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. Perl continues to support the old non
45 UTF-8 locales as well. There are currently no UTF-8 locales for EBCDIC
46 platforms.
47 (Unicode is also creating "CLDR", the "Common Locale Data Repository",
49 <http://cldr.unicode.org/> which includes more types of information
50 than are available in the POSIX locale system. At the time of this
51 writing, there was no CPAN module that provides access to this XML-
52 encoded data. However, it is possible to compute the POSIX locale data
53 from them, and earlier CLDR versions had these already extracted for
54 you as UTF-8 locales <http://unicode.org/Public/cldr/2.0.1/>.)
55
57 A locale is a set of data that describes various aspects of how various
58 communities in the world categorize their world. These categories are
59 broken down into the following types (some of which include a brief
60 note here):
61 Category "LC_NUMERIC": Numeric formatting
63 This indicates how numbers should be formatted for human
64 readability, for example the character used as the decimal point.
65 Category "LC_MONETARY": Formatting of monetary amounts
67 Category "LC_TIME": Date/Time formatting
70 Category "LC_MESSAGES": Error and other messages
73 This is used by Perl itself only for accessing operating system
74 error messages via $! and $^E.
75 Category "LC_COLLATE": Collation
77 This indicates the ordering of letters for comparison and sorting.
78 In Latin alphabets, for example, "b", generally follows "a".
79 Category "LC_CTYPE": Character Types
81 This indicates, for example if a character is an uppercase letter.
82 Other categories
84 Some platforms have other categories, dealing with such things as
85 measurement units and paper sizes. None of these are used directly
86 by Perl, but outside operations that Perl interacts with may use
87 these. See "Not within the scope of "use locale"" below.
88 More details on the categories used by Perl are given below in "LOCALE
90 CATEGORIES".
91 Together, these categories go a long way towards being able to
93 customize a single program to run in many different locations. But
94 there are deficiencies, so keep reading.
95
97 Perl itself (outside the POSIX module) will not use locales unless
98 specifically requested to (but again note that Perl may interact with
99 code that does use them). Even if there is such a request, all of the
100 following must be true for it to work properly:
101 · Your operating system must support the locale system. If it does,
103 you should find that the "setlocale()" function is a documented
104 part of its C library.
105 · Definitions for locales that you use must be installed. You, or
107 your system administrator, must make sure that this is the case.
108 The available locales, the location in which they are kept, and the
109 manner in which they are installed all vary from system to system.
110 Some systems provide only a few, hard-wired locales and do not
111 allow more to be added. Others allow you to add "canned" locales
112 provided by the system supplier. Still others allow you or the
113 system administrator to define and add arbitrary locales. (You may
114 have to ask your supplier to provide canned locales that are not
115 delivered with your operating system.) Read your system
116 documentation for further illumination.
117 · Perl must believe that the locale system is supported. If it does,
119 "perl -V:d_setlocale" will say that the value for "d_setlocale" is
120 "define".
121 If you want a Perl application to process and present your data
123 according to a particular locale, the application code should include
124 the "use locale" pragma (see "The "use locale" pragma") where
125 appropriate, and at least one of the following must be true:
126 1. The locale-determining environment variables (see "ENVIRONMENT")
128 must be correctly set up at the time the application is started,
129 either by yourself or by whomever set up your system account; or
130 2. The application must set its own locale using the method described
132 in "The setlocale function".
133
135 The "use locale" pragma
136 Starting in Perl 5.28, this pragma may be used in multi-threaded
137 applications on systems that have thread-safe locale ability. Some
138 caveats apply, see "Multi-threaded" below. On systems without this
139 capability, or in earlier Perls, do NOT use this pragma in scripts that
140 have multiple threads active. The locale in these cases is not local
141 to a single thread. Another thread may change the locale at any time,
142 which could cause at a minimum that a given thread is operating in a
143 locale it isn't expecting to be in. On some platforms, segfaults can
144 also occur. The locale change need not be explicit; some operations
145 cause perl to change the locale itself. You are vulnerable simply by
146 having done a "use locale".
147 By default, Perl itself (outside the POSIX module) ignores the current
149 locale. The "use locale" pragma tells Perl to use the current locale
150 for some operations. Starting in v5.16, there are optional parameters
151 to this pragma, described below, which restrict which operations are
152 affected by it.
153 The current locale is set at execution time by setlocale() described
155 below. If that function hasn't yet been called in the course of the
156 program's execution, the current locale is that which was determined by
157 the "ENVIRONMENT" in effect at the start of the program. If there is
158 no valid environment, the current locale is whatever the system default
159 has been set to. On POSIX systems, it is likely, but not necessarily,
160 the "C" locale. On Windows, the default is set via the computer's
161 "Control Panel->Regional and Language Options" (or its current
162 equivalent).
163 The operations that are affected by locale are:
165 Not within the scope of "use locale"
167 Only certain operations (all originating outside Perl) should be
168 affected, as follows:
169 · The current locale is used when going outside of Perl with
171 operations like system() or qx//, if those operations are
172 locale-sensitive.
173 · Also Perl gives access to various C library functions through
175 the POSIX module. Some of those functions are always affected
176 by the current locale. For example, "POSIX::strftime()" uses
177 "LC_TIME"; "POSIX::strtod()" uses "LC_NUMERIC";
178 "POSIX::strcoll()" and "POSIX::strxfrm()" use "LC_COLLATE".
179 All such functions will behave according to the current
180 underlying locale, even if that locale isn't exposed to Perl
181 space.
182 This applies as well to I18N::Langinfo.
184 · XS modules for all categories but "LC_NUMERIC" get the
186 underlying locale, and hence any C library functions they call
187 will use that underlying locale. For more discussion, see
188 "CAVEATS" in perlxs.
189 Note that all C programs (including the perl interpreter, which is
191 written in C) always have an underlying locale. That locale is the
192 "C" locale unless changed by a call to setlocale(). When Perl
193 starts up, it changes the underlying locale to the one which is
194 indicated by the "ENVIRONMENT". When using the POSIX module or
195 writing XS code, it is important to keep in mind that the
196 underlying locale may be something other than "C", even if the
197 program hasn't explicitly changed it.
198 Lingering effects of "use locale"
202 Certain Perl operations that are set-up within the scope of a "use
203 locale" retain that effect even outside the scope. These include:
204 · The output format of a write() is determined by an earlier
206 format declaration ("format" in perlfunc), so whether or not
207 the output is affected by locale is determined by if the
208 "format()" is within the scope of a "use locale", not whether
209 the "write()" is.
210 · Regular expression patterns can be compiled using qr// with
212 actual matching deferred to later. Again, it is whether or not
213 the compilation was done within the scope of "use locale" that
214 determines the match behavior, not if the matches are done
215 within such a scope or not.
216 Under ""use locale";"
220 · All the above operations
221 · Format declarations ("format" in perlfunc) and hence any
223 subsequent "write()"s use "LC_NUMERIC".
224 · stringification and output use "LC_NUMERIC". These include the
226 results of "print()", "printf()", "say()", and "sprintf()".
227 · The comparison operators ("lt", "le", "cmp", "ge", and "gt")
229 use "LC_COLLATE". "sort()" is also affected if used without an
230 explicit comparison function, because it uses "cmp" by default.
231 Note: "eq" and "ne" are unaffected by locale: they always
233 perform a char-by-char comparison of their scalar operands.
234 What's more, if "cmp" finds that its operands are equal
235 according to the collation sequence specified by the current
236 locale, it goes on to perform a char-by-char comparison, and
237 only returns 0 (equal) if the operands are char-for-char
238 identical. If you really want to know whether two
239 strings--which "eq" and "cmp" may consider different--are equal
240 as far as collation in the locale is concerned, see the
241 discussion in "Category "LC_COLLATE": Collation".
242 · Regular expressions and case-modification functions ("uc()",
244 "lc()", "ucfirst()", and "lcfirst()") use "LC_CTYPE"
245 · The variables $! (and its synonyms $ERRNO and $OS_ERROR) and
247 $^E (and its synonym $EXTENDED_OS_ERROR) when used as strings
248 use "LC_MESSAGES".
249 The default behavior is restored with the "no locale" pragma, or upon
251 reaching the end of the block enclosing "use locale". Note that "use
252 locale" calls may be nested, and that what is in effect within an inner
253 scope will revert to the outer scope's rules at the end of the inner
254 scope.
255 The string result of any operation that uses locale information is
257 tainted, as it is possible for a locale to be untrustworthy. See
258 "SECURITY".
259 Starting in Perl v5.16 in a very limited way, and more generally in
261 v5.22, you can restrict which category or categories are enabled by
262 this particular instance of the pragma by adding parameters to it. For
263 example,
264 use locale qw(:ctype :numeric);
266 enables locale awareness within its scope of only those operations
268 (listed above) that are affected by "LC_CTYPE" and "LC_NUMERIC".
269 The possible categories are: ":collate", ":ctype", ":messages",
271 ":monetary", ":numeric", ":time", and the pseudo category ":characters"
272 (described below).
273 Thus you can say
275 use locale ':messages';
277 and only $! and $^E will be locale aware. Everything else is
279 unaffected.
280 Since Perl doesn't currently do anything with the "LC_MONETARY"
282 category, specifying ":monetary" does effectively nothing. Some
283 systems have other categories, such as "LC_PAPER", but Perl also
284 doesn't do anything with them, and there is no way to specify them in
285 this pragma's arguments.
286 You can also easily say to use all categories but one, by either, for
288 example,
289 use locale ':!ctype';
291 use locale ':not_ctype';
292 both of which mean to enable locale awarness of all categories but
294 "LC_CTYPE". Only one category argument may be specified in a
295 "use locale" if it is of the negated form.
296 Prior to v5.22 only one form of the pragma with arguments is available:
298 use locale ':not_characters';
300 (and you have to say "not_"; you can't use the bang "!" form). This
302 pseudo category is a shorthand for specifying both ":collate" and
303 ":ctype". Hence, in the negated form, it is nearly the same thing as
304 saying
305 use locale qw(:messages :monetary :numeric :time);
307 We use the term "nearly", because ":not_characters" also turns on
309 "use feature 'unicode_strings'" within its scope. This form is less
310 useful in v5.20 and later, and is described fully in "Unicode and
311 UTF-8", but briefly, it tells Perl to not use the character portions of
312 the locale definition, that is the "LC_CTYPE" and "LC_COLLATE"
313 categories. Instead it will use the native character set (extended by
314 Unicode). When using this parameter, you are responsible for getting
315 the external character set translated into the native/Unicode one
316 (which it already will be if it is one of the increasingly popular
317 UTF-8 locales). There are convenient ways of doing this, as described
318 in "Unicode and UTF-8".
319 The setlocale function
321 WARNING! Prior to Perl 5.28 or on a system that does not support
322 thread-safe locale operations, do NOT use this function in a thread.
323 The locale will change in all other threads at the same time, and
324 should your thread get paused by the operating system, and another
325 started, that thread will not have the locale it is expecting. On some
326 platforms, there can be a race leading to segfaults if two threads call
327 this function nearly simultaneously.
328 You can switch locales as often as you wish at run time with the
330 "POSIX::setlocale()" function:
331 # Import locale-handling tool set from POSIX module.
333 # This example uses: setlocale -- the function call
334 # LC_CTYPE -- explained below
335 # (Showing the testing for success/failure of operations is
336 # omitted in these examples to avoid distracting from the main
337 # point)
338 use POSIX qw(locale_h);
340 use locale;
341 my $old_locale;
342 # query and save the old locale
344 $old_locale = setlocale(LC_CTYPE);
345 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
347 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
348 setlocale(LC_CTYPE, "");
350 # LC_CTYPE now reset to the default defined by the
351 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
352 # default. See below for documentation.
353 # restore the old locale
355 setlocale(LC_CTYPE, $old_locale);
356 The first argument of "setlocale()" gives the category, the second the
358 locale. The category tells in what aspect of data processing you want
359 to apply locale-specific rules. Category names are discussed in
360 "LOCALE CATEGORIES" and "ENVIRONMENT". The locale is the name of a
361 collection of customization information corresponding to a particular
362 combination of language, country or territory, and codeset. Read on
363 for hints on the naming of locales: not all systems name locales as in
364 the example.
365 If no second argument is provided and the category is something other
367 than "LC_ALL", the function returns a string naming the current locale
368 for the category. You can use this value as the second argument in a
369 subsequent call to "setlocale()", but on some platforms the string is
370 opaque, not something that most people would be able to decipher as to
371 what locale it means.
372 If no second argument is provided and the category is "LC_ALL", the
374 result is implementation-dependent. It may be a string of concatenated
375 locale names (separator also implementation-dependent) or a single
376 locale name. Please consult your setlocale(3) man page for details.
377 If a second argument is given and it corresponds to a valid locale, the
379 locale for the category is set to that value, and the function returns
380 the now-current locale value. You can then use this in yet another
381 call to "setlocale()". (In some implementations, the return value may
382 sometimes differ from the value you gave as the second argument--think
383 of it as an alias for the value you gave.)
384 As the example shows, if the second argument is an empty string, the
386 category's locale is returned to the default specified by the
387 corresponding environment variables. Generally, this results in a
388 return to the default that was in force when Perl started up: changes
389 to the environment made by the application after startup may or may not
390 be noticed, depending on your system's C library.
391 Note that when a form of "use locale" that doesn't include all
393 categories is specified, Perl ignores the excluded categories.
394 If "set_locale()" fails for some reason (for example, an attempt to set
396 to a locale unknown to the system), the locale for the category is not
397 changed, and the function returns "undef".
398 Starting in Perl 5.28, on multi-threaded perls compiled on systems that
400 implement POSIX 2008 thread-safe locale operations, this function
401 doesn't actually call the system "setlocale". Instead those thread-
402 safe operations are used to emulate the "setlocale" function, but in a
403 thread-safe manner.
404 For further information about the categories, consult setlocale(3).
406 Multi-threaded operation
408 Beginning in Perl 5.28, multi-threaded locale operation is supported on
409 systems that implement either the POSIX 2008 or Windows-specific
410 thread-safe locale operations. Many modern systems, such as various
411 Unix variants and Darwin do have this.
412 You can tell if using locales is safe on your system by looking at the
414 read-only boolean variable "${^SAFE_LOCALES}". The value is 1 if the
415 perl is not threaded, or if it is using thread-safe locale operations.
416 Thread-safe operations are supported in Windows starting in Visual
418 Studio 2005, and in systems compatible with POSIX 2008. Some platforms
419 claim to support POSIX 2008, but have buggy implementations, so that
420 the hints files for compiling to run on them turn off attempting to use
421 thread-safety. "${^SAFE_LOCALES}" will be 0 on them.
422 Be aware that writing a multi-threaded application will not be portable
424 to a platform which lacks the native thread-safe locale support. On
425 systems that do have it, you automatically get this behavior for
426 threaded perls, without having to do anything. If for some reason, you
427 don't want to use this capability (perhaps the POSIX 2008 support is
428 buggy on your system), you can manually compile Perl to use the old
429 non-thread-safe implementation by passing the argument
430 "-Accflags='-DNO_THREAD_SAFE_LOCALE'" to Configure. Except on Windows,
431 this will continue to use certain of the POSIX 2008 functions in some
432 situations. If these are buggy, you can pass the following to
433 Configure instead or additionally:
434 "-Accflags='-DNO_POSIX_2008_LOCALE'". This will also keep the code
435 from using thread-safe locales. "${^SAFE_LOCALES}" will be 0 on
436 systems that turn off the thread-safe operations.
437 The initial program is started up using the locale specified from the
439 environment, as currently, described in "ENVIRONMENT". All newly
440 created threads start with "LC_ALL" set to "C">. Each thread may use
441 "POSIX::setlocale()" to query or switch its locale at any time, without
442 affecting any other thread. All locale-dependent operations
443 automatically use their thread's locale.
444 This should be completely transparent to any applications written
446 entirely in Perl (minus a few rarely encountered caveats given in the
447 "Multi-threaded" section). Information for XS module writers is given
448 in "Locale-aware XS code" in perlxs.
449 Finding locales
451 For locales available in your system, consult also setlocale(3) to see
452 whether it leads to the list of available locales (search for the SEE
453 ALSO section). If that fails, try the following command lines:
454 locale -a
456 nlsinfo
458 ls /usr/lib/nls/loc
460 ls /usr/lib/locale
462 ls /usr/lib/nls
464 ls /usr/share/locale
466 and see whether they list something resembling these
468 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
470 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
471 en_US de_DE ru_RU
472 en de ru
473 english german russian
474 english.iso88591 german.iso88591 russian.iso88595
475 english.roman8 russian.koi8r
476 Sadly, even though the calling interface for "setlocale()" has been
478 standardized, names of locales and the directories where the
479 configuration resides have not been. The basic form of the name is
480 language_territory.codeset, but the latter parts after language are not
481 always present. The language and country are usually from the
482 standards ISO 3166 and ISO 639, the two-letter abbreviations for the
483 countries and the languages of the world, respectively. The codeset
484 part often mentions some ISO 8859 character set, the Latin codesets.
485 For example, "ISO 8859-1" is the so-called "Western European codeset"
486 that can be used to encode most Western European languages adequately.
487 Again, there are several ways to write even the name of that one
488 standard. Lamentably.
489 Two special locales are worth particular mention: "C" and "POSIX".
491 Currently these are effectively the same locale: the difference is
492 mainly that the first one is defined by the C standard, the second by
493 the POSIX standard. They define the default locale in which every
494 program starts in the absence of locale information in its environment.
495 (The default default locale, if you will.) Its language is (American)
496 English and its character codeset ASCII or, rarely, a superset thereof
497 (such as the "DEC Multinational Character Set (DEC-MCS)"). Warning.
498 The C locale delivered by some vendors may not actually exactly match
499 what the C standard calls for. So beware.
500 NOTE: Not all systems have the "POSIX" locale (not all systems are
502 POSIX-conformant), so use "C" when you need explicitly to specify this
503 default locale.
504 LOCALE PROBLEMS
506 You may encounter the following warning message at Perl startup:
507 perl: warning: Setting locale failed.
509 perl: warning: Please check that your locale settings:
510 LC_ALL = "En_US",
511 LANG = (unset)
512 are supported and installed on your system.
513 perl: warning: Falling back to the standard locale ("C").
514 This means that your locale settings had "LC_ALL" set to "En_US" and
516 LANG exists but has no value. Perl tried to believe you but could not.
517 Instead, Perl gave up and fell back to the "C" locale, the default
518 locale that is supposed to work no matter what. (On Windows, it first
519 tries falling back to the system default locale.) This usually means
520 your locale settings were wrong, they mention locales your system has
521 never heard of, or the locale installation in your system has problems
522 (for example, some system files are broken or missing). There are
523 quick and temporary fixes to these problems, as well as more thorough
524 and lasting fixes.
525 Testing for broken locales
527 If you are building Perl from source, the Perl test suite file
528 lib/locale.t can be used to test the locales on your system. Setting
529 the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it to
530 output detailed results. For example, on Linux, you could say
531 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
533 Besides many other tests, it will test every locale it finds on your
535 system to see if they conform to the POSIX standard. If any have
536 errors, it will include a summary near the end of the output of which
537 locales passed all its tests, and which failed, and why.
538 Temporarily fixing locale problems
540 The two quickest fixes are either to render Perl silent about any
541 locale inconsistencies or to run Perl under the default locale "C".
542 Perl's moaning about locale problems can be silenced by setting the
544 environment variable "PERL_BADLANG" to "0" or "". This method really
545 just sweeps the problem under the carpet: you tell Perl to shut up even
546 when Perl sees that something is wrong. Do not be surprised if later
547 something locale-dependent misbehaves.
548 Perl can be run under the "C" locale by setting the environment
550 variable "LC_ALL" to "C". This method is perhaps a bit more civilized
551 than the "PERL_BADLANG" approach, but setting "LC_ALL" (or other locale
552 variables) may affect other programs as well, not just Perl. In
553 particular, external programs run from within Perl will see these
554 changes. If you make the new settings permanent (read on), all
555 programs you run see the changes. See "ENVIRONMENT" for the full list
556 of relevant environment variables and "USING LOCALES" for their effects
557 in Perl. Effects in other programs are easily deducible. For example,
558 the variable "LC_COLLATE" may well affect your sort program (or
559 whatever the program that arranges "records" alphabetically in your
560 system is called).
561 You can test out changing these variables temporarily, and if the new
563 settings seem to help, put those settings into your shell startup
564 files. Consult your local documentation for the exact details. For
565 Bourne-like shells (sh, ksh, bash, zsh):
566 LC_ALL=en_US.ISO8859-1
568 export LC_ALL
569 This assumes that we saw the locale "en_US.ISO8859-1" using the
571 commands discussed above. We decided to try that instead of the above
572 faulty locale "En_US"--and in Cshish shells (csh, tcsh)
573 setenv LC_ALL en_US.ISO8859-1
575 or if you have the "env" application you can do (in any shell)
577 env LC_ALL=en_US.ISO8859-1 perl ...
579 If you do not know what shell you have, consult your local helpdesk or
581 the equivalent.
582 Permanently fixing locale problems
584 The slower but superior fixes are when you may be able to yourself fix
585 the misconfiguration of your own environment variables. The
586 mis(sing)configuration of the whole system's locales usually requires
587 the help of your friendly system administrator.
588 First, see earlier in this document about "Finding locales". That
590 tells how to find which locales are really supported--and more
591 importantly, installed--on your system. In our example error message,
592 environment variables affecting the locale are listed in the order of
593 decreasing importance (and unset variables do not matter). Therefore,
594 having LC_ALL set to "En_US" must have been the bad choice, as shown by
595 the error message. First try fixing locale settings listed first.
596 Second, if using the listed commands you see something exactly (prefix
598 matches do not count and case usually counts) like "En_US" without the
599 quotes, then you should be okay because you are using a locale name
600 that should be installed and available in your system. In this case,
601 see "Permanently fixing your system's locale configuration".
602 Permanently fixing your system's locale configuration
604 This is when you see something like:
605 perl: warning: Please check that your locale settings:
607 LC_ALL = "En_US",
608 LANG = (unset)
609 are supported and installed on your system.
610 but then cannot see that "En_US" listed by the above-mentioned
612 commands. You may see things like "en_US.ISO8859-1", but that isn't
613 the same. In this case, try running under a locale that you can list
614 and which somehow matches what you tried. The rules for matching
615 locale names are a bit vague because standardization is weak in this
616 area. See again the "Finding locales" about general rules.
617 Fixing system locale configuration
619 Contact a system administrator (preferably your own) and report the
620 exact error message you get, and ask them to read this same
621 documentation you are now reading. They should be able to check
622 whether there is something wrong with the locale configuration of the
623 system. The "Finding locales" section is unfortunately a bit vague
624 about the exact commands and places because these things are not that
625 standardized.
626 The localeconv function
628 The "POSIX::localeconv()" function allows you to get particulars of the
629 locale-dependent numeric formatting information specified by the
630 current underlying "LC_NUMERIC" and "LC_MONETARY" locales (regardless
631 of whether called from within the scope of "use locale" or not). (If
632 you just want the name of the current locale for a particular category,
633 use "POSIX::setlocale()" with a single parameter--see "The setlocale
634 function".)
635 use POSIX qw(locale_h);
637 # Get a reference to a hash of locale-dependent info
639 $locale_values = localeconv();
640 # Output sorted list of the values
642 for (sort keys %$locale_values) {
643 printf "%-20s = %s\n", $_, $locale_values->{$_}
644 }
645 "localeconv()" takes no arguments, and returns a reference to a hash.
647 The keys of this hash are variable names for formatting, such as
648 "decimal_point" and "thousands_sep". The values are the corresponding,
649 er, values. See "localeconv" in POSIX for a longer example listing the
650 categories an implementation might be expected to provide; some provide
651 more and others fewer. You don't need an explicit "use locale",
652 because "localeconv()" always observes the current locale.
653 Here's a simple-minded example program that rewrites its command-line
655 parameters as integers correctly formatted in the current locale:
656 use POSIX qw(locale_h);
658 # Get some of locale's numeric formatting parameters
660 my ($thousands_sep, $grouping) =
661 @{localeconv()}{'thousands_sep', 'grouping'};
662 # Apply defaults if values are missing
664 $thousands_sep = ',' unless $thousands_sep;
665 # grouping and mon_grouping are packed lists
667 # of small integers (characters) telling the
668 # grouping (thousand_seps and mon_thousand_seps
669 # being the group dividers) of numbers and
670 # monetary quantities. The integers' meanings:
671 # 255 means no more grouping, 0 means repeat
672 # the previous grouping, 1-254 means use that
673 # as the current grouping. Grouping goes from
674 # right to left (low to high digits). In the
675 # below we cheat slightly by never using anything
676 # else than the first grouping (whatever that is).
677 if ($grouping) {
678 @grouping = unpack("C*", $grouping);
679 } else {
680 @grouping = (3);
681 }
682 # Format command line params for current locale
684 for (@ARGV) {
685 $_ = int; # Chop non-integer part
686 1 while
687 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
688 print "$_";
689 }
690 print "\n";
691 Note that if the platform doesn't have "LC_NUMERIC" and/or
693 "LC_MONETARY" available or enabled, the corresponding elements of the
694 hash will be missing.
695 I18N::Langinfo
697 Another interface for querying locale-dependent information is the
698 "I18N::Langinfo::langinfo()" function.
699 The following example will import the "langinfo()" function itself and
701 three constants to be used as arguments to "langinfo()": a constant for
702 the abbreviated first day of the week (the numbering starts from Sunday
703 = 1) and two more constants for the affirmative and negative answers
704 for a yes/no question in the current locale.
705 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
707 my ($abday_1, $yesstr, $nostr)
709 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
710 print "$abday_1? [$yesstr/$nostr] ";
712 In other words, in the "C" (or English) locale the above will probably
714 print something like:
715 Sun? [yes/no]
717 See I18N::Langinfo for more information.
719
721 The following subsections describe basic locale categories. Beyond
722 these, some combination categories allow manipulation of more than one
723 basic category at a time. See "ENVIRONMENT" for a discussion of these.
724 Category "LC_COLLATE": Collation: Text Comparisons and Sorting
726 In the scope of a "use locale" form that includes collation, Perl looks
727 to the "LC_COLLATE" environment variable to determine the application's
728 notions on collation (ordering) of characters. For example, "b"
729 follows "a" in Latin alphabets, but where do "a" and "aa" belong? And
730 while "color" follows "chocolate" in English, what about in traditional
731 Spanish?
732 The following collations all make sense and you may meet any of them if
734 you "use locale".
735 A B C D E a b c d e
737 A a B b C c D d E e
738 a A b B c C d D e E
739 a b c d e A B C D E
740 Here is a code snippet to tell what "word" characters are in the
742 current locale, in that locale's order:
743 use locale;
745 print +(sort grep /\w/, map { chr } 0..255), "\n";
746 Compare this with the characters that you see and their order if you
748 state explicitly that the locale should be ignored:
749 no locale;
751 print +(sort grep /\w/, map { chr } 0..255), "\n";
752 This machine-native collation (which is what you get unless
754 "use locale" has appeared earlier in the same block) must be used for
755 sorting raw binary data, whereas the locale-dependent collation of the
756 first example is useful for natural text.
757 As noted in "USING LOCALES", "cmp" compares according to the current
759 collation locale when "use locale" is in effect, but falls back to a
760 char-by-char comparison for strings that the locale says are equal. You
761 can use "POSIX::strcoll()" if you don't want this fall-back:
762 use POSIX qw(strcoll);
764 $equal_in_locale =
765 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
766 $equal_in_locale will be true if the collation locale specifies a
768 dictionary-like ordering that ignores space characters completely and
769 which folds case.
770 Perl uses the platform's C library collation functions "strcoll()" and
772 "strxfrm()". That means you get whatever they give. On some
773 platforms, these functions work well on UTF-8 locales, giving a
774 reasonable default collation for the code points that are important in
775 that locale. (And if they aren't working well, the problem may only be
776 that the locale definition is deficient, so can be fixed by using a
777 better definition file. Unicode's definitions (see "Freely available
778 locale definitions") provide reasonable UTF-8 locale collation
779 definitions.) Starting in Perl v5.26, Perl's use of these functions
780 has been made more seamless. This may be sufficient for your needs.
781 For more control, and to make sure strings containing any code point
782 (not just the ones important in the locale) collate properly, the
783 Unicode::Collate module is suggested.
784 In non-UTF-8 locales (hence single byte), code points above 0xFF are
786 technically invalid. But if present, again starting in v5.26, they
787 will collate to the same position as the highest valid code point does.
788 This generally gives good results, but the collation order may be
789 skewed if the valid code point gets special treatment when it forms
790 particular sequences with other characters as defined by the locale.
791 When two strings collate identically, the code point order is used as a
792 tie breaker.
793 If Perl detects that there are problems with the locale collation
795 order, it reverts to using non-locale collation rules for that locale.
796 If you have a single string that you want to check for "equality in
798 locale" against several others, you might think you could gain a little
799 efficiency by using "POSIX::strxfrm()" in conjunction with "eq":
800 use POSIX qw(strxfrm);
802 $xfrm_string = strxfrm("Mixed-case string");
803 print "locale collation ignores spaces\n"
804 if $xfrm_string eq strxfrm("Mixed-casestring");
805 print "locale collation ignores hyphens\n"
806 if $xfrm_string eq strxfrm("Mixedcase string");
807 print "locale collation ignores case\n"
808 if $xfrm_string eq strxfrm("mixed-case string");
809 "strxfrm()" takes a string and maps it into a transformed string for
811 use in char-by-char comparisons against other transformed strings
812 during collation. "Under the hood", locale-affected Perl comparison
813 operators call "strxfrm()" for both operands, then do a char-by-char
814 comparison of the transformed strings. By calling "strxfrm()"
815 explicitly and using a non locale-affected comparison, the example
816 attempts to save a couple of transformations. But in fact, it doesn't
817 save anything: Perl magic (see "Magic Variables" in perlguts) creates
818 the transformed version of a string the first time it's needed in a
819 comparison, then keeps this version around in case it's needed again.
820 An example rewritten the easy way with "cmp" runs just about as fast.
821 It also copes with null characters embedded in strings; if you call
822 "strxfrm()" directly, it treats the first null it finds as a
823 terminator. Don't expect the transformed strings it produces to be
824 portable across systems--or even from one revision of your operating
825 system to the next. In short, don't call "strxfrm()" directly: let
826 Perl do it for you.
827 Note: "use locale" isn't shown in some of these examples because it
829 isn't needed: "strcoll()" and "strxfrm()" are POSIX functions which use
830 the standard system-supplied "libc" functions that always obey the
831 current "LC_COLLATE" locale.
832 Category "LC_CTYPE": Character Types
834 In the scope of a "use locale" form that includes "LC_CTYPE", Perl
835 obeys the "LC_CTYPE" locale setting. This controls the application's
836 notion of which characters are alphabetic, numeric, punctuation, etc.
837 This affects Perl's "\w" regular expression metanotation, which stands
838 for alphanumeric characters--that is, alphabetic, numeric, and the
839 platform's native underscore. (Consult perlre for more information
840 about regular expressions.) Thanks to "LC_CTYPE", depending on your
841 locale setting, characters like "ae", "d`", "ss", and "o" may be
842 understood as "\w" characters. It also affects things like "\s", "\D",
843 and the POSIX character classes, like "[[:graph:]]". (See
844 perlrecharclass for more information on all these.)
845 The "LC_CTYPE" locale also provides the map used in transliterating
847 characters between lower and uppercase. This affects the case-mapping
848 functions--"fc()", "lc()", "lcfirst()", "uc()", and "ucfirst()"; case-
849 mapping interpolation with "\F", "\l", "\L", "\u", or "\U" in double-
850 quoted strings and "s///" substitutions; and case-insensitive regular
851 expression pattern matching using the "i" modifier.
852 Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
854 otherwise Perl only supports single-byte locales, such as the ISO 8859
855 series. This means that wide character locales, for example for Asian
856 languages, are not well-supported. Use of these locales may cause core
857 dumps. If the platform has the capability for Perl to detect such a
858 locale, starting in Perl v5.22, Perl will warn, default enabled, using
859 the "locale" warning category, whenever such a locale is switched into.
860 The UTF-8 locale support is actually a superset of POSIX locales,
861 because it is really full Unicode behavior as if no "LC_CTYPE" locale
862 were in effect at all (except for tainting; see "SECURITY"). POSIX
863 locales, even UTF-8 ones, are lacking certain concepts in Unicode, such
864 as the idea that changing the case of a character could expand to be
865 more than one character. Perl in a UTF-8 locale, will give you that
866 expansion. Prior to v5.20, Perl treated a UTF-8 locale on some
867 platforms like an ISO 8859-1 one, with some restrictions, and on other
868 platforms more like the "C" locale. For releases v5.16 and v5.18,
869 "use locale 'not_characters" could be used as a workaround for this
870 (see "Unicode and UTF-8").
871 Note that there are quite a few things that are unaffected by the
873 current locale. Any literal character is the native character for the
874 given platform. Hence 'A' means the character at code point 65 on
875 ASCII platforms, and 193 on EBCDIC. That may or may not be an 'A' in
876 the current locale, if that locale even has an 'A'. Similarly, all the
877 escape sequences for particular characters, "\n" for example, always
878 mean the platform's native one. This means, for example, that "\N" in
879 regular expressions (every character but new-line) works on the
880 platform character set.
881 Starting in v5.22, Perl will by default warn when switching into a
883 locale that redefines any ASCII printable character (plus "\t" and
884 "\n") into a different class than expected. This is likely to happen
885 on modern locales only on EBCDIC platforms, where, for example, a CCSID
886 0037 locale on a CCSID 1047 machine moves "[", but it can happen on
887 ASCII platforms with the ISO 646 and other 7-bit locales that are
888 essentially obsolete. Things may still work, depending on what
889 features of Perl are used by the program. For example, in the example
890 from above where "|" becomes a "\w", and there are no regular
891 expressions where this matters, the program may still work properly.
892 The warning lists all the characters that it can determine could be
893 adversely affected.
894 Note: A broken or malicious "LC_CTYPE" locale definition may result in
896 clearly ineligible characters being considered to be alphanumeric by
897 your application. For strict matching of (mundane) ASCII letters and
898 digits--for example, in command strings--locale-aware applications
899 should use "\w" with the "/a" regular expression modifier. See
900 "SECURITY".
901 Category "LC_NUMERIC": Numeric Formatting
903 After a proper "POSIX::setlocale()" call, and within the scope of of a
904 "use locale" form that includes numerics, Perl obeys the "LC_NUMERIC"
905 locale information, which controls an application's idea of how numbers
906 should be formatted for human readability. In most implementations the
907 only effect is to change the character used for the decimal
908 point--perhaps from "." to ",". The functions aren't aware of such
909 niceties as thousands separation and so on. (See "The localeconv
910 function" if you care about these things.)
911 use POSIX qw(strtod setlocale LC_NUMERIC);
913 use locale;
914 setlocale LC_NUMERIC, "";
916 $n = 5/2; # Assign numeric 2.5 to $n
918 $a = " $n"; # Locale-dependent conversion to string
920 print "half five is $n\n"; # Locale-dependent output
922 printf "half five is %g\n", $n; # Locale-dependent output
924 print "DECIMAL POINT IS COMMA\n"
926 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
927 See also I18N::Langinfo and "RADIXCHAR".
929 Category "LC_MONETARY": Formatting of monetary amounts
931 The C standard defines the "LC_MONETARY" category, but not a function
932 that is affected by its contents. (Those with experience of standards
933 committees will recognize that the working group decided to punt on the
934 issue.) Consequently, Perl essentially takes no notice of it. If you
935 really want to use "LC_MONETARY", you can query its contents--see "The
936 localeconv function"--and use the information that it returns in your
937 application's own formatting of currency amounts. However, you may
938 well find that the information, voluminous and complex though it may
939 be, still does not quite meet your requirements: currency formatting is
940 a hard nut to crack.
941 See also I18N::Langinfo and "CRNCYSTR".
943 Category "LC_TIME": Respresentation of time
945 Output produced by "POSIX::strftime()", which builds a formatted human-
946 readable date/time string, is affected by the current "LC_TIME" locale.
947 Thus, in a French locale, the output produced by the %B format element
948 (full month name) for the first month of the year would be "janvier".
949 Here's how to get a list of long month names in the current locale:
950 use POSIX qw(strftime);
952 for (0..11) {
953 $long_month_name[$_] =
954 strftime("%B", 0, 0, 0, 1, $_, 96);
955 }
956 Note: "use locale" isn't needed in this example: "strftime()" is a
958 POSIX function which uses the standard system-supplied "libc" function
959 that always obeys the current "LC_TIME" locale.
960 See also I18N::Langinfo and "ABDAY_1".."ABDAY_7", "DAY_1".."DAY_7",
962 "ABMON_1".."ABMON_12", and "ABMON_1".."ABMON_12".
963 Other categories
965 The remaining locale categories are not currently used by Perl itself.
966 But again note that things Perl interacts with may use these, including
967 extensions outside the standard Perl distribution, and by the operating
968 system and its utilities. Note especially that the string value of $!
969 and the error messages given by external utilities may be changed by
970 "LC_MESSAGES". If you want to have portable error codes, use "%!".
971 See Errno.
972
974 Although the main discussion of Perl security issues can be found in
975 perlsec, a discussion of Perl's locale handling would be incomplete if
976 it did not draw your attention to locale-dependent security issues.
977 Locales--particularly on systems that allow unprivileged users to build
978 their own locales--are untrustworthy. A malicious (or just plain
979 broken) locale can make a locale-aware application give unexpected
980 results. Here are a few possibilities:
981 · Regular expression checks for safe file names or mail addresses
983 using "\w" may be spoofed by an "LC_CTYPE" locale that claims that
984 characters such as ">" and "|" are alphanumeric.
985 · String interpolation with case-mapping, as in, say, "$dest =
987 "C:\U$name.$ext"", may produce dangerous results if a bogus
988 "LC_CTYPE" case-mapping table is in effect.
989 · A sneaky "LC_COLLATE" locale could result in the names of students
991 with "D" grades appearing ahead of those with "A"s.
992 · An application that takes the trouble to use information in
994 "LC_MONETARY" may format debits as if they were credits and vice
995 versa if that locale has been subverted. Or it might make payments
996 in US dollars instead of Hong Kong dollars.
997 · The date and day names in dates formatted by "strftime()" could be
999 manipulated to advantage by a malicious user able to subvert the
1000 "LC_DATE" locale. ("Look--it says I wasn't in the building on
1001 Sunday.")
1002 Such dangers are not peculiar to the locale system: any aspect of an
1004 application's environment which may be modified maliciously presents
1005 similar challenges. Similarly, they are not specific to Perl: any
1006 programming language that allows you to write programs that take
1007 account of their environment exposes you to these issues.
1008 Perl cannot protect you from all possibilities shown in the
1010 examples--there is no substitute for your own vigilance--but, when "use
1011 locale" is in effect, Perl uses the tainting mechanism (see perlsec) to
1012 mark string results that become locale-dependent, and which may be
1013 untrustworthy in consequence. Here is a summary of the tainting
1014 behavior of operators and functions that may be affected by the locale:
1015 · Comparison operators ("lt", "le", "ge", "gt" and "cmp"):
1017 Scalar true/false (or less/equal/greater) result is never tainted.
1019 · Case-mapping interpolation (with "\l", "\L", "\u", "\U", or "\F")
1021 The result string containing interpolated material is tainted if a
1023 "use locale" form that includes "LC_CTYPE" is in effect.
1024 · Matching operator ("m//"):
1026 Scalar true/false result never tainted.
1028 All subpatterns, either delivered as a list-context result or as $1
1030 etc., are tainted if a "use locale" form that includes "LC_CTYPE"
1031 is in effect, and the subpattern regular expression contains a
1032 locale-dependent construct. These constructs include "\w" (to
1033 match an alphanumeric character), "\W" (non-alphanumeric
1034 character), "\b" and "\B" (word-boundary and non-boundardy, which
1035 depend on what "\w" and "\W" match), "\s" (whitespace character),
1036 "\S" (non whitespace character), "\d" and "\D" (digits and non-
1037 digits), and the POSIX character classes, such as "[:alpha:]" (see
1038 "POSIX Character Classes" in perlrecharclass).
1039 Tainting is also likely if the pattern is to be matched case-
1041 insensitively (via "/i"). The exception is if all the code points
1042 to be matched this way are above 255 and do not have folds under
1043 Unicode rules to below 256. Tainting is not done for these because
1044 Perl only uses Unicode rules for such code points, and those rules
1045 are the same no matter what the current locale.
1046 The matched-pattern variables, $&, "$`" (pre-match), "$'" (post-
1048 match), and $+ (last match) also are tainted.
1049 · Substitution operator ("s///"):
1051 Has the same behavior as the match operator. Also, the left
1053 operand of "=~" becomes tainted when a "use locale" form that
1054 includes "LC_CTYPE" is in effect, if modified as a result of a
1055 substitution based on a regular expression match involving any of
1056 the things mentioned in the previous item, or of case-mapping, such
1057 as "\l", "\L","\u", "\U", or "\F".
1058 · Output formatting functions ("printf()" and "write()"):
1060 Results are never tainted because otherwise even output from print,
1062 for example "print(1/7)", should be tainted if "use locale" is in
1063 effect.
1064 · Case-mapping functions ("lc()", "lcfirst()", "uc()", "ucfirst()"):
1066 Results are tainted if a "use locale" form that includes "LC_CTYPE"
1068 is in effect.
1069 · POSIX locale-dependent functions ("localeconv()", "strcoll()",
1071 "strftime()", "strxfrm()"):
1072 Results are never tainted.
1074 Three examples illustrate locale-dependent tainting. The first
1076 program, which ignores its locale, won't run: a value taken directly
1077 from the command line may not be used to name an output file when taint
1078 checks are enabled.
1079 #/usr/local/bin/perl -T
1081 # Run with taint checking
1082 # Command line sanity check omitted...
1084 $tainted_output_file = shift;
1085 open(F, ">$tainted_output_file")
1087 or warn "Open of $tainted_output_file failed: $!\n";
1088 The program can be made to run by "laundering" the tainted value
1090 through a regular expression: the second example--which still ignores
1091 locale information--runs, creating the file named on its command line
1092 if it can.
1093 #/usr/local/bin/perl -T
1095 $tainted_output_file = shift;
1097 $tainted_output_file =~ m%[\w/]+%;
1098 $untainted_output_file = $&;
1099 open(F, ">$untainted_output_file")
1101 or warn "Open of $untainted_output_file failed: $!\n";
1102 Compare this with a similar but locale-aware program:
1104 #/usr/local/bin/perl -T
1106 $tainted_output_file = shift;
1108 use locale;
1109 $tainted_output_file =~ m%[\w/]+%;
1110 $localized_output_file = $&;
1111 open(F, ">$localized_output_file")
1113 or warn "Open of $localized_output_file failed: $!\n";
1114 This third program fails to run because $& is tainted: it is the result
1116 of a match involving "\w" while "use locale" is in effect.
1117
1119 PERL_SKIP_LOCALE_INIT
1120 This environment variable, available starting in Perl
1121 v5.20, if set (to any value), tells Perl to not use the
1122 rest of the environment variables to initialize with.
1123 Instead, Perl uses whatever the current locale settings
1124 are. This is particularly useful in embedded environments,
1125 see "Using embedded Perl with POSIX locales" in perlembed.
1126 PERL_BADLANG
1128 A string that can suppress Perl's warning about failed
1129 locale settings at startup. Failure can occur if the
1130 locale support in the operating system is lacking (broken)
1131 in some way--or if you mistyped the name of a locale when
1132 you set up your environment. If this environment variable
1133 is absent, or has a value other than "0" or "", Perl will
1134 complain about locale setting failures.
1135 NOTE: "PERL_BADLANG" only gives you a way to hide the
1137 warning message. The message tells about some problem in
1138 your system's locale support, and you should investigate
1139 what the problem is.
1140 The following environment variables are not specific to Perl: They are
1142 part of the standardized (ISO C, XPG4, POSIX 1.c) "setlocale()" method
1143 for controlling an application's opinion on data. Windows is non-
1144 POSIX, but Perl arranges for the following to work as described anyway.
1145 If the locale given by an environment variable is not valid, Perl tries
1146 the next lower one in priority. If none are valid, on Windows, the
1147 system default locale is then tried. If all else fails, the "C" locale
1148 is used. If even that doesn't work, something is badly broken, but
1149 Perl tries to forge ahead with whatever the locale settings might be.
1150 "LC_ALL" "LC_ALL" is the "override-all" locale environment variable.
1152 If set, it overrides all the rest of the locale environment
1153 variables.
1154 "LANGUAGE" NOTE: "LANGUAGE" is a GNU extension, it affects you only if
1156 you are using the GNU libc. This is the case if you are
1157 using e.g. Linux. If you are using "commercial" Unixes you
1158 are most probably not using GNU libc and you can ignore
1159 "LANGUAGE".
1160 However, in the case you are using "LANGUAGE": it affects
1162 the language of informational, warning, and error messages
1163 output by commands (in other words, it's like
1164 "LC_MESSAGES") but it has higher priority than "LC_ALL".
1165 Moreover, it's not a single value but instead a "path"
1166 (":"-separated list) of languages (not locales). See the
1167 GNU "gettext" library documentation for more information.
1168 "LC_CTYPE" In the absence of "LC_ALL", "LC_CTYPE" chooses the
1170 character type locale. In the absence of both "LC_ALL" and
1171 "LC_CTYPE", "LANG" chooses the character type locale.
1172 "LC_COLLATE"
1174 In the absence of "LC_ALL", "LC_COLLATE" chooses the
1175 collation (sorting) locale. In the absence of both
1176 "LC_ALL" and "LC_COLLATE", "LANG" chooses the collation
1177 locale.
1178 "LC_MONETARY"
1180 In the absence of "LC_ALL", "LC_MONETARY" chooses the
1181 monetary formatting locale. In the absence of both
1182 "LC_ALL" and "LC_MONETARY", "LANG" chooses the monetary
1183 formatting locale.
1184 "LC_NUMERIC"
1186 In the absence of "LC_ALL", "LC_NUMERIC" chooses the
1187 numeric format locale. In the absence of both "LC_ALL" and
1188 "LC_NUMERIC", "LANG" chooses the numeric format.
1189 "LC_TIME" In the absence of "LC_ALL", "LC_TIME" chooses the date and
1191 time formatting locale. In the absence of both "LC_ALL"
1192 and "LC_TIME", "LANG" chooses the date and time formatting
1193 locale.
1194 "LANG" "LANG" is the "catch-all" locale environment variable. If
1196 it is set, it is used as the last resort after the overall
1197 "LC_ALL" and the category-specific "LC_foo".
1198 Examples
1200 The "LC_NUMERIC" controls the numeric output:
1201 use locale;
1203 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1204 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1205 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1206 and also how strings are parsed by "POSIX::strtod()" as numbers:
1208 use locale;
1210 use POSIX qw(locale_h strtod);
1211 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1212 my $x = strtod("2,34") + 5;
1213 print $x, "\n"; # Probably shows 7,34.
1214
1216 String "eval" and "LC_NUMERIC"
1217 A string eval parses its expression as standard Perl. It is therefore
1218 expecting the decimal point to be a dot. If "LC_NUMERIC" is set to
1219 have this be a comma instead, the parsing will be confused, perhaps
1220 silently.
1221 use locale;
1223 use POSIX qw(locale_h);
1224 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1225 my $a = 1.2;
1226 print eval "$a + 1.5";
1227 print "\n";
1228 prints "13,5". This is because in that locale, the comma is the
1230 decimal point character. The "eval" thus expands to:
1231 eval "1,2 + 1.5"
1233 and the result is not what you likely expected. No warnings are
1235 generated. If you do string "eval"'s within the scope of "use locale",
1236 you should instead change the "eval" line to do something like:
1237 print eval "no locale; $a + 1.5";
1239 This prints 2.7.
1241 You could also exclude "LC_NUMERIC", if you don't need it, by
1243 use locale ':!numeric';
1245 Backward compatibility
1247 Versions of Perl prior to 5.004 mostly ignored locale information,
1248 generally behaving as if something similar to the "C" locale were
1249 always in force, even if the program environment suggested otherwise
1250 (see "The setlocale function"). By default, Perl still behaves this
1251 way for backward compatibility. If you want a Perl application to pay
1252 attention to locale information, you must use the "use locale" pragma
1253 (see "The "use locale" pragma") or, in the unlikely event that you want
1254 to do so for just pattern matching, the "/l" regular expression
1255 modifier (see "Character set modifiers" in perlre) to instruct it to do
1256 so.
1257 Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE" information
1259 if available; that is, "\w" did understand what were the letters
1260 according to the locale environment variables. The problem was that
1261 the user had no control over the feature: if the C library supported
1262 locales, Perl used them.
1263 I18N:Collate obsolete
1265 In versions of Perl prior to 5.004, per-locale collation was possible
1266 using the "I18N::Collate" library module. This module is now mildly
1267 obsolete and should be avoided in new applications. The "LC_COLLATE"
1268 functionality is now integrated into the Perl core language: One can
1269 use locale-specific scalar data completely normally with "use locale",
1270 so there is no longer any need to juggle with the scalar references of
1271 "I18N::Collate".
1272 Sort speed and memory use impacts
1274 Comparing and sorting by locale is usually slower than the default
1275 sorting; slow-downs of two to four times have been observed. It will
1276 also consume more memory: once a Perl scalar variable has participated
1277 in any string comparison or sorting operation obeying the locale
1278 collation rules, it will take 3-15 times more memory than before. (The
1279 exact multiplier depends on the string's contents, the operating system
1280 and the locale.) These downsides are dictated more by the operating
1281 system's implementation of the locale system than by Perl.
1282 Freely available locale definitions
1284 The Unicode CLDR project extracts the POSIX portion of many of its
1285 locales, available at
1286 http://unicode.org/Public/cldr/2.0.1/
1288 (Newer versions of CLDR require you to compute the POSIX data yourself.
1290 See <http://unicode.org/Public/cldr/latest/>.)
1291 There is a large collection of locale definitions at:
1293 http://std.dkuug.dk/i18n/WG15-collection/locales/
1295 You should be aware that it is unsupported, and is not claimed to be
1297 fit for any purpose. If your system allows installation of arbitrary
1298 locales, you may find the definitions useful as they are, or as a basis
1299 for the development of your own locales.
1300 I18n and l10n
1302 "Internationalization" is often abbreviated as i18n because its first
1303 and last letters are separated by eighteen others. (You may guess why
1304 the internalin ... internaliti ... i18n tends to get abbreviated.) In
1305 the same way, "localization" is often abbreviated to l10n.
1306 An imperfect standard
1308 Internationalization, as defined in the C and POSIX standards, can be
1309 criticized as incomplete and ungainly. They also have a tendency, like
1310 standards groups, to divide the world into nations, when we all know
1311 that the world can equally well be divided into bankers, bikers,
1312 gamers, and so on.
1313
1315 The support of Unicode is new starting from Perl version v5.6, and more
1316 fully implemented in versions v5.8 and later. See perluniintro.
1317 Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1319 "LC_COLLATE" is only partially supported; collation support is improved
1320 in Perl v5.26 to a level that may be sufficient for your needs (see
1321 "Category "LC_COLLATE": Collation: Text Comparisons and Sorting").
1322 If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1324 use locale ':not_characters';
1326 When this form of the pragma is used, only the non-character portions
1328 of locales are used by Perl, for example "LC_NUMERIC". Perl assumes
1329 that you have translated all the characters it is to operate on into
1330 Unicode (actually the platform's native character set (ASCII or EBCDIC)
1331 plus Unicode). For data in files, this can conveniently be done by
1332 also specifying
1333 use open ':locale';
1335 This pragma arranges for all inputs from files to be translated into
1337 Unicode from the current locale as specified in the environment (see
1338 "ENVIRONMENT"), and all outputs to files to be translated back into the
1339 locale. (See open). On a per-filehandle basis, you can instead use
1340 the PerlIO::locale module, or the Encode::Locale module, both available
1341 from CPAN. The latter module also has methods to ease the handling of
1342 "ARGV" and environment variables, and can be used on individual
1343 strings. If you know that all your locales will be UTF-8, as many are
1344 these days, you can use the -C command line switch.
1345 This form of the pragma allows essentially seamless handling of locales
1347 with Unicode. The collation order will be by Unicode code point order.
1348 Unicode::Collate can be used to get Unicode rules collation.
1349 All the modules and switches just described can be used in v5.20 with
1351 just plain "use locale", and, should the input locales not be UTF-8,
1352 you'll get the less than ideal behavior, described below, that you get
1353 with pre-v5.16 Perls, or when you use the locale pragma without the
1354 ":not_characters" parameter in v5.16 and v5.18. If you are using
1355 exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1356 does not apply to you.
1357 There are two cases, multi-byte and single-byte locales. First multi-
1359 byte:
1360 The only multi-byte (or wide character) locale that Perl is ever likely
1362 to support is UTF-8. This is due to the difficulty of implementation,
1363 the fact that high quality UTF-8 locales are now published for every
1364 area of the world (<http://unicode.org/Public/cldr/2.0.1/> for ones
1365 that are already set-up, but from an earlier version;
1366 <http://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1367 you have to extract the POSIX information yourself), and that failing
1368 all that you can use the Encode module to translate to/from your
1369 locale. So, you'll have to do one of those things if you're using one
1370 of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1371 Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1372 work reasonably well (depending on your C library implementation)
1373 simply because both they and Perl store characters that take up
1374 multiple bytes the same way. However, some, if not most, C library
1375 implementations may not process the characters in the upper half of the
1376 Latin-1 range (128 - 255) properly under "LC_CTYPE". To see if a
1377 character is a particular type under a locale, Perl uses the functions
1378 like "isalnum()". Your C library may not work for UTF-8 locales with
1379 those functions, instead only working under the newer wide library
1380 functions like "iswalnum()", which Perl does not use. These multi-byte
1381 locales are treated like single-byte locales, and will have the
1382 restrictions described below. Starting in Perl v5.22 a warning message
1383 is raised when Perl detects a multi-byte locale that it doesn't fully
1384 support.
1385 For single-byte locales, Perl generally takes the tack to use locale
1387 rules on code points that can fit in a single byte, and Unicode rules
1388 for those that can't (though this isn't uniformly applied, see the note
1389 at the end of this section). This prevents many problems in locales
1390 that aren't UTF-8. Suppose the locale is ISO8859-7, Greek. The
1391 character at 0xD7 there is a capital Chi. But in the ISO8859-1 locale,
1392 Latin1, it is a multiplication sign. The POSIX regular expression
1393 character class "[[:alpha:]]" will magically match 0xD7 in the Greek
1394 locale but not in the Latin one.
1395 However, there are places where this breaks down. Certain Perl
1397 constructs are for Unicode only, such as "\p{Alpha}". They assume that
1398 0xD7 always has its Unicode meaning (or the equivalent on EBCDIC
1399 platforms). Since Latin1 is a subset of Unicode and 0xD7 is the
1400 multiplication sign in both Latin1 and Unicode, "\p{Alpha}" will never
1401 match it, regardless of locale. A similar issue occurs with "\N{...}".
1402 Prior to v5.20, it is therefore a bad idea to use "\p{}" or "\N{}"
1403 under plain "use locale"--unless you can guarantee that the locale will
1404 be ISO8859-1. Use POSIX character classes instead.
1405 Another problem with this approach is that operations that cross the
1407 single byte/multiple byte boundary are not well-defined, and so are
1408 disallowed. (This boundary is between the codepoints at 255/256.) For
1409 example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1410 should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1411 Greek locale, for example, there is no character at 0xFF, and Perl has
1412 no way of knowing what the character at 0xFF is really supposed to
1413 represent. Thus it disallows the operation. In this mode, the
1414 lowercase of U+0178 is itself.
1415 The same problems ensue if you enable automatic UTF-8-ification of your
1417 standard file handles, default "open()" layer, and @ARGV on
1418 non-ISO8859-1, non-UTF-8 locales (by using either the -C command line
1419 switch or the "PERL_UNICODE" environment variable; see perlrun).
1420 Things are read in as UTF-8, which would normally imply a Unicode
1421 interpretation, but the presence of a locale causes them to be
1422 interpreted in that locale instead. For example, a 0xD7 code point in
1423 the Unicode input, which should mean the multiplication sign, won't be
1424 interpreted by Perl that way under the Greek locale. This is not a
1425 problem provided you make certain that all locales will always and only
1426 be either an ISO8859-1, or, if you don't have a deficient C library, a
1427 UTF-8 locale.
1428 Still another problem is that this approach can lead to two code points
1430 meaning the same character. Thus in a Greek locale, both U+03A7 and
1431 U+00D7 are GREEK CAPITAL LETTER CHI.
1432 Because of all these problems, starting in v5.22, Perl will raise a
1434 warning if a multi-byte (hence Unicode) code point is used when a
1435 single-byte locale is in effect. (Although it doesn't check for this
1436 if doing so would unreasonably slow execution down.)
1437 Vendor locales are notoriously buggy, and it is difficult for Perl to
1439 test its locale-handling code because this interacts with code that
1440 Perl has no control over; therefore the locale-handling code in Perl
1441 may be buggy as well. (However, the Unicode-supplied locales should be
1442 better, and there is a feed back mechanism to correct any problems.
1443 See "Freely available locale definitions".)
1444 If you have Perl v5.16, the problems mentioned above go away if you use
1446 the ":not_characters" parameter to the locale pragma (except for vendor
1447 bugs in the non-character portions). If you don't have v5.16, and you
1448 do have locales that work, using them may be worthwhile for certain
1449 specific purposes, as long as you keep in mind the gotchas already
1450 mentioned. For example, if the collation for your locales works, it
1451 runs faster under locales than under Unicode::Collate; and you gain
1452 access to such things as the local currency symbol and the names of the
1453 months and days of the week. (But to hammer home the point, in v5.16,
1454 you get this access without the downsides of locales by using the
1455 ":not_characters" form of the pragma.)
1456 Note: The policy of using locale rules for code points that can fit in
1458 a byte, and Unicode rules for those that can't is not uniformly
1459 applied. Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied
1460 fairly consistently to regular expression matching except for bracketed
1461 character classes; in v5.14 it was extended to all regex matches; and
1462 in v5.16 to the casing operations such as "\L" and "uc()". For
1463 collation, in all releases so far, the system's "strxfrm()" function is
1464 called, and whatever it does is what you get. Starting in v5.26,
1465 various bugs are fixed with the way perl uses this function.
1466
1468 Collation of strings containing embedded "NUL" characters
1469 "NUL" characters will sort the same as the lowest collating control
1470 character does, or to "\001" in the unlikely event that there are no
1471 control characters at all in the locale. In cases where the strings
1472 don't contain this non-"NUL" control, the results will be correct, and
1473 in many locales, this control, whatever it might be, will rarely be
1474 encountered. But there are cases where a "NUL" should sort before this
1475 control, but doesn't. If two strings do collate identically, the one
1476 containing the "NUL" will sort to earlier. Prior to 5.26, there were
1477 more bugs.
1478 Multi-threaded
1480 XS code or C-language libraries called from it that use the system
1481 setlocale(3) function (except on Windows) likely will not work from a
1482 multi-threaded application without changes. See "Locale-aware XS code"
1483 in perlxs.
1484 An XS module that is locale-dependent could have been written under the
1486 assumption that it will never be called in a multi-threaded
1487 environment, and so uses other non-locale constructs that aren't multi-
1488 thread-safe. See "Thread-aware system interfaces" in perlxs.
1489 POSIX does not define a way to get the name of the current per-thread
1491 locale. Some systems, such as Darwin and NetBSD do implement a
1492 function, querylocale(3) to do this. On non-Windows systems without
1493 it, such as Linux, there are some additional caveats:
1494 · An embedded perl needs to be started up while the global locale is
1496 in effect. See "Using embedded Perl with POSIX locales" in
1497 perlembed.
1498 · It becomes more important for perl to know about all the possible
1500 locale categories on the platform, even if they aren't apparently
1501 used in your program. Perl knows all of the Linux ones. If your
1502 platform has others, you can send email to
1503 <mailto:perlbug@perl.org> for inclusion of it in the next release.
1504 In the meantime, it is possible to edit the Perl source to teach it
1505 about the category, and then recompile. Search for instances of,
1506 say, "LC_PAPER" in the source, and use that as a template to add
1507 the omitted one.
1508 · It is possible, though hard to do, to call "POSIX::setlocale" with
1510 a locale that it doesn't recognize as syntactically legal, but
1511 actually is legal on that system. This should happen only with
1512 embedded perls, or if you hand-craft a locale name yourself.
1513 Broken systems
1515 In certain systems, the operating system's locale support is broken and
1516 cannot be fixed or used by Perl. Such deficiencies can and will result
1517 in mysterious hangs and/or Perl core dumps when "use locale" is in
1518 effect. When confronted with such a system, please report in
1519 excruciating detail to <perlbug@perl.org>, and also contact your
1520 vendor: bug fixes may exist for these problems in your operating
1521 system. Sometimes such bug fixes are called an operating system
1522 upgrade. If you have the source for Perl, include in the perlbug email
1523 the output of the test described above in "Testing for broken locales".
1524
1526 I18N::Langinfo, perluniintro, perlunicode, open, "localeconv" in POSIX,
1527 "setlocale" in POSIX, "strcoll" in POSIX, "strftime" in POSIX, "strtod"
1528 in POSIX, "strxfrm" in POSIX.
1529 For special considerations when Perl is embedded in a C program, see
1531 "Using embedded Perl with POSIX locales" in perlembed.
1532
1534 Jarkko Hietaniemi's original perli18n.pod heavily hacked by Dominic
1535 Dunlop, assisted by the perl5-porters. Prose worked over a bit by Tom
1536 Christiansen, and now maintained by Perl 5 porters.
1537perl v5.28.2 2018-11-01 PERLLOCALE(1)