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 Normally on unthreaded builds, the traditional C<setlocale()> is used
521 and not the thread-safe locale functions. You can force the use of these
522 on systems that have them by adding the
523 C<-Accflags='-DUSE_THREAD_SAFE_LOCALE'> to F<Configure>.
525 The initial program is started up using the locale specified from the
526 environment, as currently, described in L</ENVIRONMENT>. All newly
527 created threads start with C<LC_ALL> set to C<"C">>. Each thread may
528 use C<POSIX::setlocale()> to query or switch its locale at any time,
529 without affecting any other thread. All locale-dependent operations
530 automatically use their thread's locale.
532 This should be completely transparent to any applications written
533 entirely in Perl (minus a few rarely encountered caveats given in the
534 L</Multi-threaded> section). Information for XS module writers is given
535 in L<perlxs/Locale-aware XS code>.
537 =head2 Finding locales
539 For locales available in your system, consult also L<setlocale(3)> to
540 see whether it leads to the list of available locales (search for the
541 I<SEE ALSO> section). If that fails, try the following command lines:
555 and see whether they list something resembling these
557 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
558 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
561 english german russian
562 english.iso88591 german.iso88591 russian.iso88595
563 english.roman8 russian.koi8r
565 Sadly, even though the calling interface for C<setlocale()> has been
566 standardized, names of locales and the directories where the
567 configuration resides have not been. The basic form of the name is
568 I<language_territory>B<.>I<codeset>, but the latter parts after
569 I<language> are not always present. The I<language> and I<country>
570 are usually from the standards B<ISO 3166> and B<ISO 639>, the
571 two-letter abbreviations for the countries and the languages of the
572 world, respectively. The I<codeset> part often mentions some B<ISO
573 8859> character set, the Latin codesets. For example, C<ISO 8859-1>
574 is the so-called "Western European codeset" that can be used to encode
575 most Western European languages adequately. Again, there are several
576 ways to write even the name of that one standard. Lamentably.
578 Two special locales are worth particular mention: "C" and "POSIX".
579 Currently these are effectively the same locale: the difference is
580 mainly that the first one is defined by the C standard, the second by
581 the POSIX standard. They define the B<default locale> in which
582 every program starts in the absence of locale information in its
583 environment. (The I<default> default locale, if you will.) Its language
584 is (American) English and its character codeset ASCII or, rarely, a
585 superset thereof (such as the "DEC Multinational Character Set
586 (DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
587 may not actually exactly match what the C standard calls for. So
590 B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
591 POSIX-conformant), so use "C" when you need explicitly to specify this
594 =head2 LOCALE PROBLEMS
596 You may encounter the following warning message at Perl startup:
598 perl: warning: Setting locale failed.
599 perl: warning: Please check that your locale settings:
602 are supported and installed on your system.
603 perl: warning: Falling back to the standard locale ("C").
605 This means that your locale settings had C<LC_ALL> set to "En_US" and
606 LANG exists but has no value. Perl tried to believe you but could not.
607 Instead, Perl gave up and fell back to the "C" locale, the default locale
608 that is supposed to work no matter what. (On Windows, it first tries
609 falling back to the system default locale.) This usually means your
610 locale settings were wrong, they mention locales your system has never
611 heard of, or the locale installation in your system has problems (for
612 example, some system files are broken or missing). There are quick and
613 temporary fixes to these problems, as well as more thorough and lasting
616 =head2 Testing for broken locales
618 If you are building Perl from source, the Perl test suite file
619 F<lib/locale.t> can be used to test the locales on your system.
620 Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
621 will cause it to output detailed results. For example, on Linux, you
624 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
626 Besides many other tests, it will test every locale it finds on your
627 system to see if they conform to the POSIX standard. If any have
628 errors, it will include a summary near the end of the output of which
629 locales passed all its tests, and which failed, and why.
631 =head2 Temporarily fixing locale problems
633 The two quickest fixes are either to render Perl silent about any
634 locale inconsistencies or to run Perl under the default locale "C".
636 Perl's moaning about locale problems can be silenced by setting the
637 environment variable C<PERL_BADLANG> to "0" or "".
638 This method really just sweeps the problem under the carpet: you tell
639 Perl to shut up even when Perl sees that something is wrong. Do not
640 be surprised if later something locale-dependent misbehaves.
642 Perl can be run under the "C" locale by setting the environment
643 variable C<LC_ALL> to "C". This method is perhaps a bit more civilized
644 than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or
645 other locale variables) may affect other programs as well, not just
646 Perl. In particular, external programs run from within Perl will see
647 these changes. If you make the new settings permanent (read on), all
648 programs you run see the changes. See L</"ENVIRONMENT"> for
649 the full list of relevant environment variables and L</"USING LOCALES">
650 for their effects in Perl. Effects in other programs are
651 easily deducible. For example, the variable C<LC_COLLATE> may well affect
652 your B<sort> program (or whatever the program that arranges "records"
653 alphabetically in your system is called).
655 You can test out changing these variables temporarily, and if the
656 new settings seem to help, put those settings into your shell startup
657 files. Consult your local documentation for the exact details. For
658 Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
660 LC_ALL=en_US.ISO8859-1
663 This assumes that we saw the locale "en_US.ISO8859-1" using the commands
664 discussed above. We decided to try that instead of the above faulty
665 locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
667 setenv LC_ALL en_US.ISO8859-1
669 or if you have the "env" application you can do (in any shell)
671 env LC_ALL=en_US.ISO8859-1 perl ...
673 If you do not know what shell you have, consult your local
674 helpdesk or the equivalent.
676 =head2 Permanently fixing locale problems
678 The slower but superior fixes are when you may be able to yourself
679 fix the misconfiguration of your own environment variables. The
680 mis(sing)configuration of the whole system's locales usually requires
681 the help of your friendly system administrator.
683 First, see earlier in this document about L</Finding locales>. That tells
684 how to find which locales are really supported--and more importantly,
685 installed--on your system. In our example error message, environment
686 variables affecting the locale are listed in the order of decreasing
687 importance (and unset variables do not matter). Therefore, having
688 LC_ALL set to "En_US" must have been the bad choice, as shown by the
689 error message. First try fixing locale settings listed first.
691 Second, if using the listed commands you see something B<exactly>
692 (prefix matches do not count and case usually counts) like "En_US"
693 without the quotes, then you should be okay because you are using a
694 locale name that should be installed and available in your system.
695 In this case, see L</Permanently fixing your system's locale configuration>.
697 =head2 Permanently fixing your system's locale configuration
699 This is when you see something like:
701 perl: warning: Please check that your locale settings:
704 are supported and installed on your system.
706 but then cannot see that "En_US" listed by the above-mentioned
707 commands. You may see things like "en_US.ISO8859-1", but that isn't
708 the same. In this case, try running under a locale
709 that you can list and which somehow matches what you tried. The
710 rules for matching locale names are a bit vague because
711 standardization is weak in this area. See again the
712 L</Finding locales> about general rules.
714 =head2 Fixing system locale configuration
716 Contact a system administrator (preferably your own) and report the exact
717 error message you get, and ask them to read this same documentation you
718 are now reading. They should be able to check whether there is something
719 wrong with the locale configuration of the system. The L</Finding locales>
720 section is unfortunately a bit vague about the exact commands and places
721 because these things are not that standardized.
723 =head2 The localeconv function
725 The C<POSIX::localeconv()> function allows you to get particulars of the
726 locale-dependent numeric formatting information specified by the current
727 underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of
728 whether called from within the scope of C<S<use locale>> or not). (If
729 you just want the name of
730 the current locale for a particular category, use C<POSIX::setlocale()>
731 with a single parameter--see L</The setlocale function>.)
733 use POSIX qw(locale_h);
735 # Get a reference to a hash of locale-dependent info
736 $locale_values = localeconv();
738 # Output sorted list of the values
739 for (sort keys %$locale_values) {
740 printf "%-20s = %s\n", $_, $locale_values->{$_}
743 C<localeconv()> takes no arguments, and returns B<a reference to> a hash.
744 The keys of this hash are variable names for formatting, such as
745 C<decimal_point> and C<thousands_sep>. The values are the
746 corresponding, er, values. See L<POSIX/localeconv> for a longer
747 example listing the categories an implementation might be expected to
748 provide; some provide more and others fewer. You don't need an
749 explicit C<use locale>, because C<localeconv()> always observes the
752 Here's a simple-minded example program that rewrites its command-line
753 parameters as integers correctly formatted in the current locale:
755 use POSIX qw(locale_h);
757 # Get some of locale's numeric formatting parameters
758 my ($thousands_sep, $grouping) =
759 @{localeconv()}{'thousands_sep', 'grouping'};
761 # Apply defaults if values are missing
762 $thousands_sep = ',' unless $thousands_sep;
764 # grouping and mon_grouping are packed lists
765 # of small integers (characters) telling the
766 # grouping (thousand_seps and mon_thousand_seps
767 # being the group dividers) of numbers and
768 # monetary quantities. The integers' meanings:
769 # 255 means no more grouping, 0 means repeat
770 # the previous grouping, 1-254 means use that
771 # as the current grouping. Grouping goes from
772 # right to left (low to high digits). In the
773 # below we cheat slightly by never using anything
774 # else than the first grouping (whatever that is).
776 @grouping = unpack("C*", $grouping);
781 # Format command line params for current locale
783 $_ = int; # Chop non-integer part
785 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
790 Note that if the platform doesn't have C<LC_NUMERIC> and/or
791 C<LC_MONETARY> available or enabled, the corresponding elements of the
792 hash will be missing.
794 =head2 I18N::Langinfo
796 Another interface for querying locale-dependent information is the
797 C<I18N::Langinfo::langinfo()> function.
799 The following example will import the C<langinfo()> function itself and
800 three constants to be used as arguments to C<langinfo()>: a constant for
801 the abbreviated first day of the week (the numbering starts from
802 Sunday = 1) and two more constants for the affirmative and negative
803 answers for a yes/no question in the current locale.
805 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
807 my ($abday_1, $yesstr, $nostr)
808 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
810 print "$abday_1? [$yesstr/$nostr] ";
812 In other words, in the "C" (or English) locale the above will probably
813 print something like:
817 See L<I18N::Langinfo> for more information.
819 =head1 LOCALE CATEGORIES
821 The following subsections describe basic locale categories. Beyond these,
822 some combination categories allow manipulation of more than one
823 basic category at a time. See L</"ENVIRONMENT"> for a discussion of these.
825 =head2 Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting
827 In the scope of a S<C<use locale>> form that includes collation, Perl
828 looks to the C<LC_COLLATE>
829 environment variable to determine the application's notions on collation
830 (ordering) of characters. For example, "b" follows "a" in Latin
831 alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
832 "color" follows "chocolate" in English, what about in traditional Spanish?
834 The following collations all make sense and you may meet any of them
835 if you C<"use locale">.
842 Here is a code snippet to tell what "word"
843 characters are in the current locale, in that locale's order:
846 print +(sort grep /\w/, map { chr } 0..255), "\n";
848 Compare this with the characters that you see and their order if you
849 state explicitly that the locale should be ignored:
852 print +(sort grep /\w/, map { chr } 0..255), "\n";
854 This machine-native collation (which is what you get unless S<C<use
855 locale>> has appeared earlier in the same block) must be used for
856 sorting raw binary data, whereas the locale-dependent collation of the
857 first example is useful for natural text.
859 As noted in L</USING LOCALES>, C<cmp> compares according to the current
860 collation locale when C<use locale> is in effect, but falls back to a
861 char-by-char comparison for strings that the locale says are equal. You
862 can use C<POSIX::strcoll()> if you don't want this fall-back:
864 use POSIX qw(strcoll);
866 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
868 C<$equal_in_locale> will be true if the collation locale specifies a
869 dictionary-like ordering that ignores space characters completely and
872 Perl uses the platform's C library collation functions C<strcoll()> and
873 C<strxfrm()>. That means you get whatever they give. On some
874 platforms, these functions work well on UTF-8 locales, giving
875 a reasonable default collation for the code points that are important in
876 that locale. (And if they aren't working well, the problem may only be
877 that the locale definition is deficient, so can be fixed by using a
878 better definition file. Unicode's definitions (see L</Freely available
879 locale definitions>) provide reasonable UTF-8 locale collation
880 definitions.) Starting in Perl v5.26, Perl's use of these functions has
881 been made more seamless. This may be sufficient for your needs. For
882 more control, and to make sure strings containing any code point (not
883 just the ones important in the locale) collate properly, the
884 L<Unicode::Collate> module is suggested.
886 In non-UTF-8 locales (hence single byte), code points above 0xFF are
887 technically invalid. But if present, again starting in v5.26, they will
888 collate to the same position as the highest valid code point does. This
889 generally gives good results, but the collation order may be skewed if
890 the valid code point gets special treatment when it forms particular
891 sequences with other characters as defined by the locale.
892 When two strings collate identically, the code point order is used as a
895 If Perl detects that there are problems with the locale collation order,
896 it reverts to using non-locale collation rules for that locale.
898 If you have a single string that you want to check for "equality in
899 locale" against several others, you might think you could gain a little
900 efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
902 use POSIX qw(strxfrm);
903 $xfrm_string = strxfrm("Mixed-case string");
904 print "locale collation ignores spaces\n"
905 if $xfrm_string eq strxfrm("Mixed-casestring");
906 print "locale collation ignores hyphens\n"
907 if $xfrm_string eq strxfrm("Mixedcase string");
908 print "locale collation ignores case\n"
909 if $xfrm_string eq strxfrm("mixed-case string");
911 C<strxfrm()> takes a string and maps it into a transformed string for use
912 in char-by-char comparisons against other transformed strings during
913 collation. "Under the hood", locale-affected Perl comparison operators
914 call C<strxfrm()> for both operands, then do a char-by-char
915 comparison of the transformed strings. By calling C<strxfrm()> explicitly
916 and using a non locale-affected comparison, the example attempts to save
917 a couple of transformations. But in fact, it doesn't save anything: Perl
918 magic (see L<perlguts/Magic Variables>) creates the transformed version of a
919 string the first time it's needed in a comparison, then keeps this version around
920 in case it's needed again. An example rewritten the easy way with
921 C<cmp> runs just about as fast. It also copes with null characters
922 embedded in strings; if you call C<strxfrm()> directly, it treats the first
923 null it finds as a terminator. Don't expect the transformed strings
924 it produces to be portable across systems--or even from one revision
925 of your operating system to the next. In short, don't call C<strxfrm()>
926 directly: let Perl do it for you.
928 Note: C<use locale> isn't shown in some of these examples because it isn't
929 needed: C<strcoll()> and C<strxfrm()> are POSIX functions
930 which use the standard system-supplied C<libc> functions that
931 always obey the current C<LC_COLLATE> locale.
933 =head2 Category C<LC_CTYPE>: Character Types
935 In the scope of a S<C<use locale>> form that includes C<LC_CTYPE>, Perl
936 obeys the C<LC_CTYPE> locale
937 setting. This controls the application's notion of which characters are
938 alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
939 regular expression metanotation,
940 which stands for alphanumeric characters--that is, alphabetic,
941 numeric, and the platform's native underscore.
942 (Consult L<perlre> for more information about
943 regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
944 setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
945 "E<oslash>" may be understood as C<\w> characters.
946 It also affects things like C<\s>, C<\D>, and the POSIX character
947 classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
948 information on all these.)
950 The C<LC_CTYPE> locale also provides the map used in transliterating
951 characters between lower and uppercase. This affects the case-mapping
952 functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>;
954 interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
955 strings and C<s///> substitutions; and case-insensitive regular expression
956 pattern matching using the C<i> modifier.
958 Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
959 otherwise Perl only supports single-byte locales, such as the ISO 8859
960 series. This means that wide character locales, for example for Asian
961 languages, are not well-supported. Use of these locales may cause core
962 dumps. If the platform has the capability for Perl to detect such a
963 locale, starting in Perl v5.22, L<Perl will warn, default
964 enabled|warnings/Category Hierarchy>, using the C<locale> warning
965 category, whenever such a locale is switched into. The UTF-8 locale
966 support is actually a
967 superset of POSIX locales, because it is really full Unicode behavior
968 as if no C<LC_CTYPE> locale were in effect at all (except for tainting;
969 see L</SECURITY>). POSIX locales, even UTF-8 ones,
970 are lacking certain concepts in Unicode, such as the idea that changing
971 the case of a character could expand to be more than one character.
972 Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
973 Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
974 with some restrictions, and on other platforms more like the "C" locale.
975 For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
976 used as a workaround for this (see L</Unicode and UTF-8>).
978 Note that there are quite a few things that are unaffected by the
979 current locale. Any literal character is the native character for the
980 given platform. Hence 'A' means the character at code point 65 on ASCII
981 platforms, and 193 on EBCDIC. That may or may not be an 'A' in the
982 current locale, if that locale even has an 'A'.
983 Similarly, all the escape sequences for particular characters,
984 C<\n> for example, always mean the platform's native one. This means,
985 for example, that C<\N> in regular expressions (every character
986 but new-line) works on the platform character set.
988 Starting in v5.22, Perl will by default warn when switching into a
989 locale that redefines any ASCII printable character (plus C<\t> and
990 C<\n>) into a different class than expected. This is likely to
991 happen on modern locales only on EBCDIC platforms, where, for example,
992 a CCSID 0037 locale on a CCSID 1047 machine moves C<"[">, but it can
993 happen on ASCII platforms with the ISO 646 and other
994 7-bit locales that are essentially obsolete. Things may still work,
995 depending on what features of Perl are used by the program. For
996 example, in the example from above where C<"|"> becomes a C<\w>, and
997 there are no regular expressions where this matters, the program may
998 still work properly. The warning lists all the characters that
999 it can determine could be adversely affected.
1001 B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
1002 in clearly ineligible characters being considered to be alphanumeric by
1003 your application. For strict matching of (mundane) ASCII letters and
1004 digits--for example, in command strings--locale-aware applications
1005 should use C<\w> with the C</a> regular expression modifier. See L</"SECURITY">.
1007 =head2 Category C<LC_NUMERIC>: Numeric Formatting
1009 After a proper C<POSIX::setlocale()> call, and within the scope of
1010 of a C<use locale> form that includes numerics, Perl obeys the
1011 C<LC_NUMERIC> locale information, which controls an application's idea
1012 of how numbers should be formatted for human readability.
1013 In most implementations the only effect is to
1014 change the character used for the decimal point--perhaps from "." to ",".
1015 The functions aren't aware of such niceties as thousands separation and
1016 so on. (See L</The localeconv function> if you care about these things.)
1018 use POSIX qw(strtod setlocale LC_NUMERIC);
1021 setlocale LC_NUMERIC, "";
1023 $n = 5/2; # Assign numeric 2.5 to $n
1025 $a = " $n"; # Locale-dependent conversion to string
1027 print "half five is $n\n"; # Locale-dependent output
1029 printf "half five is %g\n", $n; # Locale-dependent output
1031 print "DECIMAL POINT IS COMMA\n"
1032 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
1034 See also L<I18N::Langinfo> and C<RADIXCHAR>.
1036 =head2 Category C<LC_MONETARY>: Formatting of monetary amounts
1038 The C standard defines the C<LC_MONETARY> category, but not a function
1039 that is affected by its contents. (Those with experience of standards
1040 committees will recognize that the working group decided to punt on the
1041 issue.) Consequently, Perl essentially takes no notice of it. If you
1042 really want to use C<LC_MONETARY>, you can query its contents--see
1043 L</The localeconv function>--and use the information that it returns in your
1044 application's own formatting of currency amounts. However, you may well
1045 find that the information, voluminous and complex though it may be, still
1046 does not quite meet your requirements: currency formatting is a hard nut
1049 See also L<I18N::Langinfo> and C<CRNCYSTR>.
1051 =head2 Category C<LC_TIME>: Respresentation of time
1053 Output produced by C<POSIX::strftime()>, which builds a formatted
1054 human-readable date/time string, is affected by the current C<LC_TIME>
1055 locale. Thus, in a French locale, the output produced by the C<%B>
1056 format element (full month name) for the first month of the year would
1057 be "janvier". Here's how to get a list of long month names in the
1060 use POSIX qw(strftime);
1062 $long_month_name[$_] =
1063 strftime("%B", 0, 0, 0, 1, $_, 96);
1066 Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
1067 function which uses the standard system-supplied C<libc> function that
1068 always obeys the current C<LC_TIME> locale.
1070 See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
1071 C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
1073 =head2 Other categories
1075 The remaining locale categories are not currently used by Perl itself.
1076 But again note that things Perl interacts with may use these, including
1077 extensions outside the standard Perl distribution, and by the
1078 operating system and its utilities. Note especially that the string
1079 value of C<$!> and the error messages given by external utilities may
1080 be changed by C<LC_MESSAGES>. If you want to have portable error
1081 codes, use C<%!>. See L<Errno>.
1085 Although the main discussion of Perl security issues can be found in
1086 L<perlsec>, a discussion of Perl's locale handling would be incomplete
1087 if it did not draw your attention to locale-dependent security issues.
1088 Locales--particularly on systems that allow unprivileged users to
1089 build their own locales--are untrustworthy. A malicious (or just plain
1090 broken) locale can make a locale-aware application give unexpected
1091 results. Here are a few possibilities:
1097 Regular expression checks for safe file names or mail addresses using
1098 C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
1099 characters such as C<"E<gt>"> and C<"|"> are alphanumeric.
1103 String interpolation with case-mapping, as in, say, C<$dest =
1104 "C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE>
1105 case-mapping table is in effect.
1109 A sneaky C<LC_COLLATE> locale could result in the names of students with
1110 "D" grades appearing ahead of those with "A"s.
1114 An application that takes the trouble to use information in
1115 C<LC_MONETARY> may format debits as if they were credits and vice versa
1116 if that locale has been subverted. Or it might make payments in US
1117 dollars instead of Hong Kong dollars.
1121 The date and day names in dates formatted by C<strftime()> could be
1122 manipulated to advantage by a malicious user able to subvert the
1123 C<LC_DATE> locale. ("Look--it says I wasn't in the building on
1128 Such dangers are not peculiar to the locale system: any aspect of an
1129 application's environment which may be modified maliciously presents
1130 similar challenges. Similarly, they are not specific to Perl: any
1131 programming language that allows you to write programs that take
1132 account of their environment exposes you to these issues.
1134 Perl cannot protect you from all possibilities shown in the
1135 examples--there is no substitute for your own vigilance--but, when
1136 C<use locale> is in effect, Perl uses the tainting mechanism (see
1137 L<perlsec>) to mark string results that become locale-dependent, and
1138 which may be untrustworthy in consequence. Here is a summary of the
1139 tainting behavior of operators and functions that may be affected by
1146 B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
1148 Scalar true/false (or less/equal/greater) result is never tainted.
1152 B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
1154 The result string containing interpolated material is tainted if
1155 a C<use locale> form that includes C<LC_CTYPE> is in effect.
1159 B<Matching operator> (C<m//>):
1161 Scalar true/false result never tainted.
1163 All subpatterns, either delivered as a list-context result or as C<$1>
1164 I<etc>., are tainted if a C<use locale> form that includes
1165 C<LC_CTYPE> is in effect, and the subpattern
1166 regular expression contains a locale-dependent construct. These
1167 constructs include C<\w> (to match an alphanumeric character), C<\W>
1168 (non-alphanumeric character), C<\b> and C<\B> (word-boundary and
1169 non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
1170 (whitespace character), C<\S> (non whitespace character), C<\d> and
1171 C<\D> (digits and non-digits), and the POSIX character classes, such as
1172 C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
1174 Tainting is also likely if the pattern is to be matched
1175 case-insensitively (via C</i>). The exception is if all the code points
1176 to be matched this way are above 255 and do not have folds under Unicode
1177 rules to below 256. Tainting is not done for these because Perl
1178 only uses Unicode rules for such code points, and those rules are the
1179 same no matter what the current locale.
1181 The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
1182 (post-match), and C<$+> (last match) also are tainted.
1186 B<Substitution operator> (C<s///>):
1188 Has the same behavior as the match operator. Also, the left
1189 operand of C<=~> becomes tainted when a C<use locale>
1190 form that includes C<LC_CTYPE> is in effect, if modified as
1191 a result of a substitution based on a regular
1192 expression match involving any of the things mentioned in the previous
1193 item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
1197 B<Output formatting functions> (C<printf()> and C<write()>):
1199 Results are never tainted because otherwise even output from print,
1200 for example C<print(1/7)>, should be tainted if C<use locale> is in
1205 B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
1207 Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is
1212 B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
1213 C<strftime()>, C<strxfrm()>):
1215 Results are never tainted.
1219 Three examples illustrate locale-dependent tainting.
1220 The first program, which ignores its locale, won't run: a value taken
1221 directly from the command line may not be used to name an output file
1222 when taint checks are enabled.
1224 #/usr/local/bin/perl -T
1225 # Run with taint checking
1227 # Command line sanity check omitted...
1228 $tainted_output_file = shift;
1230 open(F, ">$tainted_output_file")
1231 or warn "Open of $tainted_output_file failed: $!\n";
1233 The program can be made to run by "laundering" the tainted value through
1234 a regular expression: the second example--which still ignores locale
1235 information--runs, creating the file named on its command line
1238 #/usr/local/bin/perl -T
1240 $tainted_output_file = shift;
1241 $tainted_output_file =~ m%[\w/]+%;
1242 $untainted_output_file = $&;
1244 open(F, ">$untainted_output_file")
1245 or warn "Open of $untainted_output_file failed: $!\n";
1247 Compare this with a similar but locale-aware program:
1249 #/usr/local/bin/perl -T
1251 $tainted_output_file = shift;
1253 $tainted_output_file =~ m%[\w/]+%;
1254 $localized_output_file = $&;
1256 open(F, ">$localized_output_file")
1257 or warn "Open of $localized_output_file failed: $!\n";
1259 This third program fails to run because C<$&> is tainted: it is the result
1260 of a match involving C<\w> while C<use locale> is in effect.
1266 =item PERL_SKIP_LOCALE_INIT
1268 This environment variable, available starting in Perl v5.20, if set
1269 (to any value), tells Perl to not use the rest of the
1270 environment variables to initialize with. Instead, Perl uses whatever
1271 the current locale settings are. This is particularly useful in
1272 embedded environments, see
1273 L<perlembed/Using embedded Perl with POSIX locales>.
1277 A string that can suppress Perl's warning about failed locale settings
1278 at startup. Failure can occur if the locale support in the operating
1279 system is lacking (broken) in some way--or if you mistyped the name of
1280 a locale when you set up your environment. If this environment
1281 variable is absent, or has a value other than "0" or "", Perl will
1282 complain about locale setting failures.
1284 B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message.
1285 The message tells about some problem in your system's locale support,
1286 and you should investigate what the problem is.
1290 The following environment variables are not specific to Perl: They are
1291 part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
1292 for controlling an application's opinion on data. Windows is non-POSIX,
1293 but Perl arranges for the following to work as described anyway.
1294 If the locale given by an environment variable is not valid, Perl tries
1295 the next lower one in priority. If none are valid, on Windows, the
1296 system default locale is then tried. If all else fails, the C<"C">
1297 locale is used. If even that doesn't work, something is badly broken,
1298 but Perl tries to forge ahead with whatever the locale settings might
1305 C<LC_ALL> is the "override-all" locale environment variable. If
1306 set, it overrides all the rest of the locale environment variables.
1310 B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
1311 are using the GNU libc. This is the case if you are using e.g. Linux.
1312 If you are using "commercial" Unixes you are most probably I<not>
1313 using GNU libc and you can ignore C<LANGUAGE>.
1315 However, in the case you are using C<LANGUAGE>: it affects the
1316 language of informational, warning, and error messages output by
1317 commands (in other words, it's like C<LC_MESSAGES>) but it has higher
1318 priority than C<LC_ALL>. Moreover, it's not a single value but
1319 instead a "path" (":"-separated list) of I<languages> (not locales).
1320 See the GNU C<gettext> library documentation for more information.
1324 In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
1325 locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
1326 chooses the character type locale.
1330 In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
1331 (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
1332 C<LANG> chooses the collation locale.
1334 =item C<LC_MONETARY>
1336 In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
1337 formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
1338 C<LANG> chooses the monetary formatting locale.
1342 In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
1343 locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
1344 chooses the numeric format.
1348 In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
1349 formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
1350 C<LANG> chooses the date and time formatting locale.
1354 C<LANG> is the "catch-all" locale environment variable. If it is set, it
1355 is used as the last resort after the overall C<LC_ALL> and the
1356 category-specific C<LC_I<foo>>.
1362 The C<LC_NUMERIC> controls the numeric output:
1365 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1366 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1367 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1369 and also how strings are parsed by C<POSIX::strtod()> as numbers:
1372 use POSIX qw(locale_h strtod);
1373 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1374 my $x = strtod("2,34") + 5;
1375 print $x, "\n"; # Probably shows 7,34.
1379 =head2 String C<eval> and C<LC_NUMERIC>
1381 A string L<eval|perlfunc/eval EXPR> parses its expression as standard
1382 Perl. It is therefore expecting the decimal point to be a dot. If
1383 C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
1384 be confused, perhaps silently.
1387 use POSIX qw(locale_h);
1388 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1390 print eval "$a + 1.5";
1393 prints C<13,5>. This is because in that locale, the comma is the
1394 decimal point character. The C<eval> thus expands to:
1398 and the result is not what you likely expected. No warnings are
1399 generated. If you do string C<eval>'s within the scope of
1400 S<C<use locale>>, you should instead change the C<eval> line to do
1403 print eval "no locale; $a + 1.5";
1407 You could also exclude C<LC_NUMERIC>, if you don't need it, by
1409 use locale ':!numeric';
1411 =head2 Backward compatibility
1413 Versions of Perl prior to 5.004 B<mostly> ignored locale information,
1414 generally behaving as if something similar to the C<"C"> locale were
1415 always in force, even if the program environment suggested otherwise
1416 (see L</The setlocale function>). By default, Perl still behaves this
1417 way for backward compatibility. If you want a Perl application to pay
1418 attention to locale information, you B<must> use the S<C<use locale>>
1419 pragma (see L</The "use locale" pragma>) or, in the unlikely event
1420 that you want to do so for just pattern matching, the
1421 C</l> regular expression modifier (see L<perlre/Character set
1422 modifiers>) to instruct it to do so.
1424 Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
1425 information if available; that is, C<\w> did understand what
1426 were the letters according to the locale environment variables.
1427 The problem was that the user had no control over the feature:
1428 if the C library supported locales, Perl used them.
1430 =head2 I18N:Collate obsolete
1432 In versions of Perl prior to 5.004, per-locale collation was possible
1433 using the C<I18N::Collate> library module. This module is now mildly
1434 obsolete and should be avoided in new applications. The C<LC_COLLATE>
1435 functionality is now integrated into the Perl core language: One can
1436 use locale-specific scalar data completely normally with C<use locale>,
1437 so there is no longer any need to juggle with the scalar references of
1440 =head2 Sort speed and memory use impacts
1442 Comparing and sorting by locale is usually slower than the default
1443 sorting; slow-downs of two to four times have been observed. It will
1444 also consume more memory: once a Perl scalar variable has participated
1445 in any string comparison or sorting operation obeying the locale
1446 collation rules, it will take 3-15 times more memory than before. (The
1447 exact multiplier depends on the string's contents, the operating system
1448 and the locale.) These downsides are dictated more by the operating
1449 system's implementation of the locale system than by Perl.
1451 =head2 Freely available locale definitions
1453 The Unicode CLDR project extracts the POSIX portion of many of its
1454 locales, available at
1456 http://unicode.org/Public/cldr/2.0.1/
1458 (Newer versions of CLDR require you to compute the POSIX data yourself.
1459 See L<http://unicode.org/Public/cldr/latest/>.)
1461 There is a large collection of locale definitions at:
1463 http://std.dkuug.dk/i18n/WG15-collection/locales/
1465 You should be aware that it is
1466 unsupported, and is not claimed to be fit for any purpose. If your
1467 system allows installation of arbitrary locales, you may find the
1468 definitions useful as they are, or as a basis for the development of
1471 =head2 I18n and l10n
1473 "Internationalization" is often abbreviated as B<i18n> because its first
1474 and last letters are separated by eighteen others. (You may guess why
1475 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1476 the same way, "localization" is often abbreviated to B<l10n>.
1478 =head2 An imperfect standard
1480 Internationalization, as defined in the C and POSIX standards, can be
1481 criticized as incomplete and ungainly. They also have a tendency, like
1482 standards groups, to divide the world into nations, when we all know
1483 that the world can equally well be divided into bankers, bikers, gamers,
1486 =head1 Unicode and UTF-8
1488 The support of Unicode is new starting from Perl version v5.6, and more fully
1489 implemented in versions v5.8 and later. See L<perluniintro>.
1491 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1492 C<LC_COLLATE> is only partially supported; collation support is improved
1493 in Perl v5.26 to a level that may be sufficient for your needs
1494 (see L</Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting>).
1496 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1498 use locale ':not_characters';
1500 When this form of the pragma is used, only the non-character portions of
1501 locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
1502 you have translated all the characters it is to operate on into Unicode
1503 (actually the platform's native character set (ASCII or EBCDIC) plus
1504 Unicode). For data in files, this can conveniently be done by also
1509 This pragma arranges for all inputs from files to be translated into
1510 Unicode from the current locale as specified in the environment (see
1511 L</ENVIRONMENT>), and all outputs to files to be translated back
1512 into the locale. (See L<open>). On a per-filehandle basis, you can
1513 instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
1514 module, both available from CPAN. The latter module also has methods to
1515 ease the handling of C<ARGV> and environment variables, and can be used
1516 on individual strings. If you know that all your locales will be
1517 UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
1518 command line switch.
1520 This form of the pragma allows essentially seamless handling of locales
1521 with Unicode. The collation order will be by Unicode code point order.
1522 L<Unicode::Collate> can be used to get Unicode rules collation.
1524 All the modules and switches just described can be used in v5.20 with
1525 just plain C<use locale>, and, should the input locales not be UTF-8,
1526 you'll get the less than ideal behavior, described below, that you get
1527 with pre-v5.16 Perls, or when you use the locale pragma without the
1528 C<:not_characters> parameter in v5.16 and v5.18. If you are using
1529 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1530 does not apply to you.
1532 There are two cases, multi-byte and single-byte locales. First
1535 The only multi-byte (or wide character) locale that Perl is ever likely
1536 to support is UTF-8. This is due to the difficulty of implementation,
1537 the fact that high quality UTF-8 locales are now published for every
1538 area of the world (L<http://unicode.org/Public/cldr/2.0.1/> for
1539 ones that are already set-up, but from an earlier version;
1540 L<http://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1541 you have to extract the POSIX information yourself), and that
1542 failing all that you can use the L<Encode> module to translate to/from
1543 your locale. So, you'll have to do one of those things if you're using
1544 one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1545 Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1546 work reasonably well (depending on your C library implementation)
1548 they and Perl store characters that take up multiple bytes the same way.
1549 However, some, if not most, C library implementations may not process
1550 the characters in the upper half of the Latin-1 range (128 - 255)
1551 properly under C<LC_CTYPE>. To see if a character is a particular type
1552 under a locale, Perl uses the functions like C<isalnum()>. Your C
1553 library may not work for UTF-8 locales with those functions, instead
1554 only working under the newer wide library functions like C<iswalnum()>,
1555 which Perl does not use.
1556 These multi-byte locales are treated like single-byte locales, and will
1557 have the restrictions described below. Starting in Perl v5.22 a warning
1558 message is raised when Perl detects a multi-byte locale that it doesn't
1561 For single-byte locales,
1562 Perl generally takes the tack to use locale rules on code points that can fit
1563 in a single byte, and Unicode rules for those that can't (though this
1564 isn't uniformly applied, see the note at the end of this section). This
1565 prevents many problems in locales that aren't UTF-8. Suppose the locale
1566 is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
1567 in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
1568 regular expression character class C<[[:alpha:]]> will magically match
1569 0xD7 in the Greek locale but not in the Latin one.
1571 However, there are places where this breaks down. Certain Perl constructs are
1572 for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
1573 Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
1574 subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
1575 Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
1576 issue occurs with C<\N{...}>. Prior to v5.20, it is therefore a bad
1577 idea to use C<\p{}> or
1578 C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
1579 locale will be ISO8859-1. Use POSIX character classes instead.
1581 Another problem with this approach is that operations that cross the
1582 single byte/multiple byte boundary are not well-defined, and so are
1583 disallowed. (This boundary is between the codepoints at 255/256.)
1584 For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1585 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1586 Greek locale, for example, there is no character at 0xFF, and Perl
1587 has no way of knowing what the character at 0xFF is really supposed to
1588 represent. Thus it disallows the operation. In this mode, the
1589 lowercase of U+0178 is itself.
1591 The same problems ensue if you enable automatic UTF-8-ification of your
1592 standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
1593 non-UTF-8 locales (by using either the B<-C> command line switch or the
1594 C<PERL_UNICODE> environment variable; see L<perlrun>).
1595 Things are read in as UTF-8, which would normally imply a Unicode
1596 interpretation, but the presence of a locale causes them to be interpreted
1597 in that locale instead. For example, a 0xD7 code point in the Unicode
1598 input, which should mean the multiplication sign, won't be interpreted by
1599 Perl that way under the Greek locale. This is not a problem
1600 I<provided> you make certain that all locales will always and only be either
1601 an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
1603 Still another problem is that this approach can lead to two code
1604 points meaning the same character. Thus in a Greek locale, both U+03A7
1605 and U+00D7 are GREEK CAPITAL LETTER CHI.
1607 Because of all these problems, starting in v5.22, Perl will raise a
1608 warning if a multi-byte (hence Unicode) code point is used when a
1609 single-byte locale is in effect. (Although it doesn't check for this if
1610 doing so would unreasonably slow execution down.)
1612 Vendor locales are notoriously buggy, and it is difficult for Perl to test
1613 its locale-handling code because this interacts with code that Perl has no
1614 control over; therefore the locale-handling code in Perl may be buggy as
1615 well. (However, the Unicode-supplied locales should be better, and
1616 there is a feed back mechanism to correct any problems. See
1617 L</Freely available locale definitions>.)
1619 If you have Perl v5.16, the problems mentioned above go away if you use
1620 the C<:not_characters> parameter to the locale pragma (except for vendor
1621 bugs in the non-character portions). If you don't have v5.16, and you
1622 I<do> have locales that work, using them may be worthwhile for certain
1623 specific purposes, as long as you keep in mind the gotchas already
1624 mentioned. For example, if the collation for your locales works, it
1625 runs faster under locales than under L<Unicode::Collate>; and you gain
1626 access to such things as the local currency symbol and the names of the
1627 months and days of the week. (But to hammer home the point, in v5.16,
1628 you get this access without the downsides of locales by using the
1629 C<:not_characters> form of the pragma.)
1631 Note: The policy of using locale rules for code points that can fit in a
1632 byte, and Unicode rules for those that can't is not uniformly applied.
1633 Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
1634 consistently to regular expression matching except for bracketed
1635 character classes; in v5.14 it was extended to all regex matches; and in
1636 v5.16 to the casing operations such as C<\L> and C<uc()>. For
1637 collation, in all releases so far, the system's C<strxfrm()> function is
1638 called, and whatever it does is what you get. Starting in v5.26, various
1639 bugs are fixed with the way perl uses this function.
1643 =head2 Collation of strings containing embedded C<NUL> characters
1645 C<NUL> characters will sort the same as the lowest collating control
1646 character does, or to C<"\001"> in the unlikely event that there are no
1647 control characters at all in the locale. In cases where the strings
1648 don't contain this non-C<NUL> control, the results will be correct, and
1649 in many locales, this control, whatever it might be, will rarely be
1650 encountered. But there are cases where a C<NUL> should sort before this
1651 control, but doesn't. If two strings do collate identically, the one
1652 containing the C<NUL> will sort to earlier. Prior to 5.26, there were
1655 =head2 Multi-threaded
1657 XS code or C-language libraries called from it that use the system
1658 L<C<setlocale(3)>> function (except on Windows) likely will not work
1659 from a multi-threaded application without changes. See
1660 L<perlxs/Locale-aware XS code>.
1662 An XS module that is locale-dependent could have been written under the
1663 assumption that it will never be called in a multi-threaded environment,
1664 and so uses other non-locale constructs that aren't multi-thread-safe.
1665 See L<perlxs/Thread-aware system interfaces>.
1667 POSIX does not define a way to get the name of the current per-thread
1668 locale. Some systems, such as Darwin and NetBSD do implement a
1669 function, L<querylocale(3)> to do this. On non-Windows systems without
1670 it, such as Linux, there are some additional caveats:
1676 An embedded perl needs to be started up while the global locale is in
1677 effect. See L<perlembed/Using embedded Perl with POSIX locales>.
1681 It becomes more important for perl to know about all the possible
1682 locale categories on the platform, even if they aren't apparently used
1683 in your program. Perl knows all of the Linux ones. If your platform
1684 has others, you can send email to L<mailto:perlbug@perl.org> for
1685 inclusion of it in the next release. In the meantime, it is possible to
1686 edit the Perl source to teach it about the category, and then recompile.
1687 Search for instances of, say, C<LC_PAPER> in the source, and use that as
1688 a template to add the omitted one.
1692 It is possible, though hard to do, to call C<POSIX::setlocale> with a
1693 locale that it doesn't recognize as syntactically legal, but actually is
1694 legal on that system. This should happen only with embedded perls, or
1695 if you hand-craft a locale name yourself.
1699 =head2 Broken systems
1701 In certain systems, the operating system's locale support
1702 is broken and cannot be fixed or used by Perl. Such deficiencies can
1703 and will result in mysterious hangs and/or Perl core dumps when
1704 C<use locale> is in effect. When confronted with such a system,
1705 please report in excruciating detail to <F<perlbug@perl.org>>, and
1706 also contact your vendor: bug fixes may exist for these problems
1707 in your operating system. Sometimes such bug fixes are called an
1708 operating system upgrade. If you have the source for Perl, include in
1709 the perlbug email the output of the test described above in L</Testing
1710 for broken locales>.
1714 L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
1715 L<POSIX/localeconv>,
1716 L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
1717 L<POSIX/strtod>, L<POSIX/strxfrm>.
1719 For special considerations when Perl is embedded in a C program,
1720 see L<perlembed/Using embedded Perl with POSIX locales>.
1724 Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
1725 Dunlop, assisted by the perl5-porters. Prose worked over a bit by
1726 Tom Christiansen, and now maintained by Perl 5 porters.