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 part
113 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"; POSIX::strcoll()
187 and POSIX::strxfrm() use "LC_COLLATE". All such functions will
188 behave according to the current underlying locale, even if that
189 locale isn't exposed to Perl space.
190 This applies as well to I18N::Langinfo.
192 • XS modules for all categories but "LC_NUMERIC" get the
194 underlying locale, and hence any C library functions they call
195 will use that underlying locale. For more discussion, see
196 "CAVEATS" in perlxs.
197 Note that all C programs (including the perl interpreter, which is
199 written in C) always have an underlying locale. That locale is the
200 "C" locale unless changed by a call to setlocale(). When Perl
201 starts up, it changes the underlying locale to the one which is
202 indicated by the "ENVIRONMENT". When using the POSIX module or
203 writing XS code, it is important to keep in mind that the
204 underlying locale may be something other than "C", even if the
205 program hasn't explicitly changed it.
206 Lingering effects of "use locale"
210 Certain Perl operations that are set-up within the scope of a "use
211 locale" retain that effect even outside the scope. These include:
212 • The output format of a write() is determined by an earlier
214 format declaration ("format" in perlfunc), so whether or not
215 the output is affected by locale is determined by if the
216 format() is within the scope of a "use locale", not whether the
217 write() is.
218 • Regular expression patterns can be compiled using qr// with
220 actual matching deferred to later. Again, it is whether or not
221 the compilation was done within the scope of "use locale" that
222 determines the match behavior, not if the matches are done
223 within such a scope or not.
224 Under ""use locale";"
228 • All the above operations
229 • Format declarations ("format" in perlfunc) and hence any
231 subsequent write()s use "LC_NUMERIC".
232 • stringification and output use "LC_NUMERIC". These include the
234 results of print(), printf(), say(), and sprintf().
235 • The comparison operators ("lt", "le", "cmp", "ge", and "gt")
237 use "LC_COLLATE". sort() is also affected if used without an
238 explicit comparison function, because it uses "cmp" by default.
239 Note: "eq" and "ne" are unaffected by locale: they always
241 perform a char-by-char comparison of their scalar operands.
242 What's more, if "cmp" finds that its operands are equal
243 according to the collation sequence specified by the current
244 locale, it goes on to perform a char-by-char comparison, and
245 only returns 0 (equal) if the operands are char-for-char
246 identical. If you really want to know whether two
247 strings--which "eq" and "cmp" may consider different--are equal
248 as far as collation in the locale is concerned, see the
249 discussion in "Category "LC_COLLATE": Collation".
250 • Regular expressions and case-modification functions (uc(),
252 lc(), ucfirst(), and lcfirst()) use "LC_CTYPE"
253 • The variables $! (and its synonyms $ERRNO and $OS_ERROR) and
255 $^E> (and its synonym $EXTENDED_OS_ERROR) when used as strings
256 use "LC_MESSAGES".
257 The default behavior is restored with the "no locale" pragma, or upon
259 reaching the end of the block enclosing "use locale". Note that "use
260 locale" calls may be nested, and that what is in effect within an inner
261 scope will revert to the outer scope's rules at the end of the inner
262 scope.
263 The string result of any operation that uses locale information is
265 tainted (if your perl supports taint checking), as it is possible for a
266 locale to be untrustworthy. See "SECURITY".
267 Starting in Perl v5.16 in a very limited way, and more generally in
269 v5.22, you can restrict which category or categories are enabled by
270 this particular instance of the pragma by adding parameters to it. For
271 example,
272 use locale qw(:ctype :numeric);
274 enables locale awareness within its scope of only those operations
276 (listed above) that are affected by "LC_CTYPE" and "LC_NUMERIC".
277 The possible categories are: ":collate", ":ctype", ":messages",
279 ":monetary", ":numeric", ":time", and the pseudo category ":characters"
280 (described below).
281 Thus you can say
283 use locale ':messages';
285 and only $! and $^E will be locale aware. Everything else is
287 unaffected.
288 Since Perl doesn't currently do anything with the "LC_MONETARY"
290 category, specifying ":monetary" does effectively nothing. Some
291 systems have other categories, such as "LC_PAPER", but Perl also
292 doesn't do anything with them, and there is no way to specify them in
293 this pragma's arguments.
294 You can also easily say to use all categories but one, by either, for
296 example,
297 use locale ':!ctype';
299 use locale ':not_ctype';
300 both of which mean to enable locale awareness of all categories but
302 "LC_CTYPE". Only one category argument may be specified in a
303 "use locale" if it is of the negated form.
304 Prior to v5.22 only one form of the pragma with arguments is available:
306 use locale ':not_characters';
308 (and you have to say "not_"; you can't use the bang "!" form). This
310 pseudo category is a shorthand for specifying both ":collate" and
311 ":ctype". Hence, in the negated form, it is nearly the same thing as
312 saying
313 use locale qw(:messages :monetary :numeric :time);
315 We use the term "nearly", because ":not_characters" also turns on
317 "use feature 'unicode_strings'" within its scope. This form is less
318 useful in v5.20 and later, and is described fully in "Unicode and
319 UTF-8", but briefly, it tells Perl to not use the character portions of
320 the locale definition, that is the "LC_CTYPE" and "LC_COLLATE"
321 categories. Instead it will use the native character set (extended by
322 Unicode). When using this parameter, you are responsible for getting
323 the external character set translated into the native/Unicode one
324 (which it already will be if it is one of the increasingly popular
325 UTF-8 locales). There are convenient ways of doing this, as described
326 in "Unicode and UTF-8".
327 The setlocale function
329 WARNING! Prior to Perl 5.28 or on a system that does not support
330 thread-safe locale operations, do NOT use this function in a thread.
331 The locale will change in all other threads at the same time, and
332 should your thread get paused by the operating system, and another
333 started, that thread will not have the locale it is expecting. On some
334 platforms, there can be a race leading to segfaults if two threads call
335 this function nearly simultaneously. This warning does not apply on
336 unthreaded builds, or on perls where "${^SAFE_LOCALES}" exists and is
337 non-zero; namely Perl 5.28 and later unthreaded or compiled to be
338 locale-thread-safe. On z/OS systems, this function becomes a no-op
339 once any thread is started. Thus, on that system, you can set up the
340 locale before creating any threads, and that locale will be the one in
341 effect for the entire program.
342 Otherwise, you can switch locales as often as you wish at run time with
344 the POSIX::setlocale() function:
345 # Import locale-handling tool set from POSIX module.
347 # This example uses: setlocale -- the function call
348 # LC_CTYPE -- explained below
349 # (Showing the testing for success/failure of operations is
350 # omitted in these examples to avoid distracting from the main
351 # point)
352 use POSIX qw(locale_h);
354 use locale;
355 my $old_locale;
356 # query and save the old locale
358 $old_locale = setlocale(LC_CTYPE);
359 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
361 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
362 setlocale(LC_CTYPE, "");
364 # LC_CTYPE now reset to the default defined by the
365 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
366 # default. See below for documentation.
367 # restore the old locale
369 setlocale(LC_CTYPE, $old_locale);
370 The first argument of setlocale() gives the category, the second the
372 locale. The category tells in what aspect of data processing you want
373 to apply locale-specific rules. Category names are discussed in
374 "LOCALE CATEGORIES" and "ENVIRONMENT". The locale is the name of a
375 collection of customization information corresponding to a particular
376 combination of language, country or territory, and codeset. Read on
377 for hints on the naming of locales: not all systems name locales as in
378 the example.
379 If no second argument is provided and the category is something other
381 than "LC_ALL", the function returns a string naming the current locale
382 for the category. You can use this value as the second argument in a
383 subsequent call to setlocale(), but on some platforms the string is
384 opaque, not something that most people would be able to decipher as to
385 what locale it means.
386 If no second argument is provided and the category is "LC_ALL", the
388 result is implementation-dependent. It may be a string of concatenated
389 locale names (separator also implementation-dependent) or a single
390 locale name. Please consult your setlocale(3) man page for details.
391 If a second argument is given and it corresponds to a valid locale, the
393 locale for the category is set to that value, and the function returns
394 the now-current locale value. You can then use this in yet another
395 call to setlocale(). (In some implementations, the return value may
396 sometimes differ from the value you gave as the second argument--think
397 of it as an alias for the value you gave.)
398 As the example shows, if the second argument is an empty string, the
400 category's locale is returned to the default specified by the
401 corresponding environment variables. Generally, this results in a
402 return to the default that was in force when Perl started up: changes
403 to the environment made by the application after startup may or may not
404 be noticed, depending on your system's C library.
405 Note that when a form of "use locale" that doesn't include all
407 categories is specified, Perl ignores the excluded categories.
408 If setlocale() fails for some reason (for example, an attempt to set to
410 a locale unknown to the system), the locale for the category is not
411 changed, and the function returns "undef".
412 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
414 implement POSIX 2008 thread-safe locale operations, this function
415 doesn't actually call the system "setlocale". Instead those thread-
416 safe operations are used to emulate the "setlocale" function, but in a
417 thread-safe manner.
418 You can force the thread-safe locale operations to always be used (if
420 available) by recompiling perl with
421 -Accflags='-DUSE_THREAD_SAFE_LOCALE'
423 added to your call to Configure.
425 For further information about the categories, consult setlocale(3).
427 Multi-threaded operation
429 Beginning in Perl 5.28, multi-threaded locale operation is supported on
430 systems that implement either the POSIX 2008 or Windows-specific
431 thread-safe locale operations. Many modern systems, such as various
432 Unix variants and Darwin do have this.
433 You can tell if using locales is safe on your system by looking at the
435 read-only boolean variable "${^SAFE_LOCALES}". The value is 1 if the
436 perl is not threaded, or if it is using thread-safe locale operations.
437 Thread-safe operations are supported in Windows starting in Visual
439 Studio 2005, and in systems compatible with POSIX 2008. Some platforms
440 claim to support POSIX 2008, but have buggy implementations, so that
441 the hints files for compiling to run on them turn off attempting to use
442 thread-safety. "${^SAFE_LOCALES}" will be 0 on them.
443 Be aware that writing a multi-threaded application will not be portable
445 to a platform which lacks the native thread-safe locale support. On
446 systems that do have it, you automatically get this behavior for
447 threaded perls, without having to do anything. If for some reason, you
448 don't want to use this capability (perhaps the POSIX 2008 support is
449 buggy on your system), you can manually compile Perl to use the old
450 non-thread-safe implementation by passing the argument
451 "-Accflags='-DNO_THREAD_SAFE_LOCALE'" to Configure. Except on Windows,
452 this will continue to use certain of the POSIX 2008 functions in some
453 situations. If these are buggy, you can pass the following to
454 Configure instead or additionally:
455 "-Accflags='-DNO_POSIX_2008_LOCALE'". This will also keep the code
456 from using thread-safe locales. "${^SAFE_LOCALES}" will be 0 on
457 systems that turn off the thread-safe operations.
458 Normally on unthreaded builds, the traditional setlocale() is used and
460 not the thread-safe locale functions. You can force the use of these
461 on systems that have them by adding the
462 "-Accflags='-DUSE_THREAD_SAFE_LOCALE'" to Configure.
463 The initial program is started up using the locale specified from the
465 environment, as currently, described in "ENVIRONMENT". All newly
466 created threads start with "LC_ALL" set to "C". Each thread may use
467 POSIX::setlocale() to query or switch its locale at any time, without
468 affecting any other thread. All locale-dependent operations
469 automatically use their thread's locale.
470 This should be completely transparent to any applications written
472 entirely in Perl (minus a few rarely encountered caveats given in the
473 "Multi-threaded" section). Information for XS module writers is given
474 in "Locale-aware XS code" in perlxs.
475 Finding locales
477 For locales available in your system, consult also setlocale(3) to see
478 whether it leads to the list of available locales (search for the SEE
479 ALSO section). If that fails, try the following command lines:
480 locale -a
482 nlsinfo
484 ls /usr/lib/nls/loc
486 ls /usr/lib/locale
488 ls /usr/lib/nls
490 ls /usr/share/locale
492 and see whether they list something resembling these
494 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
496 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
497 en_US de_DE ru_RU
498 en de ru
499 english german russian
500 english.iso88591 german.iso88591 russian.iso88595
501 english.roman8 russian.koi8r
502 Sadly, even though the calling interface for setlocale() has been
504 standardized, names of locales and the directories where the
505 configuration resides have not been. The basic form of the name is
506 language_territory.codeset, but the latter parts after language are not
507 always present. The language and country are usually from the
508 standards ISO 3166 and ISO 639, the two-letter abbreviations for the
509 countries and the languages of the world, respectively. The codeset
510 part often mentions some ISO 8859 character set, the Latin codesets.
511 For example, "ISO 8859-1" is the so-called "Western European codeset"
512 that can be used to encode most Western European languages adequately.
513 Again, there are several ways to write even the name of that one
514 standard. Lamentably.
515 Two special locales are worth particular mention: "C" and "POSIX".
517 Currently these are effectively the same locale: the difference is
518 mainly that the first one is defined by the C standard, the second by
519 the POSIX standard. They define the default locale in which every
520 program starts in the absence of locale information in its environment.
521 (The default default locale, if you will.) Its language is (American)
522 English and its character codeset ASCII or, rarely, a superset thereof
523 (such as the "DEC Multinational Character Set (DEC-MCS)"). Warning.
524 The C locale delivered by some vendors may not actually exactly match
525 what the C standard calls for. So beware.
526 NOTE: Not all systems have the "POSIX" locale (not all systems are
528 POSIX-conformant), so use "C" when you need explicitly to specify this
529 default locale.
530 LOCALE PROBLEMS
532 You may encounter the following warning message at Perl startup:
533 perl: warning: Setting locale failed.
535 perl: warning: Please check that your locale settings:
536 LC_ALL = "En_US",
537 LANG = (unset)
538 are supported and installed on your system.
539 perl: warning: Falling back to the standard locale ("C").
540 This means that your locale settings had "LC_ALL" set to "En_US" and
542 LANG exists but has no value. Perl tried to believe you but could not.
543 Instead, Perl gave up and fell back to the "C" locale, the default
544 locale that is supposed to work no matter what. (On Windows, it first
545 tries falling back to the system default locale.) This usually means
546 your locale settings were wrong, they mention locales your system has
547 never heard of, or the locale installation in your system has problems
548 (for example, some system files are broken or missing). There are
549 quick and temporary fixes to these problems, as well as more thorough
550 and lasting fixes.
551 Testing for broken locales
553 If you are building Perl from source, the Perl test suite file
554 lib/locale.t can be used to test the locales on your system. Setting
555 the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it to
556 output detailed results. For example, on Linux, you could say
557 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
559 Besides many other tests, it will test every locale it finds on your
561 system to see if they conform to the POSIX standard. If any have
562 errors, it will include a summary near the end of the output of which
563 locales passed all its tests, and which failed, and why.
564 Temporarily fixing locale problems
566 The two quickest fixes are either to render Perl silent about any
567 locale inconsistencies or to run Perl under the default locale "C".
568 Perl's moaning about locale problems can be silenced by setting the
570 environment variable "PERL_BADLANG" to "0" or "". This method really
571 just sweeps the problem under the carpet: you tell Perl to shut up even
572 when Perl sees that something is wrong. Do not be surprised if later
573 something locale-dependent misbehaves.
574 Perl can be run under the "C" locale by setting the environment
576 variable "LC_ALL" to "C". This method is perhaps a bit more civilized
577 than the "PERL_BADLANG" approach, but setting "LC_ALL" (or other locale
578 variables) may affect other programs as well, not just Perl. In
579 particular, external programs run from within Perl will see these
580 changes. If you make the new settings permanent (read on), all
581 programs you run see the changes. See "ENVIRONMENT" for the full list
582 of relevant environment variables and "USING LOCALES" for their effects
583 in Perl. Effects in other programs are easily deducible. For example,
584 the variable "LC_COLLATE" may well affect your sort program (or
585 whatever the program that arranges "records" alphabetically in your
586 system is called).
587 You can test out changing these variables temporarily, and if the new
589 settings seem to help, put those settings into your shell startup
590 files. Consult your local documentation for the exact details. For
591 Bourne-like shells (sh, ksh, bash, zsh):
592 LC_ALL=en_US.ISO8859-1
594 export LC_ALL
595 This assumes that we saw the locale "en_US.ISO8859-1" using the
597 commands discussed above. We decided to try that instead of the above
598 faulty locale "En_US"--and in Cshish shells (csh, tcsh)
599 setenv LC_ALL en_US.ISO8859-1
601 or if you have the "env" application you can do (in any shell)
603 env LC_ALL=en_US.ISO8859-1 perl ...
605 If you do not know what shell you have, consult your local helpdesk or
607 the equivalent.
608 Permanently fixing locale problems
610 The slower but superior fixes are when you may be able to yourself fix
611 the misconfiguration of your own environment variables. The
612 mis(sing)configuration of the whole system's locales usually requires
613 the help of your friendly system administrator.
614 First, see earlier in this document about "Finding locales". That
616 tells how to find which locales are really supported--and more
617 importantly, installed--on your system. In our example error message,
618 environment variables affecting the locale are listed in the order of
619 decreasing importance (and unset variables do not matter). Therefore,
620 having LC_ALL set to "En_US" must have been the bad choice, as shown by
621 the error message. First try fixing locale settings listed first.
622 Second, if using the listed commands you see something exactly (prefix
624 matches do not count and case usually counts) like "En_US" without the
625 quotes, then you should be okay because you are using a locale name
626 that should be installed and available in your system. In this case,
627 see "Permanently fixing your system's locale configuration".
628 Permanently fixing your system's locale configuration
630 This is when you see something like:
631 perl: warning: Please check that your locale settings:
633 LC_ALL = "En_US",
634 LANG = (unset)
635 are supported and installed on your system.
636 but then cannot see that "En_US" listed by the above-mentioned
638 commands. You may see things like "en_US.ISO8859-1", but that isn't
639 the same. In this case, try running under a locale that you can list
640 and which somehow matches what you tried. The rules for matching
641 locale names are a bit vague because standardization is weak in this
642 area. See again the "Finding locales" about general rules.
643 Fixing system locale configuration
645 Contact a system administrator (preferably your own) and report the
646 exact error message you get, and ask them to read this same
647 documentation you are now reading. They should be able to check
648 whether there is something wrong with the locale configuration of the
649 system. The "Finding locales" section is unfortunately a bit vague
650 about the exact commands and places because these things are not that
651 standardized.
652 The localeconv function
654 The POSIX::localeconv() function allows you to get particulars of the
655 locale-dependent numeric formatting information specified by the
656 current underlying "LC_NUMERIC" and "LC_MONETARY" locales (regardless
657 of whether called from within the scope of "use locale" or not). (If
658 you just want the name of the current locale for a particular category,
659 use POSIX::setlocale() with a single parameter--see "The setlocale
660 function".)
661 use POSIX qw(locale_h);
663 # Get a reference to a hash of locale-dependent info
665 $locale_values = localeconv();
666 # Output sorted list of the values
668 for (sort keys %$locale_values) {
669 printf "%-20s = %s\n", $_, $locale_values->{$_}
670 }
671 localeconv() takes no arguments, and returns a reference to a hash.
673 The keys of this hash are variable names for formatting, such as
674 "decimal_point" and "thousands_sep". The values are the corresponding,
675 er, values. See "localeconv" in POSIX for a longer example listing the
676 categories an implementation might be expected to provide; some provide
677 more and others fewer. You don't need an explicit "use locale",
678 because localeconv() always observes the current locale.
679 Here's a simple-minded example program that rewrites its command-line
681 parameters as integers correctly formatted in the current locale:
682 use POSIX qw(locale_h);
684 # Get some of locale's numeric formatting parameters
686 my ($thousands_sep, $grouping) =
687 @{localeconv()}{'thousands_sep', 'grouping'};
688 # Apply defaults if values are missing
690 $thousands_sep = ',' unless $thousands_sep;
691 # grouping and mon_grouping are packed lists
693 # of small integers (characters) telling the
694 # grouping (thousand_seps and mon_thousand_seps
695 # being the group dividers) of numbers and
696 # monetary quantities. The integers' meanings:
697 # 255 means no more grouping, 0 means repeat
698 # the previous grouping, 1-254 means use that
699 # as the current grouping. Grouping goes from
700 # right to left (low to high digits). In the
701 # below we cheat slightly by never using anything
702 # else than the first grouping (whatever that is).
703 if ($grouping) {
704 @grouping = unpack("C*", $grouping);
705 } else {
706 @grouping = (3);
707 }
708 # Format command line params for current locale
710 for (@ARGV) {
711 $_ = int; # Chop non-integer part
712 1 while
713 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
714 print "$_";
715 }
716 print "\n";
717 Note that if the platform doesn't have "LC_NUMERIC" and/or
719 "LC_MONETARY" available or enabled, the corresponding elements of the
720 hash will be missing.
721 I18N::Langinfo
723 Another interface for querying locale-dependent information is the
724 I18N::Langinfo::langinfo() function.
725 The following example will import the langinfo() function itself and
727 three constants to be used as arguments to langinfo(): a constant for
728 the abbreviated first day of the week (the numbering starts from Sunday
729 = 1) and two more constants for the affirmative and negative answers
730 for a yes/no question in the current locale.
731 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
733 my ($abday_1, $yesstr, $nostr)
735 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
736 print "$abday_1? [$yesstr/$nostr] ";
738 In other words, in the "C" (or English) locale the above will probably
740 print something like:
741 Sun? [yes/no]
743 See I18N::Langinfo for more information.
745
747 The following subsections describe basic locale categories. Beyond
748 these, some combination categories allow manipulation of more than one
749 basic category at a time. See "ENVIRONMENT" for a discussion of these.
750 Category "LC_COLLATE": Collation: Text Comparisons and Sorting
752 In the scope of a "use locale" form that includes collation, Perl looks
753 to the "LC_COLLATE" environment variable to determine the application's
754 notions on collation (ordering) of characters. For example, "b"
755 follows "a" in Latin alphabets, but where do "á" and "å" belong? And
756 while "color" follows "chocolate" in English, what about in traditional
757 Spanish?
758 The following collations all make sense and you may meet any of them if
760 you "use locale".
761 A B C D E a b c d e
763 A a B b C c D d E e
764 a A b B c C d D e E
765 a b c d e A B C D E
766 Here is a code snippet to tell what "word" characters are in the
768 current locale, in that locale's order:
769 use locale;
771 print +(sort grep /\w/, map { chr } 0..255), "\n";
772 Compare this with the characters that you see and their order if you
774 state explicitly that the locale should be ignored:
775 no locale;
777 print +(sort grep /\w/, map { chr } 0..255), "\n";
778 This machine-native collation (which is what you get unless
780 "use locale" has appeared earlier in the same block) must be used for
781 sorting raw binary data, whereas the locale-dependent collation of the
782 first example is useful for natural text.
783 As noted in "USING LOCALES", "cmp" compares according to the current
785 collation locale when "use locale" is in effect, but falls back to a
786 char-by-char comparison for strings that the locale says are equal. You
787 can use POSIX::strcoll() if you don't want this fall-back:
788 use POSIX qw(strcoll);
790 $equal_in_locale =
791 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
792 $equal_in_locale will be true if the collation locale specifies a
794 dictionary-like ordering that ignores space characters completely and
795 which folds case.
796 Perl uses the platform's C library collation functions strcoll() and
798 strxfrm(). That means you get whatever they give. On some platforms,
799 these functions work well on UTF-8 locales, giving a reasonable default
800 collation for the code points that are important in that locale. (And
801 if they aren't working well, the problem may only be that the locale
802 definition is deficient, so can be fixed by using a better definition
803 file. Unicode's definitions (see "Freely available locale
804 definitions") provide reasonable UTF-8 locale collation definitions.)
805 Starting in Perl v5.26, Perl's use of these functions has been made
806 more seamless. This may be sufficient for your needs. For more
807 control, and to make sure strings containing any code point (not just
808 the ones important in the locale) collate properly, the
809 Unicode::Collate module is suggested.
810 In non-UTF-8 locales (hence single byte), code points above 0xFF are
812 technically invalid. But if present, again starting in v5.26, they
813 will collate to the same position as the highest valid code point does.
814 This generally gives good results, but the collation order may be
815 skewed if the valid code point gets special treatment when it forms
816 particular sequences with other characters as defined by the locale.
817 When two strings collate identically, the code point order is used as a
818 tie breaker.
819 If Perl detects that there are problems with the locale collation
821 order, it reverts to using non-locale collation rules for that locale.
822 If you have a single string that you want to check for "equality in
824 locale" against several others, you might think you could gain a little
825 efficiency by using POSIX::strxfrm() in conjunction with "eq":
826 use POSIX qw(strxfrm);
828 $xfrm_string = strxfrm("Mixed-case string");
829 print "locale collation ignores spaces\n"
830 if $xfrm_string eq strxfrm("Mixed-casestring");
831 print "locale collation ignores hyphens\n"
832 if $xfrm_string eq strxfrm("Mixedcase string");
833 print "locale collation ignores case\n"
834 if $xfrm_string eq strxfrm("mixed-case string");
835 strxfrm() takes a string and maps it into a transformed string for use
837 in char-by-char comparisons against other transformed strings during
838 collation. "Under the hood", locale-affected Perl comparison operators
839 call strxfrm() for both operands, then do a char-by-char comparison of
840 the transformed strings. By calling strxfrm() explicitly and using a
841 non locale-affected comparison, the example attempts to save a couple
842 of transformations. But in fact, it doesn't save anything: Perl magic
843 (see "Magic Variables" in perlguts) creates the transformed version of
844 a string the first time it's needed in a comparison, then keeps this
845 version around in case it's needed again. An example rewritten the
846 easy way with "cmp" runs just about as fast. It also copes with null
847 characters embedded in strings; if you call strxfrm() directly, it
848 treats the first null it finds as a terminator. Don't expect the
849 transformed strings it produces to be portable across systems--or even
850 from one revision of your operating system to the next. In short,
851 don't call strxfrm() directly: let Perl do it for you.
852 Note: "use locale" isn't shown in some of these examples because it
854 isn't needed: strcoll() and strxfrm() are POSIX functions which use the
855 standard system-supplied "libc" functions that always obey the current
856 "LC_COLLATE" locale.
857 Category "LC_CTYPE": Character Types
859 In the scope of a "use locale" form that includes "LC_CTYPE", Perl
860 obeys the "LC_CTYPE" locale setting. This controls the application's
861 notion of which characters are alphabetic, numeric, punctuation, etc.
862 This affects Perl's "\w" regular expression metanotation, which stands
863 for alphanumeric characters--that is, alphabetic, numeric, and the
864 platform's native underscore. (Consult perlre for more information
865 about regular expressions.) Thanks to "LC_CTYPE", depending on your
866 locale setting, characters like "æ", "ð", "ß", and "ø" may be
867 understood as "\w" characters. It also affects things like "\s", "\D",
868 and the POSIX character classes, like "[[:graph:]]". (See
869 perlrecharclass for more information on all these.)
870 The "LC_CTYPE" locale also provides the map used in transliterating
872 characters between lower and uppercase. This affects the case-mapping
873 functions--fc(), lc(), lcfirst(), uc(), and ucfirst(); case-mapping
874 interpolation with "\F", "\l", "\L", "\u", or "\U" in double-quoted
875 strings and "s///" substitutions; and case-insensitive regular
876 expression pattern matching using the "i" modifier.
877 Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
879 otherwise Perl only supports single-byte locales, such as the ISO 8859
880 series. This means that wide character locales, for example for Asian
881 languages, are not well-supported. Use of these locales may cause core
882 dumps. If the platform has the capability for Perl to detect such a
883 locale, starting in Perl v5.22, Perl will warn, default enabled, using
884 the "locale" warning category, whenever such a locale is switched into.
885 The UTF-8 locale support is actually a superset of POSIX locales,
886 because it is really full Unicode behavior as if no "LC_CTYPE" locale
887 were in effect at all (except for tainting; see "SECURITY"). POSIX
888 locales, even UTF-8 ones, are lacking certain concepts in Unicode, such
889 as the idea that changing the case of a character could expand to be
890 more than one character. Perl in a UTF-8 locale, will give you that
891 expansion. Prior to v5.20, Perl treated a UTF-8 locale on some
892 platforms like an ISO 8859-1 one, with some restrictions, and on other
893 platforms more like the "C" locale. For releases v5.16 and v5.18,
894 "use locale 'not_characters" could be used as a workaround for this
895 (see "Unicode and UTF-8").
896 Note that there are quite a few things that are unaffected by the
898 current locale. Any literal character is the native character for the
899 given platform. Hence 'A' means the character at code point 65 on
900 ASCII platforms, and 193 on EBCDIC. That may or may not be an 'A' in
901 the current locale, if that locale even has an 'A'. Similarly, all the
902 escape sequences for particular characters, "\n" for example, always
903 mean the platform's native one. This means, for example, that "\N" in
904 regular expressions (every character but new-line) works on the
905 platform character set.
906 Starting in v5.22, Perl will by default warn when switching into a
908 locale that redefines any ASCII printable character (plus "\t" and
909 "\n") into a different class than expected. This is likely to happen
910 on modern locales only on EBCDIC platforms, where, for example, a CCSID
911 0037 locale on a CCSID 1047 machine moves "[", but it can happen on
912 ASCII platforms with the ISO 646 and other 7-bit locales that are
913 essentially obsolete. Things may still work, depending on what
914 features of Perl are used by the program. For example, in the example
915 from above where "|" becomes a "\w", and there are no regular
916 expressions where this matters, the program may still work properly.
917 The warning lists all the characters that it can determine could be
918 adversely affected.
919 Note: A broken or malicious "LC_CTYPE" locale definition may result in
921 clearly ineligible characters being considered to be alphanumeric by
922 your application. For strict matching of (mundane) ASCII letters and
923 digits--for example, in command strings--locale-aware applications
924 should use "\w" with the "/a" regular expression modifier. See
925 "SECURITY".
926 Category "LC_NUMERIC": Numeric Formatting
928 After a proper POSIX::setlocale() call, and within the scope of a "use
929 locale" form that includes numerics, Perl obeys the "LC_NUMERIC" locale
930 information, which controls an application's idea of how numbers should
931 be formatted for human readability. In most implementations the only
932 effect is to change the character used for the decimal point--perhaps
933 from "." to ",". The functions aren't aware of such niceties as
934 thousands separation and so on. (See "The localeconv function" if you
935 care about these things.)
936 use POSIX qw(strtod setlocale LC_NUMERIC);
938 use locale;
939 setlocale LC_NUMERIC, "";
941 $n = 5/2; # Assign numeric 2.5 to $n
943 $a = " $n"; # Locale-dependent conversion to string
945 print "half five is $n\n"; # Locale-dependent output
947 printf "half five is %g\n", $n; # Locale-dependent output
949 print "DECIMAL POINT IS COMMA\n"
951 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
952 See also I18N::Langinfo and "RADIXCHAR".
954 Category "LC_MONETARY": Formatting of monetary amounts
956 The C standard defines the "LC_MONETARY" category, but not a function
957 that is affected by its contents. (Those with experience of standards
958 committees will recognize that the working group decided to punt on the
959 issue.) Consequently, Perl essentially takes no notice of it. If you
960 really want to use "LC_MONETARY", you can query its contents--see "The
961 localeconv function"--and use the information that it returns in your
962 application's own formatting of currency amounts. However, you may
963 well find that the information, voluminous and complex though it may
964 be, still does not quite meet your requirements: currency formatting is
965 a hard nut to crack.
966 See also I18N::Langinfo and "CRNCYSTR".
968 Category "LC_TIME": Respresentation of time
970 Output produced by POSIX::strftime(), which builds a formatted human-
971 readable date/time string, is affected by the current "LC_TIME" locale.
972 Thus, in a French locale, the output produced by the %B format element
973 (full month name) for the first month of the year would be "janvier".
974 Here's how to get a list of long month names in the current locale:
975 use POSIX qw(strftime);
977 for (0..11) {
978 $long_month_name[$_] =
979 strftime("%B", 0, 0, 0, 1, $_, 96);
980 }
981 Note: "use locale" isn't needed in this example: strftime() is a POSIX
983 function which uses the standard system-supplied "libc" function that
984 always obeys the current "LC_TIME" locale.
985 See also I18N::Langinfo and "ABDAY_1".."ABDAY_7", "DAY_1".."DAY_7",
987 "ABMON_1".."ABMON_12", and "ABMON_1".."ABMON_12".
988 Other categories
990 The remaining locale categories are not currently used by Perl itself.
991 But again note that things Perl interacts with may use these, including
992 extensions outside the standard Perl distribution, and by the operating
993 system and its utilities. Note especially that the string value of $!
994 and the error messages given by external utilities may be changed by
995 "LC_MESSAGES". If you want to have portable error codes, use "%!".
996 See Errno.
997
999 Although the main discussion of Perl security issues can be found in
1000 perlsec, a discussion of Perl's locale handling would be incomplete if
1001 it did not draw your attention to locale-dependent security issues.
1002 Locales--particularly on systems that allow unprivileged users to build
1003 their own locales--are untrustworthy. A malicious (or just plain
1004 broken) locale can make a locale-aware application give unexpected
1005 results. Here are a few possibilities:
1006 • Regular expression checks for safe file names or mail addresses
1008 using "\w" may be spoofed by an "LC_CTYPE" locale that claims that
1009 characters such as ">" and "|" are alphanumeric.
1010 • String interpolation with case-mapping, as in, say, $dest =
1012 "C:\U$name.$ext", may produce dangerous results if a bogus
1013 "LC_CTYPE" case-mapping table is in effect.
1014 • A sneaky "LC_COLLATE" locale could result in the names of students
1016 with "D" grades appearing ahead of those with "A"s.
1017 • An application that takes the trouble to use information in
1019 "LC_MONETARY" may format debits as if they were credits and vice
1020 versa if that locale has been subverted. Or it might make payments
1021 in US dollars instead of Hong Kong dollars.
1022 • The date and day names in dates formatted by strftime() could be
1024 manipulated to advantage by a malicious user able to subvert the
1025 "LC_DATE" locale. ("Look--it says I wasn't in the building on
1026 Sunday.")
1027 Such dangers are not peculiar to the locale system: any aspect of an
1029 application's environment which may be modified maliciously presents
1030 similar challenges. Similarly, they are not specific to Perl: any
1031 programming language that allows you to write programs that take
1032 account of their environment exposes you to these issues.
1033 Perl cannot protect you from all possibilities shown in the
1035 examples--there is no substitute for your own vigilance--but, when "use
1036 locale" is in effect, Perl uses the tainting mechanism (see perlsec) to
1037 mark string results that become locale-dependent, and which may be
1038 untrustworthy in consequence.
1039 Note that it is possible to compile Perl without taint support, in
1041 which case all taint features silently do nothing.
1042 Here is a summary of the tainting behavior of operators and functions
1044 that may be affected by the locale:
1045 • Comparison operators ("lt", "le", "ge", "gt" and "cmp"):
1047 Scalar true/false (or less/equal/greater) result is never tainted.
1049 • Case-mapping interpolation (with "\l", "\L", "\u", "\U", or "\F")
1051 The result string containing interpolated material is tainted if a
1053 "use locale" form that includes "LC_CTYPE" is in effect.
1054 • Matching operator ("m//"):
1056 Scalar true/false result never tainted.
1058 All subpatterns, either delivered as a list-context result or as $1
1060 etc., are tainted if a "use locale" form that includes "LC_CTYPE"
1061 is in effect, and the subpattern regular expression contains a
1062 locale-dependent construct. These constructs include "\w" (to
1063 match an alphanumeric character), "\W" (non-alphanumeric
1064 character), "\b" and "\B" (word-boundary and non-boundardy, which
1065 depend on what "\w" and "\W" match), "\s" (whitespace character),
1066 "\S" (non whitespace character), "\d" and "\D" (digits and non-
1067 digits), and the POSIX character classes, such as "[:alpha:]" (see
1068 "POSIX Character Classes" in perlrecharclass).
1069 Tainting is also likely if the pattern is to be matched case-
1071 insensitively (via "/i"). The exception is if all the code points
1072 to be matched this way are above 255 and do not have folds under
1073 Unicode rules to below 256. Tainting is not done for these because
1074 Perl only uses Unicode rules for such code points, and those rules
1075 are the same no matter what the current locale.
1076 The matched-pattern variables, $&, "$`" (pre-match), "$'" (post-
1078 match), and $+ (last match) also are tainted.
1079 • Substitution operator ("s///"):
1081 Has the same behavior as the match operator. Also, the left
1083 operand of "=~" becomes tainted when a "use locale" form that
1084 includes "LC_CTYPE" is in effect, if modified as a result of a
1085 substitution based on a regular expression match involving any of
1086 the things mentioned in the previous item, or of case-mapping, such
1087 as "\l", "\L","\u", "\U", or "\F".
1088 • Output formatting functions (printf() and write()):
1090 Results are never tainted because otherwise even output from print,
1092 for example print(1/7), should be tainted if "use locale" is in
1093 effect.
1094 • Case-mapping functions (lc(), lcfirst(), uc(), ucfirst()):
1096 Results are tainted if a "use locale" form that includes "LC_CTYPE"
1098 is in effect.
1099 • POSIX locale-dependent functions (localeconv(), strcoll(),
1101 strftime(), strxfrm()):
1102 Results are never tainted.
1104 Three examples illustrate locale-dependent tainting. The first
1106 program, which ignores its locale, won't run: a value taken directly
1107 from the command line may not be used to name an output file when taint
1108 checks are enabled.
1109 #/usr/local/bin/perl -T
1111 # Run with taint checking
1112 # Command line sanity check omitted...
1114 $tainted_output_file = shift;
1115 open(F, ">$tainted_output_file")
1117 or warn "Open of $tainted_output_file failed: $!\n";
1118 The program can be made to run by "laundering" the tainted value
1120 through a regular expression: the second example--which still ignores
1121 locale information--runs, creating the file named on its command line
1122 if it can.
1123 #/usr/local/bin/perl -T
1125 $tainted_output_file = shift;
1127 $tainted_output_file =~ m%[\w/]+%;
1128 $untainted_output_file = $&;
1129 open(F, ">$untainted_output_file")
1131 or warn "Open of $untainted_output_file failed: $!\n";
1132 Compare this with a similar but locale-aware program:
1134 #/usr/local/bin/perl -T
1136 $tainted_output_file = shift;
1138 use locale;
1139 $tainted_output_file =~ m%[\w/]+%;
1140 $localized_output_file = $&;
1141 open(F, ">$localized_output_file")
1143 or warn "Open of $localized_output_file failed: $!\n";
1144 This third program fails to run because $& is tainted: it is the result
1146 of a match involving "\w" while "use locale" is in effect.
1147
1149 PERL_SKIP_LOCALE_INIT
1150 This environment variable, available starting in Perl
1151 v5.20, if set (to any value), tells Perl to not use the
1152 rest of the environment variables to initialize with.
1153 Instead, Perl uses whatever the current locale settings
1154 are. This is particularly useful in embedded environments,
1155 see "Using embedded Perl with POSIX locales" in perlembed.
1156 PERL_BADLANG
1158 A string that can suppress Perl's warning about failed
1159 locale settings at startup. Failure can occur if the
1160 locale support in the operating system is lacking (broken)
1161 in some way--or if you mistyped the name of a locale when
1162 you set up your environment. If this environment variable
1163 is absent, or has a value other than "0" or "", Perl will
1164 complain about locale setting failures.
1165 NOTE: "PERL_BADLANG" only gives you a way to hide the
1167 warning message. The message tells about some problem in
1168 your system's locale support, and you should investigate
1169 what the problem is.
1170 The following environment variables are not specific to Perl: They are
1172 part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method
1173 for controlling an application's opinion on data. Windows is non-
1174 POSIX, but Perl arranges for the following to work as described anyway.
1175 If the locale given by an environment variable is not valid, Perl tries
1176 the next lower one in priority. If none are valid, on Windows, the
1177 system default locale is then tried. If all else fails, the "C" locale
1178 is used. If even that doesn't work, something is badly broken, but
1179 Perl tries to forge ahead with whatever the locale settings might be.
1180 "LC_ALL" "LC_ALL" is the "override-all" locale environment variable.
1182 If set, it overrides all the rest of the locale environment
1183 variables.
1184 "LANGUAGE" NOTE: "LANGUAGE" is a GNU extension, it affects you only if
1186 you are using the GNU libc. This is the case if you are
1187 using e.g. Linux. If you are using "commercial" Unixes you
1188 are most probably not using GNU libc and you can ignore
1189 "LANGUAGE".
1190 However, in the case you are using "LANGUAGE": it affects
1192 the language of informational, warning, and error messages
1193 output by commands (in other words, it's like
1194 "LC_MESSAGES") but it has higher priority than "LC_ALL".
1195 Moreover, it's not a single value but instead a "path"
1196 (":"-separated list) of languages (not locales). See the
1197 GNU "gettext" library documentation for more information.
1198 "LC_CTYPE" In the absence of "LC_ALL", "LC_CTYPE" chooses the
1200 character type locale. In the absence of both "LC_ALL" and
1201 "LC_CTYPE", "LANG" chooses the character type locale.
1202 "LC_COLLATE"
1204 In the absence of "LC_ALL", "LC_COLLATE" chooses the
1205 collation (sorting) locale. In the absence of both
1206 "LC_ALL" and "LC_COLLATE", "LANG" chooses the collation
1207 locale.
1208 "LC_MONETARY"
1210 In the absence of "LC_ALL", "LC_MONETARY" chooses the
1211 monetary formatting locale. In the absence of both
1212 "LC_ALL" and "LC_MONETARY", "LANG" chooses the monetary
1213 formatting locale.
1214 "LC_NUMERIC"
1216 In the absence of "LC_ALL", "LC_NUMERIC" chooses the
1217 numeric format locale. In the absence of both "LC_ALL" and
1218 "LC_NUMERIC", "LANG" chooses the numeric format.
1219 "LC_TIME" In the absence of "LC_ALL", "LC_TIME" chooses the date and
1221 time formatting locale. In the absence of both "LC_ALL"
1222 and "LC_TIME", "LANG" chooses the date and time formatting
1223 locale.
1224 "LANG" "LANG" is the "catch-all" locale environment variable. If
1226 it is set, it is used as the last resort after the overall
1227 "LC_ALL" and the category-specific "LC_foo".
1228 Examples
1230 The "LC_NUMERIC" controls the numeric output:
1231 use locale;
1233 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1234 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1235 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1236 and also how strings are parsed by POSIX::strtod() as numbers:
1238 use locale;
1240 use POSIX qw(locale_h strtod);
1241 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1242 my $x = strtod("2,34") + 5;
1243 print $x, "\n"; # Probably shows 7,34.
1244
1246 String "eval" and "LC_NUMERIC"
1247 A string eval parses its expression as standard Perl. It is therefore
1248 expecting the decimal point to be a dot. If "LC_NUMERIC" is set to
1249 have this be a comma instead, the parsing will be confused, perhaps
1250 silently.
1251 use locale;
1253 use POSIX qw(locale_h);
1254 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1255 my $a = 1.2;
1256 print eval "$a + 1.5";
1257 print "\n";
1258 prints "13,5". This is because in that locale, the comma is the
1260 decimal point character. The "eval" thus expands to:
1261 eval "1,2 + 1.5"
1263 and the result is not what you likely expected. No warnings are
1265 generated. If you do string "eval"'s within the scope of "use locale",
1266 you should instead change the "eval" line to do something like:
1267 print eval "no locale; $a + 1.5";
1269 This prints 2.7.
1271 You could also exclude "LC_NUMERIC", if you don't need it, by
1273 use locale ':!numeric';
1275 Backward compatibility
1277 Versions of Perl prior to 5.004 mostly ignored locale information,
1278 generally behaving as if something similar to the "C" locale were
1279 always in force, even if the program environment suggested otherwise
1280 (see "The setlocale function"). By default, Perl still behaves this
1281 way for backward compatibility. If you want a Perl application to pay
1282 attention to locale information, you must use the "use locale" pragma
1283 (see "The "use locale" pragma") or, in the unlikely event that you want
1284 to do so for just pattern matching, the "/l" regular expression
1285 modifier (see "Character set modifiers" in perlre) to instruct it to do
1286 so.
1287 Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE" information
1289 if available; that is, "\w" did understand what were the letters
1290 according to the locale environment variables. The problem was that
1291 the user had no control over the feature: if the C library supported
1292 locales, Perl used them.
1293 I18N:Collate obsolete
1295 In versions of Perl prior to 5.004, per-locale collation was possible
1296 using the "I18N::Collate" library module. This module is now mildly
1297 obsolete and should be avoided in new applications. The "LC_COLLATE"
1298 functionality is now integrated into the Perl core language: One can
1299 use locale-specific scalar data completely normally with "use locale",
1300 so there is no longer any need to juggle with the scalar references of
1301 "I18N::Collate".
1302 Sort speed and memory use impacts
1304 Comparing and sorting by locale is usually slower than the default
1305 sorting; slow-downs of two to four times have been observed. It will
1306 also consume more memory: once a Perl scalar variable has participated
1307 in any string comparison or sorting operation obeying the locale
1308 collation rules, it will take 3-15 times more memory than before. (The
1309 exact multiplier depends on the string's contents, the operating system
1310 and the locale.) These downsides are dictated more by the operating
1311 system's implementation of the locale system than by Perl.
1312 Freely available locale definitions
1314 The Unicode CLDR project extracts the POSIX portion of many of its
1315 locales, available at
1316 https://unicode.org/Public/cldr/2.0.1/
1318 (Newer versions of CLDR require you to compute the POSIX data yourself.
1320 See <http://unicode.org/Public/cldr/latest/>.)
1321 There is a large collection of locale definitions at:
1323 http://std.dkuug.dk/i18n/WG15-collection/locales/
1325 You should be aware that it is unsupported, and is not claimed to be
1327 fit for any purpose. If your system allows installation of arbitrary
1328 locales, you may find the definitions useful as they are, or as a basis
1329 for the development of your own locales.
1330 I18n and l10n
1332 "Internationalization" is often abbreviated as i18n because its first
1333 and last letters are separated by eighteen others. (You may guess why
1334 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1335 the same way, "localization" is often abbreviated to l10n.
1336 An imperfect standard
1338 Internationalization, as defined in the C and POSIX standards, can be
1339 criticized as incomplete and ungainly. They also have a tendency, like
1340 standards groups, to divide the world into nations, when we all know
1341 that the world can equally well be divided into bankers, bikers,
1342 gamers, and so on.
1343
1345 The support of Unicode is new starting from Perl version v5.6, and more
1346 fully implemented in versions v5.8 and later. See perluniintro.
1347 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1349 "LC_COLLATE" is only partially supported; collation support is improved
1350 in Perl v5.26 to a level that may be sufficient for your needs (see
1351 "Category "LC_COLLATE": Collation: Text Comparisons and Sorting").
1352 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1354 use locale ':not_characters';
1356 When this form of the pragma is used, only the non-character portions
1358 of locales are used by Perl, for example "LC_NUMERIC". Perl assumes
1359 that you have translated all the characters it is to operate on into
1360 Unicode (actually the platform's native character set (ASCII or EBCDIC)
1361 plus Unicode). For data in files, this can conveniently be done by
1362 also specifying
1363 use open ':locale';
1365 This pragma arranges for all inputs from files to be translated into
1367 Unicode from the current locale as specified in the environment (see
1368 "ENVIRONMENT"), and all outputs to files to be translated back into the
1369 locale. (See open). On a per-filehandle basis, you can instead use
1370 the PerlIO::locale module, or the Encode::Locale module, both available
1371 from CPAN. The latter module also has methods to ease the handling of
1372 "ARGV" and environment variables, and can be used on individual
1373 strings. If you know that all your locales will be UTF-8, as many are
1374 these days, you can use the -C command line switch.
1375 This form of the pragma allows essentially seamless handling of locales
1377 with Unicode. The collation order will be by Unicode code point order.
1378 Unicode::Collate can be used to get Unicode rules collation.
1379 All the modules and switches just described can be used in v5.20 with
1381 just plain "use locale", and, should the input locales not be UTF-8,
1382 you'll get the less than ideal behavior, described below, that you get
1383 with pre-v5.16 Perls, or when you use the locale pragma without the
1384 ":not_characters" parameter in v5.16 and v5.18. If you are using
1385 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1386 does not apply to you.
1387 There are two cases, multi-byte and single-byte locales. First multi-
1389 byte:
1390 The only multi-byte (or wide character) locale that Perl is ever likely
1392 to support is UTF-8. This is due to the difficulty of implementation,
1393 the fact that high quality UTF-8 locales are now published for every
1394 area of the world (<https://unicode.org/Public/cldr/2.0.1/> for ones
1395 that are already set-up, but from an earlier version;
1396 <https://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1397 you have to extract the POSIX information yourself), and failing all
1398 that, you can use the Encode module to translate to/from your locale.
1399 So, you'll have to do one of those things if you're using one of these
1400 locales, such as Big5 or Shift JIS. For UTF-8 locales, in Perls (pre
1401 v5.20) that don't have full UTF-8 locale support, they may work
1402 reasonably well (depending on your C library implementation) simply
1403 because both they and Perl store characters that take up multiple bytes
1404 the same way. However, some, if not most, C library implementations
1405 may not process the characters in the upper half of the Latin-1 range
1406 (128 - 255) properly under "LC_CTYPE". To see if a character is a
1407 particular type under a locale, Perl uses the functions like isalnum().
1408 Your C library may not work for UTF-8 locales with those functions,
1409 instead only working under the newer wide library functions like
1410 iswalnum(), which Perl does not use. These multi-byte locales are
1411 treated like single-byte locales, and will have the restrictions
1412 described below. Starting in Perl v5.22 a warning message is raised
1413 when Perl detects a multi-byte locale that it doesn't fully support.
1414 For single-byte locales, Perl generally takes the tack to use locale
1416 rules on code points that can fit in a single byte, and Unicode rules
1417 for those that can't (though this isn't uniformly applied, see the note
1418 at the end of this section). This prevents many problems in locales
1419 that aren't UTF-8. Suppose the locale is ISO8859-7, Greek. The
1420 character at 0xD7 there is a capital Chi. But in the ISO8859-1 locale,
1421 Latin1, it is a multiplication sign. The POSIX regular expression
1422 character class "[[:alpha:]]" will magically match 0xD7 in the Greek
1423 locale but not in the Latin one.
1424 However, there are places where this breaks down. Certain Perl
1426 constructs are for Unicode only, such as "\p{Alpha}". They assume that
1427 0xD7 always has its Unicode meaning (or the equivalent on EBCDIC
1428 platforms). Since Latin1 is a subset of Unicode and 0xD7 is the
1429 multiplication sign in both Latin1 and Unicode, "\p{Alpha}" will never
1430 match it, regardless of locale. A similar issue occurs with "\N{...}".
1431 Prior to v5.20, it is therefore a bad idea to use "\p{}" or "\N{}"
1432 under plain "use locale"--unless you can guarantee that the locale will
1433 be ISO8859-1. Use POSIX character classes instead.
1434 Another problem with this approach is that operations that cross the
1436 single byte/multiple byte boundary are not well-defined, and so are
1437 disallowed. (This boundary is between the codepoints at 255/256.) For
1438 example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1439 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1440 Greek locale, for example, there is no character at 0xFF, and Perl has
1441 no way of knowing what the character at 0xFF is really supposed to
1442 represent. Thus it disallows the operation. In this mode, the
1443 lowercase of U+0178 is itself.
1444 The same problems ensue if you enable automatic UTF-8-ification of your
1446 standard file handles, default open() layer, and @ARGV on
1447 non-ISO8859-1, non-UTF-8 locales (by using either the -C command line
1448 switch or the "PERL_UNICODE" environment variable; see perlrun).
1449 Things are read in as UTF-8, which would normally imply a Unicode
1450 interpretation, but the presence of a locale causes them to be
1451 interpreted in that locale instead. For example, a 0xD7 code point in
1452 the Unicode input, which should mean the multiplication sign, won't be
1453 interpreted by Perl that way under the Greek locale. This is not a
1454 problem provided you make certain that all locales will always and only
1455 be either an ISO8859-1, or, if you don't have a deficient C library, a
1456 UTF-8 locale.
1457 Still another problem is that this approach can lead to two code points
1459 meaning the same character. Thus in a Greek locale, both U+03A7 and
1460 U+00D7 are GREEK CAPITAL LETTER CHI.
1461 Because of all these problems, starting in v5.22, Perl will raise a
1463 warning if a multi-byte (hence Unicode) code point is used when a
1464 single-byte locale is in effect. (Although it doesn't check for this
1465 if doing so would unreasonably slow execution down.)
1466 Vendor locales are notoriously buggy, and it is difficult for Perl to
1468 test its locale-handling code because this interacts with code that
1469 Perl has no control over; therefore the locale-handling code in Perl
1470 may be buggy as well. (However, the Unicode-supplied locales should be
1471 better, and there is a feed back mechanism to correct any problems.
1472 See "Freely available locale definitions".)
1473 If you have Perl v5.16, the problems mentioned above go away if you use
1475 the ":not_characters" parameter to the locale pragma (except for vendor
1476 bugs in the non-character portions). If you don't have v5.16, and you
1477 do have locales that work, using them may be worthwhile for certain
1478 specific purposes, as long as you keep in mind the gotchas already
1479 mentioned. For example, if the collation for your locales works, it
1480 runs faster under locales than under Unicode::Collate; and you gain
1481 access to such things as the local currency symbol and the names of the
1482 months and days of the week. (But to hammer home the point, in v5.16,
1483 you get this access without the downsides of locales by using the
1484 ":not_characters" form of the pragma.)
1485 Note: The policy of using locale rules for code points that can fit in
1487 a byte, and Unicode rules for those that can't is not uniformly
1488 applied. Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied
1489 fairly consistently to regular expression matching except for bracketed
1490 character classes; in v5.14 it was extended to all regex matches; and
1491 in v5.16 to the casing operations such as "\L" and uc(). For
1492 collation, in all releases so far, the system's strxfrm() function is
1493 called, and whatever it does is what you get. Starting in v5.26,
1494 various bugs are fixed with the way perl uses this function.
1495
1497 Collation of strings containing embedded "NUL" characters
1498 "NUL" characters will sort the same as the lowest collating control
1499 character does, or to "\001" in the unlikely event that there are no
1500 control characters at all in the locale. In cases where the strings
1501 don't contain this non-"NUL" control, the results will be correct, and
1502 in many locales, this control, whatever it might be, will rarely be
1503 encountered. But there are cases where a "NUL" should sort before this
1504 control, but doesn't. If two strings do collate identically, the one
1505 containing the "NUL" will sort to earlier. Prior to 5.26, there were
1506 more bugs.
1507 Multi-threaded
1509 XS code or C-language libraries called from it that use the system
1510 setlocale(3) function (except on Windows) likely will not work from a
1511 multi-threaded application without changes. See "Locale-aware XS code"
1512 in perlxs.
1513 An XS module that is locale-dependent could have been written under the
1515 assumption that it will never be called in a multi-threaded
1516 environment, and so uses other non-locale constructs that aren't multi-
1517 thread-safe. See "Thread-aware system interfaces" in perlxs.
1518 POSIX does not define a way to get the name of the current per-thread
1520 locale. Some systems, such as Darwin and FreeBSD do implement a
1521 function, querylocale(3) to do this. On non-Windows systems without
1522 it, such as Linux, there are some additional caveats:
1523 • An embedded perl needs to be started up while the global locale is
1525 in effect. See "Using embedded Perl with POSIX locales" in
1526 perlembed.
1527 • It becomes more important for perl to know about all the possible
1529 locale categories on the platform, even if they aren't apparently
1530 used in your program. Perl knows all of the Linux ones. If your
1531 platform has others, you can submit an issue at
1532 <https://github.com/Perl/perl5/issues> for inclusion of it in the
1533 next release. In the meantime, it is possible to edit the Perl
1534 source to teach it about the category, and then recompile. Search
1535 for instances of, say, "LC_PAPER" in the source, and use that as a
1536 template to add the omitted one.
1537 • It is possible, though hard to do, to call "POSIX::setlocale" with
1539 a locale that it doesn't recognize as syntactically legal, but
1540 actually is legal on that system. This should happen only with
1541 embedded perls, or if you hand-craft a locale name yourself.
1542 Broken systems
1544 In certain systems, the operating system's locale support is broken and
1545 cannot be fixed or used by Perl. Such deficiencies can and will result
1546 in mysterious hangs and/or Perl core dumps when "use locale" is in
1547 effect. When confronted with such a system, please report in
1548 excruciating detail to <<https://github.com/Perl/perl5/issues>>, and
1549 also contact your vendor: bug fixes may exist for these problems in
1550 your operating system. Sometimes such bug fixes are called an
1551 operating system upgrade. If you have the source for Perl, include in
1552 the bug report the output of the test described above in "Testing for
1553 broken locales".
1554
1556 I18N::Langinfo, perluniintro, perlunicode, open, "localeconv" in POSIX,
1557 "setlocale" in POSIX, "strcoll" in POSIX, "strftime" in POSIX, "strtod"
1558 in POSIX, "strxfrm" in POSIX.
1559 For special considerations when Perl is embedded in a C program, see
1561 "Using embedded Perl with POSIX locales" in perlembed.
1562
1564 Jarkko Hietaniemi's original perli18n.pod heavily hacked by Dominic
1565 Dunlop, assisted by the perl5-porters. Prose worked over a bit by Tom
1566 Christiansen, and now maintained by Perl 5 porters.
1567perl v5.38.2 2023-11-30 PERLLOCALE(1)