1PERLLOCALE(1) Perl Programmers Reference Guide PERLLOCALE(1)
2
6 perllocale - Perl locale handling (internationalization and
7 localization)
8
10 In the beginning there was ASCII, the "American Standard Code for
11 Information Interchange", which works quite well for Americans with
12 their English alphabet and dollar-denominated currency. But it doesn't
13 work so well even for other English speakers, who may use different
14 currencies, such as the pound sterling (as the symbol for that currency
15 is not in ASCII); and it's hopelessly inadequate for many of the
16 thousands of the world's other languages.
17 To address these deficiencies, the concept of locales was invented
19 (formally the ISO C, XPG4, POSIX 1.c "locale system"). And
20 applications were and are being written that use the locale mechanism.
21 The process of making such an application take account of its users'
22 preferences in these kinds of matters is called internationalization
23 (often abbreviated as i18n); telling such an application about a
24 particular set of preferences is known as localization (l10n).
25 Perl has been extended to support certain types of locales available in
27 the locale system. This is controlled per application by using one
28 pragma, one function call, and several environment variables.
29 Perl supports single-byte locales that are supersets of ASCII, such as
31 the ISO 8859 ones, and one multi-byte-type locale, UTF-8 ones,
32 described in the next paragraph. Perl doesn't support any other multi-
33 byte locales, such as the ones for East Asian languages.
34 Unfortunately, there are quite a few deficiencies with the design (and
36 often, the implementations) of locales. Unicode was invented (see
37 perlunitut for an introduction to that) in part to address these design
38 deficiencies, and nowadays, there is a series of "UTF-8 locales", based
39 on Unicode. These are locales whose character set is Unicode, encoded
40 in UTF-8. Starting in v5.20, Perl fully supports UTF-8 locales, except
41 for sorting and string comparisons like "lt" and "ge". Starting in
42 v5.26, Perl can handle these reasonably as well, depending on the
43 platform's implementation. However, for earlier releases or for better
44 control, use Unicode::Collate. There are actually two slightly
45 different types of UTF-8 locales: one for Turkic languages and one for
46 everything else. Starting in Perl v5.30, Perl seamlessly handles both
47 types; previously only the non-Turkic one was supported.
48 Perl continues to support the old non UTF-8 locales as well. There are
50 currently no UTF-8 locales for EBCDIC platforms.
51 (Unicode is also creating "CLDR", the "Common Locale Data Repository",
53 <http://cldr.unicode.org/> which includes more types of information
54 than are available in the POSIX locale system. At the time of this
55 writing, there was no CPAN module that provides access to this XML-
56 encoded data. However, it is possible to compute the POSIX locale data
57 from them, and earlier CLDR versions had these already extracted for
58 you as UTF-8 locales <http://unicode.org/Public/cldr/2.0.1/>.)
59
61 A locale is a set of data that describes various aspects of how various
62 communities in the world categorize their world. These categories are
63 broken down into the following types (some of which include a brief
64 note here):
65 Category "LC_NUMERIC": Numeric formatting
67 This indicates how numbers should be formatted for human
68 readability, for example the character used as the decimal point.
69 Category "LC_MONETARY": Formatting of monetary amounts
71 Category "LC_TIME": Date/Time formatting
74 Category "LC_MESSAGES": Error and other messages
77 This is used by Perl itself only for accessing operating system
78 error messages via $! and $^E.
79 Category "LC_COLLATE": Collation
81 This indicates the ordering of letters for comparison and sorting.
82 In Latin alphabets, for example, "b", generally follows "a".
83 Category "LC_CTYPE": Character Types
85 This indicates, for example if a character is an uppercase letter.
86 Other categories
88 Some platforms have other categories, dealing with such things as
89 measurement units and paper sizes. None of these are used directly
90 by Perl, but outside operations that Perl interacts with may use
91 these. See "Not within the scope of "use locale"" below.
92 More details on the categories used by Perl are given below in "LOCALE
94 CATEGORIES".
95 Together, these categories go a long way towards being able to
97 customize a single program to run in many different locations. But
98 there are deficiencies, so keep reading.
99
101 Perl itself (outside the POSIX module) will not use locales unless
102 specifically requested to (but again note that Perl may interact with
103 code that does use them). Even if there is such a request, all of the
104 following must be true for it to work properly:
105 · Your operating system must support the locale system. If it does,
107 you should find that the "setlocale()" function is a documented
108 part of its C library.
109 · Definitions for locales that you use must be installed. You, or
111 your system administrator, must make sure that this is the case.
112 The available locales, the location in which they are kept, and the
113 manner in which they are installed all vary from system to system.
114 Some systems provide only a few, hard-wired locales and do not
115 allow more to be added. Others allow you to add "canned" locales
116 provided by the system supplier. Still others allow you or the
117 system administrator to define and add arbitrary locales. (You may
118 have to ask your supplier to provide canned locales that are not
119 delivered with your operating system.) Read your system
120 documentation for further illumination.
121 · Perl must believe that the locale system is supported. If it does,
123 "perl -V:d_setlocale" will say that the value for "d_setlocale" is
124 "define".
125 If you want a Perl application to process and present your data
127 according to a particular locale, the application code should include
128 the "use locale" pragma (see "The "use locale" pragma") where
129 appropriate, and at least one of the following must be true:
130 1. The locale-determining environment variables (see "ENVIRONMENT")
132 must be correctly set up at the time the application is started,
133 either by yourself or by whomever set up your system account; or
134 2. The application must set its own locale using the method described
136 in "The setlocale function".
137
139 The "use locale" pragma
140 Starting in Perl 5.28, this pragma may be used in multi-threaded
141 applications on systems that have thread-safe locale ability. Some
142 caveats apply, see "Multi-threaded" below. On systems without this
143 capability, or in earlier Perls, do NOT use this pragma in scripts that
144 have multiple threads active. The locale in these cases is not local
145 to a single thread. Another thread may change the locale at any time,
146 which could cause at a minimum that a given thread is operating in a
147 locale it isn't expecting to be in. On some platforms, segfaults can
148 also occur. The locale change need not be explicit; some operations
149 cause perl to change the locale itself. You are vulnerable simply by
150 having done a "use locale".
151 By default, Perl itself (outside the POSIX module) ignores the current
153 locale. The "use locale" pragma tells Perl to use the current locale
154 for some operations. Starting in v5.16, there are optional parameters
155 to this pragma, described below, which restrict which operations are
156 affected by it.
157 The current locale is set at execution time by setlocale() described
159 below. If that function hasn't yet been called in the course of the
160 program's execution, the current locale is that which was determined by
161 the "ENVIRONMENT" in effect at the start of the program. If there is
162 no valid environment, the current locale is whatever the system default
163 has been set to. On POSIX systems, it is likely, but not necessarily,
164 the "C" locale. On Windows, the default is set via the computer's
165 "Control Panel->Regional and Language Options" (or its current
166 equivalent).
167 The operations that are affected by locale are:
169 Not within the scope of "use locale"
171 Only certain operations (all originating outside Perl) should be
172 affected, as follows:
173 · The current locale is used when going outside of Perl with
175 operations like system() or qx//, if those operations are
176 locale-sensitive.
177 · Also Perl gives access to various C library functions through
179 the POSIX module. Some of those functions are always affected
180 by the current locale. For example, "POSIX::strftime()" uses
181 "LC_TIME"; "POSIX::strtod()" uses "LC_NUMERIC";
182 "POSIX::strcoll()" and "POSIX::strxfrm()" use "LC_COLLATE".
183 All such functions will behave according to the current
184 underlying locale, even if that locale isn't exposed to Perl
185 space.
186 This applies as well to I18N::Langinfo.
188 · XS modules for all categories but "LC_NUMERIC" get the
190 underlying locale, and hence any C library functions they call
191 will use that underlying locale. For more discussion, see
192 "CAVEATS" in perlxs.
193 Note that all C programs (including the perl interpreter, which is
195 written in C) always have an underlying locale. That locale is the
196 "C" locale unless changed by a call to setlocale(). When Perl
197 starts up, it changes the underlying locale to the one which is
198 indicated by the "ENVIRONMENT". When using the POSIX module or
199 writing XS code, it is important to keep in mind that the
200 underlying locale may be something other than "C", even if the
201 program hasn't explicitly changed it.
202 Lingering effects of "use locale"
206 Certain Perl operations that are set-up within the scope of a "use
207 locale" retain that effect even outside the scope. These include:
208 · The output format of a write() is determined by an earlier
210 format declaration ("format" in perlfunc), so whether or not
211 the output is affected by locale is determined by if the
212 "format()" is within the scope of a "use locale", not whether
213 the "write()" is.
214 · Regular expression patterns can be compiled using qr// with
216 actual matching deferred to later. Again, it is whether or not
217 the compilation was done within the scope of "use locale" that
218 determines the match behavior, not if the matches are done
219 within such a scope or not.
220 Under ""use locale";"
224 · All the above operations
225 · Format declarations ("format" in perlfunc) and hence any
227 subsequent "write()"s use "LC_NUMERIC".
228 · stringification and output use "LC_NUMERIC". These include the
230 results of "print()", "printf()", "say()", and "sprintf()".
231 · The comparison operators ("lt", "le", "cmp", "ge", and "gt")
233 use "LC_COLLATE". "sort()" is also affected if used without an
234 explicit comparison function, because it uses "cmp" by default.
235 Note: "eq" and "ne" are unaffected by locale: they always
237 perform a char-by-char comparison of their scalar operands.
238 What's more, if "cmp" finds that its operands are equal
239 according to the collation sequence specified by the current
240 locale, it goes on to perform a char-by-char comparison, and
241 only returns 0 (equal) if the operands are char-for-char
242 identical. If you really want to know whether two
243 strings--which "eq" and "cmp" may consider different--are equal
244 as far as collation in the locale is concerned, see the
245 discussion in "Category "LC_COLLATE": Collation".
246 · Regular expressions and case-modification functions ("uc()",
248 "lc()", "ucfirst()", and "lcfirst()") use "LC_CTYPE"
249 · The variables $! (and its synonyms $ERRNO and $OS_ERROR) and
251 $^E (and its synonym $EXTENDED_OS_ERROR) when used as strings
252 use "LC_MESSAGES".
253 The default behavior is restored with the "no locale" pragma, or upon
255 reaching the end of the block enclosing "use locale". Note that "use
256 locale" calls may be nested, and that what is in effect within an inner
257 scope will revert to the outer scope's rules at the end of the inner
258 scope.
259 The string result of any operation that uses locale information is
261 tainted, as it is possible for a locale to be untrustworthy. See
262 "SECURITY".
263 Starting in Perl v5.16 in a very limited way, and more generally in
265 v5.22, you can restrict which category or categories are enabled by
266 this particular instance of the pragma by adding parameters to it. For
267 example,
268 use locale qw(:ctype :numeric);
270 enables locale awareness within its scope of only those operations
272 (listed above) that are affected by "LC_CTYPE" and "LC_NUMERIC".
273 The possible categories are: ":collate", ":ctype", ":messages",
275 ":monetary", ":numeric", ":time", and the pseudo category ":characters"
276 (described below).
277 Thus you can say
279 use locale ':messages';
281 and only $! and $^E will be locale aware. Everything else is
283 unaffected.
284 Since Perl doesn't currently do anything with the "LC_MONETARY"
286 category, specifying ":monetary" does effectively nothing. Some
287 systems have other categories, such as "LC_PAPER", but Perl also
288 doesn't do anything with them, and there is no way to specify them in
289 this pragma's arguments.
290 You can also easily say to use all categories but one, by either, for
292 example,
293 use locale ':!ctype';
295 use locale ':not_ctype';
296 both of which mean to enable locale awarness of all categories but
298 "LC_CTYPE". Only one category argument may be specified in a
299 "use locale" if it is of the negated form.
300 Prior to v5.22 only one form of the pragma with arguments is available:
302 use locale ':not_characters';
304 (and you have to say "not_"; you can't use the bang "!" form). This
306 pseudo category is a shorthand for specifying both ":collate" and
307 ":ctype". Hence, in the negated form, it is nearly the same thing as
308 saying
309 use locale qw(:messages :monetary :numeric :time);
311 We use the term "nearly", because ":not_characters" also turns on
313 "use feature 'unicode_strings'" within its scope. This form is less
314 useful in v5.20 and later, and is described fully in "Unicode and
315 UTF-8", but briefly, it tells Perl to not use the character portions of
316 the locale definition, that is the "LC_CTYPE" and "LC_COLLATE"
317 categories. Instead it will use the native character set (extended by
318 Unicode). When using this parameter, you are responsible for getting
319 the external character set translated into the native/Unicode one
320 (which it already will be if it is one of the increasingly popular
321 UTF-8 locales). There are convenient ways of doing this, as described
322 in "Unicode and UTF-8".
323 The setlocale function
325 WARNING! Prior to Perl 5.28 or on a system that does not support
326 thread-safe locale operations, do NOT use this function in a thread.
327 The locale will change in all other threads at the same time, and
328 should your thread get paused by the operating system, and another
329 started, that thread will not have the locale it is expecting. On some
330 platforms, there can be a race leading to segfaults if two threads call
331 this function nearly simultaneously.
332 You can switch locales as often as you wish at run time with the
334 "POSIX::setlocale()" function:
335 # Import locale-handling tool set from POSIX module.
337 # This example uses: setlocale -- the function call
338 # LC_CTYPE -- explained below
339 # (Showing the testing for success/failure of operations is
340 # omitted in these examples to avoid distracting from the main
341 # point)
342 use POSIX qw(locale_h);
344 use locale;
345 my $old_locale;
346 # query and save the old locale
348 $old_locale = setlocale(LC_CTYPE);
349 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
351 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
352 setlocale(LC_CTYPE, "");
354 # LC_CTYPE now reset to the default defined by the
355 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
356 # default. See below for documentation.
357 # restore the old locale
359 setlocale(LC_CTYPE, $old_locale);
360 The first argument of "setlocale()" gives the category, the second the
362 locale. The category tells in what aspect of data processing you want
363 to apply locale-specific rules. Category names are discussed in
364 "LOCALE CATEGORIES" and "ENVIRONMENT". The locale is the name of a
365 collection of customization information corresponding to a particular
366 combination of language, country or territory, and codeset. Read on
367 for hints on the naming of locales: not all systems name locales as in
368 the example.
369 If no second argument is provided and the category is something other
371 than "LC_ALL", the function returns a string naming the current locale
372 for the category. You can use this value as the second argument in a
373 subsequent call to "setlocale()", but on some platforms the string is
374 opaque, not something that most people would be able to decipher as to
375 what locale it means.
376 If no second argument is provided and the category is "LC_ALL", the
378 result is implementation-dependent. It may be a string of concatenated
379 locale names (separator also implementation-dependent) or a single
380 locale name. Please consult your setlocale(3) man page for details.
381 If a second argument is given and it corresponds to a valid locale, the
383 locale for the category is set to that value, and the function returns
384 the now-current locale value. You can then use this in yet another
385 call to "setlocale()". (In some implementations, the return value may
386 sometimes differ from the value you gave as the second argument--think
387 of it as an alias for the value you gave.)
388 As the example shows, if the second argument is an empty string, the
390 category's locale is returned to the default specified by the
391 corresponding environment variables. Generally, this results in a
392 return to the default that was in force when Perl started up: changes
393 to the environment made by the application after startup may or may not
394 be noticed, depending on your system's C library.
395 Note that when a form of "use locale" that doesn't include all
397 categories is specified, Perl ignores the excluded categories.
398 If "set_locale()" fails for some reason (for example, an attempt to set
400 to a locale unknown to the system), the locale for the category is not
401 changed, and the function returns "undef".
402 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
404 implement POSIX 2008 thread-safe locale operations, this function
405 doesn't actually call the system "setlocale". Instead those thread-
406 safe operations are used to emulate the "setlocale" function, but in a
407 thread-safe manner.
408 You can force the thread-safe locale operations to always be used (if
410 available) by recompiling perl with
411 -Accflags='-DUSE_THREAD_SAFE_LOCALE'
413 added to your call to Configure.
415 For further information about the categories, consult setlocale(3).
417 Multi-threaded operation
419 Beginning in Perl 5.28, multi-threaded locale operation is supported on
420 systems that implement either the POSIX 2008 or Windows-specific
421 thread-safe locale operations. Many modern systems, such as various
422 Unix variants and Darwin do have this.
423 You can tell if using locales is safe on your system by looking at the
425 read-only boolean variable "${^SAFE_LOCALES}". The value is 1 if the
426 perl is not threaded, or if it is using thread-safe locale operations.
427 Thread-safe operations are supported in Windows starting in Visual
429 Studio 2005, and in systems compatible with POSIX 2008. Some platforms
430 claim to support POSIX 2008, but have buggy implementations, so that
431 the hints files for compiling to run on them turn off attempting to use
432 thread-safety. "${^SAFE_LOCALES}" will be 0 on them.
433 Be aware that writing a multi-threaded application will not be portable
435 to a platform which lacks the native thread-safe locale support. On
436 systems that do have it, you automatically get this behavior for
437 threaded perls, without having to do anything. If for some reason, you
438 don't want to use this capability (perhaps the POSIX 2008 support is
439 buggy on your system), you can manually compile Perl to use the old
440 non-thread-safe implementation by passing the argument
441 "-Accflags='-DNO_THREAD_SAFE_LOCALE'" to Configure. Except on Windows,
442 this will continue to use certain of the POSIX 2008 functions in some
443 situations. If these are buggy, you can pass the following to
444 Configure instead or additionally:
445 "-Accflags='-DNO_POSIX_2008_LOCALE'". This will also keep the code
446 from using thread-safe locales. "${^SAFE_LOCALES}" will be 0 on
447 systems that turn off the thread-safe operations.
448 Normally on unthreaded builds, the traditional "setlocale()" is used
450 and not the thread-safe locale functions. You can force the use of
451 these on systems that have them by adding the
452 "-Accflags='-DUSE_THREAD_SAFE_LOCALE'" to Configure.
453 The initial program is started up using the locale specified from the
455 environment, as currently, described in "ENVIRONMENT". All newly
456 created threads start with "LC_ALL" set to "C">. Each thread may use
457 "POSIX::setlocale()" to query or switch its locale at any time, without
458 affecting any other thread. All locale-dependent operations
459 automatically use their thread's locale.
460 This should be completely transparent to any applications written
462 entirely in Perl (minus a few rarely encountered caveats given in the
463 "Multi-threaded" section). Information for XS module writers is given
464 in "Locale-aware XS code" in perlxs.
465 Finding locales
467 For locales available in your system, consult also setlocale(3) to see
468 whether it leads to the list of available locales (search for the SEE
469 ALSO section). If that fails, try the following command lines:
470 locale -a
472 nlsinfo
474 ls /usr/lib/nls/loc
476 ls /usr/lib/locale
478 ls /usr/lib/nls
480 ls /usr/share/locale
482 and see whether they list something resembling these
484 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
486 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
487 en_US de_DE ru_RU
488 en de ru
489 english german russian
490 english.iso88591 german.iso88591 russian.iso88595
491 english.roman8 russian.koi8r
492 Sadly, even though the calling interface for "setlocale()" has been
494 standardized, names of locales and the directories where the
495 configuration resides have not been. The basic form of the name is
496 language_territory.codeset, but the latter parts after language are not
497 always present. The language and country are usually from the
498 standards ISO 3166 and ISO 639, the two-letter abbreviations for the
499 countries and the languages of the world, respectively. The codeset
500 part often mentions some ISO 8859 character set, the Latin codesets.
501 For example, "ISO 8859-1" is the so-called "Western European codeset"
502 that can be used to encode most Western European languages adequately.
503 Again, there are several ways to write even the name of that one
504 standard. Lamentably.
505 Two special locales are worth particular mention: "C" and "POSIX".
507 Currently these are effectively the same locale: the difference is
508 mainly that the first one is defined by the C standard, the second by
509 the POSIX standard. They define the default locale in which every
510 program starts in the absence of locale information in its environment.
511 (The default default locale, if you will.) Its language is (American)
512 English and its character codeset ASCII or, rarely, a superset thereof
513 (such as the "DEC Multinational Character Set (DEC-MCS)"). Warning.
514 The C locale delivered by some vendors may not actually exactly match
515 what the C standard calls for. So beware.
516 NOTE: Not all systems have the "POSIX" locale (not all systems are
518 POSIX-conformant), so use "C" when you need explicitly to specify this
519 default locale.
520 LOCALE PROBLEMS
522 You may encounter the following warning message at Perl startup:
523 perl: warning: Setting locale failed.
525 perl: warning: Please check that your locale settings:
526 LC_ALL = "En_US",
527 LANG = (unset)
528 are supported and installed on your system.
529 perl: warning: Falling back to the standard locale ("C").
530 This means that your locale settings had "LC_ALL" set to "En_US" and
532 LANG exists but has no value. Perl tried to believe you but could not.
533 Instead, Perl gave up and fell back to the "C" locale, the default
534 locale that is supposed to work no matter what. (On Windows, it first
535 tries falling back to the system default locale.) This usually means
536 your locale settings were wrong, they mention locales your system has
537 never heard of, or the locale installation in your system has problems
538 (for example, some system files are broken or missing). There are
539 quick and temporary fixes to these problems, as well as more thorough
540 and lasting fixes.
541 Testing for broken locales
543 If you are building Perl from source, the Perl test suite file
544 lib/locale.t can be used to test the locales on your system. Setting
545 the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it to
546 output detailed results. For example, on Linux, you could say
547 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
549 Besides many other tests, it will test every locale it finds on your
551 system to see if they conform to the POSIX standard. If any have
552 errors, it will include a summary near the end of the output of which
553 locales passed all its tests, and which failed, and why.
554 Temporarily fixing locale problems
556 The two quickest fixes are either to render Perl silent about any
557 locale inconsistencies or to run Perl under the default locale "C".
558 Perl's moaning about locale problems can be silenced by setting the
560 environment variable "PERL_BADLANG" to "0" or "". This method really
561 just sweeps the problem under the carpet: you tell Perl to shut up even
562 when Perl sees that something is wrong. Do not be surprised if later
563 something locale-dependent misbehaves.
564 Perl can be run under the "C" locale by setting the environment
566 variable "LC_ALL" to "C". This method is perhaps a bit more civilized
567 than the "PERL_BADLANG" approach, but setting "LC_ALL" (or other locale
568 variables) may affect other programs as well, not just Perl. In
569 particular, external programs run from within Perl will see these
570 changes. If you make the new settings permanent (read on), all
571 programs you run see the changes. See "ENVIRONMENT" for the full list
572 of relevant environment variables and "USING LOCALES" for their effects
573 in Perl. Effects in other programs are easily deducible. For example,
574 the variable "LC_COLLATE" may well affect your sort program (or
575 whatever the program that arranges "records" alphabetically in your
576 system is called).
577 You can test out changing these variables temporarily, and if the new
579 settings seem to help, put those settings into your shell startup
580 files. Consult your local documentation for the exact details. For
581 Bourne-like shells (sh, ksh, bash, zsh):
582 LC_ALL=en_US.ISO8859-1
584 export LC_ALL
585 This assumes that we saw the locale "en_US.ISO8859-1" using the
587 commands discussed above. We decided to try that instead of the above
588 faulty locale "En_US"--and in Cshish shells (csh, tcsh)
589 setenv LC_ALL en_US.ISO8859-1
591 or if you have the "env" application you can do (in any shell)
593 env LC_ALL=en_US.ISO8859-1 perl ...
595 If you do not know what shell you have, consult your local helpdesk or
597 the equivalent.
598 Permanently fixing locale problems
600 The slower but superior fixes are when you may be able to yourself fix
601 the misconfiguration of your own environment variables. The
602 mis(sing)configuration of the whole system's locales usually requires
603 the help of your friendly system administrator.
604 First, see earlier in this document about "Finding locales". That
606 tells how to find which locales are really supported--and more
607 importantly, installed--on your system. In our example error message,
608 environment variables affecting the locale are listed in the order of
609 decreasing importance (and unset variables do not matter). Therefore,
610 having LC_ALL set to "En_US" must have been the bad choice, as shown by
611 the error message. First try fixing locale settings listed first.
612 Second, if using the listed commands you see something exactly (prefix
614 matches do not count and case usually counts) like "En_US" without the
615 quotes, then you should be okay because you are using a locale name
616 that should be installed and available in your system. In this case,
617 see "Permanently fixing your system's locale configuration".
618 Permanently fixing your system's locale configuration
620 This is when you see something like:
621 perl: warning: Please check that your locale settings:
623 LC_ALL = "En_US",
624 LANG = (unset)
625 are supported and installed on your system.
626 but then cannot see that "En_US" listed by the above-mentioned
628 commands. You may see things like "en_US.ISO8859-1", but that isn't
629 the same. In this case, try running under a locale that you can list
630 and which somehow matches what you tried. The rules for matching
631 locale names are a bit vague because standardization is weak in this
632 area. See again the "Finding locales" about general rules.
633 Fixing system locale configuration
635 Contact a system administrator (preferably your own) and report the
636 exact error message you get, and ask them to read this same
637 documentation you are now reading. They should be able to check
638 whether there is something wrong with the locale configuration of the
639 system. The "Finding locales" section is unfortunately a bit vague
640 about the exact commands and places because these things are not that
641 standardized.
642 The localeconv function
644 The "POSIX::localeconv()" function allows you to get particulars of the
645 locale-dependent numeric formatting information specified by the
646 current underlying "LC_NUMERIC" and "LC_MONETARY" locales (regardless
647 of whether called from within the scope of "use locale" or not). (If
648 you just want the name of the current locale for a particular category,
649 use "POSIX::setlocale()" with a single parameter--see "The setlocale
650 function".)
651 use POSIX qw(locale_h);
653 # Get a reference to a hash of locale-dependent info
655 $locale_values = localeconv();
656 # Output sorted list of the values
658 for (sort keys %$locale_values) {
659 printf "%-20s = %s\n", $_, $locale_values->{$_}
660 }
661 "localeconv()" takes no arguments, and returns a reference to a hash.
663 The keys of this hash are variable names for formatting, such as
664 "decimal_point" and "thousands_sep". The values are the corresponding,
665 er, values. See "localeconv" in POSIX for a longer example listing the
666 categories an implementation might be expected to provide; some provide
667 more and others fewer. You don't need an explicit "use locale",
668 because "localeconv()" always observes the current locale.
669 Here's a simple-minded example program that rewrites its command-line
671 parameters as integers correctly formatted in the current locale:
672 use POSIX qw(locale_h);
674 # Get some of locale's numeric formatting parameters
676 my ($thousands_sep, $grouping) =
677 @{localeconv()}{'thousands_sep', 'grouping'};
678 # Apply defaults if values are missing
680 $thousands_sep = ',' unless $thousands_sep;
681 # grouping and mon_grouping are packed lists
683 # of small integers (characters) telling the
684 # grouping (thousand_seps and mon_thousand_seps
685 # being the group dividers) of numbers and
686 # monetary quantities. The integers' meanings:
687 # 255 means no more grouping, 0 means repeat
688 # the previous grouping, 1-254 means use that
689 # as the current grouping. Grouping goes from
690 # right to left (low to high digits). In the
691 # below we cheat slightly by never using anything
692 # else than the first grouping (whatever that is).
693 if ($grouping) {
694 @grouping = unpack("C*", $grouping);
695 } else {
696 @grouping = (3);
697 }
698 # Format command line params for current locale
700 for (@ARGV) {
701 $_ = int; # Chop non-integer part
702 1 while
703 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
704 print "$_";
705 }
706 print "\n";
707 Note that if the platform doesn't have "LC_NUMERIC" and/or
709 "LC_MONETARY" available or enabled, the corresponding elements of the
710 hash will be missing.
711 I18N::Langinfo
713 Another interface for querying locale-dependent information is the
714 "I18N::Langinfo::langinfo()" function.
715 The following example will import the "langinfo()" function itself and
717 three constants to be used as arguments to "langinfo()": a constant for
718 the abbreviated first day of the week (the numbering starts from Sunday
719 = 1) and two more constants for the affirmative and negative answers
720 for a yes/no question in the current locale.
721 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
723 my ($abday_1, $yesstr, $nostr)
725 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
726 print "$abday_1? [$yesstr/$nostr] ";
728 In other words, in the "C" (or English) locale the above will probably
730 print something like:
731 Sun? [yes/no]
733 See I18N::Langinfo for more information.
735
737 The following subsections describe basic locale categories. Beyond
738 these, some combination categories allow manipulation of more than one
739 basic category at a time. See "ENVIRONMENT" for a discussion of these.
740 Category "LC_COLLATE": Collation: Text Comparisons and Sorting
742 In the scope of a "use locale" form that includes collation, Perl looks
743 to the "LC_COLLATE" environment variable to determine the application's
744 notions on collation (ordering) of characters. For example, "b"
745 follows "a" in Latin alphabets, but where do "a" and "aa" belong? And
746 while "color" follows "chocolate" in English, what about in traditional
747 Spanish?
748 The following collations all make sense and you may meet any of them if
750 you "use locale".
751 A B C D E a b c d e
753 A a B b C c D d E e
754 a A b B c C d D e E
755 a b c d e A B C D E
756 Here is a code snippet to tell what "word" characters are in the
758 current locale, in that locale's order:
759 use locale;
761 print +(sort grep /\w/, map { chr } 0..255), "\n";
762 Compare this with the characters that you see and their order if you
764 state explicitly that the locale should be ignored:
765 no locale;
767 print +(sort grep /\w/, map { chr } 0..255), "\n";
768 This machine-native collation (which is what you get unless
770 "use locale" has appeared earlier in the same block) must be used for
771 sorting raw binary data, whereas the locale-dependent collation of the
772 first example is useful for natural text.
773 As noted in "USING LOCALES", "cmp" compares according to the current
775 collation locale when "use locale" is in effect, but falls back to a
776 char-by-char comparison for strings that the locale says are equal. You
777 can use "POSIX::strcoll()" if you don't want this fall-back:
778 use POSIX qw(strcoll);
780 $equal_in_locale =
781 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
782 $equal_in_locale will be true if the collation locale specifies a
784 dictionary-like ordering that ignores space characters completely and
785 which folds case.
786 Perl uses the platform's C library collation functions "strcoll()" and
788 "strxfrm()". That means you get whatever they give. On some
789 platforms, these functions work well on UTF-8 locales, giving a
790 reasonable default collation for the code points that are important in
791 that locale. (And if they aren't working well, the problem may only be
792 that the locale definition is deficient, so can be fixed by using a
793 better definition file. Unicode's definitions (see "Freely available
794 locale definitions") provide reasonable UTF-8 locale collation
795 definitions.) Starting in Perl v5.26, Perl's use of these functions
796 has been made more seamless. This may be sufficient for your needs.
797 For more control, and to make sure strings containing any code point
798 (not just the ones important in the locale) collate properly, the
799 Unicode::Collate module is suggested.
800 In non-UTF-8 locales (hence single byte), code points above 0xFF are
802 technically invalid. But if present, again starting in v5.26, they
803 will collate to the same position as the highest valid code point does.
804 This generally gives good results, but the collation order may be
805 skewed if the valid code point gets special treatment when it forms
806 particular sequences with other characters as defined by the locale.
807 When two strings collate identically, the code point order is used as a
808 tie breaker.
809 If Perl detects that there are problems with the locale collation
811 order, it reverts to using non-locale collation rules for that locale.
812 If you have a single string that you want to check for "equality in
814 locale" against several others, you might think you could gain a little
815 efficiency by using "POSIX::strxfrm()" in conjunction with "eq":
816 use POSIX qw(strxfrm);
818 $xfrm_string = strxfrm("Mixed-case string");
819 print "locale collation ignores spaces\n"
820 if $xfrm_string eq strxfrm("Mixed-casestring");
821 print "locale collation ignores hyphens\n"
822 if $xfrm_string eq strxfrm("Mixedcase string");
823 print "locale collation ignores case\n"
824 if $xfrm_string eq strxfrm("mixed-case string");
825 "strxfrm()" takes a string and maps it into a transformed string for
827 use in char-by-char comparisons against other transformed strings
828 during collation. "Under the hood", locale-affected Perl comparison
829 operators call "strxfrm()" for both operands, then do a char-by-char
830 comparison of the transformed strings. By calling "strxfrm()"
831 explicitly and using a non locale-affected comparison, the example
832 attempts to save a couple of transformations. But in fact, it doesn't
833 save anything: Perl magic (see "Magic Variables" in perlguts) creates
834 the transformed version of a string the first time it's needed in a
835 comparison, then keeps this version around in case it's needed again.
836 An example rewritten the easy way with "cmp" runs just about as fast.
837 It also copes with null characters embedded in strings; if you call
838 "strxfrm()" directly, it treats the first null it finds as a
839 terminator. Don't expect the transformed strings it produces to be
840 portable across systems--or even from one revision of your operating
841 system to the next. In short, don't call "strxfrm()" directly: let
842 Perl do it for you.
843 Note: "use locale" isn't shown in some of these examples because it
845 isn't needed: "strcoll()" and "strxfrm()" are POSIX functions which use
846 the standard system-supplied "libc" functions that always obey the
847 current "LC_COLLATE" locale.
848 Category "LC_CTYPE": Character Types
850 In the scope of a "use locale" form that includes "LC_CTYPE", Perl
851 obeys the "LC_CTYPE" locale setting. This controls the application's
852 notion of which characters are alphabetic, numeric, punctuation, etc.
853 This affects Perl's "\w" regular expression metanotation, which stands
854 for alphanumeric characters--that is, alphabetic, numeric, and the
855 platform's native underscore. (Consult perlre for more information
856 about regular expressions.) Thanks to "LC_CTYPE", depending on your
857 locale setting, characters like "ae", "d`", "ss", and "o" may be
858 understood as "\w" characters. It also affects things like "\s", "\D",
859 and the POSIX character classes, like "[[:graph:]]". (See
860 perlrecharclass for more information on all these.)
861 The "LC_CTYPE" locale also provides the map used in transliterating
863 characters between lower and uppercase. This affects the case-mapping
864 functions--"fc()", "lc()", "lcfirst()", "uc()", and "ucfirst()"; case-
865 mapping interpolation with "\F", "\l", "\L", "\u", or "\U" in double-
866 quoted strings and "s///" substitutions; and case-insensitive regular
867 expression pattern matching using the "i" modifier.
868 Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
870 otherwise Perl only supports single-byte locales, such as the ISO 8859
871 series. This means that wide character locales, for example for Asian
872 languages, are not well-supported. Use of these locales may cause core
873 dumps. If the platform has the capability for Perl to detect such a
874 locale, starting in Perl v5.22, Perl will warn, default enabled, using
875 the "locale" warning category, whenever such a locale is switched into.
876 The UTF-8 locale support is actually a superset of POSIX locales,
877 because it is really full Unicode behavior as if no "LC_CTYPE" locale
878 were in effect at all (except for tainting; see "SECURITY"). POSIX
879 locales, even UTF-8 ones, are lacking certain concepts in Unicode, such
880 as the idea that changing the case of a character could expand to be
881 more than one character. Perl in a UTF-8 locale, will give you that
882 expansion. Prior to v5.20, Perl treated a UTF-8 locale on some
883 platforms like an ISO 8859-1 one, with some restrictions, and on other
884 platforms more like the "C" locale. For releases v5.16 and v5.18,
885 "use locale 'not_characters" could be used as a workaround for this
886 (see "Unicode and UTF-8").
887 Note that there are quite a few things that are unaffected by the
889 current locale. Any literal character is the native character for the
890 given platform. Hence 'A' means the character at code point 65 on
891 ASCII platforms, and 193 on EBCDIC. That may or may not be an 'A' in
892 the current locale, if that locale even has an 'A'. Similarly, all the
893 escape sequences for particular characters, "\n" for example, always
894 mean the platform's native one. This means, for example, that "\N" in
895 regular expressions (every character but new-line) works on the
896 platform character set.
897 Starting in v5.22, Perl will by default warn when switching into a
899 locale that redefines any ASCII printable character (plus "\t" and
900 "\n") into a different class than expected. This is likely to happen
901 on modern locales only on EBCDIC platforms, where, for example, a CCSID
902 0037 locale on a CCSID 1047 machine moves "[", but it can happen on
903 ASCII platforms with the ISO 646 and other 7-bit locales that are
904 essentially obsolete. Things may still work, depending on what
905 features of Perl are used by the program. For example, in the example
906 from above where "|" becomes a "\w", and there are no regular
907 expressions where this matters, the program may still work properly.
908 The warning lists all the characters that it can determine could be
909 adversely affected.
910 Note: A broken or malicious "LC_CTYPE" locale definition may result in
912 clearly ineligible characters being considered to be alphanumeric by
913 your application. For strict matching of (mundane) ASCII letters and
914 digits--for example, in command strings--locale-aware applications
915 should use "\w" with the "/a" regular expression modifier. See
916 "SECURITY".
917 Category "LC_NUMERIC": Numeric Formatting
919 After a proper "POSIX::setlocale()" call, and within the scope of of a
920 "use locale" form that includes numerics, Perl obeys the "LC_NUMERIC"
921 locale information, which controls an application's idea of how numbers
922 should be formatted for human readability. In most implementations the
923 only effect is to change the character used for the decimal
924 point--perhaps from "." to ",". The functions aren't aware of such
925 niceties as thousands separation and so on. (See "The localeconv
926 function" if you care about these things.)
927 use POSIX qw(strtod setlocale LC_NUMERIC);
929 use locale;
930 setlocale LC_NUMERIC, "";
932 $n = 5/2; # Assign numeric 2.5 to $n
934 $a = " $n"; # Locale-dependent conversion to string
936 print "half five is $n\n"; # Locale-dependent output
938 printf "half five is %g\n", $n; # Locale-dependent output
940 print "DECIMAL POINT IS COMMA\n"
942 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
943 See also I18N::Langinfo and "RADIXCHAR".
945 Category "LC_MONETARY": Formatting of monetary amounts
947 The C standard defines the "LC_MONETARY" category, but not a function
948 that is affected by its contents. (Those with experience of standards
949 committees will recognize that the working group decided to punt on the
950 issue.) Consequently, Perl essentially takes no notice of it. If you
951 really want to use "LC_MONETARY", you can query its contents--see "The
952 localeconv function"--and use the information that it returns in your
953 application's own formatting of currency amounts. However, you may
954 well find that the information, voluminous and complex though it may
955 be, still does not quite meet your requirements: currency formatting is
956 a hard nut to crack.
957 See also I18N::Langinfo and "CRNCYSTR".
959 Category "LC_TIME": Respresentation of time
961 Output produced by "POSIX::strftime()", which builds a formatted human-
962 readable date/time string, is affected by the current "LC_TIME" locale.
963 Thus, in a French locale, the output produced by the %B format element
964 (full month name) for the first month of the year would be "janvier".
965 Here's how to get a list of long month names in the current locale:
966 use POSIX qw(strftime);
968 for (0..11) {
969 $long_month_name[$_] =
970 strftime("%B", 0, 0, 0, 1, $_, 96);
971 }
972 Note: "use locale" isn't needed in this example: "strftime()" is a
974 POSIX function which uses the standard system-supplied "libc" function
975 that always obeys the current "LC_TIME" locale.
976 See also I18N::Langinfo and "ABDAY_1".."ABDAY_7", "DAY_1".."DAY_7",
978 "ABMON_1".."ABMON_12", and "ABMON_1".."ABMON_12".
979 Other categories
981 The remaining locale categories are not currently used by Perl itself.
982 But again note that things Perl interacts with may use these, including
983 extensions outside the standard Perl distribution, and by the operating
984 system and its utilities. Note especially that the string value of $!
985 and the error messages given by external utilities may be changed by
986 "LC_MESSAGES". If you want to have portable error codes, use "%!".
987 See Errno.
988
990 Although the main discussion of Perl security issues can be found in
991 perlsec, a discussion of Perl's locale handling would be incomplete if
992 it did not draw your attention to locale-dependent security issues.
993 Locales--particularly on systems that allow unprivileged users to build
994 their own locales--are untrustworthy. A malicious (or just plain
995 broken) locale can make a locale-aware application give unexpected
996 results. Here are a few possibilities:
997 · Regular expression checks for safe file names or mail addresses
999 using "\w" may be spoofed by an "LC_CTYPE" locale that claims that
1000 characters such as ">" and "|" are alphanumeric.
1001 · String interpolation with case-mapping, as in, say, "$dest =
1003 "C:\U$name.$ext"", may produce dangerous results if a bogus
1004 "LC_CTYPE" case-mapping table is in effect.
1005 · A sneaky "LC_COLLATE" locale could result in the names of students
1007 with "D" grades appearing ahead of those with "A"s.
1008 · An application that takes the trouble to use information in
1010 "LC_MONETARY" may format debits as if they were credits and vice
1011 versa if that locale has been subverted. Or it might make payments
1012 in US dollars instead of Hong Kong dollars.
1013 · The date and day names in dates formatted by "strftime()" could be
1015 manipulated to advantage by a malicious user able to subvert the
1016 "LC_DATE" locale. ("Look--it says I wasn't in the building on
1017 Sunday.")
1018 Such dangers are not peculiar to the locale system: any aspect of an
1020 application's environment which may be modified maliciously presents
1021 similar challenges. Similarly, they are not specific to Perl: any
1022 programming language that allows you to write programs that take
1023 account of their environment exposes you to these issues.
1024 Perl cannot protect you from all possibilities shown in the
1026 examples--there is no substitute for your own vigilance--but, when "use
1027 locale" is in effect, Perl uses the tainting mechanism (see perlsec) to
1028 mark string results that become locale-dependent, and which may be
1029 untrustworthy in consequence. Here is a summary of the tainting
1030 behavior of operators and functions that may be affected by the locale:
1031 · Comparison operators ("lt", "le", "ge", "gt" and "cmp"):
1033 Scalar true/false (or less/equal/greater) result is never tainted.
1035 · Case-mapping interpolation (with "\l", "\L", "\u", "\U", or "\F")
1037 The result string containing interpolated material is tainted if a
1039 "use locale" form that includes "LC_CTYPE" is in effect.
1040 · Matching operator ("m//"):
1042 Scalar true/false result never tainted.
1044 All subpatterns, either delivered as a list-context result or as $1
1046 etc., are tainted if a "use locale" form that includes "LC_CTYPE"
1047 is in effect, and the subpattern regular expression contains a
1048 locale-dependent construct. These constructs include "\w" (to
1049 match an alphanumeric character), "\W" (non-alphanumeric
1050 character), "\b" and "\B" (word-boundary and non-boundardy, which
1051 depend on what "\w" and "\W" match), "\s" (whitespace character),
1052 "\S" (non whitespace character), "\d" and "\D" (digits and non-
1053 digits), and the POSIX character classes, such as "[:alpha:]" (see
1054 "POSIX Character Classes" in perlrecharclass).
1055 Tainting is also likely if the pattern is to be matched case-
1057 insensitively (via "/i"). The exception is if all the code points
1058 to be matched this way are above 255 and do not have folds under
1059 Unicode rules to below 256. Tainting is not done for these because
1060 Perl only uses Unicode rules for such code points, and those rules
1061 are the same no matter what the current locale.
1062 The matched-pattern variables, $&, "$`" (pre-match), "$'" (post-
1064 match), and $+ (last match) also are tainted.
1065 · Substitution operator ("s///"):
1067 Has the same behavior as the match operator. Also, the left
1069 operand of "=~" becomes tainted when a "use locale" form that
1070 includes "LC_CTYPE" is in effect, if modified as a result of a
1071 substitution based on a regular expression match involving any of
1072 the things mentioned in the previous item, or of case-mapping, such
1073 as "\l", "\L","\u", "\U", or "\F".
1074 · Output formatting functions ("printf()" and "write()"):
1076 Results are never tainted because otherwise even output from print,
1078 for example "print(1/7)", should be tainted if "use locale" is in
1079 effect.
1080 · Case-mapping functions ("lc()", "lcfirst()", "uc()", "ucfirst()"):
1082 Results are tainted if a "use locale" form that includes "LC_CTYPE"
1084 is in effect.
1085 · POSIX locale-dependent functions ("localeconv()", "strcoll()",
1087 "strftime()", "strxfrm()"):
1088 Results are never tainted.
1090 Three examples illustrate locale-dependent tainting. The first
1092 program, which ignores its locale, won't run: a value taken directly
1093 from the command line may not be used to name an output file when taint
1094 checks are enabled.
1095 #/usr/local/bin/perl -T
1097 # Run with taint checking
1098 # Command line sanity check omitted...
1100 $tainted_output_file = shift;
1101 open(F, ">$tainted_output_file")
1103 or warn "Open of $tainted_output_file failed: $!\n";
1104 The program can be made to run by "laundering" the tainted value
1106 through a regular expression: the second example--which still ignores
1107 locale information--runs, creating the file named on its command line
1108 if it can.
1109 #/usr/local/bin/perl -T
1111 $tainted_output_file = shift;
1113 $tainted_output_file =~ m%[\w/]+%;
1114 $untainted_output_file = $&;
1115 open(F, ">$untainted_output_file")
1117 or warn "Open of $untainted_output_file failed: $!\n";
1118 Compare this with a similar but locale-aware program:
1120 #/usr/local/bin/perl -T
1122 $tainted_output_file = shift;
1124 use locale;
1125 $tainted_output_file =~ m%[\w/]+%;
1126 $localized_output_file = $&;
1127 open(F, ">$localized_output_file")
1129 or warn "Open of $localized_output_file failed: $!\n";
1130 This third program fails to run because $& is tainted: it is the result
1132 of a match involving "\w" while "use locale" is in effect.
1133
1135 PERL_SKIP_LOCALE_INIT
1136 This environment variable, available starting in Perl
1137 v5.20, if set (to any value), tells Perl to not use the
1138 rest of the environment variables to initialize with.
1139 Instead, Perl uses whatever the current locale settings
1140 are. This is particularly useful in embedded environments,
1141 see "Using embedded Perl with POSIX locales" in perlembed.
1142 PERL_BADLANG
1144 A string that can suppress Perl's warning about failed
1145 locale settings at startup. Failure can occur if the
1146 locale support in the operating system is lacking (broken)
1147 in some way--or if you mistyped the name of a locale when
1148 you set up your environment. If this environment variable
1149 is absent, or has a value other than "0" or "", Perl will
1150 complain about locale setting failures.
1151 NOTE: "PERL_BADLANG" only gives you a way to hide the
1153 warning message. The message tells about some problem in
1154 your system's locale support, and you should investigate
1155 what the problem is.
1156 The following environment variables are not specific to Perl: They are
1158 part of the standardized (ISO C, XPG4, POSIX 1.c) "setlocale()" method
1159 for controlling an application's opinion on data. Windows is non-
1160 POSIX, but Perl arranges for the following to work as described anyway.
1161 If the locale given by an environment variable is not valid, Perl tries
1162 the next lower one in priority. If none are valid, on Windows, the
1163 system default locale is then tried. If all else fails, the "C" locale
1164 is used. If even that doesn't work, something is badly broken, but
1165 Perl tries to forge ahead with whatever the locale settings might be.
1166 "LC_ALL" "LC_ALL" is the "override-all" locale environment variable.
1168 If set, it overrides all the rest of the locale environment
1169 variables.
1170 "LANGUAGE" NOTE: "LANGUAGE" is a GNU extension, it affects you only if
1172 you are using the GNU libc. This is the case if you are
1173 using e.g. Linux. If you are using "commercial" Unixes you
1174 are most probably not using GNU libc and you can ignore
1175 "LANGUAGE".
1176 However, in the case you are using "LANGUAGE": it affects
1178 the language of informational, warning, and error messages
1179 output by commands (in other words, it's like
1180 "LC_MESSAGES") but it has higher priority than "LC_ALL".
1181 Moreover, it's not a single value but instead a "path"
1182 (":"-separated list) of languages (not locales). See the
1183 GNU "gettext" library documentation for more information.
1184 "LC_CTYPE" In the absence of "LC_ALL", "LC_CTYPE" chooses the
1186 character type locale. In the absence of both "LC_ALL" and
1187 "LC_CTYPE", "LANG" chooses the character type locale.
1188 "LC_COLLATE"
1190 In the absence of "LC_ALL", "LC_COLLATE" chooses the
1191 collation (sorting) locale. In the absence of both
1192 "LC_ALL" and "LC_COLLATE", "LANG" chooses the collation
1193 locale.
1194 "LC_MONETARY"
1196 In the absence of "LC_ALL", "LC_MONETARY" chooses the
1197 monetary formatting locale. In the absence of both
1198 "LC_ALL" and "LC_MONETARY", "LANG" chooses the monetary
1199 formatting locale.
1200 "LC_NUMERIC"
1202 In the absence of "LC_ALL", "LC_NUMERIC" chooses the
1203 numeric format locale. In the absence of both "LC_ALL" and
1204 "LC_NUMERIC", "LANG" chooses the numeric format.
1205 "LC_TIME" In the absence of "LC_ALL", "LC_TIME" chooses the date and
1207 time formatting locale. In the absence of both "LC_ALL"
1208 and "LC_TIME", "LANG" chooses the date and time formatting
1209 locale.
1210 "LANG" "LANG" is the "catch-all" locale environment variable. If
1212 it is set, it is used as the last resort after the overall
1213 "LC_ALL" and the category-specific "LC_foo".
1214 Examples
1216 The "LC_NUMERIC" controls the numeric output:
1217 use locale;
1219 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1220 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1221 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1222 and also how strings are parsed by "POSIX::strtod()" as numbers:
1224 use locale;
1226 use POSIX qw(locale_h strtod);
1227 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1228 my $x = strtod("2,34") + 5;
1229 print $x, "\n"; # Probably shows 7,34.
1230
1232 String "eval" and "LC_NUMERIC"
1233 A string eval parses its expression as standard Perl. It is therefore
1234 expecting the decimal point to be a dot. If "LC_NUMERIC" is set to
1235 have this be a comma instead, the parsing will be confused, perhaps
1236 silently.
1237 use locale;
1239 use POSIX qw(locale_h);
1240 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1241 my $a = 1.2;
1242 print eval "$a + 1.5";
1243 print "\n";
1244 prints "13,5". This is because in that locale, the comma is the
1246 decimal point character. The "eval" thus expands to:
1247 eval "1,2 + 1.5"
1249 and the result is not what you likely expected. No warnings are
1251 generated. If you do string "eval"'s within the scope of "use locale",
1252 you should instead change the "eval" line to do something like:
1253 print eval "no locale; $a + 1.5";
1255 This prints 2.7.
1257 You could also exclude "LC_NUMERIC", if you don't need it, by
1259 use locale ':!numeric';
1261 Backward compatibility
1263 Versions of Perl prior to 5.004 mostly ignored locale information,
1264 generally behaving as if something similar to the "C" locale were
1265 always in force, even if the program environment suggested otherwise
1266 (see "The setlocale function"). By default, Perl still behaves this
1267 way for backward compatibility. If you want a Perl application to pay
1268 attention to locale information, you must use the "use locale" pragma
1269 (see "The "use locale" pragma") or, in the unlikely event that you want
1270 to do so for just pattern matching, the "/l" regular expression
1271 modifier (see "Character set modifiers" in perlre) to instruct it to do
1272 so.
1273 Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE" information
1275 if available; that is, "\w" did understand what were the letters
1276 according to the locale environment variables. The problem was that
1277 the user had no control over the feature: if the C library supported
1278 locales, Perl used them.
1279 I18N:Collate obsolete
1281 In versions of Perl prior to 5.004, per-locale collation was possible
1282 using the "I18N::Collate" library module. This module is now mildly
1283 obsolete and should be avoided in new applications. The "LC_COLLATE"
1284 functionality is now integrated into the Perl core language: One can
1285 use locale-specific scalar data completely normally with "use locale",
1286 so there is no longer any need to juggle with the scalar references of
1287 "I18N::Collate".
1288 Sort speed and memory use impacts
1290 Comparing and sorting by locale is usually slower than the default
1291 sorting; slow-downs of two to four times have been observed. It will
1292 also consume more memory: once a Perl scalar variable has participated
1293 in any string comparison or sorting operation obeying the locale
1294 collation rules, it will take 3-15 times more memory than before. (The
1295 exact multiplier depends on the string's contents, the operating system
1296 and the locale.) These downsides are dictated more by the operating
1297 system's implementation of the locale system than by Perl.
1298 Freely available locale definitions
1300 The Unicode CLDR project extracts the POSIX portion of many of its
1301 locales, available at
1302 http://unicode.org/Public/cldr/2.0.1/
1304 (Newer versions of CLDR require you to compute the POSIX data yourself.
1306 See <http://unicode.org/Public/cldr/latest/>.)
1307 There is a large collection of locale definitions at:
1309 http://std.dkuug.dk/i18n/WG15-collection/locales/
1311 You should be aware that it is unsupported, and is not claimed to be
1313 fit for any purpose. If your system allows installation of arbitrary
1314 locales, you may find the definitions useful as they are, or as a basis
1315 for the development of your own locales.
1316 I18n and l10n
1318 "Internationalization" is often abbreviated as i18n because its first
1319 and last letters are separated by eighteen others. (You may guess why
1320 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1321 the same way, "localization" is often abbreviated to l10n.
1322 An imperfect standard
1324 Internationalization, as defined in the C and POSIX standards, can be
1325 criticized as incomplete and ungainly. They also have a tendency, like
1326 standards groups, to divide the world into nations, when we all know
1327 that the world can equally well be divided into bankers, bikers,
1328 gamers, and so on.
1329
1331 The support of Unicode is new starting from Perl version v5.6, and more
1332 fully implemented in versions v5.8 and later. See perluniintro.
1333 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1335 "LC_COLLATE" is only partially supported; collation support is improved
1336 in Perl v5.26 to a level that may be sufficient for your needs (see
1337 "Category "LC_COLLATE": Collation: Text Comparisons and Sorting").
1338 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1340 use locale ':not_characters';
1342 When this form of the pragma is used, only the non-character portions
1344 of locales are used by Perl, for example "LC_NUMERIC". Perl assumes
1345 that you have translated all the characters it is to operate on into
1346 Unicode (actually the platform's native character set (ASCII or EBCDIC)
1347 plus Unicode). For data in files, this can conveniently be done by
1348 also specifying
1349 use open ':locale';
1351 This pragma arranges for all inputs from files to be translated into
1353 Unicode from the current locale as specified in the environment (see
1354 "ENVIRONMENT"), and all outputs to files to be translated back into the
1355 locale. (See open). On a per-filehandle basis, you can instead use
1356 the PerlIO::locale module, or the Encode::Locale module, both available
1357 from CPAN. The latter module also has methods to ease the handling of
1358 "ARGV" and environment variables, and can be used on individual
1359 strings. If you know that all your locales will be UTF-8, as many are
1360 these days, you can use the -C command line switch.
1361 This form of the pragma allows essentially seamless handling of locales
1363 with Unicode. The collation order will be by Unicode code point order.
1364 Unicode::Collate can be used to get Unicode rules collation.
1365 All the modules and switches just described can be used in v5.20 with
1367 just plain "use locale", and, should the input locales not be UTF-8,
1368 you'll get the less than ideal behavior, described below, that you get
1369 with pre-v5.16 Perls, or when you use the locale pragma without the
1370 ":not_characters" parameter in v5.16 and v5.18. If you are using
1371 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1372 does not apply to you.
1373 There are two cases, multi-byte and single-byte locales. First multi-
1375 byte:
1376 The only multi-byte (or wide character) locale that Perl is ever likely
1378 to support is UTF-8. This is due to the difficulty of implementation,
1379 the fact that high quality UTF-8 locales are now published for every
1380 area of the world (<http://unicode.org/Public/cldr/2.0.1/> for ones
1381 that are already set-up, but from an earlier version;
1382 <http://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1383 you have to extract the POSIX information yourself), and that failing
1384 all that you can use the Encode module to translate to/from your
1385 locale. So, you'll have to do one of those things if you're using one
1386 of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1387 Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1388 work reasonably well (depending on your C library implementation)
1389 simply because both they and Perl store characters that take up
1390 multiple bytes the same way. However, some, if not most, C library
1391 implementations may not process the characters in the upper half of the
1392 Latin-1 range (128 - 255) properly under "LC_CTYPE". To see if a
1393 character is a particular type under a locale, Perl uses the functions
1394 like "isalnum()". Your C library may not work for UTF-8 locales with
1395 those functions, instead only working under the newer wide library
1396 functions like "iswalnum()", which Perl does not use. These multi-byte
1397 locales are treated like single-byte locales, and will have the
1398 restrictions described below. Starting in Perl v5.22 a warning message
1399 is raised when Perl detects a multi-byte locale that it doesn't fully
1400 support.
1401 For single-byte locales, Perl generally takes the tack to use locale
1403 rules on code points that can fit in a single byte, and Unicode rules
1404 for those that can't (though this isn't uniformly applied, see the note
1405 at the end of this section). This prevents many problems in locales
1406 that aren't UTF-8. Suppose the locale is ISO8859-7, Greek. The
1407 character at 0xD7 there is a capital Chi. But in the ISO8859-1 locale,
1408 Latin1, it is a multiplication sign. The POSIX regular expression
1409 character class "[[:alpha:]]" will magically match 0xD7 in the Greek
1410 locale but not in the Latin one.
1411 However, there are places where this breaks down. Certain Perl
1413 constructs are for Unicode only, such as "\p{Alpha}". They assume that
1414 0xD7 always has its Unicode meaning (or the equivalent on EBCDIC
1415 platforms). Since Latin1 is a subset of Unicode and 0xD7 is the
1416 multiplication sign in both Latin1 and Unicode, "\p{Alpha}" will never
1417 match it, regardless of locale. A similar issue occurs with "\N{...}".
1418 Prior to v5.20, it is therefore a bad idea to use "\p{}" or "\N{}"
1419 under plain "use locale"--unless you can guarantee that the locale will
1420 be ISO8859-1. Use POSIX character classes instead.
1421 Another problem with this approach is that operations that cross the
1423 single byte/multiple byte boundary are not well-defined, and so are
1424 disallowed. (This boundary is between the codepoints at 255/256.) For
1425 example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1426 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1427 Greek locale, for example, there is no character at 0xFF, and Perl has
1428 no way of knowing what the character at 0xFF is really supposed to
1429 represent. Thus it disallows the operation. In this mode, the
1430 lowercase of U+0178 is itself.
1431 The same problems ensue if you enable automatic UTF-8-ification of your
1433 standard file handles, default "open()" layer, and @ARGV on
1434 non-ISO8859-1, non-UTF-8 locales (by using either the -C command line
1435 switch or the "PERL_UNICODE" environment variable; see perlrun).
1436 Things are read in as UTF-8, which would normally imply a Unicode
1437 interpretation, but the presence of a locale causes them to be
1438 interpreted in that locale instead. For example, a 0xD7 code point in
1439 the Unicode input, which should mean the multiplication sign, won't be
1440 interpreted by Perl that way under the Greek locale. This is not a
1441 problem provided you make certain that all locales will always and only
1442 be either an ISO8859-1, or, if you don't have a deficient C library, a
1443 UTF-8 locale.
1444 Still another problem is that this approach can lead to two code points
1446 meaning the same character. Thus in a Greek locale, both U+03A7 and
1447 U+00D7 are GREEK CAPITAL LETTER CHI.
1448 Because of all these problems, starting in v5.22, Perl will raise a
1450 warning if a multi-byte (hence Unicode) code point is used when a
1451 single-byte locale is in effect. (Although it doesn't check for this
1452 if doing so would unreasonably slow execution down.)
1453 Vendor locales are notoriously buggy, and it is difficult for Perl to
1455 test its locale-handling code because this interacts with code that
1456 Perl has no control over; therefore the locale-handling code in Perl
1457 may be buggy as well. (However, the Unicode-supplied locales should be
1458 better, and there is a feed back mechanism to correct any problems.
1459 See "Freely available locale definitions".)
1460 If you have Perl v5.16, the problems mentioned above go away if you use
1462 the ":not_characters" parameter to the locale pragma (except for vendor
1463 bugs in the non-character portions). If you don't have v5.16, and you
1464 do have locales that work, using them may be worthwhile for certain
1465 specific purposes, as long as you keep in mind the gotchas already
1466 mentioned. For example, if the collation for your locales works, it
1467 runs faster under locales than under Unicode::Collate; and you gain
1468 access to such things as the local currency symbol and the names of the
1469 months and days of the week. (But to hammer home the point, in v5.16,
1470 you get this access without the downsides of locales by using the
1471 ":not_characters" form of the pragma.)
1472 Note: The policy of using locale rules for code points that can fit in
1474 a byte, and Unicode rules for those that can't is not uniformly
1475 applied. Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied
1476 fairly consistently to regular expression matching except for bracketed
1477 character classes; in v5.14 it was extended to all regex matches; and
1478 in v5.16 to the casing operations such as "\L" and "uc()". For
1479 collation, in all releases so far, the system's "strxfrm()" function is
1480 called, and whatever it does is what you get. Starting in v5.26,
1481 various bugs are fixed with the way perl uses this function.
1482
1484 Collation of strings containing embedded "NUL" characters
1485 "NUL" characters will sort the same as the lowest collating control
1486 character does, or to "\001" in the unlikely event that there are no
1487 control characters at all in the locale. In cases where the strings
1488 don't contain this non-"NUL" control, the results will be correct, and
1489 in many locales, this control, whatever it might be, will rarely be
1490 encountered. But there are cases where a "NUL" should sort before this
1491 control, but doesn't. If two strings do collate identically, the one
1492 containing the "NUL" will sort to earlier. Prior to 5.26, there were
1493 more bugs.
1494 Multi-threaded
1496 XS code or C-language libraries called from it that use the system
1497 setlocale(3) function (except on Windows) likely will not work from a
1498 multi-threaded application without changes. See "Locale-aware XS code"
1499 in perlxs.
1500 An XS module that is locale-dependent could have been written under the
1502 assumption that it will never be called in a multi-threaded
1503 environment, and so uses other non-locale constructs that aren't multi-
1504 thread-safe. See "Thread-aware system interfaces" in perlxs.
1505 POSIX does not define a way to get the name of the current per-thread
1507 locale. Some systems, such as Darwin and NetBSD do implement a
1508 function, querylocale(3) to do this. On non-Windows systems without
1509 it, such as Linux, there are some additional caveats:
1510 · An embedded perl needs to be started up while the global locale is
1512 in effect. See "Using embedded Perl with POSIX locales" in
1513 perlembed.
1514 · It becomes more important for perl to know about all the possible
1516 locale categories on the platform, even if they aren't apparently
1517 used in your program. Perl knows all of the Linux ones. If your
1518 platform has others, you can submit an issue at
1519 <https://github.com/Perl/perl5/issues> for inclusion of it in the
1520 next release. In the meantime, it is possible to edit the Perl
1521 source to teach it about the category, and then recompile. Search
1522 for instances of, say, "LC_PAPER" in the source, and use that as a
1523 template to add the omitted one.
1524 · It is possible, though hard to do, to call "POSIX::setlocale" with
1526 a locale that it doesn't recognize as syntactically legal, but
1527 actually is legal on that system. This should happen only with
1528 embedded perls, or if you hand-craft a locale name yourself.
1529 Broken systems
1531 In certain systems, the operating system's locale support is broken and
1532 cannot be fixed or used by Perl. Such deficiencies can and will result
1533 in mysterious hangs and/or Perl core dumps when "use locale" is in
1534 effect. When confronted with such a system, please report in
1535 excruciating detail to <<https://github.com/Perl/perl5/issues>>, and
1536 also contact your vendor: bug fixes may exist for these problems in
1537 your operating system. Sometimes such bug fixes are called an
1538 operating system upgrade. If you have the source for Perl, include in
1539 the bug report the output of the test described above in "Testing for
1540 broken locales".
1541
1543 I18N::Langinfo, perluniintro, perlunicode, open, "localeconv" in POSIX,
1544 "setlocale" in POSIX, "strcoll" in POSIX, "strftime" in POSIX, "strtod"
1545 in POSIX, "strxfrm" in POSIX.
1546 For special considerations when Perl is embedded in a C program, see
1548 "Using embedded Perl with POSIX locales" in perlembed.
1549
1551 Jarkko Hietaniemi's original perli18n.pod heavily hacked by Dominic
1552 Dunlop, assisted by the perl5-porters. Prose worked over a bit by Tom
1553 Christiansen, and now maintained by Perl 5 porters.
1554perl v5.30.2 2020-03-27 PERLLOCALE(1)