:
699 are supported and installed on your system.
701 but then cannot see that "En_US" listed by the above-mentioned
702 commands. You may see things like "en_US.ISO8859-1", but that isn't
703 the same. In this case, try running under a locale
704 that you can list and which somehow matches what you tried. The
705 rules for matching locale names are a bit vague because
706 standardization is weak in this area. See again the
707 L</Finding locales> about general rules.
709 =head2 Fixing system locale configuration
711 Contact a system administrator (preferably your own) and report the exact
712 error message you get, and ask them to read this same documentation you
713 are now reading. They should be able to check whether there is something
714 wrong with the locale configuration of the system. The L</Finding locales>
715 section is unfortunately a bit vague about the exact commands and places
716 because these things are not that standardized.
718 =head2 The localeconv function
720 The C<POSIX::localeconv()> function allows you to get particulars of the
721 locale-dependent numeric formatting information specified by the current
722 underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of
723 whether called from within the scope of C<S<use locale>> or not). (If
724 you just want the name of
725 the current locale for a particular category, use C<POSIX::setlocale()>
726 with a single parameter--see L</The setlocale function>.)
728 use POSIX qw(locale_h);
730 # Get a reference to a hash of locale-dependent info
731 $locale_values = localeconv();
733 # Output sorted list of the values
734 for (sort keys %$locale_values) {
735 printf "%-20s = %s\n", $_, $locale_values->{$_}
738 C<localeconv()> takes no arguments, and returns B<a reference to> a hash.
739 The keys of this hash are variable names for formatting, such as
740 C<decimal_point> and C<thousands_sep>. The values are the
741 corresponding, er, values. See L<POSIX/localeconv> for a longer
742 example listing the categories an implementation might be expected to
743 provide; some provide more and others fewer. You don't need an
744 explicit C<use locale>, because C<localeconv()> always observes the
747 Here's a simple-minded example program that rewrites its command-line
748 parameters as integers correctly formatted in the current locale:
750 use POSIX qw(locale_h);
752 # Get some of locale's numeric formatting parameters
753 my ($thousands_sep, $grouping) =
754 @{localeconv()}{'thousands_sep', 'grouping'};
756 # Apply defaults if values are missing
757 $thousands_sep = ',' unless $thousands_sep;
759 # grouping and mon_grouping are packed lists
760 # of small integers (characters) telling the
761 # grouping (thousand_seps and mon_thousand_seps
762 # being the group dividers) of numbers and
763 # monetary quantities. The integers' meanings:
764 # 255 means no more grouping, 0 means repeat
765 # the previous grouping, 1-254 means use that
766 # as the current grouping. Grouping goes from
767 # right to left (low to high digits). In the
768 # below we cheat slightly by never using anything
769 # else than the first grouping (whatever that is).
771 @grouping = unpack("C*", $grouping);
776 # Format command line params for current locale
778 $_ = int; # Chop non-integer part
780 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
785 Note that if the platform doesn't have C<LC_NUMERIC> and/or
786 C<LC_MONETARY> available or enabled, the corresponding elements of the
787 hash will be missing.
789 =head2 I18N::Langinfo
791 Another interface for querying locale-dependent information is the
792 C<I18N::Langinfo::langinfo()> function.
794 The following example will import the C<langinfo()> function itself and
795 three constants to be used as arguments to C<langinfo()>: a constant for
796 the abbreviated first day of the week (the numbering starts from
797 Sunday = 1) and two more constants for the affirmative and negative
798 answers for a yes/no question in the current locale.
800 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
802 my ($abday_1, $yesstr, $nostr)
803 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
805 print "$abday_1? [$yesstr/$nostr] ";
807 In other words, in the "C" (or English) locale the above will probably
808 print something like:
812 See L<I18N::Langinfo> for more information.
814 =head1 LOCALE CATEGORIES
816 The following subsections describe basic locale categories. Beyond these,
817 some combination categories allow manipulation of more than one
818 basic category at a time. See L</"ENVIRONMENT"> for a discussion of these.
820 =head2 Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting
822 In the scope of a S<C<use locale>> form that includes collation, Perl
823 looks to the C<LC_COLLATE>
824 environment variable to determine the application's notions on collation
825 (ordering) of characters. For example, "b" follows "a" in Latin
826 alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
827 "color" follows "chocolate" in English, what about in traditional Spanish?
829 The following collations all make sense and you may meet any of them
830 if you C<"use locale">.
837 Here is a code snippet to tell what "word"
838 characters are in the current locale, in that locale's order:
841 print +(sort grep /\w/, map { chr } 0..255), "\n";
843 Compare this with the characters that you see and their order if you
844 state explicitly that the locale should be ignored:
847 print +(sort grep /\w/, map { chr } 0..255), "\n";
849 This machine-native collation (which is what you get unless S<C<use
850 locale>> has appeared earlier in the same block) must be used for
851 sorting raw binary data, whereas the locale-dependent collation of the
852 first example is useful for natural text.
854 As noted in L</USING LOCALES>, C<cmp> compares according to the current
855 collation locale when C<use locale> is in effect, but falls back to a
856 char-by-char comparison for strings that the locale says are equal. You
857 can use C<POSIX::strcoll()> if you don't want this fall-back:
859 use POSIX qw(strcoll);
861 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
863 C<$equal_in_locale> will be true if the collation locale specifies a
864 dictionary-like ordering that ignores space characters completely and
867 Perl uses the platform's C library collation functions C<strcoll()> and
868 C<strxfrm()>. That means you get whatever they give. On some
869 platforms, these functions work well on UTF-8 locales, giving
870 a reasonable default collation for the code points that are important in
871 that locale. (And if they aren't working well, the problem may only be
872 that the locale definition is deficient, so can be fixed by using a
873 better definition file. Unicode's definitions (see L</Freely available
874 locale definitions>) provide reasonable UTF-8 locale collation
875 definitions.) Starting in Perl v5.26, Perl's use of these functions has
876 been made more seamless. This may be sufficient for your needs. For
877 more control, and to make sure strings containing any code point (not
878 just the ones important in the locale) collate properly, the
879 L<Unicode::Collate> module is suggested.
881 In non-UTF-8 locales (hence single byte), code points above 0xFF are
882 technically invalid. But if present, again starting in v5.26, they will
883 collate to the same position as the highest valid code point does. This
884 generally gives good results, but the collation order may be skewed if
885 the valid code point gets special treatment when it forms particular
886 sequences with other characters as defined by the locale.
887 When two strings collate identically, the code point order is used as a
890 If Perl detects that there are problems with the locale collation order,
891 it reverts to using non-locale collation rules for that locale.
893 If you have a single string that you want to check for "equality in
894 locale" against several others, you might think you could gain a little
895 efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
897 use POSIX qw(strxfrm);
898 $xfrm_string = strxfrm("Mixed-case string");
899 print "locale collation ignores spaces\n"
900 if $xfrm_string eq strxfrm("Mixed-casestring");
901 print "locale collation ignores hyphens\n"
902 if $xfrm_string eq strxfrm("Mixedcase string");
903 print "locale collation ignores case\n"
904 if $xfrm_string eq strxfrm("mixed-case string");
906 C<strxfrm()> takes a string and maps it into a transformed string for use
907 in char-by-char comparisons against other transformed strings during
908 collation. "Under the hood", locale-affected Perl comparison operators
909 call C<strxfrm()> for both operands, then do a char-by-char
910 comparison of the transformed strings. By calling C<strxfrm()> explicitly
911 and using a non locale-affected comparison, the example attempts to save
912 a couple of transformations. But in fact, it doesn't save anything: Perl
913 magic (see L<perlguts/Magic Variables>) creates the transformed version of a
914 string the first time it's needed in a comparison, then keeps this version around
915 in case it's needed again. An example rewritten the easy way with
916 C<cmp> runs just about as fast. It also copes with null characters
917 embedded in strings; if you call C<strxfrm()> directly, it treats the first
918 null it finds as a terminator. Don't expect the transformed strings
919 it produces to be portable across systems--or even from one revision
920 of your operating system to the next. In short, don't call C<strxfrm()>
921 directly: let Perl do it for you.
923 Note: C<use locale> isn't shown in some of these examples because it isn't
924 needed: C<strcoll()> and C<strxfrm()> are POSIX functions
925 which use the standard system-supplied C<libc> functions that
926 always obey the current C<LC_COLLATE> locale.
928 =head2 Category C<LC_CTYPE>: Character Types
930 In the scope of a S<C<use locale>> form that includes C<LC_CTYPE>, Perl
931 obeys the C<LC_CTYPE> locale
932 setting. This controls the application's notion of which characters are
933 alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
934 regular expression metanotation,
935 which stands for alphanumeric characters--that is, alphabetic,
936 numeric, and the platform's native underscore.
937 (Consult L<perlre> for more information about
938 regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
939 setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
940 "E<oslash>" may be understood as C<\w> characters.
941 It also affects things like C<\s>, C<\D>, and the POSIX character
942 classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
943 information on all these.)
945 The C<LC_CTYPE> locale also provides the map used in transliterating
946 characters between lower and uppercase. This affects the case-mapping
947 functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>;
949 interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
950 strings and C<s///> substitutions; and case-insensitive regular expression
951 pattern matching using the C<i> modifier.
953 Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
954 otherwise Perl only supports single-byte locales, such as the ISO 8859
955 series. This means that wide character locales, for example for Asian
956 languages, are not well-supported. Use of these locales may cause core
957 dumps. If the platform has the capability for Perl to detect such a
958 locale, starting in Perl v5.22, L<Perl will warn, default
959 enabled|warnings/Category Hierarchy>, using the C<locale> warning
960 category, whenever such a locale is switched into. The UTF-8 locale
961 support is actually a
962 superset of POSIX locales, because it is really full Unicode behavior
963 as if no C<LC_CTYPE> locale were in effect at all (except for tainting;
964 see L</SECURITY>). POSIX locales, even UTF-8 ones,
965 are lacking certain concepts in Unicode, such as the idea that changing
966 the case of a character could expand to be more than one character.
967 Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
968 Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
969 with some restrictions, and on other platforms more like the "C" locale.
970 For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
971 used as a workaround for this (see L</Unicode and UTF-8>).
973 Note that there are quite a few things that are unaffected by the
974 current locale. Any literal character is the native character for the
975 given platform. Hence 'A' means the character at code point 65 on ASCII
976 platforms, and 193 on EBCDIC. That may or may not be an 'A' in the
977 current locale, if that locale even has an 'A'.
978 Similarly, all the escape sequences for particular characters,
979 C<\n> for example, always mean the platform's native one. This means,
980 for example, that C<\N> in regular expressions (every character
981 but new-line) works on the platform character set.
983 Starting in v5.22, Perl will by default warn when switching into a
984 locale that redefines any ASCII printable character (plus C<\t> and
985 C<\n>) into a different class than expected. This is likely to
986 happen on modern locales only on EBCDIC platforms, where, for example,
987 a CCSID 0037 locale on a CCSID 1047 machine moves C<"[">, but it can
988 happen on ASCII platforms with the ISO 646 and other
989 7-bit locales that are essentially obsolete. Things may still work,
990 depending on what features of Perl are used by the program. For
991 example, in the example from above where C<"|"> becomes a C<\w>, and
992 there are no regular expressions where this matters, the program may
993 still work properly. The warning lists all the characters that
994 it can determine could be adversely affected.
996 B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
997 in clearly ineligible characters being considered to be alphanumeric by
998 your application. For strict matching of (mundane) ASCII letters and
999 digits--for example, in command strings--locale-aware applications
1000 should use C<\w> with the C</a> regular expression modifier. See L</"SECURITY">.
1002 =head2 Category C<LC_NUMERIC>: Numeric Formatting
1004 After a proper C<POSIX::setlocale()> call, and within the scope of
1005 of a C<use locale> form that includes numerics, Perl obeys the
1006 C<LC_NUMERIC> locale information, which controls an application's idea
1007 of how numbers should be formatted for human readability.
1008 In most implementations the only effect is to
1009 change the character used for the decimal point--perhaps from "." to ",".
1010 The functions aren't aware of such niceties as thousands separation and
1011 so on. (See L</The localeconv function> if you care about these things.)
1013 use POSIX qw(strtod setlocale LC_NUMERIC);
1016 setlocale LC_NUMERIC, "";
1018 $n = 5/2; # Assign numeric 2.5 to $n
1020 $a = " $n"; # Locale-dependent conversion to string
1022 print "half five is $n\n"; # Locale-dependent output
1024 printf "half five is %g\n", $n; # Locale-dependent output
1026 print "DECIMAL POINT IS COMMA\n"
1027 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
1029 See also L<I18N::Langinfo> and C<RADIXCHAR>.
1031 =head2 Category C<LC_MONETARY>: Formatting of monetary amounts
1033 The C standard defines the C<LC_MONETARY> category, but not a function
1034 that is affected by its contents. (Those with experience of standards
1035 committees will recognize that the working group decided to punt on the
1036 issue.) Consequently, Perl essentially takes no notice of it. If you
1037 really want to use C<LC_MONETARY>, you can query its contents--see
1038 L</The localeconv function>--and use the information that it returns in your
1039 application's own formatting of currency amounts. However, you may well
1040 find that the information, voluminous and complex though it may be, still
1041 does not quite meet your requirements: currency formatting is a hard nut
1044 See also L<I18N::Langinfo> and C<CRNCYSTR>.
1046 =head2 Category C<LC_TIME>: Respresentation of time
1048 Output produced by C<POSIX::strftime()>, which builds a formatted
1049 human-readable date/time string, is affected by the current C<LC_TIME>
1050 locale. Thus, in a French locale, the output produced by the C<%B>
1051 format element (full month name) for the first month of the year would
1052 be "janvier". Here's how to get a list of long month names in the
1055 use POSIX qw(strftime);
1057 $long_month_name[$_] =
1058 strftime("%B", 0, 0, 0, 1, $_, 96);
1061 Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
1062 function which uses the standard system-supplied C<libc> function that
1063 always obeys the current C<LC_TIME> locale.
1065 See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
1066 C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
1068 =head2 Other categories
1070 The remaining locale categories are not currently used by Perl itself.
1071 But again note that things Perl interacts with may use these, including
1072 extensions outside the standard Perl distribution, and by the
1073 operating system and its utilities. Note especially that the string
1074 value of C<$!> and the error messages given by external utilities may
1075 be changed by C<LC_MESSAGES>. If you want to have portable error
1076 codes, use C<%!>. See L<Errno>.
1080 Although the main discussion of Perl security issues can be found in
1081 L<perlsec>, a discussion of Perl's locale handling would be incomplete
1082 if it did not draw your attention to locale-dependent security issues.
1083 Locales--particularly on systems that allow unprivileged users to
1084 build their own locales--are untrustworthy. A malicious (or just plain
1085 broken) locale can make a locale-aware application give unexpected
1086 results. Here are a few possibilities:
1092 Regular expression checks for safe file names or mail addresses using
1093 C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
1094 characters such as C<"E<gt>"> and C<"|"> are alphanumeric.
1098 String interpolation with case-mapping, as in, say, C<$dest =
1099 "C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE>
1100 case-mapping table is in effect.
1104 A sneaky C<LC_COLLATE> locale could result in the names of students with
1105 "D" grades appearing ahead of those with "A"s.
1109 An application that takes the trouble to use information in
1110 C<LC_MONETARY> may format debits as if they were credits and vice versa
1111 if that locale has been subverted. Or it might make payments in US
1112 dollars instead of Hong Kong dollars.
1116 The date and day names in dates formatted by C<strftime()> could be
1117 manipulated to advantage by a malicious user able to subvert the
1118 C<LC_DATE> locale. ("Look--it says I wasn't in the building on
1123 Such dangers are not peculiar to the locale system: any aspect of an
1124 application's environment which may be modified maliciously presents
1125 similar challenges. Similarly, they are not specific to Perl: any
1126 programming language that allows you to write programs that take
1127 account of their environment exposes you to these issues.
1129 Perl cannot protect you from all possibilities shown in the
1130 examples--there is no substitute for your own vigilance--but, when
1131 C<use locale> is in effect, Perl uses the tainting mechanism (see
1132 L<perlsec>) to mark string results that become locale-dependent, and
1133 which may be untrustworthy in consequence. Here is a summary of the
1134 tainting behavior of operators and functions that may be affected by
1141 B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
1143 Scalar true/false (or less/equal/greater) result is never tainted.
1147 B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
1149 The result string containing interpolated material is tainted if
1150 a C<use locale> form that includes C<LC_CTYPE> is in effect.
1154 B<Matching operator> (C<m//>):
1156 Scalar true/false result never tainted.
1158 All subpatterns, either delivered as a list-context result or as C<$1>
1159 I<etc>., are tainted if a C<use locale> form that includes
1160 C<LC_CTYPE> is in effect, and the subpattern
1161 regular expression contains a locale-dependent construct. These
1162 constructs include C<\w> (to match an alphanumeric character), C<\W>
1163 (non-alphanumeric character), C<\b> and C<\B> (word-boundary and
1164 non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
1165 (whitespace character), C<\S> (non whitespace character), C<\d> and
1166 C<\D> (digits and non-digits), and the POSIX character classes, such as
1167 C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
1169 Tainting is also likely if the pattern is to be matched
1170 case-insensitively (via C</i>). The exception is if all the code points
1171 to be matched this way are above 255 and do not have folds under Unicode
1172 rules to below 256. Tainting is not done for these because Perl
1173 only uses Unicode rules for such code points, and those rules are the
1174 same no matter what the current locale.
1176 The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
1177 (post-match), and C<$+> (last match) also are tainted.
1181 B<Substitution operator> (C<s///>):
1183 Has the same behavior as the match operator. Also, the left
1184 operand of C<=~> becomes tainted when a C<use locale>
1185 form that includes C<LC_CTYPE> is in effect, if modified as
1186 a result of a substitution based on a regular
1187 expression match involving any of the things mentioned in the previous
1188 item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
1192 B<Output formatting functions> (C<printf()> and C<write()>):
1194 Results are never tainted because otherwise even output from print,
1195 for example C<print(1/7)>, should be tainted if C<use locale> is in
1200 B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
1202 Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is
1207 B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
1208 C<strftime()>, C<strxfrm()>):
1210 Results are never tainted.
1214 Three examples illustrate locale-dependent tainting.
1215 The first program, which ignores its locale, won't run: a value taken
1216 directly from the command line may not be used to name an output file
1217 when taint checks are enabled.
1219 #/usr/local/bin/perl -T
1220 # Run with taint checking
1222 # Command line sanity check omitted...
1223 $tainted_output_file = shift;
1225 open(F, ">$tainted_output_file")
1226 or warn "Open of $tainted_output_file failed: $!\n";
1228 The program can be made to run by "laundering" the tainted value through
1229 a regular expression: the second example--which still ignores locale
1230 information--runs, creating the file named on its command line
1233 #/usr/local/bin/perl -T
1235 $tainted_output_file = shift;
1236 $tainted_output_file =~ m%[\w/]+%;
1237 $untainted_output_file = $&;
1239 open(F, ">$untainted_output_file")
1240 or warn "Open of $untainted_output_file failed: $!\n";
1242 Compare this with a similar but locale-aware program:
1244 #/usr/local/bin/perl -T
1246 $tainted_output_file = shift;
1248 $tainted_output_file =~ m%[\w/]+%;
1249 $localized_output_file = $&;
1251 open(F, ">$localized_output_file")
1252 or warn "Open of $localized_output_file failed: $!\n";
1254 This third program fails to run because C<$&> is tainted: it is the result
1255 of a match involving C<\w> while C<use locale> is in effect.
1261 =item PERL_SKIP_LOCALE_INIT
1263 This environment variable, available starting in Perl v5.20, if set
1264 (to any value), tells Perl to not use the rest of the
1265 environment variables to initialize with. Instead, Perl uses whatever
1266 the current locale settings are. This is particularly useful in
1267 embedded environments, see
1268 L<perlembed/Using embedded Perl with POSIX locales>.
1272 A string that can suppress Perl's warning about failed locale settings
1273 at startup. Failure can occur if the locale support in the operating
1274 system is lacking (broken) in some way--or if you mistyped the name of
1275 a locale when you set up your environment. If this environment
1276 variable is absent, or has a value other than "0" or "", Perl will
1277 complain about locale setting failures.
1279 B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message.
1280 The message tells about some problem in your system's locale support,
1281 and you should investigate what the problem is.
1285 The following environment variables are not specific to Perl: They are
1286 part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
1287 for controlling an application's opinion on data. Windows is non-POSIX,
1288 but Perl arranges for the following to work as described anyway.
1289 If the locale given by an environment variable is not valid, Perl tries
1290 the next lower one in priority. If none are valid, on Windows, the
1291 system default locale is then tried. If all else fails, the C<"C">
1292 locale is used. If even that doesn't work, something is badly broken,
1293 but Perl tries to forge ahead with whatever the locale settings might
1300 C<LC_ALL> is the "override-all" locale environment variable. If
1301 set, it overrides all the rest of the locale environment variables.
1305 B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
1306 are using the GNU libc. This is the case if you are using e.g. Linux.
1307 If you are using "commercial" Unixes you are most probably I<not>
1308 using GNU libc and you can ignore C<LANGUAGE>.
1310 However, in the case you are using C<LANGUAGE>: it affects the
1311 language of informational, warning, and error messages output by
1312 commands (in other words, it's like C<LC_MESSAGES>) but it has higher
1313 priority than C<LC_ALL>. Moreover, it's not a single value but
1314 instead a "path" (":"-separated list) of I<languages> (not locales).
1315 See the GNU C<gettext> library documentation for more information.
1319 In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
1320 locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
1321 chooses the character type locale.
1325 In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
1326 (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
1327 C<LANG> chooses the collation locale.
1329 =item C<LC_MONETARY>
1331 In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
1332 formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
1333 C<LANG> chooses the monetary formatting locale.
1337 In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
1338 locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
1339 chooses the numeric format.
1343 In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
1344 formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
1345 C<LANG> chooses the date and time formatting locale.
1349 C<LANG> is the "catch-all" locale environment variable. If it is set, it
1350 is used as the last resort after the overall C<LC_ALL> and the
1351 category-specific C<LC_I<foo>>.
1357 The C<LC_NUMERIC> controls the numeric output:
1360 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1361 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1362 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1364 and also how strings are parsed by C<POSIX::strtod()> as numbers:
1367 use POSIX qw(locale_h strtod);
1368 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1369 my $x = strtod("2,34") + 5;
1370 print $x, "\n"; # Probably shows 7,34.
1374 =head2 String C<eval> and C<LC_NUMERIC>
1376 A string L<eval|perlfunc/eval EXPR> parses its expression as standard
1377 Perl. It is therefore expecting the decimal point to be a dot. If
1378 C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
1379 be confused, perhaps silently.
1382 use POSIX qw(locale_h);
1383 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1385 print eval "$a + 1.5";
1388 prints C<13,5>. This is because in that locale, the comma is the
1389 decimal point character. The C<eval> thus expands to:
1393 and the result is not what you likely expected. No warnings are
1394 generated. If you do string C<eval>'s within the scope of
1395 S<C<use locale>>, you should instead change the C<eval> line to do
1398 print eval "no locale; $a + 1.5";
1402 You could also exclude C<LC_NUMERIC>, if you don't need it, by
1404 use locale ':!numeric';
1406 =head2 Backward compatibility
1408 Versions of Perl prior to 5.004 B<mostly> ignored locale information,
1409 generally behaving as if something similar to the C<"C"> locale were
1410 always in force, even if the program environment suggested otherwise
1411 (see L</The setlocale function>). By default, Perl still behaves this
1412 way for backward compatibility. If you want a Perl application to pay
1413 attention to locale information, you B<must> use the S<C<use locale>>
1414 pragma (see L</The "use locale" pragma>) or, in the unlikely event
1415 that you want to do so for just pattern matching, the
1416 C</l> regular expression modifier (see L<perlre/Character set
1417 modifiers>) to instruct it to do so.
1419 Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
1420 information if available; that is, C<\w> did understand what
1421 were the letters according to the locale environment variables.
1422 The problem was that the user had no control over the feature:
1423 if the C library supported locales, Perl used them.
1425 =head2 I18N:Collate obsolete
1427 In versions of Perl prior to 5.004, per-locale collation was possible
1428 using the C<I18N::Collate> library module. This module is now mildly
1429 obsolete and should be avoided in new applications. The C<LC_COLLATE>
1430 functionality is now integrated into the Perl core language: One can
1431 use locale-specific scalar data completely normally with C<use locale>,
1432 so there is no longer any need to juggle with the scalar references of
1435 =head2 Sort speed and memory use impacts
1437 Comparing and sorting by locale is usually slower than the default
1438 sorting; slow-downs of two to four times have been observed. It will
1439 also consume more memory: once a Perl scalar variable has participated
1440 in any string comparison or sorting operation obeying the locale
1441 collation rules, it will take 3-15 times more memory than before. (The
1442 exact multiplier depends on the string's contents, the operating system
1443 and the locale.) These downsides are dictated more by the operating
1444 system's implementation of the locale system than by Perl.
1446 =head2 Freely available locale definitions
1448 The Unicode CLDR project extracts the POSIX portion of many of its
1449 locales, available at
1451 http://unicode.org/Public/cldr/2.0.1/
1453 (Newer versions of CLDR require you to compute the POSIX data yourself.
1454 See L<http://unicode.org/Public/cldr/latest/>.)
1456 There is a large collection of locale definitions at:
1458 http://std.dkuug.dk/i18n/WG15-collection/locales/
1460 You should be aware that it is
1461 unsupported, and is not claimed to be fit for any purpose. If your
1462 system allows installation of arbitrary locales, you may find the
1463 definitions useful as they are, or as a basis for the development of
1466 =head2 I18n and l10n
1468 "Internationalization" is often abbreviated as B<i18n> because its first
1469 and last letters are separated by eighteen others. (You may guess why
1470 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1471 the same way, "localization" is often abbreviated to B<l10n>.
1473 =head2 An imperfect standard
1475 Internationalization, as defined in the C and POSIX standards, can be
1476 criticized as incomplete and ungainly. They also have a tendency, like
1477 standards groups, to divide the world into nations, when we all know
1478 that the world can equally well be divided into bankers, bikers, gamers,
1481 =head1 Unicode and UTF-8
1483 The support of Unicode is new starting from Perl version v5.6, and more fully
1484 implemented in versions v5.8 and later. See L<perluniintro>.
1486 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1487 C<LC_COLLATE> is only partially supported; collation support is improved
1488 in Perl v5.26 to a level that may be sufficient for your needs
1489 (see L</Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting>).
1491 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1493 use locale ':not_characters';
1495 When this form of the pragma is used, only the non-character portions of
1496 locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
1497 you have translated all the characters it is to operate on into Unicode
1498 (actually the platform's native character set (ASCII or EBCDIC) plus
1499 Unicode). For data in files, this can conveniently be done by also
1504 This pragma arranges for all inputs from files to be translated into
1505 Unicode from the current locale as specified in the environment (see
1506 L</ENVIRONMENT>), and all outputs to files to be translated back
1507 into the locale. (See L<open>). On a per-filehandle basis, you can
1508 instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
1509 module, both available from CPAN. The latter module also has methods to
1510 ease the handling of C<ARGV> and environment variables, and can be used
1511 on individual strings. If you know that all your locales will be
1512 UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
1513 command line switch.
1515 This form of the pragma allows essentially seamless handling of locales
1516 with Unicode. The collation order will be by Unicode code point order.
1517 L<Unicode::Collate> can be used to get Unicode rules collation.
1519 All the modules and switches just described can be used in v5.20 with
1520 just plain C<use locale>, and, should the input locales not be UTF-8,
1521 you'll get the less than ideal behavior, described below, that you get
1522 with pre-v5.16 Perls, or when you use the locale pragma without the
1523 C<:not_characters> parameter in v5.16 and v5.18. If you are using
1524 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1525 does not apply to you.
1527 There are two cases, multi-byte and single-byte locales. First
1530 The only multi-byte (or wide character) locale that Perl is ever likely
1531 to support is UTF-8. This is due to the difficulty of implementation,
1532 the fact that high quality UTF-8 locales are now published for every
1533 area of the world (L<http://unicode.org/Public/cldr/2.0.1/> for
1534 ones that are already set-up, but from an earlier version;
1535 L<http://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1536 you have to extract the POSIX information yourself), and that
1537 failing all that you can use the L<Encode> module to translate to/from
1538 your locale. So, you'll have to do one of those things if you're using
1539 one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1540 Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1541 work reasonably well (depending on your C library implementation)
1543 they and Perl store characters that take up multiple bytes the same way.
1544 However, some, if not most, C library implementations may not process
1545 the characters in the upper half of the Latin-1 range (128 - 255)
1546 properly under C<LC_CTYPE>. To see if a character is a particular type
1547 under a locale, Perl uses the functions like C<isalnum()>. Your C
1548 library may not work for UTF-8 locales with those functions, instead
1549 only working under the newer wide library functions like C<iswalnum()>,
1550 which Perl does not use.
1551 These multi-byte locales are treated like single-byte locales, and will
1552 have the restrictions described below. Starting in Perl v5.22 a warning
1553 message is raised when Perl detects a multi-byte locale that it doesn't
1556 For single-byte locales,
1557 Perl generally takes the tack to use locale rules on code points that can fit
1558 in a single byte, and Unicode rules for those that can't (though this
1559 isn't uniformly applied, see the note at the end of this section). This
1560 prevents many problems in locales that aren't UTF-8. Suppose the locale
1561 is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
1562 in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
1563 regular expression character class C<[[:alpha:]]> will magically match
1564 0xD7 in the Greek locale but not in the Latin one.
1566 However, there are places where this breaks down. Certain Perl constructs are
1567 for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
1568 Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
1569 subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
1570 Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
1571 issue occurs with C<\N{...}>. Prior to v5.20, it is therefore a bad
1572 idea to use C<\p{}> or
1573 C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
1574 locale will be ISO8859-1. Use POSIX character classes instead.
1576 Another problem with this approach is that operations that cross the
1577 single byte/multiple byte boundary are not well-defined, and so are
1578 disallowed. (This boundary is between the codepoints at 255/256.)
1579 For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1580 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1581 Greek locale, for example, there is no character at 0xFF, and Perl
1582 has no way of knowing what the character at 0xFF is really supposed to
1583 represent. Thus it disallows the operation. In this mode, the
1584 lowercase of U+0178 is itself.
1586 The same problems ensue if you enable automatic UTF-8-ification of your
1587 standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
1588 non-UTF-8 locales (by using either the B<-C> command line switch or the
1589 C<PERL_UNICODE> environment variable; see L<perlrun>).
1590 Things are read in as UTF-8, which would normally imply a Unicode
1591 interpretation, but the presence of a locale causes them to be interpreted
1592 in that locale instead. For example, a 0xD7 code point in the Unicode
1593 input, which should mean the multiplication sign, won't be interpreted by
1594 Perl that way under the Greek locale. This is not a problem
1595 I<provided> you make certain that all locales will always and only be either
1596 an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
1598 Still another problem is that this approach can lead to two code
1599 points meaning the same character. Thus in a Greek locale, both U+03A7
1600 and U+00D7 are GREEK CAPITAL LETTER CHI.
1602 Because of all these problems, starting in v5.22, Perl will raise a
1603 warning if a multi-byte (hence Unicode) code point is used when a
1604 single-byte locale is in effect. (Although it doesn't check for this if
1605 doing so would unreasonably slow execution down.)
1607 Vendor locales are notoriously buggy, and it is difficult for Perl to test
1608 its locale-handling code because this interacts with code that Perl has no
1609 control over; therefore the locale-handling code in Perl may be buggy as
1610 well. (However, the Unicode-supplied locales should be better, and
1611 there is a feed back mechanism to correct any problems. See
1612 L</Freely available locale definitions>.)
1614 If you have Perl v5.16, the problems mentioned above go away if you use
1615 the C<:not_characters> parameter to the locale pragma (except for vendor
1616 bugs in the non-character portions). If you don't have v5.16, and you
1617 I<do> have locales that work, using them may be worthwhile for certain
1618 specific purposes, as long as you keep in mind the gotchas already
1619 mentioned. For example, if the collation for your locales works, it
1620 runs faster under locales than under L<Unicode::Collate>; and you gain
1621 access to such things as the local currency symbol and the names of the
1622 months and days of the week. (But to hammer home the point, in v5.16,
1623 you get this access without the downsides of locales by using the
1624 C<:not_characters> form of the pragma.)
1626 Note: The policy of using locale rules for code points that can fit in a
1627 byte, and Unicode rules for those that can't is not uniformly applied.
1628 Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
1629 consistently to regular expression matching except for bracketed
1630 character classes; in v5.14 it was extended to all regex matches; and in
1631 v5.16 to the casing operations such as C<\L> and C<uc()>. For
1632 collation, in all releases so far, the system's C<strxfrm()> function is
1633 called, and whatever it does is what you get. Starting in v5.26, various
1634 bugs are fixed with the way perl uses this function.
1638 =head2 Collation of strings containing embedded C<NUL> characters
1640 C<NUL> characters will sort the same as the lowest collating control
1641 character does, or to C<"\001"> in the unlikely event that there are no
1642 control characters at all in the locale. In cases where the strings
1643 don't contain this non-C<NUL> control, the results will be correct, and
1644 in many locales, this control, whatever it might be, will rarely be
1645 encountered. But there are cases where a C<NUL> should sort before this
1646 control, but doesn't. If two strings do collate identically, the one
1647 containing the C<NUL> will sort to earlier. Prior to 5.26, there were
1650 =head2 Multi-threaded
1652 XS code or C-language libraries called from it that use the system
1653 L<C<setlocale(3)>> function (except on Windows) likely will not work
1654 from a multi-threaded application without changes. See
1655 L<perlxs/Locale-aware XS code>.
1657 An XS module that is locale-dependent could have been written under the
1658 assumption that it will never be called in a multi-threaded environment,
1659 and so uses other non-locale constructs that aren't multi-thread-safe.
1660 See L<perlxs/Thread-aware system interfaces>.
1662 POSIX does not define a way to get the name of the current per-thread
1663 locale. Some systems, such as Darwin and NetBSD do implement a
1664 function, L<querylocale(3)> to do this. On non-Windows systems without
1665 it, such as Linux, there are some additional caveats:
1671 An embedded perl needs to be started up while the global locale is in
1672 effect. See L<perlembed/Using embedded Perl with POSIX locales>.
1676 It becomes more important for perl to know about all the possible
1677 locale categories on the platform, even if they aren't apparently used
1678 in your program. Perl knows all of the Linux ones. If your platform
1679 has others, you can send email to L<mailto:perlbug@perl.org> for
1680 inclusion of it in the next release. In the meantime, it is possible to
1681 edit the Perl source to teach it about the category, and then recompile.
1682 Search for instances of, say, C<LC_PAPER> in the source, and use that as
1683 a template to add the omitted one.
1687 It is possible, though hard to do, to call C<POSIX::setlocale> with a
1688 locale that it doesn't recognize as syntactically legal, but actually is
1689 legal on that system. This should happen only with embedded perls, or
1690 if you hand-craft a locale name yourself.
1694 =head2 Broken systems
1696 In certain systems, the operating system's locale support
1697 is broken and cannot be fixed or used by Perl. Such deficiencies can
1698 and will result in mysterious hangs and/or Perl core dumps when
1699 C<use locale> is in effect. When confronted with such a system,
1700 please report in excruciating detail to <F<perlbug@perl.org>>, and
1701 also contact your vendor: bug fixes may exist for these problems
1702 in your operating system. Sometimes such bug fixes are called an
1703 operating system upgrade. If you have the source for Perl, include in
1704 the perlbug email the output of the test described above in L</Testing
1705 for broken locales>.
1709 L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
1710 L<POSIX/localeconv>,
1711 L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
1712 L<POSIX/strtod>, L<POSIX/strxfrm>.
1714 For special considerations when Perl is embedded in a C program,
1715 see L<perlembed/Using embedded Perl with POSIX locales>.
1719 Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
1720 Dunlop, assisted by the perl5-porters. Prose worked over a bit by
1721 Tom Christiansen, and now maintained by Perl 5 porters.