1PERLLOCALE(1)          Perl Programmers Reference Guide          PERLLOCALE(1)
2
3
4

NAME

6       perllocale - Perl locale handling (internationalization and
7       localization)
8

DESCRIPTION

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
18       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
26       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
30       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
35       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
48       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
54       Perl continues to support the old non UTF-8 locales as well.  There are
55       currently no UTF-8 locales for EBCDIC platforms.
56
57       (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

WHAT IS A LOCALE

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
71       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
75       Category "LC_MONETARY": Formatting of monetary amounts
76
77
78       Category "LC_TIME": Date/Time formatting
79
80
81       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
85       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
89       Category "LC_CTYPE": Character Types
90           This indicates, for example if a character is an uppercase letter.
91
92       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
98       More details on the categories used by Perl are given below in "LOCALE
99       CATEGORIES".
100
101       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

PREPARING TO USE LOCALES

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
111Your operating system must support the locale system.  If it does,
112           you should find that the "setlocale()" function is a documented
113           part of its C library.
114
115Definitions 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
127Perl 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
131       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
136       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
140       2.  The application must set its own locale using the method described
141           in "The setlocale function".
142

USING LOCALES

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
157       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
163       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
173       The operations that are affected by locale are:
174
175       Not within the scope of "use locale"
176           Only certain operations (all originating outside Perl) should be
177           affected, as follows:
178
179           •   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
183           •   Also Perl gives access to various C library functions through
184               the POSIX module.  Some of those functions are always affected
185               by the current locale.  For example, "POSIX::strftime()" uses
186               "LC_TIME"; "POSIX::strtod()" uses "LC_NUMERIC";
187               "POSIX::strcoll()" and "POSIX::strxfrm()" use "LC_COLLATE".
188               All such functions will behave according to the current
189               underlying locale, even if that locale isn't exposed to Perl
190               space.
191
192               This applies as well to I18N::Langinfo.
193
194           •   XS modules for all categories but "LC_NUMERIC" get the
195               underlying locale, and hence any C library functions they call
196               will use that underlying locale.  For more discussion, see
197               "CAVEATS" in perlxs.
198
199           Note that all C programs (including the perl interpreter, which is
200           written in C) always have an underlying locale.  That locale is the
201           "C" locale unless changed by a call to setlocale().  When Perl
202           starts up, it changes the underlying locale to the one which is
203           indicated by the "ENVIRONMENT".  When using the POSIX module or
204           writing XS code, it is important to keep in mind that the
205           underlying locale may be something other than "C", even if the
206           program hasn't explicitly changed it.
207
208
209
210       Lingering effects of "use locale"
211           Certain Perl operations that are set-up within the scope of a "use
212           locale" retain that effect even outside the scope.  These include:
213
214           •   The output format of a write() is determined by an earlier
215               format declaration ("format" in perlfunc), so whether or not
216               the output is affected by locale is determined by if the
217               "format()" is within the scope of a "use locale", not whether
218               the "write()" is.
219
220           •   Regular expression patterns can be compiled using qr// with
221               actual matching deferred to later.  Again, it is whether or not
222               the compilation was done within the scope of "use locale" that
223               determines the match behavior, not if the matches are done
224               within such a scope or not.
225
226
227
228       Under ""use locale";"
229           •   All the above operations
230
231Format declarations ("format" in perlfunc) and hence any
232               subsequent "write()"s use "LC_NUMERIC".
233
234stringification and output use "LC_NUMERIC".  These include the
235               results of "print()", "printf()", "say()", and "sprintf()".
236
237The comparison operators ("lt", "le", "cmp", "ge", and "gt")
238               use "LC_COLLATE".  "sort()" is also affected if used without an
239               explicit comparison function, because it uses "cmp" by default.
240
241               Note: "eq" and "ne" are unaffected by locale: they always
242               perform a char-by-char comparison of their scalar operands.
243               What's more, if "cmp" finds that its operands are equal
244               according to the collation sequence specified by the current
245               locale, it goes on to perform a char-by-char comparison, and
246               only returns 0 (equal) if the operands are char-for-char
247               identical.  If you really want to know whether two
248               strings--which "eq" and "cmp" may consider different--are equal
249               as far as collation in the locale is concerned, see the
250               discussion in "Category "LC_COLLATE": Collation".
251
252Regular expressions and case-modification functions ("uc()",
253               "lc()", "ucfirst()", and "lcfirst()") use "LC_CTYPE"
254
255The variables $! (and its synonyms $ERRNO and $OS_ERROR) and
256               $^E> (and its synonym $EXTENDED_OS_ERROR) when used as strings
257               use "LC_MESSAGES".
258
259       The default behavior is restored with the "no locale" pragma, or upon
260       reaching the end of the block enclosing "use locale".  Note that "use
261       locale" calls may be nested, and that what is in effect within an inner
262       scope will revert to the outer scope's rules at the end of the inner
263       scope.
264
265       The string result of any operation that uses locale information is
266       tainted (if your perl supports taint checking), as it is possible for a
267       locale to be untrustworthy.  See "SECURITY".
268
269       Starting in Perl v5.16 in a very limited way, and more generally in
270       v5.22, you can restrict which category or categories are enabled by
271       this particular instance of the pragma by adding parameters to it.  For
272       example,
273
274        use locale qw(:ctype :numeric);
275
276       enables locale awareness within its scope of only those operations
277       (listed above) that are affected by "LC_CTYPE" and "LC_NUMERIC".
278
279       The possible categories are: ":collate", ":ctype", ":messages",
280       ":monetary", ":numeric", ":time", and the pseudo category ":characters"
281       (described below).
282
283       Thus you can say
284
285        use locale ':messages';
286
287       and only $! and $^E will be locale aware.  Everything else is
288       unaffected.
289
290       Since Perl doesn't currently do anything with the "LC_MONETARY"
291       category, specifying ":monetary" does effectively nothing.  Some
292       systems have other categories, such as "LC_PAPER", but Perl also
293       doesn't do anything with them, and there is no way to specify them in
294       this pragma's arguments.
295
296       You can also easily say to use all categories but one, by either, for
297       example,
298
299        use locale ':!ctype';
300        use locale ':not_ctype';
301
302       both of which mean to enable locale awareness of all categories but
303       "LC_CTYPE".  Only one category argument may be specified in a
304       "use locale" if it is of the negated form.
305
306       Prior to v5.22 only one form of the pragma with arguments is available:
307
308        use locale ':not_characters';
309
310       (and you have to say "not_"; you can't use the bang "!" form).  This
311       pseudo category is a shorthand for specifying both ":collate" and
312       ":ctype".  Hence, in the negated form, it is nearly the same thing as
313       saying
314
315        use locale qw(:messages :monetary :numeric :time);
316
317       We use the term "nearly", because ":not_characters" also turns on
318       "use feature 'unicode_strings'" within its scope.  This form is less
319       useful in v5.20 and later, and is described fully in "Unicode and
320       UTF-8", but briefly, it tells Perl to not use the character portions of
321       the locale definition, that is the "LC_CTYPE" and "LC_COLLATE"
322       categories.  Instead it will use the native character set (extended by
323       Unicode).  When using this parameter, you are responsible for getting
324       the external character set translated into the native/Unicode one
325       (which it already will be if it is one of the increasingly popular
326       UTF-8 locales).  There are convenient ways of doing this, as described
327       in "Unicode and UTF-8".
328
329   The setlocale function
330       WARNING!  Prior to Perl 5.28 or on a system that does not support
331       thread-safe locale operations, do NOT use this function in a thread.
332       The locale will change in all other threads at the same time, and
333       should your thread get paused by the operating system, and another
334       started, that thread will not have the locale it is expecting.  On some
335       platforms, there can be a race leading to segfaults if two threads call
336       this function nearly simultaneously.  This warning does not apply on
337       unthreaded builds, or on perls where "${^SAFE_LOCALES}" exists and is
338       non-zero; namely Perl 5.28 and later unthreaded or compiled to be
339       locale-thread-safe.  On z/OS systems, this function becomes a no-op
340       once any thread is started.  Thus, on that system, you can set up the
341       locale before creating any threads, and that locale will be the one in
342       effect for the entire program.
343
344       Otherwise, you can switch locales as often as you wish at run time with
345       the "POSIX::setlocale()" function:
346
347               # Import locale-handling tool set from POSIX module.
348               # This example uses: setlocale -- the function call
349               #                    LC_CTYPE -- explained below
350               # (Showing the testing for success/failure of operations is
351               # omitted in these examples to avoid distracting from the main
352               # point)
353
354               use POSIX qw(locale_h);
355               use locale;
356               my $old_locale;
357
358               # query and save the old locale
359               $old_locale = setlocale(LC_CTYPE);
360
361               setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
362               # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
363
364               setlocale(LC_CTYPE, "");
365               # LC_CTYPE now reset to the default defined by the
366               # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
367               # default.  See below for documentation.
368
369               # restore the old locale
370               setlocale(LC_CTYPE, $old_locale);
371
372       The first argument of "setlocale()" gives the category, the second the
373       locale.  The category tells in what aspect of data processing you want
374       to apply locale-specific rules.  Category names are discussed in
375       "LOCALE CATEGORIES" and "ENVIRONMENT".  The locale is the name of a
376       collection of customization information corresponding to a particular
377       combination of language, country or territory, and codeset.  Read on
378       for hints on the naming of locales: not all systems name locales as in
379       the example.
380
381       If no second argument is provided and the category is something other
382       than "LC_ALL", the function returns a string naming the current locale
383       for the category.  You can use this value as the second argument in a
384       subsequent call to "setlocale()", but on some platforms the string is
385       opaque, not something that most people would be able to decipher as to
386       what locale it means.
387
388       If no second argument is provided and the category is "LC_ALL", the
389       result is implementation-dependent.  It may be a string of concatenated
390       locale names (separator also implementation-dependent) or a single
391       locale name.  Please consult your setlocale(3) man page for details.
392
393       If a second argument is given and it corresponds to a valid locale, the
394       locale for the category is set to that value, and the function returns
395       the now-current locale value.  You can then use this in yet another
396       call to "setlocale()".  (In some implementations, the return value may
397       sometimes differ from the value you gave as the second argument--think
398       of it as an alias for the value you gave.)
399
400       As the example shows, if the second argument is an empty string, the
401       category's locale is returned to the default specified by the
402       corresponding environment variables.  Generally, this results in a
403       return to the default that was in force when Perl started up: changes
404       to the environment made by the application after startup may or may not
405       be noticed, depending on your system's C library.
406
407       Note that when a form of "use locale" that doesn't include all
408       categories is specified, Perl ignores the excluded categories.
409
410       If "setlocale()" fails for some reason (for example, an attempt to set
411       to a locale unknown to the system), the locale for the category is not
412       changed, and the function returns "undef".
413
414       Starting in Perl 5.28, on multi-threaded perls compiled on systems that
415       implement POSIX 2008 thread-safe locale operations, this function
416       doesn't actually call the system "setlocale".  Instead those thread-
417       safe operations are used to emulate the "setlocale" function, but in a
418       thread-safe manner.
419
420       You can force the thread-safe locale operations to always be used (if
421       available) by recompiling perl with
422
423        -Accflags='-DUSE_THREAD_SAFE_LOCALE'
424
425       added to your call to Configure.
426
427       For further information about the categories, consult setlocale(3).
428
429   Multi-threaded operation
430       Beginning in Perl 5.28, multi-threaded locale operation is supported on
431       systems that implement either the POSIX 2008 or Windows-specific
432       thread-safe locale operations.  Many modern systems, such as various
433       Unix variants and Darwin do have this.
434
435       You can tell if using locales is safe on your system by looking at the
436       read-only boolean variable "${^SAFE_LOCALES}".  The value is 1 if the
437       perl is not threaded, or if it is using thread-safe locale operations.
438
439       Thread-safe operations are supported in Windows starting in Visual
440       Studio 2005, and in systems compatible with POSIX 2008.  Some platforms
441       claim to support POSIX 2008, but have buggy implementations, so that
442       the hints files for compiling to run on them turn off attempting to use
443       thread-safety.  "${^SAFE_LOCALES}" will be 0 on them.
444
445       Be aware that writing a multi-threaded application will not be portable
446       to a platform which lacks the native thread-safe locale support.  On
447       systems that do have it, you automatically get this behavior for
448       threaded perls, without having to do anything.  If for some reason, you
449       don't want to use this capability (perhaps the POSIX 2008 support is
450       buggy on your system), you can manually compile Perl to use the old
451       non-thread-safe implementation by passing the argument
452       "-Accflags='-DNO_THREAD_SAFE_LOCALE'" to Configure.  Except on Windows,
453       this will continue to use certain of the POSIX 2008 functions in some
454       situations.  If these are buggy, you can pass the following to
455       Configure instead or additionally:
456       "-Accflags='-DNO_POSIX_2008_LOCALE'".  This will also keep the code
457       from using thread-safe locales.  "${^SAFE_LOCALES}" will be 0 on
458       systems that turn off the thread-safe operations.
459
460       Normally on unthreaded builds, the traditional "setlocale()" is used
461       and not the thread-safe locale functions.  You can force the use of
462       these on systems that have them by adding the
463       "-Accflags='-DUSE_THREAD_SAFE_LOCALE'" to Configure.
464
465       The initial program is started up using the locale specified from the
466       environment, as currently, described in "ENVIRONMENT".   All newly
467       created threads start with "LC_ALL" set to "C".  Each thread may use
468       "POSIX::setlocale()" to query or switch its locale at any time, without
469       affecting any other thread.  All locale-dependent operations
470       automatically use their thread's locale.
471
472       This should be completely transparent to any applications written
473       entirely in Perl (minus a few rarely encountered caveats given in the
474       "Multi-threaded" section).  Information for XS module writers is given
475       in "Locale-aware XS code" in perlxs.
476
477   Finding locales
478       For locales available in your system, consult also setlocale(3) to see
479       whether it leads to the list of available locales (search for the SEE
480       ALSO section).  If that fails, try the following command lines:
481
482               locale -a
483
484               nlsinfo
485
486               ls /usr/lib/nls/loc
487
488               ls /usr/lib/locale
489
490               ls /usr/lib/nls
491
492               ls /usr/share/locale
493
494       and see whether they list something resembling these
495
496               en_US.ISO8859-1     de_DE.ISO8859-1     ru_RU.ISO8859-5
497               en_US.iso88591      de_DE.iso88591      ru_RU.iso88595
498               en_US               de_DE               ru_RU
499               en                  de                  ru
500               english             german              russian
501               english.iso88591    german.iso88591     russian.iso88595
502               english.roman8                          russian.koi8r
503
504       Sadly, even though the calling interface for "setlocale()" has been
505       standardized, names of locales and the directories where the
506       configuration resides have not been.  The basic form of the name is
507       language_territory.codeset, but the latter parts after language are not
508       always present.  The language and country are usually from the
509       standards ISO 3166 and ISO 639, the two-letter abbreviations for the
510       countries and the languages of the world, respectively.  The codeset
511       part often mentions some ISO 8859 character set, the Latin codesets.
512       For example, "ISO 8859-1" is the so-called "Western European codeset"
513       that can be used to encode most Western European languages adequately.
514       Again, there are several ways to write even the name of that one
515       standard.  Lamentably.
516
517       Two special locales are worth particular mention: "C" and "POSIX".
518       Currently these are effectively the same locale: the difference is
519       mainly that the first one is defined by the C standard, the second by
520       the POSIX standard.  They define the default locale in which every
521       program starts in the absence of locale information in its environment.
522       (The default default locale, if you will.)  Its language is (American)
523       English and its character codeset ASCII or, rarely, a superset thereof
524       (such as the "DEC Multinational Character Set (DEC-MCS)").  Warning.
525       The C locale delivered by some vendors may not actually exactly match
526       what the C standard calls for.  So beware.
527
528       NOTE: Not all systems have the "POSIX" locale (not all systems are
529       POSIX-conformant), so use "C" when you need explicitly to specify this
530       default locale.
531
532   LOCALE PROBLEMS
533       You may encounter the following warning message at Perl startup:
534
535               perl: warning: Setting locale failed.
536               perl: warning: Please check that your locale settings:
537                       LC_ALL = "En_US",
538                       LANG = (unset)
539                   are supported and installed on your system.
540               perl: warning: Falling back to the standard locale ("C").
541
542       This means that your locale settings had "LC_ALL" set to "En_US" and
543       LANG exists but has no value.  Perl tried to believe you but could not.
544       Instead, Perl gave up and fell back to the "C" locale, the default
545       locale that is supposed to work no matter what.  (On Windows, it first
546       tries falling back to the system default locale.)  This usually means
547       your locale settings were wrong, they mention locales your system has
548       never heard of, or the locale installation in your system has problems
549       (for example, some system files are broken or missing).  There are
550       quick and temporary fixes to these problems, as well as more thorough
551       and lasting fixes.
552
553   Testing for broken locales
554       If you are building Perl from source, the Perl test suite file
555       lib/locale.t can be used to test the locales on your system.  Setting
556       the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it to
557       output detailed results.  For example, on Linux, you could say
558
559        PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
560
561       Besides many other tests, it will test every locale it finds on your
562       system to see if they conform to the POSIX standard.  If any have
563       errors, it will include a summary near the end of the output of which
564       locales passed all its tests, and which failed, and why.
565
566   Temporarily fixing locale problems
567       The two quickest fixes are either to render Perl silent about any
568       locale inconsistencies or to run Perl under the default locale "C".
569
570       Perl's moaning about locale problems can be silenced by setting the
571       environment variable "PERL_BADLANG" to "0" or "".  This method really
572       just sweeps the problem under the carpet: you tell Perl to shut up even
573       when Perl sees that something is wrong.  Do not be surprised if later
574       something locale-dependent misbehaves.
575
576       Perl can be run under the "C" locale by setting the environment
577       variable "LC_ALL" to "C".  This method is perhaps a bit more civilized
578       than the "PERL_BADLANG" approach, but setting "LC_ALL" (or other locale
579       variables) may affect other programs as well, not just Perl.  In
580       particular, external programs run from within Perl will see these
581       changes.  If you make the new settings permanent (read on), all
582       programs you run see the changes.  See "ENVIRONMENT" for the full list
583       of relevant environment variables and "USING LOCALES" for their effects
584       in Perl.  Effects in other programs are easily deducible.  For example,
585       the variable "LC_COLLATE" may well affect your sort program (or
586       whatever the program that arranges "records" alphabetically in your
587       system is called).
588
589       You can test out changing these variables temporarily, and if the new
590       settings seem to help, put those settings into your shell startup
591       files.  Consult your local documentation for the exact details.  For
592       Bourne-like shells (sh, ksh, bash, zsh):
593
594               LC_ALL=en_US.ISO8859-1
595               export LC_ALL
596
597       This assumes that we saw the locale "en_US.ISO8859-1" using the
598       commands discussed above.  We decided to try that instead of the above
599       faulty locale "En_US"--and in Cshish shells (csh, tcsh)
600
601               setenv LC_ALL en_US.ISO8859-1
602
603       or if you have the "env" application you can do (in any shell)
604
605               env LC_ALL=en_US.ISO8859-1 perl ...
606
607       If you do not know what shell you have, consult your local helpdesk or
608       the equivalent.
609
610   Permanently fixing locale problems
611       The slower but superior fixes are when you may be able to yourself fix
612       the misconfiguration of your own environment variables.  The
613       mis(sing)configuration of the whole system's locales usually requires
614       the help of your friendly system administrator.
615
616       First, see earlier in this document about "Finding locales".  That
617       tells how to find which locales are really supported--and more
618       importantly, installed--on your system.  In our example error message,
619       environment variables affecting the locale are listed in the order of
620       decreasing importance (and unset variables do not matter).  Therefore,
621       having LC_ALL set to "En_US" must have been the bad choice, as shown by
622       the error message.  First try fixing locale settings listed first.
623
624       Second, if using the listed commands you see something exactly (prefix
625       matches do not count and case usually counts) like "En_US" without the
626       quotes, then you should be okay because you are using a locale name
627       that should be installed and available in your system.  In this case,
628       see "Permanently fixing your system's locale configuration".
629
630   Permanently fixing your system's locale configuration
631       This is when you see something like:
632
633               perl: warning: Please check that your locale settings:
634                       LC_ALL = "En_US",
635                       LANG = (unset)
636                   are supported and installed on your system.
637
638       but then cannot see that "En_US" listed by the above-mentioned
639       commands.  You may see things like "en_US.ISO8859-1", but that isn't
640       the same.  In this case, try running under a locale that you can list
641       and which somehow matches what you tried.  The rules for matching
642       locale names are a bit vague because standardization is weak in this
643       area.  See again the "Finding locales" about general rules.
644
645   Fixing system locale configuration
646       Contact a system administrator (preferably your own) and report the
647       exact error message you get, and ask them to read this same
648       documentation you are now reading.  They should be able to check
649       whether there is something wrong with the locale configuration of the
650       system.  The "Finding locales" section is unfortunately a bit vague
651       about the exact commands and places because these things are not that
652       standardized.
653
654   The localeconv function
655       The "POSIX::localeconv()" function allows you to get particulars of the
656       locale-dependent numeric formatting information specified by the
657       current underlying "LC_NUMERIC" and "LC_MONETARY" locales (regardless
658       of whether called from within the scope of "use locale" or not).  (If
659       you just want the name of the current locale for a particular category,
660       use "POSIX::setlocale()" with a single parameter--see "The setlocale
661       function".)
662
663               use POSIX qw(locale_h);
664
665               # Get a reference to a hash of locale-dependent info
666               $locale_values = localeconv();
667
668               # Output sorted list of the values
669               for (sort keys %$locale_values) {
670                   printf "%-20s = %s\n", $_, $locale_values->{$_}
671               }
672
673       "localeconv()" takes no arguments, and returns a reference to a hash.
674       The keys of this hash are variable names for formatting, such as
675       "decimal_point" and "thousands_sep".  The values are the corresponding,
676       er, values.  See "localeconv" in POSIX for a longer example listing the
677       categories an implementation might be expected to provide; some provide
678       more and others fewer.  You don't need an explicit "use locale",
679       because "localeconv()" always observes the current locale.
680
681       Here's a simple-minded example program that rewrites its command-line
682       parameters as integers correctly formatted in the current locale:
683
684           use POSIX qw(locale_h);
685
686           # Get some of locale's numeric formatting parameters
687           my ($thousands_sep, $grouping) =
688                   @{localeconv()}{'thousands_sep', 'grouping'};
689
690           # Apply defaults if values are missing
691           $thousands_sep = ',' unless $thousands_sep;
692
693           # grouping and mon_grouping are packed lists
694           # of small integers (characters) telling the
695           # grouping (thousand_seps and mon_thousand_seps
696           # being the group dividers) of numbers and
697           # monetary quantities.  The integers' meanings:
698           # 255 means no more grouping, 0 means repeat
699           # the previous grouping, 1-254 means use that
700           # as the current grouping.  Grouping goes from
701           # right to left (low to high digits).  In the
702           # below we cheat slightly by never using anything
703           # else than the first grouping (whatever that is).
704           if ($grouping) {
705               @grouping = unpack("C*", $grouping);
706           } else {
707               @grouping = (3);
708           }
709
710           # Format command line params for current locale
711           for (@ARGV) {
712               $_ = int;    # Chop non-integer part
713               1 while
714               s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
715               print "$_";
716           }
717           print "\n";
718
719       Note that if the platform doesn't have "LC_NUMERIC" and/or
720       "LC_MONETARY" available or enabled, the corresponding elements of the
721       hash will be missing.
722
723   I18N::Langinfo
724       Another interface for querying locale-dependent information is the
725       "I18N::Langinfo::langinfo()" function.
726
727       The following example will import the "langinfo()" function itself and
728       three constants to be used as arguments to "langinfo()": a constant for
729       the abbreviated first day of the week (the numbering starts from Sunday
730       = 1) and two more constants for the affirmative and negative answers
731       for a yes/no question in the current locale.
732
733           use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
734
735           my ($abday_1, $yesstr, $nostr)
736                       = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
737
738           print "$abday_1? [$yesstr/$nostr] ";
739
740       In other words, in the "C" (or English) locale the above will probably
741       print something like:
742
743           Sun? [yes/no]
744
745       See I18N::Langinfo for more information.
746

LOCALE CATEGORIES

748       The following subsections describe basic locale categories.  Beyond
749       these, some combination categories allow manipulation of more than one
750       basic category at a time.  See "ENVIRONMENT" for a discussion of these.
751
752   Category "LC_COLLATE": Collation: Text Comparisons and Sorting
753       In the scope of a "use locale" form that includes collation, Perl looks
754       to the "LC_COLLATE" environment variable to determine the application's
755       notions on collation (ordering) of characters.  For example, "b"
756       follows "a" in Latin alphabets, but where do "a" and "aa" belong?  And
757       while "color" follows "chocolate" in English, what about in traditional
758       Spanish?
759
760       The following collations all make sense and you may meet any of them if
761       you "use locale".
762
763               A B C D E a b c d e
764               A a B b C c D d E e
765               a A b B c C d D e E
766               a b c d e A B C D E
767
768       Here is a code snippet to tell what "word" characters are in the
769       current locale, in that locale's order:
770
771               use locale;
772               print +(sort grep /\w/, map { chr } 0..255), "\n";
773
774       Compare this with the characters that you see and their order if you
775       state explicitly that the locale should be ignored:
776
777               no locale;
778               print +(sort grep /\w/, map { chr } 0..255), "\n";
779
780       This machine-native collation (which is what you get unless
781       "use locale" has appeared earlier in the same block) must be used for
782       sorting raw binary data, whereas the locale-dependent collation of the
783       first example is useful for natural text.
784
785       As noted in "USING LOCALES", "cmp" compares according to the current
786       collation locale when "use locale" is in effect, but falls back to a
787       char-by-char comparison for strings that the locale says are equal. You
788       can use "POSIX::strcoll()" if you don't want this fall-back:
789
790               use POSIX qw(strcoll);
791               $equal_in_locale =
792                   !strcoll("space and case ignored", "SpaceAndCaseIgnored");
793
794       $equal_in_locale will be true if the collation locale specifies a
795       dictionary-like ordering that ignores space characters completely and
796       which folds case.
797
798       Perl uses the platform's C library collation functions "strcoll()" and
799       "strxfrm()".  That means you get whatever they give.  On some
800       platforms, these functions work well on UTF-8 locales, giving a
801       reasonable default collation for the code points that are important in
802       that locale.  (And if they aren't working well, the problem may only be
803       that the locale definition is deficient, so can be fixed by using a
804       better definition file.  Unicode's definitions (see "Freely available
805       locale definitions") provide reasonable UTF-8 locale collation
806       definitions.)  Starting in Perl v5.26, Perl's use of these functions
807       has been made more seamless.  This may be sufficient for your needs.
808       For more control, and to make sure strings containing any code point
809       (not just the ones important in the locale) collate properly, the
810       Unicode::Collate module is suggested.
811
812       In non-UTF-8 locales (hence single byte), code points above 0xFF are
813       technically invalid.  But if present, again starting in v5.26, they
814       will collate to the same position as the highest valid code point does.
815       This generally gives good results, but the collation order may be
816       skewed if the valid code point gets special treatment when it forms
817       particular sequences with other characters as defined by the locale.
818       When two strings collate identically, the code point order is used as a
819       tie breaker.
820
821       If Perl detects that there are problems with the locale collation
822       order, it reverts to using non-locale collation rules for that locale.
823
824       If you have a single string that you want to check for "equality in
825       locale" against several others, you might think you could gain a little
826       efficiency by using "POSIX::strxfrm()" in conjunction with "eq":
827
828               use POSIX qw(strxfrm);
829               $xfrm_string = strxfrm("Mixed-case string");
830               print "locale collation ignores spaces\n"
831                   if $xfrm_string eq strxfrm("Mixed-casestring");
832               print "locale collation ignores hyphens\n"
833                   if $xfrm_string eq strxfrm("Mixedcase string");
834               print "locale collation ignores case\n"
835                   if $xfrm_string eq strxfrm("mixed-case string");
836
837       "strxfrm()" takes a string and maps it into a transformed string for
838       use in char-by-char comparisons against other transformed strings
839       during collation.  "Under the hood", locale-affected Perl comparison
840       operators call "strxfrm()" for both operands, then do a char-by-char
841       comparison of the transformed strings.  By calling "strxfrm()"
842       explicitly and using a non locale-affected comparison, the example
843       attempts to save a couple of transformations.  But in fact, it doesn't
844       save anything: Perl magic (see "Magic Variables" in perlguts) creates
845       the transformed version of a string the first time it's needed in a
846       comparison, then keeps this version around in case it's needed again.
847       An example rewritten the easy way with "cmp" runs just about as fast.
848       It also copes with null characters embedded in strings; if you call
849       "strxfrm()" directly, it treats the first null it finds as a
850       terminator.  Don't expect the transformed strings it produces to be
851       portable across systems--or even from one revision of your operating
852       system to the next.  In short, don't call "strxfrm()" directly: let
853       Perl do it for you.
854
855       Note: "use locale" isn't shown in some of these examples because it
856       isn't needed: "strcoll()" and "strxfrm()" are POSIX functions which use
857       the standard system-supplied "libc" functions that always obey the
858       current "LC_COLLATE" locale.
859
860   Category "LC_CTYPE": Character Types
861       In the scope of a "use locale" form that includes "LC_CTYPE", Perl
862       obeys the "LC_CTYPE" locale setting.  This controls the application's
863       notion of which characters are alphabetic, numeric, punctuation, etc.
864       This affects Perl's "\w" regular expression metanotation, which stands
865       for alphanumeric characters--that is, alphabetic, numeric, and the
866       platform's native underscore.  (Consult perlre for more information
867       about regular expressions.)  Thanks to "LC_CTYPE", depending on your
868       locale setting, characters like "ae", "d`", "ss", and "o" may be
869       understood as "\w" characters.  It also affects things like "\s", "\D",
870       and the POSIX character classes, like "[[:graph:]]".  (See
871       perlrecharclass for more information on all these.)
872
873       The "LC_CTYPE" locale also provides the map used in transliterating
874       characters between lower and uppercase.  This affects the case-mapping
875       functions--"fc()", "lc()", "lcfirst()", "uc()", and "ucfirst()"; case-
876       mapping interpolation with "\F", "\l", "\L", "\u", or "\U" in double-
877       quoted strings and "s///" substitutions; and case-insensitive regular
878       expression pattern matching using the "i" modifier.
879
880       Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
881       otherwise Perl only supports single-byte locales, such as the ISO 8859
882       series.  This means that wide character locales, for example for Asian
883       languages, are not well-supported.  Use of these locales may cause core
884       dumps.  If the platform has the capability for Perl to detect such a
885       locale, starting in Perl v5.22, Perl will warn, default enabled, using
886       the "locale" warning category, whenever such a locale is switched into.
887       The UTF-8 locale support is actually a superset of POSIX locales,
888       because it is really full Unicode behavior as if no "LC_CTYPE" locale
889       were in effect at all (except for tainting; see "SECURITY").  POSIX
890       locales, even UTF-8 ones, are lacking certain concepts in Unicode, such
891       as the idea that changing the case of a character could expand to be
892       more than one character.  Perl in a UTF-8 locale, will give you that
893       expansion.  Prior to v5.20, Perl treated a UTF-8 locale on some
894       platforms like an ISO 8859-1 one, with some restrictions, and on other
895       platforms more like the "C" locale.  For releases v5.16 and v5.18,
896       "use locale 'not_characters" could be used as a workaround for this
897       (see "Unicode and UTF-8").
898
899       Note that there are quite a few things that are unaffected by the
900       current locale.  Any literal character is the native character for the
901       given platform.  Hence 'A' means the character at code point 65 on
902       ASCII platforms, and 193 on EBCDIC.  That may or may not be an 'A' in
903       the current locale, if that locale even has an 'A'.  Similarly, all the
904       escape sequences for particular characters, "\n" for example, always
905       mean the platform's native one.  This means, for example, that "\N" in
906       regular expressions (every character but new-line) works on the
907       platform character set.
908
909       Starting in v5.22, Perl will by default warn when switching into a
910       locale that redefines any ASCII printable character (plus "\t" and
911       "\n") into a different class than expected.  This is likely to happen
912       on modern locales only on EBCDIC platforms, where, for example, a CCSID
913       0037 locale on a CCSID 1047 machine moves "[", but it can happen on
914       ASCII platforms with the ISO 646 and other 7-bit locales that are
915       essentially obsolete.  Things may still work, depending on what
916       features of Perl are used by the program.  For example, in the example
917       from above where "|" becomes a "\w", and there are no regular
918       expressions where this matters, the program may still work properly.
919       The warning lists all the characters that it can determine could be
920       adversely affected.
921
922       Note: A broken or malicious "LC_CTYPE" locale definition may result in
923       clearly ineligible characters being considered to be alphanumeric by
924       your application.  For strict matching of (mundane) ASCII letters and
925       digits--for example, in command strings--locale-aware applications
926       should use "\w" with the "/a" regular expression modifier.  See
927       "SECURITY".
928
929   Category "LC_NUMERIC": Numeric Formatting
930       After a proper "POSIX::setlocale()" call, and within the scope of a
931       "use locale" form that includes numerics, Perl obeys the "LC_NUMERIC"
932       locale information, which controls an application's idea of how numbers
933       should be formatted for human readability.  In most implementations the
934       only effect is to change the character used for the decimal
935       point--perhaps from "."  to ",".  The functions aren't aware of such
936       niceties as thousands separation and so on. (See "The localeconv
937       function" if you care about these things.)
938
939        use POSIX qw(strtod setlocale LC_NUMERIC);
940        use locale;
941
942        setlocale LC_NUMERIC, "";
943
944        $n = 5/2;   # Assign numeric 2.5 to $n
945
946        $a = " $n"; # Locale-dependent conversion to string
947
948        print "half five is $n\n";       # Locale-dependent output
949
950        printf "half five is %g\n", $n;  # Locale-dependent output
951
952        print "DECIMAL POINT IS COMMA\n"
953                 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
954
955       See also I18N::Langinfo and "RADIXCHAR".
956
957   Category "LC_MONETARY": Formatting of monetary amounts
958       The C standard defines the "LC_MONETARY" category, but not a function
959       that is affected by its contents.  (Those with experience of standards
960       committees will recognize that the working group decided to punt on the
961       issue.)  Consequently, Perl essentially takes no notice of it.  If you
962       really want to use "LC_MONETARY", you can query its contents--see "The
963       localeconv function"--and use the information that it returns in your
964       application's own formatting of currency amounts.  However, you may
965       well find that the information, voluminous and complex though it may
966       be, still does not quite meet your requirements: currency formatting is
967       a hard nut to crack.
968
969       See also I18N::Langinfo and "CRNCYSTR".
970
971   Category "LC_TIME": Respresentation of time
972       Output produced by "POSIX::strftime()", which builds a formatted human-
973       readable date/time string, is affected by the current "LC_TIME" locale.
974       Thus, in a French locale, the output produced by the %B format element
975       (full month name) for the first month of the year would be "janvier".
976       Here's how to get a list of long month names in the current locale:
977
978               use POSIX qw(strftime);
979               for (0..11) {
980                   $long_month_name[$_] =
981                       strftime("%B", 0, 0, 0, 1, $_, 96);
982               }
983
984       Note: "use locale" isn't needed in this example: "strftime()" is a
985       POSIX function which uses the standard system-supplied "libc" function
986       that always obeys the current "LC_TIME" locale.
987
988       See also I18N::Langinfo and "ABDAY_1".."ABDAY_7", "DAY_1".."DAY_7",
989       "ABMON_1".."ABMON_12", and "ABMON_1".."ABMON_12".
990
991   Other categories
992       The remaining locale categories are not currently used by Perl itself.
993       But again note that things Perl interacts with may use these, including
994       extensions outside the standard Perl distribution, and by the operating
995       system and its utilities.  Note especially that the string value of $!
996       and the error messages given by external utilities may be changed by
997       "LC_MESSAGES".  If you want to have portable error codes, use "%!".
998       See Errno.
999

SECURITY

1001       Although the main discussion of Perl security issues can be found in
1002       perlsec, a discussion of Perl's locale handling would be incomplete if
1003       it did not draw your attention to locale-dependent security issues.
1004       Locales--particularly on systems that allow unprivileged users to build
1005       their own locales--are untrustworthy.  A malicious (or just plain
1006       broken) locale can make a locale-aware application give unexpected
1007       results.  Here are a few possibilities:
1008
1009       •   Regular expression checks for safe file names or mail addresses
1010           using "\w" may be spoofed by an "LC_CTYPE" locale that claims that
1011           characters such as ">" and "|" are alphanumeric.
1012
1013       •   String interpolation with case-mapping, as in, say, "$dest =
1014           "C:\U$name.$ext"", may produce dangerous results if a bogus
1015           "LC_CTYPE" case-mapping table is in effect.
1016
1017       •   A sneaky "LC_COLLATE" locale could result in the names of students
1018           with "D" grades appearing ahead of those with "A"s.
1019
1020       •   An application that takes the trouble to use information in
1021           "LC_MONETARY" may format debits as if they were credits and vice
1022           versa if that locale has been subverted.  Or it might make payments
1023           in US dollars instead of Hong Kong dollars.
1024
1025       •   The date and day names in dates formatted by "strftime()" could be
1026           manipulated to advantage by a malicious user able to subvert the
1027           "LC_DATE" locale.  ("Look--it says I wasn't in the building on
1028           Sunday.")
1029
1030       Such dangers are not peculiar to the locale system: any aspect of an
1031       application's environment which may be modified maliciously presents
1032       similar challenges.  Similarly, they are not specific to Perl: any
1033       programming language that allows you to write programs that take
1034       account of their environment exposes you to these issues.
1035
1036       Perl cannot protect you from all possibilities shown in the
1037       examples--there is no substitute for your own vigilance--but, when "use
1038       locale" is in effect, Perl uses the tainting mechanism (see perlsec) to
1039       mark string results that become locale-dependent, and which may be
1040       untrustworthy in consequence.
1041
1042       Note that it is possible to compile Perl without taint support, in
1043       which case all taint features silently do nothing.
1044
1045       Here is a summary of the tainting behavior of operators and functions
1046       that may be affected by the locale:
1047
1048Comparison operators ("lt", "le", "ge", "gt" and "cmp"):
1049
1050           Scalar true/false (or less/equal/greater) result is never tainted.
1051
1052Case-mapping interpolation (with "\l", "\L", "\u", "\U", or "\F")
1053
1054           The result string containing interpolated material is tainted if a
1055           "use locale" form that includes "LC_CTYPE" is in effect.
1056
1057Matching operator ("m//"):
1058
1059           Scalar true/false result never tainted.
1060
1061           All subpatterns, either delivered as a list-context result or as $1
1062           etc., are tainted if a "use locale" form that includes "LC_CTYPE"
1063           is in effect, and the subpattern regular expression contains a
1064           locale-dependent construct.  These constructs include "\w" (to
1065           match an alphanumeric character), "\W" (non-alphanumeric
1066           character), "\b" and "\B" (word-boundary and non-boundardy, which
1067           depend on what "\w" and "\W" match), "\s" (whitespace character),
1068           "\S" (non whitespace character), "\d" and "\D" (digits and non-
1069           digits), and the POSIX character classes, such as "[:alpha:]" (see
1070           "POSIX Character Classes" in perlrecharclass).
1071
1072           Tainting is also likely if the pattern is to be matched case-
1073           insensitively (via "/i").  The exception is if all the code points
1074           to be matched this way are above 255 and do not have folds under
1075           Unicode rules to below 256.  Tainting is not done for these because
1076           Perl only uses Unicode rules for such code points, and those rules
1077           are the same no matter what the current locale.
1078
1079           The matched-pattern variables, $&, "$`" (pre-match), "$'" (post-
1080           match), and $+ (last match) also are tainted.
1081
1082Substitution operator ("s///"):
1083
1084           Has the same behavior as the match operator.  Also, the left
1085           operand of "=~" becomes tainted when a "use locale" form that
1086           includes "LC_CTYPE" is in effect, if modified as a result of a
1087           substitution based on a regular expression match involving any of
1088           the things mentioned in the previous item, or of case-mapping, such
1089           as "\l", "\L","\u", "\U", or "\F".
1090
1091Output formatting functions ("printf()" and "write()"):
1092
1093           Results are never tainted because otherwise even output from print,
1094           for example "print(1/7)", should be tainted if "use locale" is in
1095           effect.
1096
1097Case-mapping functions ("lc()", "lcfirst()", "uc()", "ucfirst()"):
1098
1099           Results are tainted if a "use locale" form that includes "LC_CTYPE"
1100           is in effect.
1101
1102POSIX locale-dependent functions ("localeconv()", "strcoll()",
1103           "strftime()", "strxfrm()"):
1104
1105           Results are never tainted.
1106
1107       Three examples illustrate locale-dependent tainting.  The first
1108       program, which ignores its locale, won't run: a value taken directly
1109       from the command line may not be used to name an output file when taint
1110       checks are enabled.
1111
1112               #/usr/local/bin/perl -T
1113               # Run with taint checking
1114
1115               # Command line sanity check omitted...
1116               $tainted_output_file = shift;
1117
1118               open(F, ">$tainted_output_file")
1119                   or warn "Open of $tainted_output_file failed: $!\n";
1120
1121       The program can be made to run by "laundering" the tainted value
1122       through a regular expression: the second example--which still ignores
1123       locale information--runs, creating the file named on its command line
1124       if it can.
1125
1126               #/usr/local/bin/perl -T
1127
1128               $tainted_output_file = shift;
1129               $tainted_output_file =~ m%[\w/]+%;
1130               $untainted_output_file = $&;
1131
1132               open(F, ">$untainted_output_file")
1133                   or warn "Open of $untainted_output_file failed: $!\n";
1134
1135       Compare this with a similar but locale-aware program:
1136
1137               #/usr/local/bin/perl -T
1138
1139               $tainted_output_file = shift;
1140               use locale;
1141               $tainted_output_file =~ m%[\w/]+%;
1142               $localized_output_file = $&;
1143
1144               open(F, ">$localized_output_file")
1145                   or warn "Open of $localized_output_file failed: $!\n";
1146
1147       This third program fails to run because $& is tainted: it is the result
1148       of a match involving "\w" while "use locale" is in effect.
1149

ENVIRONMENT

1151       PERL_SKIP_LOCALE_INIT
1152                   This environment variable, available starting in Perl
1153                   v5.20, if set (to any value), tells Perl to not use the
1154                   rest of the environment variables to initialize with.
1155                   Instead, Perl uses whatever the current locale settings
1156                   are.  This is particularly useful in embedded environments,
1157                   see "Using embedded Perl with POSIX locales" in perlembed.
1158
1159       PERL_BADLANG
1160                   A string that can suppress Perl's warning about failed
1161                   locale settings at startup.  Failure can occur if the
1162                   locale support in the operating system is lacking (broken)
1163                   in some way--or if you mistyped the name of a locale when
1164                   you set up your environment.  If this environment variable
1165                   is absent, or has a value other than "0" or "", Perl will
1166                   complain about locale setting failures.
1167
1168                   NOTE: "PERL_BADLANG" only gives you a way to hide the
1169                   warning message.  The message tells about some problem in
1170                   your system's locale support, and you should investigate
1171                   what the problem is.
1172
1173       The following environment variables are not specific to Perl: They are
1174       part of the standardized (ISO C, XPG4, POSIX 1.c) "setlocale()" method
1175       for controlling an application's opinion on data.  Windows is non-
1176       POSIX, but Perl arranges for the following to work as described anyway.
1177       If the locale given by an environment variable is not valid, Perl tries
1178       the next lower one in priority.  If none are valid, on Windows, the
1179       system default locale is then tried.  If all else fails, the "C" locale
1180       is used.  If even that doesn't work, something is badly broken, but
1181       Perl tries to forge ahead with whatever the locale settings might be.
1182
1183       "LC_ALL"    "LC_ALL" is the "override-all" locale environment variable.
1184                   If set, it overrides all the rest of the locale environment
1185                   variables.
1186
1187       "LANGUAGE"  NOTE: "LANGUAGE" is a GNU extension, it affects you only if
1188                   you are using the GNU libc.  This is the case if you are
1189                   using e.g. Linux.  If you are using "commercial" Unixes you
1190                   are most probably not using GNU libc and you can ignore
1191                   "LANGUAGE".
1192
1193                   However, in the case you are using "LANGUAGE": it affects
1194                   the language of informational, warning, and error messages
1195                   output by commands (in other words, it's like
1196                   "LC_MESSAGES") but it has higher priority than "LC_ALL".
1197                   Moreover, it's not a single value but instead a "path"
1198                   (":"-separated list) of languages (not locales).  See the
1199                   GNU "gettext" library documentation for more information.
1200
1201       "LC_CTYPE"  In the absence of "LC_ALL", "LC_CTYPE" chooses the
1202                   character type locale.  In the absence of both "LC_ALL" and
1203                   "LC_CTYPE", "LANG" chooses the character type locale.
1204
1205       "LC_COLLATE"
1206                   In the absence of "LC_ALL", "LC_COLLATE" chooses the
1207                   collation (sorting) locale.  In the absence of both
1208                   "LC_ALL" and "LC_COLLATE", "LANG" chooses the collation
1209                   locale.
1210
1211       "LC_MONETARY"
1212                   In the absence of "LC_ALL", "LC_MONETARY" chooses the
1213                   monetary formatting locale.  In the absence of both
1214                   "LC_ALL" and "LC_MONETARY", "LANG" chooses the monetary
1215                   formatting locale.
1216
1217       "LC_NUMERIC"
1218                   In the absence of "LC_ALL", "LC_NUMERIC" chooses the
1219                   numeric format locale.  In the absence of both "LC_ALL" and
1220                   "LC_NUMERIC", "LANG" chooses the numeric format.
1221
1222       "LC_TIME"   In the absence of "LC_ALL", "LC_TIME" chooses the date and
1223                   time formatting locale.  In the absence of both "LC_ALL"
1224                   and "LC_TIME", "LANG" chooses the date and time formatting
1225                   locale.
1226
1227       "LANG"      "LANG" is the "catch-all" locale environment variable. If
1228                   it is set, it is used as the last resort after the overall
1229                   "LC_ALL" and the category-specific "LC_foo".
1230
1231   Examples
1232       The "LC_NUMERIC" controls the numeric output:
1233
1234          use locale;
1235          use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1236          setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1237          printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
1238
1239       and also how strings are parsed by "POSIX::strtod()" as numbers:
1240
1241          use locale;
1242          use POSIX qw(locale_h strtod);
1243          setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1244          my $x = strtod("2,34") + 5;
1245          print $x, "\n"; # Probably shows 7,34.
1246

NOTES

1248   String "eval" and "LC_NUMERIC"
1249       A string eval parses its expression as standard Perl.  It is therefore
1250       expecting the decimal point to be a dot.  If "LC_NUMERIC" is set to
1251       have this be a comma instead, the parsing will be confused, perhaps
1252       silently.
1253
1254        use locale;
1255        use POSIX qw(locale_h);
1256        setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1257        my $a = 1.2;
1258        print eval "$a + 1.5";
1259        print "\n";
1260
1261       prints "13,5".  This is because in that locale, the comma is the
1262       decimal point character.  The "eval" thus expands to:
1263
1264        eval "1,2 + 1.5"
1265
1266       and the result is not what you likely expected.  No warnings are
1267       generated.  If you do string "eval"'s within the scope of "use locale",
1268       you should instead change the "eval" line to do something like:
1269
1270        print eval "no locale; $a + 1.5";
1271
1272       This prints 2.7.
1273
1274       You could also exclude "LC_NUMERIC", if you don't need it, by
1275
1276        use locale ':!numeric';
1277
1278   Backward compatibility
1279       Versions of Perl prior to 5.004 mostly ignored locale information,
1280       generally behaving as if something similar to the "C" locale were
1281       always in force, even if the program environment suggested otherwise
1282       (see "The setlocale function").  By default, Perl still behaves this
1283       way for backward compatibility.  If you want a Perl application to pay
1284       attention to locale information, you must use the "use locale" pragma
1285       (see "The "use locale" pragma") or, in the unlikely event that you want
1286       to do so for just pattern matching, the "/l" regular expression
1287       modifier (see "Character set modifiers" in perlre) to instruct it to do
1288       so.
1289
1290       Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE" information
1291       if available; that is, "\w" did understand what were the letters
1292       according to the locale environment variables.  The problem was that
1293       the user had no control over the feature: if the C library supported
1294       locales, Perl used them.
1295
1296   I18N:Collate obsolete
1297       In versions of Perl prior to 5.004, per-locale collation was possible
1298       using the "I18N::Collate" library module.  This module is now mildly
1299       obsolete and should be avoided in new applications.  The "LC_COLLATE"
1300       functionality is now integrated into the Perl core language: One can
1301       use locale-specific scalar data completely normally with "use locale",
1302       so there is no longer any need to juggle with the scalar references of
1303       "I18N::Collate".
1304
1305   Sort speed and memory use impacts
1306       Comparing and sorting by locale is usually slower than the default
1307       sorting; slow-downs of two to four times have been observed.  It will
1308       also consume more memory: once a Perl scalar variable has participated
1309       in any string comparison or sorting operation obeying the locale
1310       collation rules, it will take 3-15 times more memory than before.  (The
1311       exact multiplier depends on the string's contents, the operating system
1312       and the locale.) These downsides are dictated more by the operating
1313       system's implementation of the locale system than by Perl.
1314
1315   Freely available locale definitions
1316       The Unicode CLDR project extracts the POSIX portion of many of its
1317       locales, available at
1318
1319         https://unicode.org/Public/cldr/2.0.1/
1320
1321       (Newer versions of CLDR require you to compute the POSIX data yourself.
1322       See <http://unicode.org/Public/cldr/latest/>.)
1323
1324       There is a large collection of locale definitions at:
1325
1326         http://std.dkuug.dk/i18n/WG15-collection/locales/
1327
1328       You should be aware that it is unsupported, and is not claimed to be
1329       fit for any purpose.  If your system allows installation of arbitrary
1330       locales, you may find the definitions useful as they are, or as a basis
1331       for the development of your own locales.
1332
1333   I18n and l10n
1334       "Internationalization" is often abbreviated as i18n because its first
1335       and last letters are separated by eighteen others.  (You may guess why
1336       the internalin ... internaliti ... i18n tends to get abbreviated.)  In
1337       the same way, "localization" is often abbreviated to l10n.
1338
1339   An imperfect standard
1340       Internationalization, as defined in the C and POSIX standards, can be
1341       criticized as incomplete and ungainly.  They also have a tendency, like
1342       standards groups, to divide the world into nations, when we all know
1343       that the world can equally well be divided into bankers, bikers,
1344       gamers, and so on.
1345

Unicode and UTF-8

1347       The support of Unicode is new starting from Perl version v5.6, and more
1348       fully implemented in versions v5.8 and later.  See perluniintro.
1349
1350       Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
1351       "LC_COLLATE" is only partially supported; collation support is improved
1352       in Perl v5.26 to a level that may be sufficient for your needs (see
1353       "Category "LC_COLLATE": Collation: Text Comparisons and Sorting").
1354
1355       If you have Perl v5.16 or v5.18 and can't upgrade, you can use
1356
1357           use locale ':not_characters';
1358
1359       When this form of the pragma is used, only the non-character portions
1360       of locales are used by Perl, for example "LC_NUMERIC".  Perl assumes
1361       that you have translated all the characters it is to operate on into
1362       Unicode (actually the platform's native character set (ASCII or EBCDIC)
1363       plus Unicode).  For data in files, this can conveniently be done by
1364       also specifying
1365
1366           use open ':locale';
1367
1368       This pragma arranges for all inputs from files to be translated into
1369       Unicode from the current locale as specified in the environment (see
1370       "ENVIRONMENT"), and all outputs to files to be translated back into the
1371       locale.  (See open).  On a per-filehandle basis, you can instead use
1372       the PerlIO::locale module, or the Encode::Locale module, both available
1373       from CPAN.  The latter module also has methods to ease the handling of
1374       "ARGV" and environment variables, and can be used on individual
1375       strings.  If you know that all your locales will be UTF-8, as many are
1376       these days, you can use the -C command line switch.
1377
1378       This form of the pragma allows essentially seamless handling of locales
1379       with Unicode.  The collation order will be by Unicode code point order.
1380       Unicode::Collate can be used to get Unicode rules collation.
1381
1382       All the modules and switches just described can be used in v5.20 with
1383       just plain "use locale", and, should the input locales not be UTF-8,
1384       you'll get the less than ideal behavior, described below, that you get
1385       with pre-v5.16 Perls, or when you use the locale pragma without the
1386       ":not_characters" parameter in v5.16 and v5.18.  If you are using
1387       exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1388       does not apply to you.
1389
1390       There are two cases, multi-byte and single-byte locales.  First multi-
1391       byte:
1392
1393       The only multi-byte (or wide character) locale that Perl is ever likely
1394       to support is UTF-8.  This is due to the difficulty of implementation,
1395       the fact that high quality UTF-8 locales are now published for every
1396       area of the world (<https://unicode.org/Public/cldr/2.0.1/> for ones
1397       that are already set-up, but from an earlier version;
1398       <https://unicode.org/Public/cldr/latest/> for the most up-to-date, but
1399       you have to extract the POSIX information yourself), and failing all
1400       that, you can use the Encode module to translate to/from your locale.
1401       So, you'll have to do one of those things if you're using one of these
1402       locales, such as Big5 or Shift JIS.  For UTF-8 locales, in Perls (pre
1403       v5.20) that don't have full UTF-8 locale support, they may work
1404       reasonably well (depending on your C library implementation) simply
1405       because both they and Perl store characters that take up multiple bytes
1406       the same way.  However, some, if not most, C library implementations
1407       may not process the characters in the upper half of the Latin-1 range
1408       (128 - 255) properly under "LC_CTYPE".  To see if a character is a
1409       particular type under a locale, Perl uses the functions like
1410       "isalnum()".  Your C library may not work for UTF-8 locales with those
1411       functions, instead only working under the newer wide library functions
1412       like "iswalnum()", which Perl does not use.  These multi-byte locales
1413       are treated like single-byte locales, and will have the restrictions
1414       described below.  Starting in Perl v5.22 a warning message is raised
1415       when Perl detects a multi-byte locale that it doesn't fully support.
1416
1417       For single-byte locales, Perl generally takes the tack to use locale
1418       rules on code points that can fit in a single byte, and Unicode rules
1419       for those that can't (though this isn't uniformly applied, see the note
1420       at the end of this section).  This prevents many problems in locales
1421       that aren't UTF-8.  Suppose the locale is ISO8859-7, Greek.  The
1422       character at 0xD7 there is a capital Chi. But in the ISO8859-1 locale,
1423       Latin1, it is a multiplication sign.  The POSIX regular expression
1424       character class "[[:alpha:]]" will magically match 0xD7 in the Greek
1425       locale but not in the Latin one.
1426
1427       However, there are places where this breaks down.  Certain Perl
1428       constructs are for Unicode only, such as "\p{Alpha}".  They assume that
1429       0xD7 always has its Unicode meaning (or the equivalent on EBCDIC
1430       platforms).  Since Latin1 is a subset of Unicode and 0xD7 is the
1431       multiplication sign in both Latin1 and Unicode, "\p{Alpha}" will never
1432       match it, regardless of locale.  A similar issue occurs with "\N{...}".
1433       Prior to v5.20, it is therefore a bad idea to use "\p{}" or "\N{}"
1434       under plain "use locale"--unless you can guarantee that the locale will
1435       be ISO8859-1.  Use POSIX character classes instead.
1436
1437       Another problem with this approach is that operations that cross the
1438       single byte/multiple byte boundary are not well-defined, and so are
1439       disallowed.  (This boundary is between the codepoints at 255/256.)  For
1440       example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1441       should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF).  But in the
1442       Greek locale, for example, there is no character at 0xFF, and Perl has
1443       no way of knowing what the character at 0xFF is really supposed to
1444       represent.  Thus it disallows the operation.  In this mode, the
1445       lowercase of U+0178 is itself.
1446
1447       The same problems ensue if you enable automatic UTF-8-ification of your
1448       standard file handles, default "open()" layer, and @ARGV on
1449       non-ISO8859-1, non-UTF-8 locales (by using either the -C command line
1450       switch or the "PERL_UNICODE" environment variable; see perlrun).
1451       Things are read in as UTF-8, which would normally imply a Unicode
1452       interpretation, but the presence of a locale causes them to be
1453       interpreted in that locale instead.  For example, a 0xD7 code point in
1454       the Unicode input, which should mean the multiplication sign, won't be
1455       interpreted by Perl that way under the Greek locale.  This is not a
1456       problem provided you make certain that all locales will always and only
1457       be either an ISO8859-1, or, if you don't have a deficient C library, a
1458       UTF-8 locale.
1459
1460       Still another problem is that this approach can lead to two code points
1461       meaning the same character.  Thus in a Greek locale, both U+03A7 and
1462       U+00D7 are GREEK CAPITAL LETTER CHI.
1463
1464       Because of all these problems, starting in v5.22, Perl will raise a
1465       warning if a multi-byte (hence Unicode) code point is used when a
1466       single-byte locale is in effect.  (Although it doesn't check for this
1467       if doing so would unreasonably slow execution down.)
1468
1469       Vendor locales are notoriously buggy, and it is difficult for Perl to
1470       test its locale-handling code because this interacts with code that
1471       Perl has no control over; therefore the locale-handling code in Perl
1472       may be buggy as well.  (However, the Unicode-supplied locales should be
1473       better, and there is a feed back mechanism to correct any problems.
1474       See "Freely available locale definitions".)
1475
1476       If you have Perl v5.16, the problems mentioned above go away if you use
1477       the ":not_characters" parameter to the locale pragma (except for vendor
1478       bugs in the non-character portions).  If you don't have v5.16, and you
1479       do have locales that work, using them may be worthwhile for certain
1480       specific purposes, as long as you keep in mind the gotchas already
1481       mentioned.  For example, if the collation for your locales works, it
1482       runs faster under locales than under Unicode::Collate; and you gain
1483       access to such things as the local currency symbol and the names of the
1484       months and days of the week.  (But to hammer home the point, in v5.16,
1485       you get this access without the downsides of locales by using the
1486       ":not_characters" form of the pragma.)
1487
1488       Note: The policy of using locale rules for code points that can fit in
1489       a byte, and Unicode rules for those that can't is not uniformly
1490       applied.  Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied
1491       fairly consistently to regular expression matching except for bracketed
1492       character classes; in v5.14 it was extended to all regex matches; and
1493       in v5.16 to the casing operations such as "\L" and "uc()".  For
1494       collation, in all releases so far, the system's "strxfrm()" function is
1495       called, and whatever it does is what you get.  Starting in v5.26,
1496       various bugs are fixed with the way perl uses this function.
1497

BUGS

1499   Collation of strings containing embedded "NUL" characters
1500       "NUL" characters will sort the same as the lowest collating control
1501       character does, or to "\001" in the unlikely event that there are no
1502       control characters at all in the locale.  In cases where the strings
1503       don't contain this non-"NUL" control, the results will be correct, and
1504       in many locales, this control, whatever it might be, will rarely be
1505       encountered.  But there are cases where a "NUL" should sort before this
1506       control, but doesn't.  If two strings do collate identically, the one
1507       containing the "NUL" will sort to earlier.  Prior to 5.26, there were
1508       more bugs.
1509
1510   Multi-threaded
1511       XS code or C-language libraries called from it that use the system
1512       setlocale(3) function (except on Windows) likely will not work from a
1513       multi-threaded application without changes.  See "Locale-aware XS code"
1514       in perlxs.
1515
1516       An XS module that is locale-dependent could have been written under the
1517       assumption that it will never be called in a multi-threaded
1518       environment, and so uses other non-locale constructs that aren't multi-
1519       thread-safe.  See "Thread-aware system interfaces" in perlxs.
1520
1521       POSIX does not define a way to get the name of the current per-thread
1522       locale.  Some systems, such as Darwin and NetBSD do implement a
1523       function, querylocale(3) to do this.  On non-Windows systems without
1524       it, such as Linux, there are some additional caveats:
1525
1526       •   An embedded perl needs to be started up while the global locale is
1527           in effect.  See "Using embedded Perl with POSIX locales" in
1528           perlembed.
1529
1530       •   It becomes more important for perl to know about all the possible
1531           locale categories on the platform, even if they aren't apparently
1532           used in your program.  Perl knows all of the Linux ones.  If your
1533           platform has others, you can submit an issue at
1534           <https://github.com/Perl/perl5/issues> for inclusion of it in the
1535           next release.  In the meantime, it is possible to edit the Perl
1536           source to teach it about the category, and then recompile.  Search
1537           for instances of, say, "LC_PAPER" in the source, and use that as a
1538           template to add the omitted one.
1539
1540       •   It is possible, though hard to do, to call "POSIX::setlocale" with
1541           a locale that it doesn't recognize as syntactically legal, but
1542           actually is legal on that system.  This should happen only with
1543           embedded perls, or if you hand-craft a locale name yourself.
1544
1545   Broken systems
1546       In certain systems, the operating system's locale support is broken and
1547       cannot be fixed or used by Perl.  Such deficiencies can and will result
1548       in mysterious hangs and/or Perl core dumps when "use locale" is in
1549       effect.  When confronted with such a system, please report in
1550       excruciating detail to <<https://github.com/Perl/perl5/issues>>, and
1551       also contact your vendor: bug fixes may exist for these problems in
1552       your operating system.  Sometimes such bug fixes are called an
1553       operating system upgrade.  If you have the source for Perl, include in
1554       the bug report the output of the test described above in "Testing for
1555       broken locales".
1556

SEE ALSO

1558       I18N::Langinfo, perluniintro, perlunicode, open, "localeconv" in POSIX,
1559       "setlocale" in POSIX, "strcoll" in POSIX, "strftime" in POSIX, "strtod"
1560       in POSIX, "strxfrm" in POSIX.
1561
1562       For special considerations when Perl is embedded in a C program, see
1563       "Using embedded Perl with POSIX locales" in perlembed.
1564

HISTORY

1566       Jarkko Hietaniemi's original perli18n.pod heavily hacked by Dominic
1567       Dunlop, assisted by the perl5-porters.  Prose worked over a bit by Tom
1568       Christiansen, and now maintained by Perl 5 porters.
1569
1570
1571
1572perl v5.36.3                      2023-11-30                     PERLLOCALE(1)
Impressum