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1=encoding utf8
2
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3=head1 NAME
4
b0c42ed9 5perllocale - Perl locale handling (internationalization and localization)
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6
7=head1 DESCRIPTION
8
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9In the beginning there was ASCII, the "American Standard Code for
10Information Interchange", which works quite well for Americans with
11their English alphabet and dollar-denominated currency. But it doesn't
12work so well even for other English speakers, who may use different
13currencies, such as the pound sterling (as the symbol for that currency
14is not in ASCII); and it's hopelessly inadequate for many of the
15thousands of the world's other languages.
16
17To address these deficiencies, the concept of locales was invented
18(formally the ISO C, XPG4, POSIX 1.c "locale system"). And applications
19were and are being written that use the locale mechanism. The process of
20making such an application take account of its users' preferences in
21these kinds of matters is called B<internationalization> (often
22abbreviated as B<i18n>); telling such an application about a particular
23set of preferences is known as B<localization> (B<l10n>).
24
39332f68 25Perl has been extended to support the locale system. This
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26is controlled per application by using one pragma, one function call,
27and several environment variables.
28
29Unfortunately, there are quite a few deficiencies with the design (and
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30often, the implementations) of locales. Unicode was invented (see
31L<perlunitut> for an introduction to that) in part to address these
32design deficiencies, and nowadays, there is a series of "UTF-8
33locales", based on Unicode. These are locales whose character set is
34Unicode, encoded in UTF-8. Starting in v5.20, Perl fully supports
35UTF-8 locales, except for sorting and string comparisions. (Use
36L<Unicode::Collate> for these.) Perl continues to support the old
37non UTF-8 locales as well.
38
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39(Unicode is also creating C<CLDR>, the "Common Locale Data Repository",
40L<http://cldr.unicode.org/> which includes more types of information than
41are available in the POSIX locale system. At the time of this writing,
42there was no CPAN module that provides access to this XML-encoded data.
43However, many of its locales have the POSIX-only data extracted, and are
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44available as UTF-8 locales at
45L<http://unicode.org/Public/cldr/latest/>.)
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46
47=head1 WHAT IS A LOCALE
48
49A locale is a set of data that describes various aspects of how various
50communities in the world categorize their world. These categories are
51broken down into the following types (some of which include a brief
52note here):
53
54=over
55
cb88b78e 56=item Category C<LC_NUMERIC>: Numeric formatting
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57
58This indicates how numbers should be formatted for human readability,
59for example the character used as the decimal point.
60
cb88b78e 61=item Category C<LC_MONETARY>: Formatting of monetary amounts
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62
63=for comment
ebc3223b 64The nbsp below makes this look better (though not great)
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65
66E<160>
67
cb88b78e 68=item Category C<LC_TIME>: Date/Time formatting
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69
70=for comment
ebc3223b 71The nbsp below makes this look better (though not great)
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72
73E<160>
74
cb88b78e 75=item Category C<LC_MESSAGES>: Error and other messages
66cbab2c 76
2619d284 77This is used by Perl itself only for accessing operating system error
03c702c5 78messages via L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>.
66cbab2c 79
cb88b78e 80=item Category C<LC_COLLATE>: Collation
66cbab2c 81
76073c88 82This indicates the ordering of letters for comparison and sorting.
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83In Latin alphabets, for example, "b", generally follows "a".
84
cb88b78e 85=item Category C<LC_CTYPE>: Character Types
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86
87This indicates, for example if a character is an uppercase letter.
88
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89=item Other categories
90
91Some platforms have other categories, dealing with such things as
92measurement units and paper sizes. None of these are used directly by
93Perl, but outside operations that Perl interacts with may use
4c9b78f4 94these. See L</Not within the scope of any "use locale" variant> below.
2619d284 95
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96=back
97
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98More details on the categories used by Perl are given below in L</LOCALE
99CATEGORIES>.
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100
101Together, these categories go a long way towards being able to customize
102a single program to run in many different locations. But there are
103deficiencies, so keep reading.
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104
105=head1 PREPARING TO USE LOCALES
106
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107Perl itself will not use locales unless specifically requested to (but
108again note that Perl may interact with code that does use them). Even
109if there is such a request, B<all> of the following must be true
b960a36e 110for it to work properly:
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111
112=over 4
113
114=item *
115
116B<Your operating system must support the locale system>. If it does,
39332f68 117you should find that the C<setlocale()> function is a documented part of
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118its C library.
119
120=item *
121
5a964f20 122B<Definitions for locales that you use must be installed>. You, or
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123your system administrator, must make sure that this is the case. The
124available locales, the location in which they are kept, and the manner
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125in which they are installed all vary from system to system. Some systems
126provide only a few, hard-wired locales and do not allow more to be
127added. Others allow you to add "canned" locales provided by the system
128supplier. Still others allow you or the system administrator to define
14280422 129and add arbitrary locales. (You may have to ask your supplier to
5a964f20 130provide canned locales that are not delivered with your operating
14280422 131system.) Read your system documentation for further illumination.
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132
133=item *
134
135B<Perl must believe that the locale system is supported>. If it does,
136C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is
137C<define>.
138
139=back
140
141If you want a Perl application to process and present your data
142according to a particular locale, the application code should include
2ae324a7 143the S<C<use locale>> pragma (see L<The use locale pragma>) where
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144appropriate, and B<at least one> of the following must be true:
145
146=over 4
147
c052850d 148=item 1
5f05dabc 149
66cbab2c 150B<The locale-determining environment variables (see L</"ENVIRONMENT">)
5a964f20 151must be correctly set up> at the time the application is started, either
ef3087ec 152by yourself or by whomever set up your system account; or
5f05dabc 153
c052850d 154=item 2
5f05dabc 155
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156B<The application must set its own locale> using the method described in
157L<The setlocale function>.
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158
159=back
160
161=head1 USING LOCALES
162
163=head2 The use locale pragma
164
2619d284 165By default, Perl itself ignores the current locale. The S<C<use locale>>
66cbab2c 166pragma tells Perl to use the current locale for some operations.
7ee2ae1e 167Starting in v5.16, there is an optional parameter to this pragma:
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168
169 use locale ':not_characters';
170
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171This parameter allows better mixing of locales and Unicode (less useful
172in v5.20 and later), and is
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173described fully in L</Unicode and UTF-8>, but briefly, it tells Perl to
174not use the character portions of the locale definition, that is
175the C<LC_CTYPE> and C<LC_COLLATE> categories. Instead it will use the
2619d284 176native character set (extended by Unicode). When using this parameter,
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177you are responsible for getting the external character set translated
178into the native/Unicode one (which it already will be if it is one of
179the increasingly popular UTF-8 locales). There are convenient ways of
180doing this, as described in L</Unicode and UTF-8>.
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181
182The current locale is set at execution time by
183L<setlocale()|/The setlocale function> described below. If that function
184hasn't yet been called in the course of the program's execution, the
66cbab2c 185current locale is that which was determined by the L</"ENVIRONMENT"> in
ebc3223b 186effect at the start of the program.
dfcc8045 187If there is no valid environment, the current locale is whatever the
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188system default has been set to. On POSIX systems, it is likely, but
189not necessarily, the "C" locale. On Windows, the default is set via the
190computer's S<C<Control Panel-E<gt>Regional and Language Options>> (or its
191current equivalent).
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192
193The operations that are affected by locale are:
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194
195=over 4
196
4c9b78f4 197=item B<Not within the scope of any C<"use locale"> variant>
b960a36e 198
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199Only operations originating outside Perl should be affected, as follows:
200
201=over 4
202
203=item *
2619d284 204
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205The variables L<$!|perlvar/$ERRNO> (and its synonyms C<$ERRNO> and
206C<$OS_ERROR>) and L<$^E|perlvar/$EXTENDED_OS_ERROR> (and its synonym
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207C<$EXTENDED_OS_ERROR>) when used as strings always are in terms of the
208current locale and as if within the scope of L<"use bytes"|bytes>. This is
b17e32ea 209likely to change in Perl v5.22.
2619d284 210
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211=item *
212
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213The current locale is also used when going outside of Perl with
214operations like L<system()|perlfunc/system LIST> or
215L<qxE<sol>E<sol>|perlop/qxE<sol>STRINGE<sol>>, if those operations are
216locale-sensitive.
217
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218=item *
219
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220Also Perl gives access to various C library functions through the
221L<POSIX> module. Some of those functions are always affected by the
222current locale. For example, C<POSIX::strftime()> uses C<LC_TIME>;
223C<POSIX::strtod()> uses C<LC_NUMERIC>; C<POSIX::strcoll()> and
224C<POSIX::strxfrm()> use C<LC_COLLATE>; and character classification
225functions like C<POSIX::isalnum()> use C<LC_CTYPE>. All such functions
226will behave according to the current underlying locale, even if that
1d2ab946 227locale isn't exposed to Perl space.
2619d284 228
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229=item *
230
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231XS modules for all categories but C<LC_NUMERIC> get the underlying
232locale, and hence any C library functions they call will use that
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233underlying locale.
234
235Perl tries to keep C<LC_NUMERIC> set to C<"C">
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236because too many modules are unable to cope with the decimal point in a
237floating point number not being a dot (it's a comma in many locales).
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238Macros are provided for XS code to temporarily change to use the
239underlying locale when necessary; however buggy code that fails to
240restore when done can break other XS code (but not Perl code) in this
241regard. The API for these macros has not yet been nailed down, but will be
242during the course of v5.21. Send email to
243L<mailto:perl5-porters@perl.org> for guidance.
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244
245=back
246
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247=for comment
248The nbsp below makes this look better (though not great)
249
250E<160>
251
252=item B<Lingering effects of C<S<use locale>>>
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253
254Certain Perl operations that are set-up within the scope of a
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255C<use locale> variant retain that effect even outside the scope.
256These include:
257
258=over 4
259
260=item *
261
262The output format of a L<write()|perlfunc/write> is determined by an
263earlier format declaration (L<perlfunc/format>), so whether or not the
264output is affected by locale is determined by if the C<format()> is
265within the scope of a C<use locale> variant, not whether the C<write()>
266is.
267
268=item *
269
270Regular expression patterns can be compiled using
271L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodual> with actual
272matching deferred to later. Again, it is whether or not the compilation
273was done within the scope of C<use locale> that determines the match
274behavior, not if the matches are done within such a scope or not.
275
276=back
277
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278=for comment
279The nbsp below makes this look better (though not great)
280
281E<160>
282
4c9b78f4 283=item B<Under C<"use locale ':not_characters';">>
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284
285=over 4
286
287=item *
288
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289All the non-Perl operations.
290
291=item *
292
293B<Format declarations> (L<perlfunc/format>) and hence any subsequent
294C<write()>s use C<LC_NUMERIC>.
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295
296=item *
297
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298B<stringification and output> use C<LC_NUMERIC>.
299These include the results of
300C<print()>,
301C<printf()>,
302C<say()>,
303and
304C<sprintf()>.
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305
306=back
307
308=for comment
ebc3223b 309The nbsp below makes this look better (though not great)
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310
311E<160>
312
4c9b78f4 313=item B<Under just plain C<"use locale";>>
66cbab2c 314
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315=over 4
316
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317=item *
318
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319All the above operations
320
321=item *
322
323B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
39332f68 324C<LC_COLLATE>. C<sort()> is also affected if used without an
5a964f20 325explicit comparison function, because it uses C<cmp> by default.
14280422 326
5a964f20 327B<Note:> C<eq> and C<ne> are unaffected by locale: they always
de108802 328perform a char-by-char comparison of their scalar operands. What's
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329more, if C<cmp> finds that its operands are equal according to the
330collation sequence specified by the current locale, it goes on to
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331perform a char-by-char comparison, and only returns I<0> (equal) if the
332operands are char-for-char identical. If you really want to know whether
5a964f20 333two strings--which C<eq> and C<cmp> may consider different--are equal
14280422 334as far as collation in the locale is concerned, see the discussion in
cb88b78e 335L<Category C<LC_COLLATE>: Collation>.
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336
337=item *
338
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339B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
340C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
5f05dabc 341
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342=back
343
66cbab2c 344=back
5f05dabc 345
5a964f20 346The default behavior is restored with the S<C<no locale>> pragma, or
ef3087ec 347upon reaching the end of the block enclosing C<use locale>.
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348Note that C<use locale> and C<use locale ':not_characters'> may be
349nested, and that what is in effect within an inner scope will revert to
350the outer scope's rules at the end of the inner scope.
5f05dabc 351
5a964f20 352The string result of any operation that uses locale
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353information is tainted, as it is possible for a locale to be
354untrustworthy. See L<"SECURITY">.
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355
356=head2 The setlocale function
357
14280422 358You can switch locales as often as you wish at run time with the
39332f68 359C<POSIX::setlocale()> function:
5f05dabc 360
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361 # Import locale-handling tool set from POSIX module.
362 # This example uses: setlocale -- the function call
363 # LC_CTYPE -- explained below
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364 # (Showing the testing for success/failure of operations is
365 # omitted in these examples to avoid distracting from the main
ebc3223b 366 # point)
6ea81ccf 367
5f05dabc 368 use POSIX qw(locale_h);
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369 use locale;
370 my $old_locale;
5f05dabc 371
14280422 372 # query and save the old locale
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373 $old_locale = setlocale(LC_CTYPE);
374
375 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
376 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
377
378 setlocale(LC_CTYPE, "");
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379 # LC_CTYPE now reset to the default defined by the
380 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
381 # default. See below for documentation.
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382
383 # restore the old locale
384 setlocale(LC_CTYPE, $old_locale);
385
39332f68 386The first argument of C<setlocale()> gives the B<category>, the second the
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387B<locale>. The category tells in what aspect of data processing you
388want to apply locale-specific rules. Category names are discussed in
66cbab2c 389L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a
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390collection of customization information corresponding to a particular
391combination of language, country or territory, and codeset. Read on for
392hints on the naming of locales: not all systems name locales as in the
393example.
394
39332f68 395If no second argument is provided and the category is something other
cb88b78e 396than C<LC_ALL>, the function returns a string naming the current locale
502a173a 397for the category. You can use this value as the second argument in a
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398subsequent call to C<setlocale()>, B<but> on some platforms the string
399is opaque, not something that most people would be able to decipher as
400to what locale it means.
502a173a 401
cb88b78e 402If no second argument is provided and the category is C<LC_ALL>, the
502a173a 403result is implementation-dependent. It may be a string of
c052850d 404concatenated locale names (separator also implementation-dependent)
39332f68 405or a single locale name. Please consult your L<setlocale(3)> man page for
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406details.
407
408If a second argument is given and it corresponds to a valid locale,
409the locale for the category is set to that value, and the function
410returns the now-current locale value. You can then use this in yet
39332f68 411another call to C<setlocale()>. (In some implementations, the return
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412value may sometimes differ from the value you gave as the second
413argument--think of it as an alias for the value you gave.)
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414
415As the example shows, if the second argument is an empty string, the
416category's locale is returned to the default specified by the
417corresponding environment variables. Generally, this results in a
5a964f20 418return to the default that was in force when Perl started up: changes
54310121 419to the environment made by the application after startup may or may not
5a964f20 420be noticed, depending on your system's C library.
5f05dabc 421
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422Note that Perl ignores the current C<LC_CTYPE> and C<LC_COLLATE> locales
423within the scope of a C<use locale ':not_characters'>.
424
f170b852 425If C<set_locale()> fails for some reason (for example, an attempt to set
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426to a locale unknown to the system), the locale for the category is not
427changed, and the function returns C<undef>.
428
2619d284 429
39332f68 430For further information about the categories, consult L<setlocale(3)>.
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431
432=head2 Finding locales
433
39332f68 434For locales available in your system, consult also L<setlocale(3)> to
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435see whether it leads to the list of available locales (search for the
436I<SEE ALSO> section). If that fails, try the following command lines:
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437
438 locale -a
439
440 nlsinfo
441
442 ls /usr/lib/nls/loc
443
444 ls /usr/lib/locale
445
446 ls /usr/lib/nls
447
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448 ls /usr/share/locale
449
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450and see whether they list something resembling these
451
2bdf8add 452 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
502a173a 453 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
2bdf8add 454 en_US de_DE ru_RU
14280422 455 en de ru
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456 english german russian
457 english.iso88591 german.iso88591 russian.iso88595
502a173a 458 english.roman8 russian.koi8r
5f05dabc 459
39332f68 460Sadly, even though the calling interface for C<setlocale()> has been
528d65ad 461standardized, names of locales and the directories where the
5a964f20 462configuration resides have not been. The basic form of the name is
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463I<language_territory>B<.>I<codeset>, but the latter parts after
464I<language> are not always present. The I<language> and I<country>
465are usually from the standards B<ISO 3166> and B<ISO 639>, the
466two-letter abbreviations for the countries and the languages of the
467world, respectively. The I<codeset> part often mentions some B<ISO
4688859> character set, the Latin codesets. For example, C<ISO 8859-1>
469is the so-called "Western European codeset" that can be used to encode
470most Western European languages adequately. Again, there are several
471ways to write even the name of that one standard. Lamentably.
5f05dabc 472
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473Two special locales are worth particular mention: "C" and "POSIX".
474Currently these are effectively the same locale: the difference is
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475mainly that the first one is defined by the C standard, the second by
476the POSIX standard. They define the B<default locale> in which
14280422 477every program starts in the absence of locale information in its
5a964f20 478environment. (The I<default> default locale, if you will.) Its language
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479is (American) English and its character codeset ASCII or, rarely, a
480superset thereof (such as the "DEC Multinational Character Set
481(DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
482may not actually exactly match what the C standard calls for. So
483beware.
5f05dabc 484
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485B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
486POSIX-conformant), so use "C" when you need explicitly to specify this
487default locale.
5f05dabc 488
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489=head2 LOCALE PROBLEMS
490
5a964f20 491You may encounter the following warning message at Perl startup:
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492
493 perl: warning: Setting locale failed.
494 perl: warning: Please check that your locale settings:
495 LC_ALL = "En_US",
496 LANG = (unset)
497 are supported and installed on your system.
498 perl: warning: Falling back to the standard locale ("C").
499
cb88b78e 500This means that your locale settings had C<LC_ALL> set to "En_US" and
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501LANG exists but has no value. Perl tried to believe you but could not.
502Instead, Perl gave up and fell back to the "C" locale, the default locale
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503that is supposed to work no matter what. (On Windows, it first tries
504falling back to the system default locale.) This usually means your
505locale settings were wrong, they mention locales your system has never
506heard of, or the locale installation in your system has problems (for
507example, some system files are broken or missing). There are quick and
508temporary fixes to these problems, as well as more thorough and lasting
509fixes.
3e6e419a 510
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511=head2 Testing for broken locales
512
513If you are building Perl from source, the Perl test suite file
514F<lib/locale.t> can be used to test the locales on your system.
515Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
516will cause it to output detailed results. For example, on Linux, you
517could say
518
1d2ab946 519 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
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520
521Besides many other tests, it will test every locale it finds on your
522system to see if they conform to the POSIX standard. If any have
523errors, it will include a summary near the end of the output of which
524locales passed all its tests, and which failed, and why.
525
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526=head2 Temporarily fixing locale problems
527
5a964f20 528The two quickest fixes are either to render Perl silent about any
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529locale inconsistencies or to run Perl under the default locale "C".
530
531Perl's moaning about locale problems can be silenced by setting the
cb88b78e 532environment variable C<PERL_BADLANG> to a zero value, for example "0".
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533This method really just sweeps the problem under the carpet: you tell
534Perl to shut up even when Perl sees that something is wrong. Do not
535be surprised if later something locale-dependent misbehaves.
3e6e419a
JH
536
537Perl can be run under the "C" locale by setting the environment
cb88b78e
KW
538variable C<LC_ALL> to "C". This method is perhaps a bit more civilized
539than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or
5a964f20
TC
540other locale variables) may affect other programs as well, not just
541Perl. In particular, external programs run from within Perl will see
3e6e419a 542these changes. If you make the new settings permanent (read on), all
f979aebc 543programs you run see the changes. See L<"ENVIRONMENT"> for
5a964f20 544the full list of relevant environment variables and L<USING LOCALES>
e05ffc7d 545for their effects in Perl. Effects in other programs are
cb88b78e 546easily deducible. For example, the variable C<LC_COLLATE> may well affect
b432a672 547your B<sort> program (or whatever the program that arranges "records"
3e6e419a
JH
548alphabetically in your system is called).
549
5a964f20
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550You can test out changing these variables temporarily, and if the
551new settings seem to help, put those settings into your shell startup
552files. Consult your local documentation for the exact details. For in
553Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
3e6e419a
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554
555 LC_ALL=en_US.ISO8859-1
556 export LC_ALL
557
5a964f20
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558This assumes that we saw the locale "en_US.ISO8859-1" using the commands
559discussed above. We decided to try that instead of the above faulty
560locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
3e6e419a
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561
562 setenv LC_ALL en_US.ISO8859-1
c47ff5f1 563
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564or if you have the "env" application you can do in any shell
565
566 env LC_ALL=en_US.ISO8859-1 perl ...
567
5a964f20 568If you do not know what shell you have, consult your local
3e6e419a
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569helpdesk or the equivalent.
570
571=head2 Permanently fixing locale problems
572
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573The slower but superior fixes are when you may be able to yourself
574fix the misconfiguration of your own environment variables. The
3e6e419a
JH
575mis(sing)configuration of the whole system's locales usually requires
576the help of your friendly system administrator.
577
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578First, see earlier in this document about L<Finding locales>. That tells
579how to find which locales are really supported--and more importantly,
580installed--on your system. In our example error message, environment
581variables affecting the locale are listed in the order of decreasing
582importance (and unset variables do not matter). Therefore, having
583LC_ALL set to "En_US" must have been the bad choice, as shown by the
584error message. First try fixing locale settings listed first.
3e6e419a 585
5a964f20
TC
586Second, if using the listed commands you see something B<exactly>
587(prefix matches do not count and case usually counts) like "En_US"
588without the quotes, then you should be okay because you are using a
589locale name that should be installed and available in your system.
4a4eefd0 590In this case, see L<Permanently fixing your system's locale configuration>.
3e6e419a 591
4a4eefd0 592=head2 Permanently fixing your system's locale configuration
3e6e419a 593
5a964f20 594This is when you see something like:
3e6e419a
JH
595
596 perl: warning: Please check that your locale settings:
597 LC_ALL = "En_US",
598 LANG = (unset)
599 are supported and installed on your system.
600
601but then cannot see that "En_US" listed by the above-mentioned
5a964f20
TC
602commands. You may see things like "en_US.ISO8859-1", but that isn't
603the same. In this case, try running under a locale
604that you can list and which somehow matches what you tried. The
3e6e419a 605rules for matching locale names are a bit vague because
e05ffc7d 606standardization is weak in this area. See again the
13a2d996 607L<Finding locales> about general rules.
3e6e419a 608
b687b08b 609=head2 Fixing system locale configuration
3e6e419a 610
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611Contact a system administrator (preferably your own) and report the exact
612error message you get, and ask them to read this same documentation you
613are now reading. They should be able to check whether there is something
614wrong with the locale configuration of the system. The L<Finding locales>
615section is unfortunately a bit vague about the exact commands and places
616because these things are not that standardized.
3e6e419a 617
5f05dabc
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618=head2 The localeconv function
619
39332f68 620The C<POSIX::localeconv()> function allows you to get particulars of the
14280422 621locale-dependent numeric formatting information specified by the current
a835cd47
KW
622underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of
623whether called from within the scope of C<S<use locale>> or not). (If
624you just want the name of
39332f68 625the current locale for a particular category, use C<POSIX::setlocale()>
5a964f20 626with a single parameter--see L<The setlocale function>.)
5f05dabc
PP
627
628 use POSIX qw(locale_h);
5f05dabc
PP
629
630 # Get a reference to a hash of locale-dependent info
631 $locale_values = localeconv();
632
633 # Output sorted list of the values
634 for (sort keys %$locale_values) {
14280422 635 printf "%-20s = %s\n", $_, $locale_values->{$_}
5f05dabc
PP
636 }
637
39332f68 638C<localeconv()> takes no arguments, and returns B<a reference to> a hash.
5a964f20 639The keys of this hash are variable names for formatting, such as
502a173a 640C<decimal_point> and C<thousands_sep>. The values are the
cea6626f 641corresponding, er, values. See L<POSIX/localeconv> for a longer
502a173a
JH
642example listing the categories an implementation might be expected to
643provide; some provide more and others fewer. You don't need an
39332f68 644explicit C<use locale>, because C<localeconv()> always observes the
502a173a 645current locale.
5f05dabc 646
5a964f20
TC
647Here's a simple-minded example program that rewrites its command-line
648parameters as integers correctly formatted in the current locale:
5f05dabc 649
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650 use POSIX qw(locale_h);
651
652 # Get some of locale's numeric formatting parameters
653 my ($thousands_sep, $grouping) =
654 @{localeconv()}{'thousands_sep', 'grouping'};
655
656 # Apply defaults if values are missing
657 $thousands_sep = ',' unless $thousands_sep;
658
659 # grouping and mon_grouping are packed lists
660 # of small integers (characters) telling the
661 # grouping (thousand_seps and mon_thousand_seps
662 # being the group dividers) of numbers and
663 # monetary quantities. The integers' meanings:
664 # 255 means no more grouping, 0 means repeat
665 # the previous grouping, 1-254 means use that
666 # as the current grouping. Grouping goes from
667 # right to left (low to high digits). In the
668 # below we cheat slightly by never using anything
669 # else than the first grouping (whatever that is).
670 if ($grouping) {
671 @grouping = unpack("C*", $grouping);
672 } else {
673 @grouping = (3);
674 }
675
676 # Format command line params for current locale
677 for (@ARGV) {
678 $_ = int; # Chop non-integer part
679 1 while
680 s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
681 print "$_";
682 }
683 print "\n";
5f05dabc 684
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685Note that if the platform doesn't have C<LC_NUMERIC> and/or
686C<LC_MONETARY> available or enabled, the corresponding elements of the
687hash will be missing.
688
74c76037 689=head2 I18N::Langinfo
4bbcc6e8
JH
690
691Another interface for querying locale-dependent information is the
39332f68 692C<I18N::Langinfo::langinfo()> function, available at least in Unix-like
4bbcc6e8
JH
693systems and VMS.
694
39332f68
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695The following example will import the C<langinfo()> function itself and
696three constants to be used as arguments to C<langinfo()>: a constant for
74c76037
JH
697the abbreviated first day of the week (the numbering starts from
698Sunday = 1) and two more constants for the affirmative and negative
699answers for a yes/no question in the current locale.
4bbcc6e8 700
74c76037 701 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
4bbcc6e8 702
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703 my ($abday_1, $yesstr, $nostr)
704 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
4bbcc6e8 705
74c76037 706 print "$abday_1? [$yesstr/$nostr] ";
4bbcc6e8 707
74c76037
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708In other words, in the "C" (or English) locale the above will probably
709print something like:
710
e05ffc7d 711 Sun? [yes/no]
4bbcc6e8
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712
713See L<I18N::Langinfo> for more information.
714
5f05dabc
PP
715=head1 LOCALE CATEGORIES
716
5a964f20
TC
717The following subsections describe basic locale categories. Beyond these,
718some combination categories allow manipulation of more than one
719basic category at a time. See L<"ENVIRONMENT"> for a discussion of these.
5f05dabc 720
cb88b78e 721=head2 Category C<LC_COLLATE>: Collation
5f05dabc 722
66cbab2c
KW
723In the scope of S<C<use locale>> (but not a
724C<use locale ':not_characters'>), Perl looks to the C<LC_COLLATE>
5a964f20 725environment variable to determine the application's notions on collation
b4ffc3db
TC
726(ordering) of characters. For example, "b" follows "a" in Latin
727alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
f87fa335 728"color" follows "chocolate" in English, what about in traditional Spanish?
5f05dabc 729
60f0fa02
JH
730The following collations all make sense and you may meet any of them
731if you "use locale".
732
733 A B C D E a b c d e
35316ca3 734 A a B b C c D d E e
60f0fa02
JH
735 a A b B c C d D e E
736 a b c d e A B C D E
737
f1cbbd6e 738Here is a code snippet to tell what "word"
5a964f20 739characters are in the current locale, in that locale's order:
5f05dabc
PP
740
741 use locale;
35316ca3 742 print +(sort grep /\w/, map { chr } 0..255), "\n";
5f05dabc 743
14280422
DD
744Compare this with the characters that you see and their order if you
745state explicitly that the locale should be ignored:
5f05dabc
PP
746
747 no locale;
35316ca3 748 print +(sort grep /\w/, map { chr } 0..255), "\n";
5f05dabc
PP
749
750This machine-native collation (which is what you get unless S<C<use
751locale>> has appeared earlier in the same block) must be used for
752sorting raw binary data, whereas the locale-dependent collation of the
b0c42ed9 753first example is useful for natural text.
5f05dabc 754
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DD
755As noted in L<USING LOCALES>, C<cmp> compares according to the current
756collation locale when C<use locale> is in effect, but falls back to a
de108802 757char-by-char comparison for strings that the locale says are equal. You
39332f68 758can use C<POSIX::strcoll()> if you don't want this fall-back:
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DD
759
760 use POSIX qw(strcoll);
761 $equal_in_locale =
762 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
763
39332f68 764C<$equal_in_locale> will be true if the collation locale specifies a
5a964f20 765dictionary-like ordering that ignores space characters completely and
9e3a2af8 766which folds case.
14280422 767
31f05a37
KW
768Perl only supports single-byte locales for C<LC_COLLATE>. This means
769that a UTF-8 locale likely will just give you machine-native ordering.
770Use L<Unicode::Collate> for the full implementation of the Unicode
771Collation Algorithm.
772
5a964f20 773If you have a single string that you want to check for "equality in
14280422 774locale" against several others, you might think you could gain a little
39332f68 775efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
14280422
DD
776
777 use POSIX qw(strxfrm);
778 $xfrm_string = strxfrm("Mixed-case string");
779 print "locale collation ignores spaces\n"
780 if $xfrm_string eq strxfrm("Mixed-casestring");
781 print "locale collation ignores hyphens\n"
782 if $xfrm_string eq strxfrm("Mixedcase string");
783 print "locale collation ignores case\n"
784 if $xfrm_string eq strxfrm("mixed-case string");
785
39332f68 786C<strxfrm()> takes a string and maps it into a transformed string for use
de108802 787in char-by-char comparisons against other transformed strings during
14280422 788collation. "Under the hood", locale-affected Perl comparison operators
39332f68
KW
789call C<strxfrm()> for both operands, then do a char-by-char
790comparison of the transformed strings. By calling C<strxfrm()> explicitly
14280422 791and using a non locale-affected comparison, the example attempts to save
5a964f20 792a couple of transformations. But in fact, it doesn't save anything: Perl
2ae324a7 793magic (see L<perlguts/Magic Variables>) creates the transformed version of a
5a964f20 794string the first time it's needed in a comparison, then keeps this version around
14280422 795in case it's needed again. An example rewritten the easy way with
e38874e2 796C<cmp> runs just about as fast. It also copes with null characters
39332f68 797embedded in strings; if you call C<strxfrm()> directly, it treats the first
5a964f20
TC
798null it finds as a terminator. don't expect the transformed strings
799it produces to be portable across systems--or even from one revision
39332f68 800of your operating system to the next. In short, don't call C<strxfrm()>
e38874e2 801directly: let Perl do it for you.
14280422 802
5a964f20 803Note: C<use locale> isn't shown in some of these examples because it isn't
dfcc8045
KW
804needed: C<strcoll()> and C<strxfrm()> are POSIX functions
805which use the standard system-supplied C<libc> functions that
806always obey the current C<LC_COLLATE> locale.
5f05dabc 807
cb88b78e 808=head2 Category C<LC_CTYPE>: Character Types
5f05dabc 809
66cbab2c
KW
810In the scope of S<C<use locale>> (but not a
811C<use locale ':not_characters'>), Perl obeys the C<LC_CTYPE> locale
14280422 812setting. This controls the application's notion of which characters are
ebc3223b
KW
813alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
814regular expression metanotation,
f1cbbd6e 815which stands for alphanumeric characters--that is, alphabetic,
ebc3223b
KW
816numeric, and the platform's native underscore.
817(Consult L<perlre> for more information about
14280422 818regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
b4ffc3db
TC
819setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
820"E<oslash>" may be understood as C<\w> characters.
ebc3223b
KW
821It also affects things like C<\s>, C<\D>, and the POSIX character
822classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
823information on all these.)
5f05dabc 824
2c268ad5 825The C<LC_CTYPE> locale also provides the map used in transliterating
68dc0745 826characters between lower and uppercase. This affects the case-mapping
39332f68 827functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>; case-mapping
b9cc4f69
KW
828interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
829strings and C<s///> substitutions; and case-independent regular expression
e38874e2
DD
830pattern matching using the C<i> modifier.
831
2da736a2 832Finally, C<LC_CTYPE> affects the (deprecated) POSIX character-class test
1d2ab946
KW
833functions--C<POSIX::isalpha()>, C<POSIX::islower()>, and so on. For
834example, if you move from the "C" locale to a 7-bit Scandinavian one,
835you may find--possibly to your surprise--that "|" moves from the
836C<POSIX::ispunct()> class to C<POSIX::isalpha()>.
ef3087ec
KW
837Unfortunately, this creates big problems for regular expressions. "|" still
838means alternation even though it matches C<\w>.
5f05dabc 839
31f05a37
KW
840Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
841otherwise Perl only supports single-byte locales, such as the ISO 8859
842series. This means that wide character locales, for example for Asian
843languages, are not supported. The UTF-8 locale support is actually a
844superset of POSIX locales, because it is really full Unicode behavior
845as if no locale were in effect at all (except for tainting; see
846L</SECURITY>). POSIX locales, even UTF-8 ones,
847are lacking certain concepts in Unicode, such as the idea that changing
848the case of a character could expand to be more than one character.
849Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
850Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
851with some restrictions, and on other platforms more like the "C" locale.
852For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
853used as a workaround for this (see L</Unicode and UTF-8>).
854
5d63e270
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855Note that there are quite a few things that are unaffected by the
856current locale. All the escape sequences for particular characters,
857C<\n> for example, always mean the platform's native one. This means,
858for example, that C<\N> in regular expressions (every character
1d2ab946 859but new-line) works on the platform character set.
5d63e270 860
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861B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
862in clearly ineligible characters being considered to be alphanumeric by
e199995e 863your application. For strict matching of (mundane) ASCII letters and
5a964f20 864digits--for example, in command strings--locale-aware applications
e199995e 865should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">.
5f05dabc 866
fee33030 867=head2 Category C<LC_NUMERIC>: Numeric Formatting
5f05dabc 868
b960a36e
KW
869After a proper C<POSIX::setlocale()> call, and within the scope of one
870of the C<use locale> variants, Perl obeys the C<LC_NUMERIC>
2095dafa 871locale information, which controls an application's idea of how numbers
b960a36e
KW
872should be formatted for human readability.
873In most implementations the only effect is to
b4ffc3db 874change the character used for the decimal point--perhaps from "." to ",".
b960a36e 875The functions aren't aware of such niceties as thousands separation and
2095dafa 876so on. (See L<The localeconv function> if you care about these things.)
5a964f20 877
b960a36e
KW
878 use POSIX qw(strtod setlocale LC_NUMERIC);
879 use locale;
5f05dabc 880
b960a36e 881 setlocale LC_NUMERIC, "";
14280422 882
b960a36e 883 $n = 5/2; # Assign numeric 2.5 to $n
5f05dabc 884
b960a36e 885 $a = " $n"; # Locale-dependent conversion to string
5f05dabc 886
b960a36e 887 print "half five is $n\n"; # Locale-dependent output
5f05dabc 888
b960a36e 889 printf "half five is %g\n", $n; # Locale-dependent output
5f05dabc 890
b960a36e
KW
891 print "DECIMAL POINT IS COMMA\n"
892 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
5f05dabc 893
4bbcc6e8
JH
894See also L<I18N::Langinfo> and C<RADIXCHAR>.
895
cb88b78e 896=head2 Category C<LC_MONETARY>: Formatting of monetary amounts
5f05dabc 897
e199995e 898The C standard defines the C<LC_MONETARY> category, but not a function
5a964f20 899that is affected by its contents. (Those with experience of standards
b0c42ed9 900committees will recognize that the working group decided to punt on the
fa9b773e
KW
901issue.) Consequently, Perl essentially takes no notice of it. If you
902really want to use C<LC_MONETARY>, you can query its contents--see
e05ffc7d
KW
903L<The localeconv function>--and use the information that it returns in your
904application's own formatting of currency amounts. However, you may well
905find that the information, voluminous and complex though it may be, still
906does not quite meet your requirements: currency formatting is a hard nut
13a2d996 907to crack.
5f05dabc 908
4bbcc6e8
JH
909See also L<I18N::Langinfo> and C<CRNCYSTR>.
910
cb88b78e 911=head2 C<LC_TIME>
5f05dabc 912
39332f68 913Output produced by C<POSIX::strftime()>, which builds a formatted
5f05dabc
PP
914human-readable date/time string, is affected by the current C<LC_TIME>
915locale. Thus, in a French locale, the output produced by the C<%B>
916format element (full month name) for the first month of the year would
5a964f20 917be "janvier". Here's how to get a list of long month names in the
5f05dabc
PP
918current locale:
919
920 use POSIX qw(strftime);
14280422
DD
921 for (0..11) {
922 $long_month_name[$_] =
923 strftime("%B", 0, 0, 0, 1, $_, 96);
5f05dabc
PP
924 }
925
2619d284
KW
926Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
927function which uses the standard system-supplied C<libc> function that
928always obeys the current C<LC_TIME> locale.
5f05dabc 929
4bbcc6e8 930See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
2a2bf5f4 931C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
4bbcc6e8 932
5f05dabc
PP
933=head2 Other categories
934
2619d284
KW
935The remaining locale categories are not currently used by Perl itself.
936But again note that things Perl interacts with may use these, including
937extensions outside the standard Perl distribution, and by the
98a6f11e 938operating system and its utilities. Note especially that the string
939value of C<$!> and the error messages given by external utilities may
940be changed by C<LC_MESSAGES>. If you want to have portable error
265f5c4a 941codes, use C<%!>. See L<Errno>.
14280422
DD
942
943=head1 SECURITY
944
5a964f20 945Although the main discussion of Perl security issues can be found in
14280422
DD
946L<perlsec>, a discussion of Perl's locale handling would be incomplete
947if it did not draw your attention to locale-dependent security issues.
5a964f20
TC
948Locales--particularly on systems that allow unprivileged users to
949build their own locales--are untrustworthy. A malicious (or just plain
14280422
DD
950broken) locale can make a locale-aware application give unexpected
951results. Here are a few possibilities:
952
953=over 4
954
955=item *
956
957Regular expression checks for safe file names or mail addresses using
5a964f20 958C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
14280422
DD
959characters such as "E<gt>" and "|" are alphanumeric.
960
961=item *
962
e38874e2 963String interpolation with case-mapping, as in, say, C<$dest =
cb88b78e 964"C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE>
e38874e2
DD
965case-mapping table is in effect.
966
967=item *
968
14280422
DD
969A sneaky C<LC_COLLATE> locale could result in the names of students with
970"D" grades appearing ahead of those with "A"s.
971
972=item *
973
5a964f20 974An application that takes the trouble to use information in
14280422 975C<LC_MONETARY> may format debits as if they were credits and vice versa
5a964f20 976if that locale has been subverted. Or it might make payments in US
14280422
DD
977dollars instead of Hong Kong dollars.
978
979=item *
980
39332f68 981The date and day names in dates formatted by C<strftime()> could be
14280422 982manipulated to advantage by a malicious user able to subvert the
5a964f20 983C<LC_DATE> locale. ("Look--it says I wasn't in the building on
14280422
DD
984Sunday.")
985
986=back
987
988Such dangers are not peculiar to the locale system: any aspect of an
5a964f20 989application's environment which may be modified maliciously presents
14280422 990similar challenges. Similarly, they are not specific to Perl: any
5a964f20 991programming language that allows you to write programs that take
14280422
DD
992account of their environment exposes you to these issues.
993
5a964f20
TC
994Perl cannot protect you from all possibilities shown in the
995examples--there is no substitute for your own vigilance--but, when
14280422 996C<use locale> is in effect, Perl uses the tainting mechanism (see
5a964f20 997L<perlsec>) to mark string results that become locale-dependent, and
14280422 998which may be untrustworthy in consequence. Here is a summary of the
5a964f20 999tainting behavior of operators and functions that may be affected by
14280422
DD
1000the locale:
1001
1002=over 4
1003
551e1d92
RB
1004=item *
1005
1006B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
14280422
DD
1007
1008Scalar true/false (or less/equal/greater) result is never tainted.
1009
551e1d92
RB
1010=item *
1011
1d2ab946 1012B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
e38874e2
DD
1013
1014Result string containing interpolated material is tainted if
66cbab2c 1015C<use locale> (but not S<C<use locale ':not_characters'>>) is in effect.
e38874e2 1016
551e1d92
RB
1017=item *
1018
1019B<Matching operator> (C<m//>):
14280422
DD
1020
1021Scalar true/false result never tainted.
1022
1d2ab946
KW
1023All subpatterns, either delivered as a list-context result or as C<$1>
1024I<etc>., are tainted if C<use locale> (but not
1025S<C<use locale ':not_characters'>>) is in effect, and the subpattern
63baef57
KW
1026regular expression contains a locale-dependent construct. These
1027constructs include C<\w> (to match an alphanumeric character), C<\W>
1028(non-alphanumeric character), C<\b> and C<\B> (word-boundary and
1029non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
1030(whitespace character), C<\S> (non whitespace character), C<\d> and
1031C<\D> (digits and non-digits), and the POSIX character classes, such as
1032C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
1033
1034Tainting is also likely if the pattern is to be matched
1035case-insensitively (via C</i>). The exception is if all the code points
1036to be matched this way are above 255 and do not have folds under Unicode
1037rules to below 256. Tainting is not done for these because Perl
1038only uses Unicode rules for such code points, and those rules are the
1039same no matter what the current locale.
1040
1d2ab946
KW
1041The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
1042(post-match), and C<$+> (last match) also are tainted.
14280422 1043
551e1d92
RB
1044=item *
1045
1046B<Substitution operator> (C<s///>):
14280422 1047
e38874e2 1048Has the same behavior as the match operator. Also, the left
66cbab2c
KW
1049operand of C<=~> becomes tainted when C<use locale>
1050(but not S<C<use locale ':not_characters'>>) is in effect if modified as
1051a result of a substitution based on a regular
1d2ab946
KW
1052expression match involving any of the things mentioned in the previous
1053item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
14280422 1054
551e1d92
RB
1055=item *
1056
39332f68 1057B<Output formatting functions> (C<printf()> and C<write()>):
14280422 1058
3cf03d68
JH
1059Results are never tainted because otherwise even output from print,
1060for example C<print(1/7)>, should be tainted if C<use locale> is in
1061effect.
14280422 1062
551e1d92
RB
1063=item *
1064
39332f68 1065B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
14280422 1066
66cbab2c
KW
1067Results are tainted if C<use locale> (but not
1068S<C<use locale ':not_characters'>>) is in effect.
14280422 1069
551e1d92
RB
1070=item *
1071
39332f68
KW
1072B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
1073C<strftime()>, C<strxfrm()>):
14280422
DD
1074
1075Results are never tainted.
1076
551e1d92
RB
1077=item *
1078
1d2ab946
KW
1079B<POSIX character class tests> (C<POSIX::isalnum()>,
1080C<POSIX::isalpha()>, C<POSIX::isdigit()>, C<POSIX::isgraph()>,
1081C<POSIX::islower()>, C<POSIX::isprint()>, C<POSIX::ispunct()>,
1082C<POSIX::isspace()>, C<POSIX::isupper()>, C<POSIX::isxdigit()>):
14280422
DD
1083
1084True/false results are never tainted.
1085
1086=back
1087
1088Three examples illustrate locale-dependent tainting.
1089The first program, which ignores its locale, won't run: a value taken
54310121 1090directly from the command line may not be used to name an output file
14280422
DD
1091when taint checks are enabled.
1092
1093 #/usr/local/bin/perl -T
1094 # Run with taint checking
1095
54310121 1096 # Command line sanity check omitted...
14280422
DD
1097 $tainted_output_file = shift;
1098
1099 open(F, ">$tainted_output_file")
3183d96c 1100 or warn "Open of $tainted_output_file failed: $!\n";
14280422
DD
1101
1102The program can be made to run by "laundering" the tainted value through
5a964f20
TC
1103a regular expression: the second example--which still ignores locale
1104information--runs, creating the file named on its command line
14280422
DD
1105if it can.
1106
1107 #/usr/local/bin/perl -T
1108
1109 $tainted_output_file = shift;
1110 $tainted_output_file =~ m%[\w/]+%;
1111 $untainted_output_file = $&;
1112
1113 open(F, ">$untainted_output_file")
1114 or warn "Open of $untainted_output_file failed: $!\n";
1115
5a964f20 1116Compare this with a similar but locale-aware program:
14280422
DD
1117
1118 #/usr/local/bin/perl -T
1119
1120 $tainted_output_file = shift;
1121 use locale;
1122 $tainted_output_file =~ m%[\w/]+%;
1123 $localized_output_file = $&;
1124
1125 open(F, ">$localized_output_file")
1126 or warn "Open of $localized_output_file failed: $!\n";
1127
1d2ab946 1128This third program fails to run because C<$&> is tainted: it is the result
5a964f20 1129of a match involving C<\w> while C<use locale> is in effect.
5f05dabc
PP
1130
1131=head1 ENVIRONMENT
1132
1133=over 12
1134
ee1ec05f
KW
1135=item PERL_SKIP_LOCALE_INIT
1136
1137This environment variable, available starting in Perl v5.20, and if it
1138evaluates to a TRUE value, tells Perl to not use the rest of the
1139environment variables to initialize with. Instead, Perl uses whatever
1140the current locale settings are. This is particularly useful in
1141embedded environments, see
1142L<perlembed/Using embedded Perl with POSIX locales>.
1143
5f05dabc
PP
1144=item PERL_BADLANG
1145
14280422 1146A string that can suppress Perl's warning about failed locale settings
54310121 1147at startup. Failure can occur if the locale support in the operating
5a964f20 1148system is lacking (broken) in some way--or if you mistyped the name of
900bd440
JH
1149a locale when you set up your environment. If this environment
1150variable is absent, or has a value that does not evaluate to integer
1151zero--that is, "0" or ""-- Perl will complain about locale setting
1152failures.
5f05dabc 1153
cb88b78e 1154B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message.
14280422
DD
1155The message tells about some problem in your system's locale support,
1156and you should investigate what the problem is.
5f05dabc
PP
1157
1158=back
1159
1160The following environment variables are not specific to Perl: They are
39332f68 1161part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
b385bb4d
KW
1162for controlling an application's opinion on data. Windows is non-POSIX,
1163but Perl arranges for the following to work as described anyway.
65ebb059
KW
1164If the locale given by an environment variable is not valid, Perl tries
1165the next lower one in priority. If none are valid, on Windows, the
1166system default locale is then tried. If all else fails, the C<"C">
1167locale is used. If even that doesn't work, something is badly broken,
c5e9a8e7 1168but Perl tries to forge ahead with whatever the locale settings might
65ebb059 1169be.
5f05dabc
PP
1170
1171=over 12
1172
cb88b78e 1173=item C<LC_ALL>
5f05dabc 1174
5a964f20 1175C<LC_ALL> is the "override-all" locale environment variable. If
5f05dabc
PP
1176set, it overrides all the rest of the locale environment variables.
1177
cb88b78e 1178=item C<LANGUAGE>
528d65ad
JH
1179
1180B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
1181are using the GNU libc. This is the case if you are using e.g. Linux.
e1020413 1182If you are using "commercial" Unixes you are most probably I<not>
22b6f60d
JH
1183using GNU libc and you can ignore C<LANGUAGE>.
1184
1185However, in the case you are using C<LANGUAGE>: it affects the
1186language of informational, warning, and error messages output by
1187commands (in other words, it's like C<LC_MESSAGES>) but it has higher
96090e4f 1188priority than C<LC_ALL>. Moreover, it's not a single value but
22b6f60d
JH
1189instead a "path" (":"-separated list) of I<languages> (not locales).
1190See the GNU C<gettext> library documentation for more information.
528d65ad 1191
cb88b78e 1192=item C<LC_CTYPE>.
5f05dabc
PP
1193
1194In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
1195locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
1196chooses the character type locale.
1197
cb88b78e 1198=item C<LC_COLLATE>
5f05dabc 1199
14280422
DD
1200In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
1201(sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
1202C<LANG> chooses the collation locale.
5f05dabc 1203
cb88b78e 1204=item C<LC_MONETARY>
5f05dabc 1205
14280422
DD
1206In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
1207formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
1208C<LANG> chooses the monetary formatting locale.
5f05dabc 1209
cb88b78e 1210=item C<LC_NUMERIC>
5f05dabc
PP
1211
1212In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
1213locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
1214chooses the numeric format.
1215
cb88b78e 1216=item C<LC_TIME>
5f05dabc 1217
14280422
DD
1218In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
1219formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
1220C<LANG> chooses the date and time formatting locale.
5f05dabc 1221
cb88b78e 1222=item C<LANG>
5f05dabc 1223
14280422
DD
1224C<LANG> is the "catch-all" locale environment variable. If it is set, it
1225is used as the last resort after the overall C<LC_ALL> and the
cb88b78e 1226category-specific C<LC_I<foo>>
5f05dabc
PP
1227
1228=back
1229
7e4353e9
RGS
1230=head2 Examples
1231
cb88b78e 1232The C<LC_NUMERIC> controls the numeric output:
7e4353e9 1233
ef3087ec
KW
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.
7e4353e9 1238
39332f68 1239and also how strings are parsed by C<POSIX::strtod()> as numbers:
7e4353e9 1240
ef3087ec
KW
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.
7e4353e9 1246
5f05dabc
PP
1247=head1 NOTES
1248
b960a36e
KW
1249=head2 String C<eval> and C<LC_NUMERIC>
1250
1251A string L<eval|perlfunc/eval EXPR> parses its expression as standard
1252Perl. It is therefore expecting the decimal point to be a dot. If
1253C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
1254be confused, perhaps silently.
1255
1256 use locale;
1257 use POSIX qw(locale_h);
1258 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1259 my $a = 1.2;
1260 print eval "$a + 1.5";
1261 print "\n";
1262
1263prints C<13,5>. This is because in that locale, the comma is the
1264decimal point character. The C<eval> thus expands to:
1265
1266 eval "1,2 + 1.5"
1267
1268and the result is not what you likely expected. No warnings are
1269generated. If you do string C<eval>'s within the scope of
1270S<C<use locale>>, you should instead change the C<eval> line to do
1271something like:
1272
1273 print eval "no locale; $a + 1.5";
1274
1275This prints C<2.7>.
1276
5f05dabc
PP
1277=head2 Backward compatibility
1278
b0c42ed9 1279Versions of Perl prior to 5.004 B<mostly> ignored locale information,
5a964f20
TC
1280generally behaving as if something similar to the C<"C"> locale were
1281always in force, even if the program environment suggested otherwise
1282(see L<The setlocale function>). By default, Perl still behaves this
1283way for backward compatibility. If you want a Perl application to pay
1284attention to locale information, you B<must> use the S<C<use locale>>
062ca197
KW
1285pragma (see L<The use locale pragma>) or, in the unlikely event
1286that you want to do so for just pattern matching, the
70709c68
KW
1287C</l> regular expression modifier (see L<perlre/Character set
1288modifiers>) to instruct it to do so.
b0c42ed9
JH
1289
1290Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
5a964f20
TC
1291information if available; that is, C<\w> did understand what
1292were the letters according to the locale environment variables.
b0c42ed9
JH
1293The problem was that the user had no control over the feature:
1294if the C library supported locales, Perl used them.
1295
1296=head2 I18N:Collate obsolete
1297
5a964f20 1298In versions of Perl prior to 5.004, per-locale collation was possible
b0c42ed9
JH
1299using the C<I18N::Collate> library module. This module is now mildly
1300obsolete and should be avoided in new applications. The C<LC_COLLATE>
1301functionality is now integrated into the Perl core language: One can
1302use locale-specific scalar data completely normally with C<use locale>,
1303so there is no longer any need to juggle with the scalar references of
1304C<I18N::Collate>.
5f05dabc 1305
14280422 1306=head2 Sort speed and memory use impacts
5f05dabc
PP
1307
1308Comparing and sorting by locale is usually slower than the default
14280422
DD
1309sorting; slow-downs of two to four times have been observed. It will
1310also consume more memory: once a Perl scalar variable has participated
1311in any string comparison or sorting operation obeying the locale
1312collation rules, it will take 3-15 times more memory than before. (The
1313exact multiplier depends on the string's contents, the operating system
1314and the locale.) These downsides are dictated more by the operating
1315system's implementation of the locale system than by Perl.
5f05dabc 1316
5f05dabc
PP
1317=head2 Freely available locale definitions
1318
66cbab2c
KW
1319The Unicode CLDR project extracts the POSIX portion of many of its
1320locales, available at
1321
1322 http://unicode.org/Public/cldr/latest/
1323
08d7a6b2
LB
1324There is a large collection of locale definitions at:
1325
1326 http://std.dkuug.dk/i18n/WG15-collection/locales/
1327
1328You should be aware that it is
14280422 1329unsupported, and is not claimed to be fit for any purpose. If your
5a964f20 1330system allows installation of arbitrary locales, you may find the
14280422
DD
1331definitions useful as they are, or as a basis for the development of
1332your own locales.
5f05dabc 1333
14280422 1334=head2 I18n and l10n
5f05dabc 1335
b0c42ed9
JH
1336"Internationalization" is often abbreviated as B<i18n> because its first
1337and last letters are separated by eighteen others. (You may guess why
1338the internalin ... internaliti ... i18n tends to get abbreviated.) In
1339the same way, "localization" is often abbreviated to B<l10n>.
14280422
DD
1340
1341=head2 An imperfect standard
1342
1343Internationalization, as defined in the C and POSIX standards, can be
1344criticized as incomplete, ungainly, and having too large a granularity.
1345(Locales apply to a whole process, when it would arguably be more useful
1346to have them apply to a single thread, window group, or whatever.) They
1347also have a tendency, like standards groups, to divide the world into
1348nations, when we all know that the world can equally well be divided
e199995e 1349into bankers, bikers, gamers, and so on.
5f05dabc 1350
b310b053
JH
1351=head1 Unicode and UTF-8
1352
7ee2ae1e 1353The support of Unicode is new starting from Perl version v5.6, and more fully
31f05a37
KW
1354implemented in versions v5.8 and later. See L<perluniintro>.
1355
1356Starting in Perl v5.20, UTF-8 locales are supported in Perl, except for
1357C<LC_COLLATE> (use L<Unicode::Collate> instead). If you have Perl v5.16
1358or v5.18 and can't upgrade, you can use
66cbab2c
KW
1359
1360 use locale ':not_characters';
1361
1362When this form of the pragma is used, only the non-character portions of
1363locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
1364you have translated all the characters it is to operate on into Unicode
1365(actually the platform's native character set (ASCII or EBCDIC) plus
1366Unicode). For data in files, this can conveniently be done by also
1367specifying
1368
1369 use open ':locale';
1370
1371This pragma arranges for all inputs from files to be translated into
1372Unicode from the current locale as specified in the environment (see
1373L</ENVIRONMENT>), and all outputs to files to be translated back
1374into the locale. (See L<open>). On a per-filehandle basis, you can
1375instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
1376module, both available from CPAN. The latter module also has methods to
1377ease the handling of C<ARGV> and environment variables, and can be used
31f05a37 1378on individual strings. If you know that all your locales will be
66cbab2c
KW
1379UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
1380command line switch.
1381
1382This form of the pragma allows essentially seamless handling of locales
31f05a37
KW
1383with Unicode. The collation order will be by Unicode code point order.
1384It is strongly
66cbab2c
KW
1385recommended that when you need to order and sort strings that you use
1386the standard module L<Unicode::Collate> which gives much better results
1387in many instances than you can get with the old-style locale handling.
1388
31f05a37
KW
1389All the modules and switches just described can be used in v5.20 with
1390just plain C<use locale>, and, should the input locales not be UTF-8,
1391you'll get the less than ideal behavior, described below, that you get
1392with pre-v5.16 Perls, or when you use the locale pragma without the
1393C<:not_characters> parameter in v5.16 and v5.18. If you are using
1394exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1395does not apply to you.
1396
1397There are two cases, multi-byte and single-byte locales. First
1398multi-byte:
1399
1400The only multi-byte (or wide character) locale that Perl is ever likely
1401to support is UTF-8. This is due to the difficulty of implementation,
1402the fact that high quality UTF-8 locales are now published for every
1403area of the world (L<http://unicode.org/Public/cldr/latest/>), and that
1404failing all that you can use the L<Encode> module to translate to/from
1405your locale. So, you'll have to do one of those things if you're using
1406one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1407Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1408work reasonably well (depending on your C library implementation)
1409simply because both
dc4bfc4b
KW
1410they and Perl store characters that take up multiple bytes the same way.
1411However, some, if not most, C library implementations may not process
1412the characters in the upper half of the Latin-1 range (128 - 255)
cb88b78e 1413properly under C<LC_CTYPE>. To see if a character is a particular type
dc4bfc4b
KW
1414under a locale, Perl uses the functions like C<isalnum()>. Your C
1415library may not work for UTF-8 locales with those functions, instead
1416only working under the newer wide library functions like C<iswalnum()>.
31f05a37
KW
1417However, they are treated like single-byte locales, and will have the
1418restrictions described below.
e199995e 1419
31f05a37 1420For single-byte locales,
e199995e 1421Perl generally takes the tack to use locale rules on code points that can fit
66cbab2c
KW
1422in a single byte, and Unicode rules for those that can't (though this
1423isn't uniformly applied, see the note at the end of this section). This
1424prevents many problems in locales that aren't UTF-8. Suppose the locale
1425is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
1426in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
1427regular expression character class C<[[:alpha:]]> will magically match
14280xD7 in the Greek locale but not in the Latin one.
e199995e 1429
1d2ab946 1430However, there are places where this breaks down. Certain Perl constructs are
b4ffc3db
TC
1431for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
1432Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
1433subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
1434Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
31f05a37
KW
1435issue occurs with C<\N{...}>. Prior to v5.20, It is therefore a bad
1436idea to use C<\p{}> or
66cbab2c
KW
1437C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
1438locale will be a ISO8859-1. Use POSIX character classes instead.
1439
1440Another problem with this approach is that operations that cross the
1441single byte/multiple byte boundary are not well-defined, and so are
4a70680a 1442disallowed. (This boundary is between the codepoints at 255/256.)
66cbab2c
KW
1443For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1444should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1445Greek locale, for example, there is no character at 0xFF, and Perl
1446has no way of knowing what the character at 0xFF is really supposed to
1447represent. Thus it disallows the operation. In this mode, the
1448lowercase of U+0178 is itself.
1449
1450The same problems ensue if you enable automatic UTF-8-ification of your
e199995e 1451standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
b4ffc3db
TC
1452non-UTF-8 locales (by using either the B<-C> command line switch or the
1453C<PERL_UNICODE> environment variable; see L<perlrun>).
1454Things are read in as UTF-8, which would normally imply a Unicode
1455interpretation, but the presence of a locale causes them to be interpreted
1456in that locale instead. For example, a 0xD7 code point in the Unicode
1457input, which should mean the multiplication sign, won't be interpreted by
66cbab2c 1458Perl that way under the Greek locale. This is not a problem
b4ffc3db 1459I<provided> you make certain that all locales will always and only be either
66cbab2c 1460an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
b4ffc3db 1461
1d2ab946
KW
1462Still another problem is that this approach can lead to two code
1463points meaning the same character. Thus in a Greek locale, both U+03A7
1464and U+00D7 are GREEK CAPITAL LETTER CHI.
1465
b4ffc3db
TC
1466Vendor locales are notoriously buggy, and it is difficult for Perl to test
1467its locale-handling code because this interacts with code that Perl has no
1468control over; therefore the locale-handling code in Perl may be buggy as
66cbab2c
KW
1469well. (However, the Unicode-supplied locales should be better, and
1470there is a feed back mechanism to correct any problems. See
1471L</Freely available locale definitions>.)
1472
7ee2ae1e 1473If you have Perl v5.16, the problems mentioned above go away if you use
66cbab2c 1474the C<:not_characters> parameter to the locale pragma (except for vendor
7ee2ae1e 1475bugs in the non-character portions). If you don't have v5.16, and you
66cbab2c
KW
1476I<do> have locales that work, using them may be worthwhile for certain
1477specific purposes, as long as you keep in mind the gotchas already
1478mentioned. For example, if the collation for your locales works, it
1479runs faster under locales than under L<Unicode::Collate>; and you gain
1480access to such things as the local currency symbol and the names of the
7ee2ae1e 1481months and days of the week. (But to hammer home the point, in v5.16,
66cbab2c
KW
1482you get this access without the downsides of locales by using the
1483C<:not_characters> form of the pragma.)
1484
1485Note: The policy of using locale rules for code points that can fit in a
1486byte, and Unicode rules for those that can't is not uniformly applied.
7ee2ae1e 1487Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
66cbab2c 1488consistently to regular expression matching except for bracketed
7ee2ae1e
KW
1489character classes; in v5.14 it was extended to all regex matches; and in
1490v5.16 to the casing operations such as C<"\L"> and C<uc()>. For
66cbab2c
KW
1491collation, in all releases, the system's C<strxfrm()> function is called,
1492and whatever it does is what you get.
b310b053 1493
5f05dabc
PP
1494=head1 BUGS
1495
1496=head2 Broken systems
1497
5a964f20 1498In certain systems, the operating system's locale support
2bdf8add 1499is broken and cannot be fixed or used by Perl. Such deficiencies can
b4ffc3db 1500and will result in mysterious hangs and/or Perl core dumps when
2bdf8add 1501C<use locale> is in effect. When confronted with such a system,
7f2de2d2 1502please report in excruciating detail to <F<perlbug@perl.org>>, and
b4ffc3db 1503also contact your vendor: bug fixes may exist for these problems
2bdf8add 1504in your operating system. Sometimes such bug fixes are called an
83fb1bf0
KW
1505operating system upgrade. If you have the source for Perl, include in
1506the perlbug email the output of the test described above in L</Testing
1507for broken locales>.
5f05dabc
PP
1508
1509=head1 SEE ALSO
1510
b310b053
JH
1511L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
1512L<POSIX/isalnum>, L<POSIX/isalpha>,
4bbcc6e8
JH
1513L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>,
1514L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>,
1515L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>,
1516L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
1517L<POSIX/strtod>, L<POSIX/strxfrm>.
5f05dabc 1518
ccd65d51
KW
1519For special considerations when Perl is embedded in a C program,
1520see L<perlembed/Using embedded Perl with POSIX locales>.
1521
5f05dabc
PP
1522=head1 HISTORY
1523
b0c42ed9 1524Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
5a964f20 1525Dunlop, assisted by the perl5-porters. Prose worked over a bit by
c052850d 1526Tom Christiansen, and updated by Perl 5 porters.