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.
47 Starting in Perl v5.30, Perl detects Turkic locales by their behaviour,
49 and seamlessly handles both types; previously only the non-Turkic one
50 was supported. The name of the locale is ignored, if your system has a
51 "tr_TR.UTF-8" locale and it doesn't behave like a Turkic locale, perl
52 will treat it like a non-Turkic locale.
53 Perl continues to support the old non UTF-8 locales as well. There are
55 currently no UTF-8 locales for EBCDIC platforms.
56 (Unicode is also creating "CLDR", the "Common Locale Data Repository",
58 <http://cldr.unicode.org/> which includes more types of information
59 than are available in the POSIX locale system. At the time of this
60 writing, there was no CPAN module that provides access to this XML-
61 encoded data. However, it is possible to compute the POSIX locale data
62 from them, and earlier CLDR versions had these already extracted for
63 you as UTF-8 locales <http://unicode.org/Public/cldr/2.0.1/>.)
64
66 A locale is a set of data that describes various aspects of how various
67 communities in the world categorize their world. These categories are
68 broken down into the following types (some of which include a brief
69 note here):
70 Category "LC_NUMERIC": Numeric formatting
72 This indicates how numbers should be formatted for human
73 readability, for example the character used as the decimal point.
74 Category "LC_MONETARY": Formatting of monetary amounts
76 Category "LC_TIME": Date/Time formatting
79 Category "LC_MESSAGES": Error and other messages
82 This is used by Perl itself only for accessing operating system
83 error messages via $! and $^E.
84 Category "LC_COLLATE": Collation
86 This indicates the ordering of letters for comparison and sorting.
87 In Latin alphabets, for example, "b", generally follows "a".
88 Category "LC_CTYPE": Character Types
90 This indicates, for example if a character is an uppercase letter.
91 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
95 by Perl, but outside operations that Perl interacts with may use
96 these. See "Not within the scope of "use locale"" below.
97 More details on the categories used by Perl are given below in "LOCALE
99 CATEGORIES".
100 Together, these categories go a long way towards being able to
102 customize a single program to run in many different locations. But
103 there are deficiencies, so keep reading.
104
106 Perl itself (outside the POSIX module) will not use locales unless
107 specifically requested to (but again note that Perl may interact with
108 code that does use them). Even if there is such a request, all of the
109 following must be true for it to work properly:
110 • Your operating system must support the locale system. If it does,
112 you should find that the "setlocale()" function is a documented
113 part of its C library.
114 • Definitions for locales that you use must be installed. You, or
116 your system administrator, must make sure that this is the case.
117 The available locales, the location in which they are kept, and the
118 manner in which they are installed all vary from system to system.
119 Some systems provide only a few, hard-wired locales and do not
120 allow more to be added. Others allow you to add "canned" locales
121 provided by the system supplier. Still others allow you or the
122 system administrator to define and add arbitrary locales. (You may
123 have to ask your supplier to provide canned locales that are not
124 delivered with your operating system.) Read your system
125 documentation for further illumination.
126 • Perl must believe that the locale system is supported. If it does,
128 "perl -V:d_setlocale" will say that the value for "d_setlocale" is
129 "define".
130 If you want a Perl application to process and present your data
132 according to a particular locale, the application code should include
133 the "use locale" pragma (see "The "use locale" pragma") where
134 appropriate, and at least one of the following must be true:
135 1. The locale-determining environment variables (see "ENVIRONMENT")
137 must be correctly set up at the time the application is started,
138 either by yourself or by whomever set up your system account; or
139 2. The application must set its own locale using the method described
141 in "The setlocale function".
142
144 The "use locale" pragma
145 Starting in Perl 5.28, this pragma may be used in multi-threaded
146 applications on systems that have thread-safe locale ability. Some
147 caveats apply, see "Multi-threaded" below. On systems without this
148 capability, or in earlier Perls, do NOT use this pragma in scripts that
149 have multiple threads active. The locale in these cases is not local
150 to a single thread. Another thread may change the locale at any time,
151 which could cause at a minimum that a given thread is operating in a
152 locale it isn't expecting to be in. On some platforms, segfaults can
153 also occur. The locale change need not be explicit; some operations
154 cause perl itself to change the locale. You are vulnerable simply by
155 having done a "use locale".
156 By default, Perl itself (outside the POSIX module) ignores the current
158 locale. The "use locale" pragma tells Perl to use the current locale
159 for some operations. Starting in v5.16, there are optional parameters
160 to this pragma, described below, which restrict which operations are
161 affected by it.
162 The current locale is set at execution time by setlocale() described
164 below. If that function hasn't yet been called in the course of the
165 program's execution, the current locale is that which was determined by
166 the "ENVIRONMENT" in effect at the start of the program. If there is
167 no valid environment, the current locale is whatever the system default
168 has been set to. On POSIX systems, it is likely, but not necessarily,
169 the "C" locale. On Windows, the default is set via the computer's
170 "Control Panel->Regional and Language Options" (or its current
171 equivalent).
172 The operations that are affected by locale are:
174 Not within the scope of "use locale"
176 Only certain operations (all originating outside Perl) should be
177 affected, as follows:
178 • The current locale is used when going outside of Perl with
180 operations like system() or qx//, if those operations are
181 locale-sensitive.
182 • Also Perl gives access to various C library functions through
184 the POSIX module. Some of those functions are always affected
185 by the current locale. For example, "POSIX::strftime()" uses
186 "LC_TIME"; "POSIX::strtod()" uses "LC_NUMERIC";
187 "POSIX::strcoll()" and "POSIX::strxfrm()" use "LC_COLLATE".
188 All such functions will behave according to the current
189 underlying locale, even if that locale isn't exposed to Perl
190 space.
191 This applies as well to I18N::Langinfo.
193 • XS modules for all categories but "LC_NUMERIC" get the
195 underlying locale, and hence any C library functions they call
196 will use that underlying locale. For more discussion, see
197 "CAVEATS" in perlxs.
198 Note that all C programs (including the perl interpreter, which is
200 written in C) always have an underlying locale. That locale is the
201 "C" locale unless changed by a call to setlocale(). When Perl
202 starts up, it changes the underlying locale to the one which is
203 indicated by the "ENVIRONMENT". When using the POSIX module or
204 writing XS code, it is important to keep in mind that the
205 underlying locale may be something other than "C", even if the
206 program hasn't explicitly changed it.
207 Lingering effects of "use locale"
211 Certain Perl operations that are set-up within the scope of a "use
212 locale" retain that effect even outside the scope. These include:
213 • The output format of a write() is determined by an earlier
215 format declaration ("format" in perlfunc), so whether or not
216 the output is affected by locale is determined by if the
217 "format()" is within the scope of a "use locale", not whether
218 the "write()" is.
219 • Regular expression patterns can be compiled using qr// with
221 actual matching deferred to later. Again, it is whether or not
222 the compilation was done within the scope of "use locale" that
223 determines the match behavior, not if the matches are done
224 within such a scope or not.
225 Under ""use locale";"
229 • All the above operations
230 • Format declarations ("format" in perlfunc) and hence any
232 subsequent "write()"s use "LC_NUMERIC".
233 • stringification and output use "LC_NUMERIC". These include the
235 results of "print()", "printf()", "say()", and "sprintf()".
236 • The comparison operators ("lt", "le", "cmp", "ge", and "gt")
238 use "LC_COLLATE". "sort()" is also affected if used without an
239 explicit comparison function, because it uses "cmp" by default.
240 Note: "eq" and "ne" are unaffected by locale: they always
242 perform a char-by-char comparison of their scalar operands.
243 What's more, if "cmp" finds that its operands are equal
244 according to the collation sequence specified by the current
245 locale, it goes on to perform a char-by-char comparison, and
246 only returns 0 (equal) if the operands are char-for-char
247 identical. If you really want to know whether two
248 strings--which "eq" and "cmp" may consider different--are equal
249 as far as collation in the locale is concerned, see the
250 discussion in "Category "LC_COLLATE": Collation".
251 • Regular expressions and case-modification functions ("uc()",
253 "lc()", "ucfirst()", and "lcfirst()") use "LC_CTYPE"
254 • The variables $! (and its synonyms $ERRNO and $OS_ERROR) and
256 $^E> (and its synonym $EXTENDED_OS_ERROR) when used as strings
257 use "LC_MESSAGES".
258 The default behavior is restored with the "no locale" pragma, or upon
260 reaching the end of the block enclosing "use locale". Note that "use
261 locale" calls may be nested, and that what is in effect within an inner
262 scope will revert to the outer scope's rules at the end of the inner
263 scope.
264 The string result of any operation that uses locale information is
266 tainted (if your perl supports taint checking), as it is possible for a
267 locale to be untrustworthy. See "SECURITY".
268 Starting in Perl v5.16 in a very limited way, and more generally in
270 v5.22, you can restrict which category or categories are enabled by
271 this particular instance of the pragma by adding parameters to it. For
272 example,
273 use locale qw(:ctype :numeric);
275 enables locale awareness within its scope of only those operations
277 (listed above) that are affected by "LC_CTYPE" and "LC_NUMERIC".
278 The possible categories are: ":collate", ":ctype", ":messages",
280 ":monetary", ":numeric", ":time", and the pseudo category ":characters"
281 (described below).
282 Thus you can say
284 use locale ':messages';
286 and only $! and $^E will be locale aware. Everything else is
288 unaffected.
289 Since Perl doesn't currently do anything with the "LC_MONETARY"
291 category, specifying ":monetary" does effectively nothing. Some
292 systems have other categories, such as "LC_PAPER", but Perl also
293 doesn't do anything with them, and there is no way to specify them in
294 this pragma's arguments.
295 You can also easily say to use all categories but one, by either, for
297 example,
298 use locale ':!ctype';
300 use locale ':not_ctype';
301 both of which mean to enable locale awareness of all categories but
303 "LC_CTYPE". Only one category argument may be specified in a
304 "use locale" if it is of the negated form.
305 Prior to v5.22 only one form of the pragma with arguments is available:
307 use locale ':not_characters';
309 (and you have to say "not_"; you can't use the bang "!" form). This
311 pseudo category is a shorthand for specifying both ":collate" and
312 ":ctype". Hence, in the negated form, it is nearly the same thing as
313 saying
314 use locale qw(:messages :monetary :numeric :time);
316 We use the term "nearly", because ":not_characters" also turns on
318 "use feature 'unicode_strings'" within its scope. This form is less
319 useful in v5.20 and later, and is described fully in "Unicode and
320 UTF-8", but briefly, it tells Perl to not use the character portions of
321 the locale definition, that is the "LC_CTYPE" and "LC_COLLATE"
322 categories. Instead it will use the native character set (extended by
323 Unicode). When using this parameter, you are responsible for getting
324 the external character set translated into the native/Unicode one
325 (which it already will be if it is one of the increasingly popular
326 UTF-8 locales). There are convenient ways of doing this, as described
327 in "Unicode and UTF-8".
328 The setlocale function
330 WARNING! Prior to Perl 5.28 or on a system that does not support
331 thread-safe locale operations, do NOT use this function in a thread.
332 The locale will change in all other threads at the same time, and
333 should your thread get paused by the operating system, and another
334 started, that thread will not have the locale it is expecting. On some
335 platforms, there can be a race leading to segfaults if two threads call
336 this function nearly simultaneously. This warning does not apply on
337 unthreaded builds, or on perls where "${^SAFE_LOCALES}" exists and is
338 non-zero; namely Perl 5.28 and later unthreaded or compiled to be
339 locale-thread-safe. On z/OS systems, this function becomes a no-op
340 once any thread is started. Thus, on that system, you can set up the
341 locale before creating any threads, and that locale will be the one in
342 effect for the entire program.
343 Otherwise, you can switch locales as often as you wish at run time with
345 the "POSIX::setlocale()" function:
346 # Import locale-handling tool set from POSIX module.
348 # This example uses: setlocale -- the function call
349 # LC_CTYPE -- explained below
350 # (Showing the testing for success/failure of operations is
351 # omitted in these examples to avoid distracting from the main
352 # point)
353 use POSIX qw(locale_h);
355 use locale;
356 my $old_locale;
357 # query and save the old locale
359 $old_locale = setlocale(LC_CTYPE);
360 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
362 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
363 setlocale(LC_CTYPE, "");
365 # LC_CTYPE now reset to the default defined by the
366 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
367 # default. See below for documentation.
368 # restore the old locale
370 setlocale(LC_CTYPE, $old_locale);
371 The first argument of "setlocale()" gives the category, the second the
373 locale. The category tells in what aspect of data processing you want
374 to apply locale-specific rules. Category names are discussed in
375 "LOCALE CATEGORIES" and "ENVIRONMENT". The locale is the name of a
376 collection of customization information corresponding to a particular
377 combination of language, country or territory, and codeset. Read on
378 for hints on the naming of locales: not all systems name locales as in
379 the example.
380 If no second argument is provided and the category is something other
382 than "LC_ALL", the function returns a string naming the current locale
383 for the category. You can use this value as the second argument in a
384 subsequent call to "setlocale()", but on some platforms the string is
385 opaque, not something that most people would be able to decipher as to
386 what locale it means.
387 If no second argument is provided and the category is "LC_ALL", the
389 result is implementation-dependent. It may be a string of concatenated
390 locale names (separator also implementation-dependent) or a single
391 locale name. Please consult your setlocale(3) man page for details.
392 If a second argument is given and it corresponds to a valid locale, the
394 locale for the category is set to that value, and the function returns
395 the now-current locale value. You can then use this in yet another
396 call to "setlocale()". (In some implementations, the return value may
397 sometimes differ from the value you gave as the second argument--think
398 of it as an alias for the value you gave.)
399 As the example shows, if the second argument is an empty string, the
401 category's locale is returned to the default specified by the
402 corresponding environment variables. Generally, this results in a
403 return to the default that was in force when Perl started up: changes
404 to the environment made by the application after startup may or may not
405 be noticed, depending on your system's C library.
406 Note that when a form of "use locale" that doesn't include all
408 categories is specified, Perl ignores the excluded categories.
409 If "setlocale()" fails for some reason (for example, an attempt to set
411 to a locale unknown to the system), the locale for the category is not
412 changed, and the function returns "undef".
413 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
415 implement POSIX 2008 thread-safe locale operations, this function
416 doesn't actually call the system "setlocale". Instead those thread-
417 safe operations are used to emulate the "setlocale" function, but in a
418 thread-safe manner.
419 You can force the thread-safe locale operations to always be used (if
421 available) by recompiling perl with
422 -Accflags='-DUSE_THREAD_SAFE_LOCALE'
424 added to your call to Configure.
426 For further information about the categories, consult setlocale(3).
428 Multi-threaded operation
430 Beginning in Perl 5.28, multi-threaded locale operation is supported on
431 systems that implement either the POSIX 2008 or Windows-specific
432 thread-safe locale operations. Many modern systems, such as various
433 Unix variants and Darwin do have this.
434 You can tell if using locales is safe on your system by looking at the
436 read-only boolean variable "${^SAFE_LOCALES}". The value is 1 if the
437 perl is not threaded, or if it is using thread-safe locale operations.
438 Thread-safe operations are supported in Windows starting in Visual
440 Studio 2005, and in systems compatible with POSIX 2008. Some platforms
441 claim to support POSIX 2008, but have buggy implementations, so that
442 the hints files for compiling to run on them turn off attempting to use
443 thread-safety. "${^SAFE_LOCALES}" will be 0 on them.
444 Be aware that writing a multi-threaded application will not be portable
446 to a platform which lacks the native thread-safe locale support. On
447 systems that do have it, you automatically get this behavior for
448 threaded perls, without having to do anything. If for some reason, you
449 don't want to use this capability (perhaps the POSIX 2008 support is
450 buggy on your system), you can manually compile Perl to use the old
451 non-thread-safe implementation by passing the argument
452 "-Accflags='-DNO_THREAD_SAFE_LOCALE'" to Configure. Except on Windows,
453 this will continue to use certain of the POSIX 2008 functions in some
454 situations. If these are buggy, you can pass the following to
455 Configure instead or additionally:
456 "-Accflags='-DNO_POSIX_2008_LOCALE'". This will also keep the code
457 from using thread-safe locales. "${^SAFE_LOCALES}" will be 0 on
458 systems that turn off the thread-safe operations.
459 Normally on unthreaded builds, the traditional "setlocale()" is used
461 and not the thread-safe locale functions. You can force the use of
462 these on systems that have them by adding the
463 "-Accflags='-DUSE_THREAD_SAFE_LOCALE'" to Configure.
464 The initial program is started up using the locale specified from the
466 environment, as currently, described in "ENVIRONMENT". All newly
467 created threads start with "LC_ALL" set to "C". Each thread may use
468 "POSIX::setlocale()" to query or switch its locale at any time, without
469 affecting any other thread. All locale-dependent operations
470 automatically use their thread's locale.
471 This should be completely transparent to any applications written
473 entirely in Perl (minus a few rarely encountered caveats given in the
474 "Multi-threaded" section). Information for XS module writers is given
475 in "Locale-aware XS code" in perlxs.
476 Finding locales
478 For locales available in your system, consult also setlocale(3) to see
479 whether it leads to the list of available locales (search for the SEE
480 ALSO section). If that fails, try the following command lines:
481 locale -a
483 nlsinfo
485 ls /usr/lib/nls/loc
487 ls /usr/lib/locale
489 ls /usr/lib/nls
491 ls /usr/share/locale
493 and see whether they list something resembling these
495 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
497 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
498 en_US de_DE ru_RU
499 en de ru
500 english german russian
501 english.iso88591 german.iso88591 russian.iso88595
502 english.roman8 russian.koi8r
503 Sadly, even though the calling interface for "setlocale()" has been
505 standardized, names of locales and the directories where the
506 configuration resides have not been. The basic form of the name is
507 language_territory.codeset, but the latter parts after language are not
508 always present. The language and country are usually from the
509 standards ISO 3166 and ISO 639, the two-letter abbreviations for the
510 countries and the languages of the world, respectively. The codeset
511 part often mentions some ISO 8859 character set, the Latin codesets.
512 For example, "ISO 8859-1" is the so-called "Western European codeset"
513 that can be used to encode most Western European languages adequately.
514 Again, there are several ways to write even the name of that one
515 standard. Lamentably.
516 Two special locales are worth particular mention: "C" and "POSIX".
518 Currently these are effectively the same locale: the difference is
519 mainly that the first one is defined by the C standard, the second by
520 the POSIX standard. They define the default locale in which every
521 program starts in the absence of locale information in its environment.
522 (The default default locale, if you will.) Its language is (American)
523 English and its character codeset ASCII or, rarely, a superset thereof
524 (such as the "DEC Multinational Character Set (DEC-MCS)"). Warning.
525 The C locale delivered by some vendors may not actually exactly match
526 what the C standard calls for. So beware.
527 NOTE: Not all systems have the "POSIX" locale (not all systems are
529 POSIX-conformant), so use "C" when you need explicitly to specify this
530 default locale.
531 LOCALE PROBLEMS
533 You may encounter the following warning message at Perl startup:
534 perl: warning: Setting locale failed.
536 perl: warning: Please check that your locale settings:
537 LC_ALL = "En_US",
538 LANG = (unset)
539 are supported and installed on your system.
540 perl: warning: Falling back to the standard locale ("C").
541 This means that your locale settings had "LC_ALL" set to "En_US" and
543 LANG exists but has no value. Perl tried to believe you but could not.
544 Instead, Perl gave up and fell back to the "C" locale, the default
545 locale that is supposed to work no matter what. (On Windows, it first
546 tries falling back to the system default locale.) This usually means
547 your locale settings were wrong, they mention locales your system has
548 never heard of, or the locale installation in your system has problems
549 (for example, some system files are broken or missing). There are
550 quick and temporary fixes to these problems, as well as more thorough
551 and lasting fixes.
552 Testing for broken locales
554 If you are building Perl from source, the Perl test suite file
555 lib/locale.t can be used to test the locales on your system. Setting
556 the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it to
557 output detailed results. For example, on Linux, you could say
558 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
560 Besides many other tests, it will test every locale it finds on your
562 system to see if they conform to the POSIX standard. If any have
563 errors, it will include a summary near the end of the output of which
564 locales passed all its tests, and which failed, and why.
565 Temporarily fixing locale problems
567 The two quickest fixes are either to render Perl silent about any
568 locale inconsistencies or to run Perl under the default locale "C".
569 Perl's moaning about locale problems can be silenced by setting the
571 environment variable "PERL_BADLANG" to "0" or "". This method really
572 just sweeps the problem under the carpet: you tell Perl to shut up even
573 when Perl sees that something is wrong. Do not be surprised if later
574 something locale-dependent misbehaves.
575 Perl can be run under the "C" locale by setting the environment
577 variable "LC_ALL" to "C". This method is perhaps a bit more civilized
578 than the "PERL_BADLANG" approach, but setting "LC_ALL" (or other locale
579 variables) may affect other programs as well, not just Perl. In
580 particular, external programs run from within Perl will see these
581 changes. If you make the new settings permanent (read on), all
582 programs you run see the changes. See "ENVIRONMENT" for the full list
583 of relevant environment variables and "USING LOCALES" for their effects
584 in Perl. Effects in other programs are easily deducible. For example,
585 the variable "LC_COLLATE" may well affect your sort program (or
586 whatever the program that arranges "records" alphabetically in your
587 system is called).
588 You can test out changing these variables temporarily, and if the new
590 settings seem to help, put those settings into your shell startup
591 files. Consult your local documentation for the exact details. For
592 Bourne-like shells (sh, ksh, bash, zsh):
593 LC_ALL=en_US.ISO8859-1
595 export LC_ALL
596 This assumes that we saw the locale "en_US.ISO8859-1" using the
598 commands discussed above. We decided to try that instead of the above
599 faulty locale "En_US"--and in Cshish shells (csh, tcsh)
600 setenv LC_ALL en_US.ISO8859-1
602 or if you have the "env" application you can do (in any shell)
604 env LC_ALL=en_US.ISO8859-1 perl ...
606 If you do not know what shell you have, consult your local helpdesk or
608 the equivalent.
609 Permanently fixing locale problems
611 The slower but superior fixes are when you may be able to yourself fix
612 the misconfiguration of your own environment variables. The
613 mis(sing)configuration of the whole system's locales usually requires
614 the help of your friendly system administrator.
615 First, see earlier in this document about "Finding locales". That
617 tells how to find which locales are really supported--and more
618 importantly, installed--on your system. In our example error message,
619 environment variables affecting the locale are listed in the order of
620 decreasing importance (and unset variables do not matter). Therefore,
621 having LC_ALL set to "En_US" must have been the bad choice, as shown by
622 the error message. First try fixing locale settings listed first.
623 Second, if using the listed commands you see something exactly (prefix
625 matches do not count and case usually counts) like "En_US" without the
626 quotes, then you should be okay because you are using a locale name
627 that should be installed and available in your system. In this case,
628 see "Permanently fixing your system's locale configuration".
629 Permanently fixing your system's locale configuration
631 This is when you see something like:
632 perl: warning: Please check that your locale settings:
634 LC_ALL = "En_US",
635 LANG = (unset)
636 are supported and installed on your system.
637 but then cannot see that "En_US" listed by the above-mentioned
639 commands. You may see things like "en_US.ISO8859-1", but that isn't
640 the same. In this case, try running under a locale that you can list
641 and which somehow matches what you tried. The rules for matching
642 locale names are a bit vague because standardization is weak in this
643 area. See again the "Finding locales" about general rules.
644 Fixing system locale configuration
646 Contact a system administrator (preferably your own) and report the
647 exact error message you get, and ask them to read this same
648 documentation you are now reading. They should be able to check
649 whether there is something wrong with the locale configuration of the
650 system. The "Finding locales" section is unfortunately a bit vague
651 about the exact commands and places because these things are not that
652 standardized.
653 The localeconv function
655 The "POSIX::localeconv()" function allows you to get particulars of the
656 locale-dependent numeric formatting information specified by the
657 current underlying "LC_NUMERIC" and "LC_MONETARY" locales (regardless
658 of whether called from within the scope of "use locale" or not). (If
659 you just want the name of the current locale for a particular category,
660 use "POSIX::setlocale()" with a single parameter--see "The setlocale
661 function".)
662 use POSIX qw(locale_h);
664 # Get a reference to a hash of locale-dependent info
666 $locale_values = localeconv();
667 # Output sorted list of the values
669 for (sort keys %$locale_values) {
670 printf "%-20s = %s\n", $_, $locale_values->{$_}
671 }
672 "localeconv()" takes no arguments, and returns a reference to a hash.
674 The keys of this hash are variable names for formatting, such as
675 "decimal_point" and "thousands_sep". The values are the corresponding,
676 er, values. See "localeconv" in POSIX for a longer example listing the
677 categories an implementation might be expected to provide; some provide
678 more and others fewer. You don't need an explicit "use locale",
679 because "localeconv()" always observes the current locale.
680 Here's a simple-minded example program that rewrites its command-line
682 parameters as integers correctly formatted in the current locale:
683 use POSIX qw(locale_h);
685 # Get some of locale's numeric formatting parameters
687 my ($thousands_sep, $grouping) =
688 @{localeconv()}{'thousands_sep', 'grouping'};
689 # Apply defaults if values are missing
691 $thousands_sep = ',' unless $thousands_sep;
692 # grouping and mon_grouping are packed lists
694 # of small integers (characters) telling the
695 # grouping (thousand_seps and mon_thousand_seps
696 # being the group dividers) of numbers and
697 # monetary quantities. The integers' meanings:
698 # 255 means no more grouping, 0 means repeat
699 # the previous grouping, 1-254 means use that
700 # as the current grouping. Grouping goes from
701 # right to left (low to high digits). In the
702 # below we cheat slightly by never using anything
703 # else than the first grouping (whatever that is).
704 if ($grouping) {
705 @grouping = unpack("C*", $grouping);
706 } else {
707 @grouping = (3);
708 }
709 # Format command line params for current locale
711 for (@ARGV) {
712 $_ = int; # Chop non-integer part
713 1 while
714 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
715 print "$_";
716 }
717 print "\n";
718 Note that if the platform doesn't have "LC_NUMERIC" and/or
720 "LC_MONETARY" available or enabled, the corresponding elements of the
721 hash will be missing.
722 I18N::Langinfo
724 Another interface for querying locale-dependent information is the
725 "I18N::Langinfo::langinfo()" function.
726 The following example will import the "langinfo()" function itself and
728 three constants to be used as arguments to "langinfo()": a constant for
729 the abbreviated first day of the week (the numbering starts from Sunday
730 = 1) and two more constants for the affirmative and negative answers
731 for a yes/no question in the current locale.
732 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
734 my ($abday_1, $yesstr, $nostr)
736 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
737 print "$abday_1? [$yesstr/$nostr] ";
739 In other words, in the "C" (or English) locale the above will probably
741 print something like:
742 Sun? [yes/no]
744 See I18N::Langinfo for more information.
746
748 The following subsections describe basic locale categories. Beyond
749 these, some combination categories allow manipulation of more than one
750 basic category at a time. See "ENVIRONMENT" for a discussion of these.
751 Category "LC_COLLATE": Collation: Text Comparisons and Sorting
753 In the scope of a "use locale" form that includes collation, Perl looks
754 to the "LC_COLLATE" environment variable to determine the application's
755 notions on collation (ordering) of characters. For example, "b"
756 follows "a" in Latin alphabets, but where do "a" and "aa" belong? And
757 while "color" follows "chocolate" in English, what about in traditional
758 Spanish?
759 The following collations all make sense and you may meet any of them if
761 you "use locale".
762 A B C D E a b c d e
764 A a B b C c D d E e
765 a A b B c C d D e E
766 a b c d e A B C D E
767 Here is a code snippet to tell what "word" characters are in the
769 current locale, in that locale's order:
770 use locale;
772 print +(sort grep /\w/, map { chr } 0..255), "\n";
773 Compare this with the characters that you see and their order if you
775 state explicitly that the locale should be ignored:
776 no locale;
778 print +(sort grep /\w/, map { chr } 0..255), "\n";
779 This machine-native collation (which is what you get unless
781 "use locale" has appeared earlier in the same block) must be used for
782 sorting raw binary data, whereas the locale-dependent collation of the
783 first example is useful for natural text.
784 As noted in "USING LOCALES", "cmp" compares according to the current
786 collation locale when "use locale" is in effect, but falls back to a
787 char-by-char comparison for strings that the locale says are equal. You
788 can use "POSIX::strcoll()" if you don't want this fall-back:
789 use POSIX qw(strcoll);
791 $equal_in_locale =
792 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
793 $equal_in_locale will be true if the collation locale specifies a
795 dictionary-like ordering that ignores space characters completely and
796 which folds case.
797 Perl uses the platform's C library collation functions "strcoll()" and
799 "strxfrm()". That means you get whatever they give. On some
800 platforms, these functions work well on UTF-8 locales, giving a
801 reasonable default collation for the code points that are important in
802 that locale. (And if they aren't working well, the problem may only be
803 that the locale definition is deficient, so can be fixed by using a
804 better definition file. Unicode's definitions (see "Freely available
805 locale definitions") provide reasonable UTF-8 locale collation
806 definitions.) Starting in Perl v5.26, Perl's use of these functions
807 has been made more seamless. This may be sufficient for your needs.
808 For more control, and to make sure strings containing any code point
809 (not just the ones important in the locale) collate properly, the
810 Unicode::Collate module is suggested.
811 In non-UTF-8 locales (hence single byte), code points above 0xFF are
813 technically invalid. But if present, again starting in v5.26, they
814 will collate to the same position as the highest valid code point does.
815 This generally gives good results, but the collation order may be
816 skewed if the valid code point gets special treatment when it forms
817 particular sequences with other characters as defined by the locale.
818 When two strings collate identically, the code point order is used as a
819 tie breaker.
820 If Perl detects that there are problems with the locale collation
822 order, it reverts to using non-locale collation rules for that locale.
823 If you have a single string that you want to check for "equality in
825 locale" against several others, you might think you could gain a little
826 efficiency by using "POSIX::strxfrm()" in conjunction with "eq":
827 use POSIX qw(strxfrm);
829 $xfrm_string = strxfrm("Mixed-case string");
830 print "locale collation ignores spaces\n"
831 if $xfrm_string eq strxfrm("Mixed-casestring");
832 print "locale collation ignores hyphens\n"
833 if $xfrm_string eq strxfrm("Mixedcase string");
834 print "locale collation ignores case\n"
835 if $xfrm_string eq strxfrm("mixed-case string");
836 "strxfrm()" takes a string and maps it into a transformed string for
838 use in char-by-char comparisons against other transformed strings
839 during collation. "Under the hood", locale-affected Perl comparison
840 operators call "strxfrm()" for both operands, then do a char-by-char
841 comparison of the transformed strings. By calling "strxfrm()"
842 explicitly and using a non locale-affected comparison, the example
843 attempts to save a couple of transformations. But in fact, it doesn't
844 save anything: Perl magic (see "Magic Variables" in perlguts) creates
845 the transformed version of a string the first time it's needed in a
846 comparison, then keeps this version around in case it's needed again.
847 An example rewritten the easy way with "cmp" runs just about as fast.
848 It also copes with null characters embedded in strings; if you call
849 "strxfrm()" directly, it treats the first null it finds as a
850 terminator. Don't expect the transformed strings it produces to be
851 portable across systems--or even from one revision of your operating
852 system to the next. In short, don't call "strxfrm()" directly: let
853 Perl do it for you.
854 Note: "use locale" isn't shown in some of these examples because it
856 isn't needed: "strcoll()" and "strxfrm()" are POSIX functions which use
857 the standard system-supplied "libc" functions that always obey the
858 current "LC_COLLATE" locale.
859 Category "LC_CTYPE": Character Types
861 In the scope of a "use locale" form that includes "LC_CTYPE", Perl
862 obeys the "LC_CTYPE" locale setting. This controls the application's
863 notion of which characters are alphabetic, numeric, punctuation, etc.
864 This affects Perl's "\w" regular expression metanotation, which stands
865 for alphanumeric characters--that is, alphabetic, numeric, and the
866 platform's native underscore. (Consult perlre for more information
867 about regular expressions.) Thanks to "LC_CTYPE", depending on your
868 locale setting, characters like "ae", "d`", "ss", and "o" may be
869 understood as "\w" characters. It also affects things like "\s", "\D",
870 and the POSIX character classes, like "[[:graph:]]". (See
871 perlrecharclass for more information on all these.)
872 The "LC_CTYPE" locale also provides the map used in transliterating
874 characters between lower and uppercase. This affects the case-mapping
875 functions--"fc()", "lc()", "lcfirst()", "uc()", and "ucfirst()"; case-
876 mapping interpolation with "\F", "\l", "\L", "\u", or "\U" in double-
877 quoted strings and "s///" substitutions; and case-insensitive regular
878 expression pattern matching using the "i" modifier.
879 Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
881 otherwise Perl only supports single-byte locales, such as the ISO 8859
882 series. This means that wide character locales, for example for Asian
883 languages, are not well-supported. Use of these locales may cause core
884 dumps. If the platform has the capability for Perl to detect such a
885 locale, starting in Perl v5.22, Perl will warn, default enabled, using
886 the "locale" warning category, whenever such a locale is switched into.
887 The UTF-8 locale support is actually a superset of POSIX locales,
888 because it is really full Unicode behavior as if no "LC_CTYPE" locale
889 were in effect at all (except for tainting; see "SECURITY"). POSIX
890 locales, even UTF-8 ones, are lacking certain concepts in Unicode, such
891 as the idea that changing the case of a character could expand to be
892 more than one character. Perl in a UTF-8 locale, will give you that
893 expansion. Prior to v5.20, Perl treated a UTF-8 locale on some
894 platforms like an ISO 8859-1 one, with some restrictions, and on other
895 platforms more like the "C" locale. For releases v5.16 and v5.18,
896 "use locale 'not_characters" could be used as a workaround for this
897 (see "Unicode and UTF-8").
898 Note that there are quite a few things that are unaffected by the
900 current locale. Any literal character is the native character for the
901 given platform. Hence 'A' means the character at code point 65 on
902 ASCII platforms, and 193 on EBCDIC. That may or may not be an 'A' in
903 the current locale, if that locale even has an 'A'. Similarly, all the
904 escape sequences for particular characters, "\n" for example, always
905 mean the platform's native one. This means, for example, that "\N" in
906 regular expressions (every character but new-line) works on the
907 platform character set.
908 Starting in v5.22, Perl will by default warn when switching into a
910 locale that redefines any ASCII printable character (plus "\t" and
911 "\n") into a different class than expected. This is likely to happen
912 on modern locales only on EBCDIC platforms, where, for example, a CCSID
913 0037 locale on a CCSID 1047 machine moves "[", but it can happen on
914 ASCII platforms with the ISO 646 and other 7-bit locales that are
915 essentially obsolete. Things may still work, depending on what
916 features of Perl are used by the program. For example, in the example
917 from above where "|" becomes a "\w", and there are no regular
918 expressions where this matters, the program may still work properly.
919 The warning lists all the characters that it can determine could be
920 adversely affected.
921 Note: A broken or malicious "LC_CTYPE" locale definition may result in
923 clearly ineligible characters being considered to be alphanumeric by
924 your application. For strict matching of (mundane) ASCII letters and
925 digits--for example, in command strings--locale-aware applications
926 should use "\w" with the "/a" regular expression modifier. See
927 "SECURITY".
928 Category "LC_NUMERIC": Numeric Formatting
930 After a proper "POSIX::setlocale()" call, and within the scope of a
931 "use locale" form that includes numerics, Perl obeys the "LC_NUMERIC"
932 locale information, which controls an application's idea of how numbers
933 should be formatted for human readability. In most implementations the
934 only effect is to change the character used for the decimal
935 point--perhaps from "." to ",". The functions aren't aware of such
936 niceties as thousands separation and so on. (See "The localeconv
937 function" if you care about these things.)
938 use POSIX qw(strtod setlocale LC_NUMERIC);
940 use locale;
941 setlocale LC_NUMERIC, "";
943 $n = 5/2; # Assign numeric 2.5 to $n
945 $a = " $n"; # Locale-dependent conversion to string
947 print "half five is $n\n"; # Locale-dependent output
949 printf "half five is %g\n", $n; # Locale-dependent output
951 print "DECIMAL POINT IS COMMA\n"
953 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
954 See also I18N::Langinfo and "RADIXCHAR".
956 Category "LC_MONETARY": Formatting of monetary amounts
958 The C standard defines the "LC_MONETARY" category, but not a function
959 that is affected by its contents. (Those with experience of standards
960 committees will recognize that the working group decided to punt on the
961 issue.) Consequently, Perl essentially takes no notice of it. If you
962 really want to use "LC_MONETARY", you can query its contents--see "The
963 localeconv function"--and use the information that it returns in your
964 application's own formatting of currency amounts. However, you may
965 well find that the information, voluminous and complex though it may
966 be, still does not quite meet your requirements: currency formatting is
967 a hard nut to crack.
968 See also I18N::Langinfo and "CRNCYSTR".
970 Category "LC_TIME": Respresentation of time
972 Output produced by "POSIX::strftime()", which builds a formatted human-
973 readable date/time string, is affected by the current "LC_TIME" locale.
974 Thus, in a French locale, the output produced by the %B format element
975 (full month name) for the first month of the year would be "janvier".
976 Here's how to get a list of long month names in the current locale:
977 use POSIX qw(strftime);
979 for (0..11) {
980 $long_month_name[$_] =
981 strftime("%B", 0, 0, 0, 1, $_, 96);
982 }
983 Note: "use locale" isn't needed in this example: "strftime()" is a
985 POSIX function which uses the standard system-supplied "libc" function
986 that always obeys the current "LC_TIME" locale.
987 See also I18N::Langinfo and "ABDAY_1".."ABDAY_7", "DAY_1".."DAY_7",
989 "ABMON_1".."ABMON_12", and "ABMON_1".."ABMON_12".
990 Other categories
992 The remaining locale categories are not currently used by Perl itself.
993 But again note that things Perl interacts with may use these, including
994 extensions outside the standard Perl distribution, and by the operating
995 system and its utilities. Note especially that the string value of $!
996 and the error messages given by external utilities may be changed by
997 "LC_MESSAGES". If you want to have portable error codes, use "%!".
998 See Errno.
999
1001 Although the main discussion of Perl security issues can be found in
1002 perlsec, a discussion of Perl's locale handling would be incomplete if
1003 it did not draw your attention to locale-dependent security issues.
1004 Locales--particularly on systems that allow unprivileged users to build
1005 their own locales--are untrustworthy. A malicious (or just plain
1006 broken) locale can make a locale-aware application give unexpected
1007 results. Here are a few possibilities:
1008 • Regular expression checks for safe file names or mail addresses
1010 using "\w" may be spoofed by an "LC_CTYPE" locale that claims that
1011 characters such as ">" and "|" are alphanumeric.
1012 • String interpolation with case-mapping, as in, say, "$dest =
1014 "C:\U$name.$ext"", may produce dangerous results if a bogus
1015 "LC_CTYPE" case-mapping table is in effect.
1016 • A sneaky "LC_COLLATE" locale could result in the names of students
1018 with "D" grades appearing ahead of those with "A"s.
1019 • An application that takes the trouble to use information in
1021 "LC_MONETARY" may format debits as if they were credits and vice
1022 versa if that locale has been subverted. Or it might make payments
1023 in US dollars instead of Hong Kong dollars.
1024 • The date and day names in dates formatted by "strftime()" could be
1026 manipulated to advantage by a malicious user able to subvert the
1027 "LC_DATE" locale. ("Look--it says I wasn't in the building on
1028 Sunday.")
1029 Such dangers are not peculiar to the locale system: any aspect of an
1031 application's environment which may be modified maliciously presents
1032 similar challenges. Similarly, they are not specific to Perl: any
1033 programming language that allows you to write programs that take
1034 account of their environment exposes you to these issues.
1035 Perl cannot protect you from all possibilities shown in the
1037 examples--there is no substitute for your own vigilance--but, when "use
1038 locale" is in effect, Perl uses the tainting mechanism (see perlsec) to
1039 mark string results that become locale-dependent, and which may be
1040 untrustworthy in consequence.
1041 Note that it is possible to compile Perl without taint support, in
1043 which case all taint features silently do nothing.
1044 Here is a summary of the tainting behavior of operators and functions
1046 that may be affected by the locale:
1047 • Comparison operators ("lt", "le", "ge", "gt" and "cmp"):
1049 Scalar true/false (or less/equal/greater) result is never tainted.
1051 • Case-mapping interpolation (with "\l", "\L", "\u", "\U", or "\F")
1053 The result string containing interpolated material is tainted if a
1055 "use locale" form that includes "LC_CTYPE" is in effect.
1056 • Matching operator ("m//"):
1058 Scalar true/false result never tainted.
1060 All subpatterns, either delivered as a list-context result or as $1
1062 etc., are tainted if a "use locale" form that includes "LC_CTYPE"
1063 is in effect, and the subpattern regular expression contains a
1064 locale-dependent construct. These constructs include "\w" (to
1065 match an alphanumeric character), "\W" (non-alphanumeric
1066 character), "\b" and "\B" (word-boundary and non-boundardy, which
1067 depend on what "\w" and "\W" match), "\s" (whitespace character),
1068 "\S" (non whitespace character), "\d" and "\D" (digits and non-
1069 digits), and the POSIX character classes, such as "[:alpha:]" (see
1070 "POSIX Character Classes" in perlrecharclass).
1071 Tainting is also likely if the pattern is to be matched case-
1073 insensitively (via "/i"). The exception is if all the code points
1074 to be matched this way are above 255 and do not have folds under
1075 Unicode rules to below 256. Tainting is not done for these because
1076 Perl only uses Unicode rules for such code points, and those rules
1077 are the same no matter what the current locale.
1078 The matched-pattern variables, $&, "$`" (pre-match), "$'" (post-
1080 match), and $+ (last match) also are tainted.
1081 • Substitution operator ("s///"):
1083 Has the same behavior as the match operator. Also, the left
1085 operand of "=~" becomes tainted when a "use locale" form that
1086 includes "LC_CTYPE" is in effect, if modified as a result of a
1087 substitution based on a regular expression match involving any of
1088 the things mentioned in the previous item, or of case-mapping, such
1089 as "\l", "\L","\u", "\U", or "\F".
1090 • Output formatting functions ("printf()" and "write()"):
1092 Results are never tainted because otherwise even output from print,
1094 for example "print(1/7)", should be tainted if "use locale" is in
1095 effect.
1096 • Case-mapping functions ("lc()", "lcfirst()", "uc()", "ucfirst()"):
1098 Results are tainted if a "use locale" form that includes "LC_CTYPE"
1100 is in effect.
1101 • POSIX locale-dependent functions ("localeconv()", "strcoll()",
1103 "strftime()", "strxfrm()"):
1104 Results are never tainted.
1106 Three examples illustrate locale-dependent tainting. The first
1108 program, which ignores its locale, won't run: a value taken directly
1109 from the command line may not be used to name an output file when taint
1110 checks are enabled.
1111 #/usr/local/bin/perl -T
1113 # Run with taint checking
1114 # Command line sanity check omitted...
1116 $tainted_output_file = shift;
1117 open(F, ">$tainted_output_file")
1119 or warn "Open of $tainted_output_file failed: $!\n";
1120 The program can be made to run by "laundering" the tainted value
1122 through a regular expression: the second example--which still ignores
1123 locale information--runs, creating the file named on its command line
1124 if it can.
1125 #/usr/local/bin/perl -T
1127 $tainted_output_file = shift;
1129 $tainted_output_file =~ m%[\w/]+%;
1130 $untainted_output_file = $&;
1131 open(F, ">$untainted_output_file")
1133 or warn "Open of $untainted_output_file failed: $!\n";
1134 Compare this with a similar but locale-aware program:
1136 #/usr/local/bin/perl -T
1138 $tainted_output_file = shift;
1140 use locale;
1141 $tainted_output_file =~ m%[\w/]+%;
1142 $localized_output_file = $&;
1143 open(F, ">$localized_output_file")
1145 or warn "Open of $localized_output_file failed: $!\n";
1146 This third program fails to run because $& is tainted: it is the result
1148 of a match involving "\w" while "use locale" is in effect.
1149
1151 PERL_SKIP_LOCALE_INIT
1152 This environment variable, available starting in Perl
1153 v5.20, if set (to any value), tells Perl to not use the
1154 rest of the environment variables to initialize with.
1155 Instead, Perl uses whatever the current locale settings
1156 are. This is particularly useful in embedded environments,
1157 see "Using embedded Perl with POSIX locales" in perlembed.
1158 PERL_BADLANG
1160 A string that can suppress Perl's warning about failed
1161 locale settings at startup. Failure can occur if the
1162 locale support in the operating system is lacking (broken)
1163 in some way--or if you mistyped the name of a locale when
1164 you set up your environment. If this environment variable
1165 is absent, or has a value other than "0" or "", Perl will
1166 complain about locale setting failures.
1167 NOTE: "PERL_BADLANG" only gives you a way to hide the
1169 warning message. The message tells about some problem in
1170 your system's locale support, and you should investigate
1171 what the problem is.
1172 The following environment variables are not specific to Perl: They are
1174 part of the standardized (ISO C, XPG4, POSIX 1.c) "setlocale()" method
1175 for controlling an application's opinion on data. Windows is non-
1176 POSIX, but Perl arranges for the following to work as described anyway.
1177 If the locale given by an environment variable is not valid, Perl tries
1178 the next lower one in priority. If none are valid, on Windows, the
1179 system default locale is then tried. If all else fails, the "C" locale
1180 is used. If even that doesn't work, something is badly broken, but
1181 Perl tries to forge ahead with whatever the locale settings might be.
1182 "LC_ALL" "LC_ALL" is the "override-all" locale environment variable.
1184 If set, it overrides all the rest of the locale environment
1185 variables.
1186 "LANGUAGE" NOTE: "LANGUAGE" is a GNU extension, it affects you only if
1188 you are using the GNU libc. This is the case if you are
1189 using e.g. Linux. If you are using "commercial" Unixes you
1190 are most probably not using GNU libc and you can ignore
1191 "LANGUAGE".
1192 However, in the case you are using "LANGUAGE": it affects
1194 the language of informational, warning, and error messages
1195 output by commands (in other words, it's like
1196 "LC_MESSAGES") but it has higher priority than "LC_ALL".
1197 Moreover, it's not a single value but instead a "path"
1198 (":"-separated list) of languages (not locales). See the
1199 GNU "gettext" library documentation for more information.
1200 "LC_CTYPE" In the absence of "LC_ALL", "LC_CTYPE" chooses the
1202 character type locale. In the absence of both "LC_ALL" and
1203 "LC_CTYPE", "LANG" chooses the character type locale.
1204 "LC_COLLATE"
1206 In the absence of "LC_ALL", "LC_COLLATE" chooses the
1207 collation (sorting) locale. In the absence of both
1208 "LC_ALL" and "LC_COLLATE", "LANG" chooses the collation
1209 locale.
1210 "LC_MONETARY"
1212 In the absence of "LC_ALL", "LC_MONETARY" chooses the
1213 monetary formatting locale. In the absence of both
1214 "LC_ALL" and "LC_MONETARY", "LANG" chooses the monetary
1215 formatting locale.
1216 "LC_NUMERIC"
1218 In the absence of "LC_ALL", "LC_NUMERIC" chooses the
1219 numeric format locale. In the absence of both "LC_ALL" and
1220 "LC_NUMERIC", "LANG" chooses the numeric format.
1221 "LC_TIME" In the absence of "LC_ALL", "LC_TIME" chooses the date and
1223 time formatting locale. In the absence of both "LC_ALL"
1224 and "LC_TIME", "LANG" chooses the date and time formatting
1225 locale.
1226 "LANG" "LANG" is the "catch-all" locale environment variable. If
1228 it is set, it is used as the last resort after the overall
1229 "LC_ALL" and the category-specific "LC_foo".
1230 Examples
1232 The "LC_NUMERIC" controls the numeric output:
1233 use locale;
1235 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1236 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1237 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1238 and also how strings are parsed by "POSIX::strtod()" as numbers:
1240 use locale;
1242 use POSIX qw(locale_h strtod);
1243 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1244 my $x = strtod("2,34") + 5;
1245 print $x, "\n"; # Probably shows 7,34.
1246
1248 String "eval" and "LC_NUMERIC"
1249 A string eval parses its expression as standard Perl. It is therefore
1250 expecting the decimal point to be a dot. If "LC_NUMERIC" is set to
1251 have this be a comma instead, the parsing will be confused, perhaps
1252 silently.
1253 use locale;
1255 use POSIX qw(locale_h);
1256 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1257 my $a = 1.2;
1258 print eval "$a + 1.5";
1259 print "\n";
1260 prints "13,5". This is because in that locale, the comma is the
1262 decimal point character. The "eval" thus expands to:
1263 eval "1,2 + 1.5"
1265 and the result is not what you likely expected. No warnings are
1267 generated. If you do string "eval"'s within the scope of "use locale",
1268 you should instead change the "eval" line to do something like:
1269 print eval "no locale; $a + 1.5";
1271 This prints 2.7.
1273 You could also exclude "LC_NUMERIC", if you don't need it, by
1275 use locale ':!numeric';
1277 Backward compatibility
1279 Versions of Perl prior to 5.004 mostly ignored locale information,
1280 generally behaving as if something similar to the "C" locale were
1281 always in force, even if the program environment suggested otherwise
1282 (see "The setlocale function"). By default, Perl still behaves this
1283 way for backward compatibility. If you want a Perl application to pay
1284 attention to locale information, you must use the "use locale" pragma
1285 (see "The "use locale" pragma") or, in the unlikely event that you want
1286 to do so for just pattern matching, the "/l" regular expression
1287 modifier (see "Character set modifiers" in perlre) to instruct it to do
1288 so.
1289 Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE" information
1291 if available; that is, "\w" did understand what were the letters
1292 according to the locale environment variables. The problem was that
1293 the user had no control over the feature: if the C library supported
1294 locales, Perl used them.
1295 I18N:Collate obsolete
1297 In versions of Perl prior to 5.004, per-locale collation was possible
1298 using the "I18N::Collate" library module. This module is now mildly
1299 obsolete and should be avoided in new applications. The "LC_COLLATE"
1300 functionality is now integrated into the Perl core language: One can
1301 use locale-specific scalar data completely normally with "use locale",
1302 so there is no longer any need to juggle with the scalar references of
1303 "I18N::Collate".
1304 Sort speed and memory use impacts
1306 Comparing and sorting by locale is usually slower than the default
1307 sorting; slow-downs of two to four times have been observed. It will
1308 also consume more memory: once a Perl scalar variable has participated
1309 in any string comparison or sorting operation obeying the locale
1310 collation rules, it will take 3-15 times more memory than before. (The
1311 exact multiplier depends on the string's contents, the operating system
1312 and the locale.) These downsides are dictated more by the operating
1313 system's implementation of the locale system than by Perl.
1314 Freely available locale definitions
1316 The Unicode CLDR project extracts the POSIX portion of many of its
1317 locales, available at
1318 https://unicode.org/Public/cldr/2.0.1/
1320 (Newer versions of CLDR require you to compute the POSIX data yourself.
1322 See <http://unicode.org/Public/cldr/latest/>.)
1323 There is a large collection of locale definitions at:
1325 http://std.dkuug.dk/i18n/WG15-collection/locales/
1327 You should be aware that it is unsupported, and is not claimed to be
1329 fit for any purpose. If your system allows installation of arbitrary
1330 locales, you may find the definitions useful as they are, or as a basis
1331 for the development of your own locales.
1332 I18n and l10n
1334 "Internationalization" is often abbreviated as i18n because its first
1335 and last letters are separated by eighteen others. (You may guess why
1336 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1337 the same way, "localization" is often abbreviated to l10n.
1338 An imperfect standard
1340 Internationalization, as defined in the C and POSIX standards, can be
1341 criticized as incomplete and ungainly. They also have a tendency, like
1342 standards groups, to divide the world into nations, when we all know
1343 that the world can equally well be divided into bankers, bikers,
1344 gamers, and so on.
1345
1347 The support of Unicode is new starting from Perl version v5.6, and more
1348 fully implemented in versions v5.8 and later. See perluniintro.
1349 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1351 "LC_COLLATE" is only partially supported; collation support is improved
1352 in Perl v5.26 to a level that may be sufficient for your needs (see
1353 "Category "LC_COLLATE": Collation: Text Comparisons and Sorting").
1354 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1356 use locale ':not_characters';
1358 When this form of the pragma is used, only the non-character portions
1360 of locales are used by Perl, for example "LC_NUMERIC". Perl assumes
1361 that you have translated all the characters it is to operate on into
1362 Unicode (actually the platform's native character set (ASCII or EBCDIC)
1363 plus Unicode). For data in files, this can conveniently be done by
1364 also specifying
1365 use open ':locale';
1367 This pragma arranges for all inputs from files to be translated into
1369 Unicode from the current locale as specified in the environment (see
1370 "ENVIRONMENT"), and all outputs to files to be translated back into the
1371 locale. (See open). On a per-filehandle basis, you can instead use
1372 the PerlIO::locale module, or the Encode::Locale module, both available
1373 from CPAN. The latter module also has methods to ease the handling of
1374 "ARGV" and environment variables, and can be used on individual
1375 strings. If you know that all your locales will be UTF-8, as many are
1376 these days, you can use the -C command line switch.
1377 This form of the pragma allows essentially seamless handling of locales
1379 with Unicode. The collation order will be by Unicode code point order.
1380 Unicode::Collate can be used to get Unicode rules collation.
1381 All the modules and switches just described can be used in v5.20 with
1383 just plain "use locale", and, should the input locales not be UTF-8,
1384 you'll get the less than ideal behavior, described below, that you get
1385 with pre-v5.16 Perls, or when you use the locale pragma without the
1386 ":not_characters" parameter in v5.16 and v5.18. If you are using
1387 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1388 does not apply to you.
1389 There are two cases, multi-byte and single-byte locales. First multi-
1391 byte:
1392 The only multi-byte (or wide character) locale that Perl is ever likely
1394 to support is UTF-8. This is due to the difficulty of implementation,
1395 the fact that high quality UTF-8 locales are now published for every
1396 area of the world (<https://unicode.org/Public/cldr/2.0.1/> for ones
1397 that are already set-up, but from an earlier version;
1398 <https://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1399 you have to extract the POSIX information yourself), and failing all
1400 that, you can use the Encode module to translate to/from your locale.
1401 So, you'll have to do one of those things if you're using one of these
1402 locales, such as Big5 or Shift JIS. For UTF-8 locales, in Perls (pre
1403 v5.20) that don't have full UTF-8 locale support, they may work
1404 reasonably well (depending on your C library implementation) simply
1405 because both they and Perl store characters that take up multiple bytes
1406 the same way. However, some, if not most, C library implementations
1407 may not process the characters in the upper half of the Latin-1 range
1408 (128 - 255) properly under "LC_CTYPE". To see if a character is a
1409 particular type under a locale, Perl uses the functions like
1410 "isalnum()". Your C library may not work for UTF-8 locales with those
1411 functions, instead only working under the newer wide library functions
1412 like "iswalnum()", which Perl does not use. These multi-byte locales
1413 are treated like single-byte locales, and will have the restrictions
1414 described below. Starting in Perl v5.22 a warning message is raised
1415 when Perl detects a multi-byte locale that it doesn't fully support.
1416 For single-byte locales, Perl generally takes the tack to use locale
1418 rules on code points that can fit in a single byte, and Unicode rules
1419 for those that can't (though this isn't uniformly applied, see the note
1420 at the end of this section). This prevents many problems in locales
1421 that aren't UTF-8. Suppose the locale is ISO8859-7, Greek. The
1422 character at 0xD7 there is a capital Chi. But in the ISO8859-1 locale,
1423 Latin1, it is a multiplication sign. The POSIX regular expression
1424 character class "[[:alpha:]]" will magically match 0xD7 in the Greek
1425 locale but not in the Latin one.
1426 However, there are places where this breaks down. Certain Perl
1428 constructs are for Unicode only, such as "\p{Alpha}". They assume that
1429 0xD7 always has its Unicode meaning (or the equivalent on EBCDIC
1430 platforms). Since Latin1 is a subset of Unicode and 0xD7 is the
1431 multiplication sign in both Latin1 and Unicode, "\p{Alpha}" will never
1432 match it, regardless of locale. A similar issue occurs with "\N{...}".
1433 Prior to v5.20, it is therefore a bad idea to use "\p{}" or "\N{}"
1434 under plain "use locale"--unless you can guarantee that the locale will
1435 be ISO8859-1. Use POSIX character classes instead.
1436 Another problem with this approach is that operations that cross the
1438 single byte/multiple byte boundary are not well-defined, and so are
1439 disallowed. (This boundary is between the codepoints at 255/256.) For
1440 example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1441 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1442 Greek locale, for example, there is no character at 0xFF, and Perl has
1443 no way of knowing what the character at 0xFF is really supposed to
1444 represent. Thus it disallows the operation. In this mode, the
1445 lowercase of U+0178 is itself.
1446 The same problems ensue if you enable automatic UTF-8-ification of your
1448 standard file handles, default "open()" layer, and @ARGV on
1449 non-ISO8859-1, non-UTF-8 locales (by using either the -C command line
1450 switch or the "PERL_UNICODE" environment variable; see perlrun).
1451 Things are read in as UTF-8, which would normally imply a Unicode
1452 interpretation, but the presence of a locale causes them to be
1453 interpreted in that locale instead. For example, a 0xD7 code point in
1454 the Unicode input, which should mean the multiplication sign, won't be
1455 interpreted by Perl that way under the Greek locale. This is not a
1456 problem provided you make certain that all locales will always and only
1457 be either an ISO8859-1, or, if you don't have a deficient C library, a
1458 UTF-8 locale.
1459 Still another problem is that this approach can lead to two code points
1461 meaning the same character. Thus in a Greek locale, both U+03A7 and
1462 U+00D7 are GREEK CAPITAL LETTER CHI.
1463 Because of all these problems, starting in v5.22, Perl will raise a
1465 warning if a multi-byte (hence Unicode) code point is used when a
1466 single-byte locale is in effect. (Although it doesn't check for this
1467 if doing so would unreasonably slow execution down.)
1468 Vendor locales are notoriously buggy, and it is difficult for Perl to
1470 test its locale-handling code because this interacts with code that
1471 Perl has no control over; therefore the locale-handling code in Perl
1472 may be buggy as well. (However, the Unicode-supplied locales should be
1473 better, and there is a feed back mechanism to correct any problems.
1474 See "Freely available locale definitions".)
1475 If you have Perl v5.16, the problems mentioned above go away if you use
1477 the ":not_characters" parameter to the locale pragma (except for vendor
1478 bugs in the non-character portions). If you don't have v5.16, and you
1479 do have locales that work, using them may be worthwhile for certain
1480 specific purposes, as long as you keep in mind the gotchas already
1481 mentioned. For example, if the collation for your locales works, it
1482 runs faster under locales than under Unicode::Collate; and you gain
1483 access to such things as the local currency symbol and the names of the
1484 months and days of the week. (But to hammer home the point, in v5.16,
1485 you get this access without the downsides of locales by using the
1486 ":not_characters" form of the pragma.)
1487 Note: The policy of using locale rules for code points that can fit in
1489 a byte, and Unicode rules for those that can't is not uniformly
1490 applied. Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied
1491 fairly consistently to regular expression matching except for bracketed
1492 character classes; in v5.14 it was extended to all regex matches; and
1493 in v5.16 to the casing operations such as "\L" and "uc()". For
1494 collation, in all releases so far, the system's "strxfrm()" function is
1495 called, and whatever it does is what you get. Starting in v5.26,
1496 various bugs are fixed with the way perl uses this function.
1497
1499 Collation of strings containing embedded "NUL" characters
1500 "NUL" characters will sort the same as the lowest collating control
1501 character does, or to "\001" in the unlikely event that there are no
1502 control characters at all in the locale. In cases where the strings
1503 don't contain this non-"NUL" control, the results will be correct, and
1504 in many locales, this control, whatever it might be, will rarely be
1505 encountered. But there are cases where a "NUL" should sort before this
1506 control, but doesn't. If two strings do collate identically, the one
1507 containing the "NUL" will sort to earlier. Prior to 5.26, there were
1508 more bugs.
1509 Multi-threaded
1511 XS code or C-language libraries called from it that use the system
1512 setlocale(3) function (except on Windows) likely will not work from a
1513 multi-threaded application without changes. See "Locale-aware XS code"
1514 in perlxs.
1515 An XS module that is locale-dependent could have been written under the
1517 assumption that it will never be called in a multi-threaded
1518 environment, and so uses other non-locale constructs that aren't multi-
1519 thread-safe. See "Thread-aware system interfaces" in perlxs.
1520 POSIX does not define a way to get the name of the current per-thread
1522 locale. Some systems, such as Darwin and NetBSD do implement a
1523 function, querylocale(3) to do this. On non-Windows systems without
1524 it, such as Linux, there are some additional caveats:
1525 • An embedded perl needs to be started up while the global locale is
1527 in effect. See "Using embedded Perl with POSIX locales" in
1528 perlembed.
1529 • It becomes more important for perl to know about all the possible
1531 locale categories on the platform, even if they aren't apparently
1532 used in your program. Perl knows all of the Linux ones. If your
1533 platform has others, you can submit an issue at
1534 <https://github.com/Perl/perl5/issues> for inclusion of it in the
1535 next release. In the meantime, it is possible to edit the Perl
1536 source to teach it about the category, and then recompile. Search
1537 for instances of, say, "LC_PAPER" in the source, and use that as a
1538 template to add the omitted one.
1539 • It is possible, though hard to do, to call "POSIX::setlocale" with
1541 a locale that it doesn't recognize as syntactically legal, but
1542 actually is legal on that system. This should happen only with
1543 embedded perls, or if you hand-craft a locale name yourself.
1544 Broken systems
1546 In certain systems, the operating system's locale support is broken and
1547 cannot be fixed or used by Perl. Such deficiencies can and will result
1548 in mysterious hangs and/or Perl core dumps when "use locale" is in
1549 effect. When confronted with such a system, please report in
1550 excruciating detail to <<https://github.com/Perl/perl5/issues>>, and
1551 also contact your vendor: bug fixes may exist for these problems in
1552 your operating system. Sometimes such bug fixes are called an
1553 operating system upgrade. If you have the source for Perl, include in
1554 the bug report the output of the test described above in "Testing for
1555 broken locales".
1556
1558 I18N::Langinfo, perluniintro, perlunicode, open, "localeconv" in POSIX,
1559 "setlocale" in POSIX, "strcoll" in POSIX, "strftime" in POSIX, "strtod"
1560 in POSIX, "strxfrm" in POSIX.
1561 For special considerations when Perl is embedded in a C program, see
1563 "Using embedded Perl with POSIX locales" in perlembed.
1564
1566 Jarkko Hietaniemi's original perli18n.pod heavily hacked by Dominic
1567 Dunlop, assisted by the perl5-porters. Prose worked over a bit by Tom
1568 Christiansen, and now maintained by Perl 5 porters.
1569perl v5.36.3 2023-11-30 PERLLOCALE(1)