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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
56=item Category LC_NUMERIC: Numeric formatting
57
58This indicates how numbers should be formatted for human readability,
59for example the character used as the decimal point.
60
61=item Category LC_MONETARY: Formatting of monetary amounts
62
63=for comment
ebc3223b 64The nbsp below makes this look better (though not great)
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65
66E<160>
67
68=item Category LC_TIME: Date/Time formatting
69
70=for comment
ebc3223b 71The nbsp below makes this look better (though not great)
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72
73E<160>
74
75=item Category LC_MESSAGES: Error and other messages
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>.
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79
80=item Category LC_COLLATE: Collation
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
85=item Category LC_CTYPE: Character Types
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
233underlying locale. Perl always initializes C<LC_NUMERIC> to C<"C">
234because too many modules are unable to cope with the decimal point in a
235floating point number not being a dot (it's a comma in many locales).
236But note that these modules are vulnerable because C<LC_NUMERIC>
237currently can be changed at any time by a call to the C C<set_locale()>
238by XS code or by something XS code calls, or by C<POSIX::setlocale()> by
239Perl code. This is true also for the Perl-provided lite wrappers for XS
240modules to use some C library C<printf> functions:
241C<Gconvert>,
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242L<my_sprintf|perlapi/my_sprintf>,
243L<my_snprintf|perlapi/my_snprintf>,
1d2ab946 244and
9fe6720f 245L<my_vsnprintf|perlapi/my_vsnprintf>.
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246
247=back
248
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249=for comment
250The nbsp below makes this look better (though not great)
251
252E<160>
253
254=item B<Lingering effects of C<S<use locale>>>
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255
256Certain Perl operations that are set-up within the scope of a
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257C<use locale> variant retain that effect even outside the scope.
258These include:
259
260=over 4
261
262=item *
263
264The output format of a L<write()|perlfunc/write> is determined by an
265earlier format declaration (L<perlfunc/format>), so whether or not the
266output is affected by locale is determined by if the C<format()> is
267within the scope of a C<use locale> variant, not whether the C<write()>
268is.
269
270=item *
271
272Regular expression patterns can be compiled using
273L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodual> with actual
274matching deferred to later. Again, it is whether or not the compilation
275was done within the scope of C<use locale> that determines the match
276behavior, not if the matches are done within such a scope or not.
277
278=back
279
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280=for comment
281The nbsp below makes this look better (though not great)
282
283E<160>
284
4c9b78f4 285=item B<Under C<"use locale ':not_characters';">>
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286
287=over 4
288
289=item *
290
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291All the non-Perl operations.
292
293=item *
294
295B<Format declarations> (L<perlfunc/format>) and hence any subsequent
296C<write()>s use C<LC_NUMERIC>.
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297
298=item *
299
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300B<stringification and output> use C<LC_NUMERIC>.
301These include the results of
302C<print()>,
303C<printf()>,
304C<say()>,
305and
306C<sprintf()>.
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307
308=back
309
310=for comment
ebc3223b 311The nbsp below makes this look better (though not great)
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312
313E<160>
314
4c9b78f4 315=item B<Under just plain C<"use locale";>>
66cbab2c 316
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317=over 4
318
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319=item *
320
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321All the above operations
322
323=item *
324
325B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
39332f68 326C<LC_COLLATE>. C<sort()> is also affected if used without an
5a964f20 327explicit comparison function, because it uses C<cmp> by default.
14280422 328
5a964f20 329B<Note:> C<eq> and C<ne> are unaffected by locale: they always
de108802 330perform a char-by-char comparison of their scalar operands. What's
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331more, if C<cmp> finds that its operands are equal according to the
332collation sequence specified by the current locale, it goes on to
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333perform a char-by-char comparison, and only returns I<0> (equal) if the
334operands are char-for-char identical. If you really want to know whether
5a964f20 335two strings--which C<eq> and C<cmp> may consider different--are equal
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336as far as collation in the locale is concerned, see the discussion in
337L<Category LC_COLLATE: Collation>.
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338
339=item *
340
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341B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
342C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
5f05dabc 343
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344=back
345
66cbab2c 346=back
5f05dabc 347
5a964f20 348The default behavior is restored with the S<C<no locale>> pragma, or
ef3087ec 349upon reaching the end of the block enclosing C<use locale>.
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350Note that C<use locale> and C<use locale ':not_characters'> may be
351nested, and that what is in effect within an inner scope will revert to
352the outer scope's rules at the end of the inner scope.
5f05dabc 353
5a964f20 354The string result of any operation that uses locale
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355information is tainted, as it is possible for a locale to be
356untrustworthy. See L<"SECURITY">.
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357
358=head2 The setlocale function
359
14280422 360You can switch locales as often as you wish at run time with the
39332f68 361C<POSIX::setlocale()> function:
5f05dabc 362
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363 # Import locale-handling tool set from POSIX module.
364 # This example uses: setlocale -- the function call
365 # LC_CTYPE -- explained below
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366 # (Showing the testing for success/failure of operations is
367 # omitted in these examples to avoid distracting from the main
ebc3223b 368 # point)
6ea81ccf 369
5f05dabc 370 use POSIX qw(locale_h);
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371 use locale;
372 my $old_locale;
5f05dabc 373
14280422 374 # query and save the old locale
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375 $old_locale = setlocale(LC_CTYPE);
376
377 setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
378 # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
379
380 setlocale(LC_CTYPE, "");
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381 # LC_CTYPE now reset to the default defined by the
382 # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
383 # default. See below for documentation.
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384
385 # restore the old locale
386 setlocale(LC_CTYPE, $old_locale);
387
39332f68 388The first argument of C<setlocale()> gives the B<category>, the second the
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389B<locale>. The category tells in what aspect of data processing you
390want to apply locale-specific rules. Category names are discussed in
66cbab2c 391L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a
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392collection of customization information corresponding to a particular
393combination of language, country or territory, and codeset. Read on for
394hints on the naming of locales: not all systems name locales as in the
395example.
396
39332f68 397If no second argument is provided and the category is something other
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398than LC_ALL, the function returns a string naming the current locale
399for the category. You can use this value as the second argument in a
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400subsequent call to C<setlocale()>, B<but> on some platforms the string
401is opaque, not something that most people would be able to decipher as
402to what locale it means.
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403
404If no second argument is provided and the category is LC_ALL, the
405result is implementation-dependent. It may be a string of
c052850d 406concatenated locale names (separator also implementation-dependent)
39332f68 407or a single locale name. Please consult your L<setlocale(3)> man page for
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408details.
409
410If a second argument is given and it corresponds to a valid locale,
411the locale for the category is set to that value, and the function
412returns the now-current locale value. You can then use this in yet
39332f68 413another call to C<setlocale()>. (In some implementations, the return
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414value may sometimes differ from the value you gave as the second
415argument--think of it as an alias for the value you gave.)
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416
417As the example shows, if the second argument is an empty string, the
418category's locale is returned to the default specified by the
419corresponding environment variables. Generally, this results in a
5a964f20 420return to the default that was in force when Perl started up: changes
54310121 421to the environment made by the application after startup may or may not
5a964f20 422be noticed, depending on your system's C library.
5f05dabc 423
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424Note that Perl ignores the current C<LC_CTYPE> and C<LC_COLLATE> locales
425within the scope of a C<use locale ':not_characters'>.
426
f170b852 427If C<set_locale()> fails for some reason (for example, an attempt to set
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428to a locale unknown to the system), the locale for the category is not
429changed, and the function returns C<undef>.
430
2619d284 431
39332f68 432For further information about the categories, consult L<setlocale(3)>.
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433
434=head2 Finding locales
435
39332f68 436For locales available in your system, consult also L<setlocale(3)> to
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437see whether it leads to the list of available locales (search for the
438I<SEE ALSO> section). If that fails, try the following command lines:
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439
440 locale -a
441
442 nlsinfo
443
444 ls /usr/lib/nls/loc
445
446 ls /usr/lib/locale
447
448 ls /usr/lib/nls
449
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450 ls /usr/share/locale
451
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452and see whether they list something resembling these
453
2bdf8add 454 en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
502a173a 455 en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
2bdf8add 456 en_US de_DE ru_RU
14280422 457 en de ru
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458 english german russian
459 english.iso88591 german.iso88591 russian.iso88595
502a173a 460 english.roman8 russian.koi8r
5f05dabc 461
39332f68 462Sadly, even though the calling interface for C<setlocale()> has been
528d65ad 463standardized, names of locales and the directories where the
5a964f20 464configuration resides have not been. The basic form of the name is
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465I<language_territory>B<.>I<codeset>, but the latter parts after
466I<language> are not always present. The I<language> and I<country>
467are usually from the standards B<ISO 3166> and B<ISO 639>, the
468two-letter abbreviations for the countries and the languages of the
469world, respectively. The I<codeset> part often mentions some B<ISO
4708859> character set, the Latin codesets. For example, C<ISO 8859-1>
471is the so-called "Western European codeset" that can be used to encode
472most Western European languages adequately. Again, there are several
473ways to write even the name of that one standard. Lamentably.
5f05dabc 474
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475Two special locales are worth particular mention: "C" and "POSIX".
476Currently these are effectively the same locale: the difference is
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477mainly that the first one is defined by the C standard, the second by
478the POSIX standard. They define the B<default locale> in which
14280422 479every program starts in the absence of locale information in its
5a964f20 480environment. (The I<default> default locale, if you will.) Its language
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481is (American) English and its character codeset ASCII or, rarely, a
482superset thereof (such as the "DEC Multinational Character Set
483(DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
484may not actually exactly match what the C standard calls for. So
485beware.
5f05dabc 486
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487B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
488POSIX-conformant), so use "C" when you need explicitly to specify this
489default locale.
5f05dabc 490
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491=head2 LOCALE PROBLEMS
492
5a964f20 493You may encounter the following warning message at Perl startup:
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494
495 perl: warning: Setting locale failed.
496 perl: warning: Please check that your locale settings:
497 LC_ALL = "En_US",
498 LANG = (unset)
499 are supported and installed on your system.
500 perl: warning: Falling back to the standard locale ("C").
501
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502This means that your locale settings had LC_ALL set to "En_US" and
503LANG exists but has no value. Perl tried to believe you but could not.
504Instead, Perl gave up and fell back to the "C" locale, the default locale
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505that is supposed to work no matter what. (On Windows, it first tries
506falling back to the system default locale.) This usually means your
507locale settings were wrong, they mention locales your system has never
508heard of, or the locale installation in your system has problems (for
509example, some system files are broken or missing). There are quick and
510temporary fixes to these problems, as well as more thorough and lasting
511fixes.
3e6e419a 512
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513=head2 Testing for broken locales
514
515If you are building Perl from source, the Perl test suite file
516F<lib/locale.t> can be used to test the locales on your system.
517Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
518will cause it to output detailed results. For example, on Linux, you
519could say
520
1d2ab946 521 PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
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522
523Besides many other tests, it will test every locale it finds on your
524system to see if they conform to the POSIX standard. If any have
525errors, it will include a summary near the end of the output of which
526locales passed all its tests, and which failed, and why.
527
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528=head2 Temporarily fixing locale problems
529
5a964f20 530The two quickest fixes are either to render Perl silent about any
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531locale inconsistencies or to run Perl under the default locale "C".
532
533Perl's moaning about locale problems can be silenced by setting the
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534environment variable PERL_BADLANG to a zero value, for example "0".
535This method really just sweeps the problem under the carpet: you tell
536Perl to shut up even when Perl sees that something is wrong. Do not
537be surprised if later something locale-dependent misbehaves.
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538
539Perl can be run under the "C" locale by setting the environment
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TC
540variable LC_ALL to "C". This method is perhaps a bit more civilized
541than the PERL_BADLANG approach, but setting LC_ALL (or
542other locale variables) may affect other programs as well, not just
543Perl. In particular, external programs run from within Perl will see
3e6e419a 544these changes. If you make the new settings permanent (read on), all
f979aebc 545programs you run see the changes. See L<"ENVIRONMENT"> for
5a964f20 546the full list of relevant environment variables and L<USING LOCALES>
e05ffc7d 547for their effects in Perl. Effects in other programs are
5a964f20 548easily deducible. For example, the variable LC_COLLATE may well affect
b432a672 549your B<sort> program (or whatever the program that arranges "records"
3e6e419a
JH
550alphabetically in your system is called).
551
5a964f20
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552You can test out changing these variables temporarily, and if the
553new settings seem to help, put those settings into your shell startup
554files. Consult your local documentation for the exact details. For in
555Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
3e6e419a
JH
556
557 LC_ALL=en_US.ISO8859-1
558 export LC_ALL
559
5a964f20
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560This assumes that we saw the locale "en_US.ISO8859-1" using the commands
561discussed above. We decided to try that instead of the above faulty
562locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
3e6e419a
JH
563
564 setenv LC_ALL en_US.ISO8859-1
c47ff5f1 565
c406981e
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566or if you have the "env" application you can do in any shell
567
568 env LC_ALL=en_US.ISO8859-1 perl ...
569
5a964f20 570If you do not know what shell you have, consult your local
3e6e419a
JH
571helpdesk or the equivalent.
572
573=head2 Permanently fixing locale problems
574
5a964f20
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575The slower but superior fixes are when you may be able to yourself
576fix the misconfiguration of your own environment variables. The
3e6e419a
JH
577mis(sing)configuration of the whole system's locales usually requires
578the help of your friendly system administrator.
579
5a964f20
TC
580First, see earlier in this document about L<Finding locales>. That tells
581how to find which locales are really supported--and more importantly,
582installed--on your system. In our example error message, environment
583variables affecting the locale are listed in the order of decreasing
584importance (and unset variables do not matter). Therefore, having
585LC_ALL set to "En_US" must have been the bad choice, as shown by the
586error message. First try fixing locale settings listed first.
3e6e419a 587
5a964f20
TC
588Second, if using the listed commands you see something B<exactly>
589(prefix matches do not count and case usually counts) like "En_US"
590without the quotes, then you should be okay because you are using a
591locale name that should be installed and available in your system.
4a4eefd0 592In this case, see L<Permanently fixing your system's locale configuration>.
3e6e419a 593
4a4eefd0 594=head2 Permanently fixing your system's locale configuration
3e6e419a 595
5a964f20 596This is when you see something like:
3e6e419a
JH
597
598 perl: warning: Please check that your locale settings:
599 LC_ALL = "En_US",
600 LANG = (unset)
601 are supported and installed on your system.
602
603but then cannot see that "En_US" listed by the above-mentioned
5a964f20
TC
604commands. You may see things like "en_US.ISO8859-1", but that isn't
605the same. In this case, try running under a locale
606that you can list and which somehow matches what you tried. The
3e6e419a 607rules for matching locale names are a bit vague because
e05ffc7d 608standardization is weak in this area. See again the
13a2d996 609L<Finding locales> about general rules.
3e6e419a 610
b687b08b 611=head2 Fixing system locale configuration
3e6e419a 612
5a964f20
TC
613Contact a system administrator (preferably your own) and report the exact
614error message you get, and ask them to read this same documentation you
615are now reading. They should be able to check whether there is something
616wrong with the locale configuration of the system. The L<Finding locales>
617section is unfortunately a bit vague about the exact commands and places
618because these things are not that standardized.
3e6e419a 619
5f05dabc
PP
620=head2 The localeconv function
621
39332f68 622The C<POSIX::localeconv()> function allows you to get particulars of the
14280422
DD
623locale-dependent numeric formatting information specified by the current
624C<LC_NUMERIC> and C<LC_MONETARY> locales. (If you 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
ef3087ec
KW
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
74c76037 685=head2 I18N::Langinfo
4bbcc6e8
JH
686
687Another interface for querying locale-dependent information is the
39332f68 688C<I18N::Langinfo::langinfo()> function, available at least in Unix-like
4bbcc6e8
JH
689systems and VMS.
690
39332f68
KW
691The following example will import the C<langinfo()> function itself and
692three constants to be used as arguments to C<langinfo()>: a constant for
74c76037
JH
693the abbreviated first day of the week (the numbering starts from
694Sunday = 1) and two more constants for the affirmative and negative
695answers for a yes/no question in the current locale.
4bbcc6e8 696
74c76037 697 use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
4bbcc6e8 698
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699 my ($abday_1, $yesstr, $nostr)
700 = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
4bbcc6e8 701
74c76037 702 print "$abday_1? [$yesstr/$nostr] ";
4bbcc6e8 703
74c76037
JH
704In other words, in the "C" (or English) locale the above will probably
705print something like:
706
e05ffc7d 707 Sun? [yes/no]
4bbcc6e8
JH
708
709See L<I18N::Langinfo> for more information.
710
5f05dabc
PP
711=head1 LOCALE CATEGORIES
712
5a964f20
TC
713The following subsections describe basic locale categories. Beyond these,
714some combination categories allow manipulation of more than one
715basic category at a time. See L<"ENVIRONMENT"> for a discussion of these.
5f05dabc
PP
716
717=head2 Category LC_COLLATE: Collation
718
66cbab2c
KW
719In the scope of S<C<use locale>> (but not a
720C<use locale ':not_characters'>), Perl looks to the C<LC_COLLATE>
5a964f20 721environment variable to determine the application's notions on collation
b4ffc3db
TC
722(ordering) of characters. For example, "b" follows "a" in Latin
723alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
f87fa335 724"color" follows "chocolate" in English, what about in traditional Spanish?
5f05dabc 725
60f0fa02
JH
726The following collations all make sense and you may meet any of them
727if you "use locale".
728
729 A B C D E a b c d e
35316ca3 730 A a B b C c D d E e
60f0fa02
JH
731 a A b B c C d D e E
732 a b c d e A B C D E
733
f1cbbd6e 734Here is a code snippet to tell what "word"
5a964f20 735characters are in the current locale, in that locale's order:
5f05dabc
PP
736
737 use locale;
35316ca3 738 print +(sort grep /\w/, map { chr } 0..255), "\n";
5f05dabc 739
14280422
DD
740Compare this with the characters that you see and their order if you
741state explicitly that the locale should be ignored:
5f05dabc
PP
742
743 no locale;
35316ca3 744 print +(sort grep /\w/, map { chr } 0..255), "\n";
5f05dabc
PP
745
746This machine-native collation (which is what you get unless S<C<use
747locale>> has appeared earlier in the same block) must be used for
748sorting raw binary data, whereas the locale-dependent collation of the
b0c42ed9 749first example is useful for natural text.
5f05dabc 750
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DD
751As noted in L<USING LOCALES>, C<cmp> compares according to the current
752collation locale when C<use locale> is in effect, but falls back to a
de108802 753char-by-char comparison for strings that the locale says are equal. You
39332f68 754can use C<POSIX::strcoll()> if you don't want this fall-back:
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DD
755
756 use POSIX qw(strcoll);
757 $equal_in_locale =
758 !strcoll("space and case ignored", "SpaceAndCaseIgnored");
759
39332f68 760C<$equal_in_locale> will be true if the collation locale specifies a
5a964f20 761dictionary-like ordering that ignores space characters completely and
9e3a2af8 762which folds case.
14280422 763
31f05a37
KW
764Perl only supports single-byte locales for C<LC_COLLATE>. This means
765that a UTF-8 locale likely will just give you machine-native ordering.
766Use L<Unicode::Collate> for the full implementation of the Unicode
767Collation Algorithm.
768
5a964f20 769If you have a single string that you want to check for "equality in
14280422 770locale" against several others, you might think you could gain a little
39332f68 771efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
14280422
DD
772
773 use POSIX qw(strxfrm);
774 $xfrm_string = strxfrm("Mixed-case string");
775 print "locale collation ignores spaces\n"
776 if $xfrm_string eq strxfrm("Mixed-casestring");
777 print "locale collation ignores hyphens\n"
778 if $xfrm_string eq strxfrm("Mixedcase string");
779 print "locale collation ignores case\n"
780 if $xfrm_string eq strxfrm("mixed-case string");
781
39332f68 782C<strxfrm()> takes a string and maps it into a transformed string for use
de108802 783in char-by-char comparisons against other transformed strings during
14280422 784collation. "Under the hood", locale-affected Perl comparison operators
39332f68
KW
785call C<strxfrm()> for both operands, then do a char-by-char
786comparison of the transformed strings. By calling C<strxfrm()> explicitly
14280422 787and using a non locale-affected comparison, the example attempts to save
5a964f20 788a couple of transformations. But in fact, it doesn't save anything: Perl
2ae324a7 789magic (see L<perlguts/Magic Variables>) creates the transformed version of a
5a964f20 790string the first time it's needed in a comparison, then keeps this version around
14280422 791in case it's needed again. An example rewritten the easy way with
e38874e2 792C<cmp> runs just about as fast. It also copes with null characters
39332f68 793embedded in strings; if you call C<strxfrm()> directly, it treats the first
5a964f20
TC
794null it finds as a terminator. don't expect the transformed strings
795it produces to be portable across systems--or even from one revision
39332f68 796of your operating system to the next. In short, don't call C<strxfrm()>
e38874e2 797directly: let Perl do it for you.
14280422 798
5a964f20 799Note: C<use locale> isn't shown in some of these examples because it isn't
dfcc8045
KW
800needed: C<strcoll()> and C<strxfrm()> are POSIX functions
801which use the standard system-supplied C<libc> functions that
802always obey the current C<LC_COLLATE> locale.
5f05dabc
PP
803
804=head2 Category LC_CTYPE: Character Types
805
66cbab2c
KW
806In the scope of S<C<use locale>> (but not a
807C<use locale ':not_characters'>), Perl obeys the C<LC_CTYPE> locale
14280422 808setting. This controls the application's notion of which characters are
ebc3223b
KW
809alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
810regular expression metanotation,
f1cbbd6e 811which stands for alphanumeric characters--that is, alphabetic,
ebc3223b
KW
812numeric, and the platform's native underscore.
813(Consult L<perlre> for more information about
14280422 814regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
b4ffc3db
TC
815setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
816"E<oslash>" may be understood as C<\w> characters.
ebc3223b
KW
817It also affects things like C<\s>, C<\D>, and the POSIX character
818classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
819information on all these.)
5f05dabc 820
2c268ad5 821The C<LC_CTYPE> locale also provides the map used in transliterating
68dc0745 822characters between lower and uppercase. This affects the case-mapping
39332f68 823functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>; case-mapping
b9cc4f69
KW
824interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
825strings and C<s///> substitutions; and case-independent regular expression
e38874e2
DD
826pattern matching using the C<i> modifier.
827
2da736a2 828Finally, C<LC_CTYPE> affects the (deprecated) POSIX character-class test
1d2ab946
KW
829functions--C<POSIX::isalpha()>, C<POSIX::islower()>, and so on. For
830example, if you move from the "C" locale to a 7-bit Scandinavian one,
831you may find--possibly to your surprise--that "|" moves from the
832C<POSIX::ispunct()> class to C<POSIX::isalpha()>.
ef3087ec
KW
833Unfortunately, this creates big problems for regular expressions. "|" still
834means alternation even though it matches C<\w>.
5f05dabc 835
31f05a37
KW
836Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
837otherwise Perl only supports single-byte locales, such as the ISO 8859
838series. This means that wide character locales, for example for Asian
839languages, are not supported. The UTF-8 locale support is actually a
840superset of POSIX locales, because it is really full Unicode behavior
841as if no locale were in effect at all (except for tainting; see
842L</SECURITY>). POSIX locales, even UTF-8 ones,
843are lacking certain concepts in Unicode, such as the idea that changing
844the case of a character could expand to be more than one character.
845Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
846Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
847with some restrictions, and on other platforms more like the "C" locale.
848For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
849used as a workaround for this (see L</Unicode and UTF-8>).
850
5d63e270
KW
851Note that there are quite a few things that are unaffected by the
852current locale. All the escape sequences for particular characters,
853C<\n> for example, always mean the platform's native one. This means,
854for example, that C<\N> in regular expressions (every character
1d2ab946 855but new-line) works on the platform character set.
5d63e270 856
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857B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
858in clearly ineligible characters being considered to be alphanumeric by
e199995e 859your application. For strict matching of (mundane) ASCII letters and
5a964f20 860digits--for example, in command strings--locale-aware applications
e199995e 861should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">.
5f05dabc
PP
862
863=head2 Category LC_NUMERIC: Numeric Formatting
864
b960a36e
KW
865After a proper C<POSIX::setlocale()> call, and within the scope of one
866of the C<use locale> variants, Perl obeys the C<LC_NUMERIC>
2095dafa 867locale information, which controls an application's idea of how numbers
b960a36e
KW
868should be formatted for human readability.
869In most implementations the only effect is to
b4ffc3db 870change the character used for the decimal point--perhaps from "." to ",".
b960a36e 871The functions aren't aware of such niceties as thousands separation and
2095dafa 872so on. (See L<The localeconv function> if you care about these things.)
5a964f20 873
b960a36e
KW
874 use POSIX qw(strtod setlocale LC_NUMERIC);
875 use locale;
5f05dabc 876
b960a36e 877 setlocale LC_NUMERIC, "";
14280422 878
b960a36e 879 $n = 5/2; # Assign numeric 2.5 to $n
5f05dabc 880
b960a36e 881 $a = " $n"; # Locale-dependent conversion to string
5f05dabc 882
b960a36e 883 print "half five is $n\n"; # Locale-dependent output
5f05dabc 884
b960a36e 885 printf "half five is %g\n", $n; # Locale-dependent output
5f05dabc 886
b960a36e
KW
887 print "DECIMAL POINT IS COMMA\n"
888 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
5f05dabc 889
4bbcc6e8
JH
890See also L<I18N::Langinfo> and C<RADIXCHAR>.
891
5f05dabc
PP
892=head2 Category LC_MONETARY: Formatting of monetary amounts
893
e199995e 894The C standard defines the C<LC_MONETARY> category, but not a function
5a964f20 895that is affected by its contents. (Those with experience of standards
b0c42ed9 896committees will recognize that the working group decided to punt on the
fa9b773e
KW
897issue.) Consequently, Perl essentially takes no notice of it. If you
898really want to use C<LC_MONETARY>, you can query its contents--see
e05ffc7d
KW
899L<The localeconv function>--and use the information that it returns in your
900application's own formatting of currency amounts. However, you may well
901find that the information, voluminous and complex though it may be, still
902does not quite meet your requirements: currency formatting is a hard nut
13a2d996 903to crack.
5f05dabc 904
4bbcc6e8
JH
905See also L<I18N::Langinfo> and C<CRNCYSTR>.
906
5f05dabc
PP
907=head2 LC_TIME
908
39332f68 909Output produced by C<POSIX::strftime()>, which builds a formatted
5f05dabc
PP
910human-readable date/time string, is affected by the current C<LC_TIME>
911locale. Thus, in a French locale, the output produced by the C<%B>
912format element (full month name) for the first month of the year would
5a964f20 913be "janvier". Here's how to get a list of long month names in the
5f05dabc
PP
914current locale:
915
916 use POSIX qw(strftime);
14280422
DD
917 for (0..11) {
918 $long_month_name[$_] =
919 strftime("%B", 0, 0, 0, 1, $_, 96);
5f05dabc
PP
920 }
921
2619d284
KW
922Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
923function which uses the standard system-supplied C<libc> function that
924always obeys the current C<LC_TIME> locale.
5f05dabc 925
4bbcc6e8 926See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
2a2bf5f4 927C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
4bbcc6e8 928
5f05dabc
PP
929=head2 Other categories
930
2619d284
KW
931The remaining locale categories are not currently used by Perl itself.
932But again note that things Perl interacts with may use these, including
933extensions outside the standard Perl distribution, and by the
98a6f11e 934operating system and its utilities. Note especially that the string
935value of C<$!> and the error messages given by external utilities may
936be changed by C<LC_MESSAGES>. If you want to have portable error
265f5c4a 937codes, use C<%!>. See L<Errno>.
14280422
DD
938
939=head1 SECURITY
940
5a964f20 941Although the main discussion of Perl security issues can be found in
14280422
DD
942L<perlsec>, a discussion of Perl's locale handling would be incomplete
943if it did not draw your attention to locale-dependent security issues.
5a964f20
TC
944Locales--particularly on systems that allow unprivileged users to
945build their own locales--are untrustworthy. A malicious (or just plain
14280422
DD
946broken) locale can make a locale-aware application give unexpected
947results. Here are a few possibilities:
948
949=over 4
950
951=item *
952
953Regular expression checks for safe file names or mail addresses using
5a964f20 954C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
14280422
DD
955characters such as "E<gt>" and "|" are alphanumeric.
956
957=item *
958
e38874e2
DD
959String interpolation with case-mapping, as in, say, C<$dest =
960"C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE
961case-mapping table is in effect.
962
963=item *
964
14280422
DD
965A sneaky C<LC_COLLATE> locale could result in the names of students with
966"D" grades appearing ahead of those with "A"s.
967
968=item *
969
5a964f20 970An application that takes the trouble to use information in
14280422 971C<LC_MONETARY> may format debits as if they were credits and vice versa
5a964f20 972if that locale has been subverted. Or it might make payments in US
14280422
DD
973dollars instead of Hong Kong dollars.
974
975=item *
976
39332f68 977The date and day names in dates formatted by C<strftime()> could be
14280422 978manipulated to advantage by a malicious user able to subvert the
5a964f20 979C<LC_DATE> locale. ("Look--it says I wasn't in the building on
14280422
DD
980Sunday.")
981
982=back
983
984Such dangers are not peculiar to the locale system: any aspect of an
5a964f20 985application's environment which may be modified maliciously presents
14280422 986similar challenges. Similarly, they are not specific to Perl: any
5a964f20 987programming language that allows you to write programs that take
14280422
DD
988account of their environment exposes you to these issues.
989
5a964f20
TC
990Perl cannot protect you from all possibilities shown in the
991examples--there is no substitute for your own vigilance--but, when
14280422 992C<use locale> is in effect, Perl uses the tainting mechanism (see
5a964f20 993L<perlsec>) to mark string results that become locale-dependent, and
14280422 994which may be untrustworthy in consequence. Here is a summary of the
5a964f20 995tainting behavior of operators and functions that may be affected by
14280422
DD
996the locale:
997
998=over 4
999
551e1d92
RB
1000=item *
1001
1002B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
14280422
DD
1003
1004Scalar true/false (or less/equal/greater) result is never tainted.
1005
551e1d92
RB
1006=item *
1007
1d2ab946 1008B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
e38874e2
DD
1009
1010Result string containing interpolated material is tainted if
66cbab2c 1011C<use locale> (but not S<C<use locale ':not_characters'>>) is in effect.
e38874e2 1012
551e1d92
RB
1013=item *
1014
1015B<Matching operator> (C<m//>):
14280422
DD
1016
1017Scalar true/false result never tainted.
1018
1d2ab946
KW
1019All subpatterns, either delivered as a list-context result or as C<$1>
1020I<etc>., are tainted if C<use locale> (but not
1021S<C<use locale ':not_characters'>>) is in effect, and the subpattern
63baef57
KW
1022regular expression contains a locale-dependent construct. These
1023constructs include C<\w> (to match an alphanumeric character), C<\W>
1024(non-alphanumeric character), C<\b> and C<\B> (word-boundary and
1025non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
1026(whitespace character), C<\S> (non whitespace character), C<\d> and
1027C<\D> (digits and non-digits), and the POSIX character classes, such as
1028C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
1029
1030Tainting is also likely if the pattern is to be matched
1031case-insensitively (via C</i>). The exception is if all the code points
1032to be matched this way are above 255 and do not have folds under Unicode
1033rules to below 256. Tainting is not done for these because Perl
1034only uses Unicode rules for such code points, and those rules are the
1035same no matter what the current locale.
1036
1d2ab946
KW
1037The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
1038(post-match), and C<$+> (last match) also are tainted.
14280422 1039
551e1d92
RB
1040=item *
1041
1042B<Substitution operator> (C<s///>):
14280422 1043
e38874e2 1044Has the same behavior as the match operator. Also, the left
66cbab2c
KW
1045operand of C<=~> becomes tainted when C<use locale>
1046(but not S<C<use locale ':not_characters'>>) is in effect if modified as
1047a result of a substitution based on a regular
1d2ab946
KW
1048expression match involving any of the things mentioned in the previous
1049item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
14280422 1050
551e1d92
RB
1051=item *
1052
39332f68 1053B<Output formatting functions> (C<printf()> and C<write()>):
14280422 1054
3cf03d68
JH
1055Results are never tainted because otherwise even output from print,
1056for example C<print(1/7)>, should be tainted if C<use locale> is in
1057effect.
14280422 1058
551e1d92
RB
1059=item *
1060
39332f68 1061B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
14280422 1062
66cbab2c
KW
1063Results are tainted if C<use locale> (but not
1064S<C<use locale ':not_characters'>>) is in effect.
14280422 1065
551e1d92
RB
1066=item *
1067
39332f68
KW
1068B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
1069C<strftime()>, C<strxfrm()>):
14280422
DD
1070
1071Results are never tainted.
1072
551e1d92
RB
1073=item *
1074
1d2ab946
KW
1075B<POSIX character class tests> (C<POSIX::isalnum()>,
1076C<POSIX::isalpha()>, C<POSIX::isdigit()>, C<POSIX::isgraph()>,
1077C<POSIX::islower()>, C<POSIX::isprint()>, C<POSIX::ispunct()>,
1078C<POSIX::isspace()>, C<POSIX::isupper()>, C<POSIX::isxdigit()>):
14280422
DD
1079
1080True/false results are never tainted.
1081
1082=back
1083
1084Three examples illustrate locale-dependent tainting.
1085The first program, which ignores its locale, won't run: a value taken
54310121 1086directly from the command line may not be used to name an output file
14280422
DD
1087when taint checks are enabled.
1088
1089 #/usr/local/bin/perl -T
1090 # Run with taint checking
1091
54310121 1092 # Command line sanity check omitted...
14280422
DD
1093 $tainted_output_file = shift;
1094
1095 open(F, ">$tainted_output_file")
3183d96c 1096 or warn "Open of $tainted_output_file failed: $!\n";
14280422
DD
1097
1098The program can be made to run by "laundering" the tainted value through
5a964f20
TC
1099a regular expression: the second example--which still ignores locale
1100information--runs, creating the file named on its command line
14280422
DD
1101if it can.
1102
1103 #/usr/local/bin/perl -T
1104
1105 $tainted_output_file = shift;
1106 $tainted_output_file =~ m%[\w/]+%;
1107 $untainted_output_file = $&;
1108
1109 open(F, ">$untainted_output_file")
1110 or warn "Open of $untainted_output_file failed: $!\n";
1111
5a964f20 1112Compare this with a similar but locale-aware program:
14280422
DD
1113
1114 #/usr/local/bin/perl -T
1115
1116 $tainted_output_file = shift;
1117 use locale;
1118 $tainted_output_file =~ m%[\w/]+%;
1119 $localized_output_file = $&;
1120
1121 open(F, ">$localized_output_file")
1122 or warn "Open of $localized_output_file failed: $!\n";
1123
1d2ab946 1124This third program fails to run because C<$&> is tainted: it is the result
5a964f20 1125of a match involving C<\w> while C<use locale> is in effect.
5f05dabc
PP
1126
1127=head1 ENVIRONMENT
1128
1129=over 12
1130
ee1ec05f
KW
1131=item PERL_SKIP_LOCALE_INIT
1132
1133This environment variable, available starting in Perl v5.20, and if it
1134evaluates to a TRUE value, tells Perl to not use the rest of the
1135environment variables to initialize with. Instead, Perl uses whatever
1136the current locale settings are. This is particularly useful in
1137embedded environments, see
1138L<perlembed/Using embedded Perl with POSIX locales>.
1139
5f05dabc
PP
1140=item PERL_BADLANG
1141
14280422 1142A string that can suppress Perl's warning about failed locale settings
54310121 1143at startup. Failure can occur if the locale support in the operating
5a964f20 1144system is lacking (broken) in some way--or if you mistyped the name of
900bd440
JH
1145a locale when you set up your environment. If this environment
1146variable is absent, or has a value that does not evaluate to integer
1147zero--that is, "0" or ""-- Perl will complain about locale setting
1148failures.
5f05dabc 1149
14280422
DD
1150B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message.
1151The message tells about some problem in your system's locale support,
1152and you should investigate what the problem is.
5f05dabc
PP
1153
1154=back
1155
1156The following environment variables are not specific to Perl: They are
39332f68 1157part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
b385bb4d
KW
1158for controlling an application's opinion on data. Windows is non-POSIX,
1159but Perl arranges for the following to work as described anyway.
65ebb059
KW
1160If the locale given by an environment variable is not valid, Perl tries
1161the next lower one in priority. If none are valid, on Windows, the
1162system default locale is then tried. If all else fails, the C<"C">
1163locale is used. If even that doesn't work, something is badly broken,
c5e9a8e7 1164but Perl tries to forge ahead with whatever the locale settings might
65ebb059 1165be.
5f05dabc
PP
1166
1167=over 12
1168
1169=item LC_ALL
1170
5a964f20 1171C<LC_ALL> is the "override-all" locale environment variable. If
5f05dabc
PP
1172set, it overrides all the rest of the locale environment variables.
1173
528d65ad
JH
1174=item LANGUAGE
1175
1176B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
1177are using the GNU libc. This is the case if you are using e.g. Linux.
e1020413 1178If you are using "commercial" Unixes you are most probably I<not>
22b6f60d
JH
1179using GNU libc and you can ignore C<LANGUAGE>.
1180
1181However, in the case you are using C<LANGUAGE>: it affects the
1182language of informational, warning, and error messages output by
1183commands (in other words, it's like C<LC_MESSAGES>) but it has higher
96090e4f 1184priority than C<LC_ALL>. Moreover, it's not a single value but
22b6f60d
JH
1185instead a "path" (":"-separated list) of I<languages> (not locales).
1186See the GNU C<gettext> library documentation for more information.
528d65ad 1187
5f05dabc
PP
1188=item LC_CTYPE
1189
1190In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
1191locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
1192chooses the character type locale.
1193
1194=item LC_COLLATE
1195
14280422
DD
1196In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
1197(sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
1198C<LANG> chooses the collation locale.
5f05dabc
PP
1199
1200=item LC_MONETARY
1201
14280422
DD
1202In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
1203formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
1204C<LANG> chooses the monetary formatting locale.
5f05dabc
PP
1205
1206=item LC_NUMERIC
1207
1208In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
1209locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
1210chooses the numeric format.
1211
1212=item LC_TIME
1213
14280422
DD
1214In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
1215formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
1216C<LANG> chooses the date and time formatting locale.
5f05dabc
PP
1217
1218=item LANG
1219
14280422
DD
1220C<LANG> is the "catch-all" locale environment variable. If it is set, it
1221is used as the last resort after the overall C<LC_ALL> and the
5f05dabc
PP
1222category-specific C<LC_...>.
1223
1224=back
1225
7e4353e9
RGS
1226=head2 Examples
1227
1228The LC_NUMERIC controls the numeric output:
1229
ef3087ec
KW
1230 use locale;
1231 use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
1232 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1233 printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
7e4353e9 1234
39332f68 1235and also how strings are parsed by C<POSIX::strtod()> as numbers:
7e4353e9 1236
ef3087ec
KW
1237 use locale;
1238 use POSIX qw(locale_h strtod);
1239 setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
1240 my $x = strtod("2,34") + 5;
1241 print $x, "\n"; # Probably shows 7,34.
7e4353e9 1242
5f05dabc
PP
1243=head1 NOTES
1244
b960a36e
KW
1245=head2 String C<eval> and C<LC_NUMERIC>
1246
1247A string L<eval|perlfunc/eval EXPR> parses its expression as standard
1248Perl. It is therefore expecting the decimal point to be a dot. If
1249C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
1250be confused, perhaps silently.
1251
1252 use locale;
1253 use POSIX qw(locale_h);
1254 setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
1255 my $a = 1.2;
1256 print eval "$a + 1.5";
1257 print "\n";
1258
1259prints C<13,5>. This is because in that locale, the comma is the
1260decimal point character. The C<eval> thus expands to:
1261
1262 eval "1,2 + 1.5"
1263
1264and the result is not what you likely expected. No warnings are
1265generated. If you do string C<eval>'s within the scope of
1266S<C<use locale>>, you should instead change the C<eval> line to do
1267something like:
1268
1269 print eval "no locale; $a + 1.5";
1270
1271This prints C<2.7>.
1272
5f05dabc
PP
1273=head2 Backward compatibility
1274
b0c42ed9 1275Versions of Perl prior to 5.004 B<mostly> ignored locale information,
5a964f20
TC
1276generally behaving as if something similar to the C<"C"> locale were
1277always in force, even if the program environment suggested otherwise
1278(see L<The setlocale function>). By default, Perl still behaves this
1279way for backward compatibility. If you want a Perl application to pay
1280attention to locale information, you B<must> use the S<C<use locale>>
062ca197
KW
1281pragma (see L<The use locale pragma>) or, in the unlikely event
1282that you want to do so for just pattern matching, the
70709c68
KW
1283C</l> regular expression modifier (see L<perlre/Character set
1284modifiers>) to instruct it to do so.
b0c42ed9
JH
1285
1286Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
5a964f20
TC
1287information if available; that is, C<\w> did understand what
1288were the letters according to the locale environment variables.
b0c42ed9
JH
1289The problem was that the user had no control over the feature:
1290if the C library supported locales, Perl used them.
1291
1292=head2 I18N:Collate obsolete
1293
5a964f20 1294In versions of Perl prior to 5.004, per-locale collation was possible
b0c42ed9
JH
1295using the C<I18N::Collate> library module. This module is now mildly
1296obsolete and should be avoided in new applications. The C<LC_COLLATE>
1297functionality is now integrated into the Perl core language: One can
1298use locale-specific scalar data completely normally with C<use locale>,
1299so there is no longer any need to juggle with the scalar references of
1300C<I18N::Collate>.
5f05dabc 1301
14280422 1302=head2 Sort speed and memory use impacts
5f05dabc
PP
1303
1304Comparing and sorting by locale is usually slower than the default
14280422
DD
1305sorting; slow-downs of two to four times have been observed. It will
1306also consume more memory: once a Perl scalar variable has participated
1307in any string comparison or sorting operation obeying the locale
1308collation rules, it will take 3-15 times more memory than before. (The
1309exact multiplier depends on the string's contents, the operating system
1310and the locale.) These downsides are dictated more by the operating
1311system's implementation of the locale system than by Perl.
5f05dabc 1312
5f05dabc
PP
1313=head2 Freely available locale definitions
1314
66cbab2c
KW
1315The Unicode CLDR project extracts the POSIX portion of many of its
1316locales, available at
1317
1318 http://unicode.org/Public/cldr/latest/
1319
08d7a6b2
LB
1320There is a large collection of locale definitions at:
1321
1322 http://std.dkuug.dk/i18n/WG15-collection/locales/
1323
1324You should be aware that it is
14280422 1325unsupported, and is not claimed to be fit for any purpose. If your
5a964f20 1326system allows installation of arbitrary locales, you may find the
14280422
DD
1327definitions useful as they are, or as a basis for the development of
1328your own locales.
5f05dabc 1329
14280422 1330=head2 I18n and l10n
5f05dabc 1331
b0c42ed9
JH
1332"Internationalization" is often abbreviated as B<i18n> because its first
1333and last letters are separated by eighteen others. (You may guess why
1334the internalin ... internaliti ... i18n tends to get abbreviated.) In
1335the same way, "localization" is often abbreviated to B<l10n>.
14280422
DD
1336
1337=head2 An imperfect standard
1338
1339Internationalization, as defined in the C and POSIX standards, can be
1340criticized as incomplete, ungainly, and having too large a granularity.
1341(Locales apply to a whole process, when it would arguably be more useful
1342to have them apply to a single thread, window group, or whatever.) They
1343also have a tendency, like standards groups, to divide the world into
1344nations, when we all know that the world can equally well be divided
e199995e 1345into bankers, bikers, gamers, and so on.
5f05dabc 1346
b310b053
JH
1347=head1 Unicode and UTF-8
1348
7ee2ae1e 1349The support of Unicode is new starting from Perl version v5.6, and more fully
31f05a37
KW
1350implemented in versions v5.8 and later. See L<perluniintro>.
1351
1352Starting in Perl v5.20, UTF-8 locales are supported in Perl, except for
1353C<LC_COLLATE> (use L<Unicode::Collate> instead). If you have Perl v5.16
1354or v5.18 and can't upgrade, you can use
66cbab2c
KW
1355
1356 use locale ':not_characters';
1357
1358When this form of the pragma is used, only the non-character portions of
1359locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
1360you have translated all the characters it is to operate on into Unicode
1361(actually the platform's native character set (ASCII or EBCDIC) plus
1362Unicode). For data in files, this can conveniently be done by also
1363specifying
1364
1365 use open ':locale';
1366
1367This pragma arranges for all inputs from files to be translated into
1368Unicode from the current locale as specified in the environment (see
1369L</ENVIRONMENT>), and all outputs to files to be translated back
1370into the locale. (See L<open>). On a per-filehandle basis, you can
1371instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
1372module, both available from CPAN. The latter module also has methods to
1373ease the handling of C<ARGV> and environment variables, and can be used
31f05a37 1374on individual strings. If you know that all your locales will be
66cbab2c
KW
1375UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
1376command line switch.
1377
1378This form of the pragma allows essentially seamless handling of locales
31f05a37
KW
1379with Unicode. The collation order will be by Unicode code point order.
1380It is strongly
66cbab2c
KW
1381recommended that when you need to order and sort strings that you use
1382the standard module L<Unicode::Collate> which gives much better results
1383in many instances than you can get with the old-style locale handling.
1384
31f05a37
KW
1385All the modules and switches just described can be used in v5.20 with
1386just plain C<use locale>, and, should the input locales not be UTF-8,
1387you'll get the less than ideal behavior, described below, that you get
1388with pre-v5.16 Perls, or when you use the locale pragma without the
1389C<:not_characters> parameter in v5.16 and v5.18. If you are using
1390exclusively UTF-8 locales in v5.20 and higher, the rest of this section
1391does not apply to you.
1392
1393There are two cases, multi-byte and single-byte locales. First
1394multi-byte:
1395
1396The only multi-byte (or wide character) locale that Perl is ever likely
1397to support is UTF-8. This is due to the difficulty of implementation,
1398the fact that high quality UTF-8 locales are now published for every
1399area of the world (L<http://unicode.org/Public/cldr/latest/>), and that
1400failing all that you can use the L<Encode> module to translate to/from
1401your locale. So, you'll have to do one of those things if you're using
1402one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
1403Perls (pre v5.20) that don't have full UTF-8 locale support, they may
1404work reasonably well (depending on your C library implementation)
1405simply because both
dc4bfc4b
KW
1406they and Perl store characters that take up multiple bytes the same way.
1407However, some, if not most, C library implementations may not process
1408the characters in the upper half of the Latin-1 range (128 - 255)
1409properly under LC_CTYPE. To see if a character is a particular type
1410under a locale, Perl uses the functions like C<isalnum()>. Your C
1411library may not work for UTF-8 locales with those functions, instead
1412only working under the newer wide library functions like C<iswalnum()>.
31f05a37
KW
1413However, they are treated like single-byte locales, and will have the
1414restrictions described below.
e199995e 1415
31f05a37 1416For single-byte locales,
e199995e 1417Perl generally takes the tack to use locale rules on code points that can fit
66cbab2c
KW
1418in a single byte, and Unicode rules for those that can't (though this
1419isn't uniformly applied, see the note at the end of this section). This
1420prevents many problems in locales that aren't UTF-8. Suppose the locale
1421is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
1422in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
1423regular expression character class C<[[:alpha:]]> will magically match
14240xD7 in the Greek locale but not in the Latin one.
e199995e 1425
1d2ab946 1426However, there are places where this breaks down. Certain Perl constructs are
b4ffc3db
TC
1427for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
1428Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
1429subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
1430Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
31f05a37
KW
1431issue occurs with C<\N{...}>. Prior to v5.20, It is therefore a bad
1432idea to use C<\p{}> or
66cbab2c
KW
1433C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
1434locale will be a ISO8859-1. Use POSIX character classes instead.
1435
1436Another problem with this approach is that operations that cross the
1437single byte/multiple byte boundary are not well-defined, and so are
4a70680a 1438disallowed. (This boundary is between the codepoints at 255/256.)
66cbab2c
KW
1439For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
1440should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
1441Greek locale, for example, there is no character at 0xFF, and Perl
1442has no way of knowing what the character at 0xFF is really supposed to
1443represent. Thus it disallows the operation. In this mode, the
1444lowercase of U+0178 is itself.
1445
1446The same problems ensue if you enable automatic UTF-8-ification of your
e199995e 1447standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
b4ffc3db
TC
1448non-UTF-8 locales (by using either the B<-C> command line switch or the
1449C<PERL_UNICODE> environment variable; see L<perlrun>).
1450Things are read in as UTF-8, which would normally imply a Unicode
1451interpretation, but the presence of a locale causes them to be interpreted
1452in that locale instead. For example, a 0xD7 code point in the Unicode
1453input, which should mean the multiplication sign, won't be interpreted by
66cbab2c 1454Perl that way under the Greek locale. This is not a problem
b4ffc3db 1455I<provided> you make certain that all locales will always and only be either
66cbab2c 1456an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
b4ffc3db 1457
1d2ab946
KW
1458Still another problem is that this approach can lead to two code
1459points meaning the same character. Thus in a Greek locale, both U+03A7
1460and U+00D7 are GREEK CAPITAL LETTER CHI.
1461
b4ffc3db
TC
1462Vendor locales are notoriously buggy, and it is difficult for Perl to test
1463its locale-handling code because this interacts with code that Perl has no
1464control over; therefore the locale-handling code in Perl may be buggy as
66cbab2c
KW
1465well. (However, the Unicode-supplied locales should be better, and
1466there is a feed back mechanism to correct any problems. See
1467L</Freely available locale definitions>.)
1468
7ee2ae1e 1469If you have Perl v5.16, the problems mentioned above go away if you use
66cbab2c 1470the C<:not_characters> parameter to the locale pragma (except for vendor
7ee2ae1e 1471bugs in the non-character portions). If you don't have v5.16, and you
66cbab2c
KW
1472I<do> have locales that work, using them may be worthwhile for certain
1473specific purposes, as long as you keep in mind the gotchas already
1474mentioned. For example, if the collation for your locales works, it
1475runs faster under locales than under L<Unicode::Collate>; and you gain
1476access to such things as the local currency symbol and the names of the
7ee2ae1e 1477months and days of the week. (But to hammer home the point, in v5.16,
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1478you get this access without the downsides of locales by using the
1479C<:not_characters> form of the pragma.)
1480
1481Note: The policy of using locale rules for code points that can fit in a
1482byte, and Unicode rules for those that can't is not uniformly applied.
7ee2ae1e 1483Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
66cbab2c 1484consistently to regular expression matching except for bracketed
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1485character classes; in v5.14 it was extended to all regex matches; and in
1486v5.16 to the casing operations such as C<"\L"> and C<uc()>. For
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1487collation, in all releases, the system's C<strxfrm()> function is called,
1488and whatever it does is what you get.
b310b053 1489
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1490=head1 BUGS
1491
1492=head2 Broken systems
1493
5a964f20 1494In certain systems, the operating system's locale support
2bdf8add 1495is broken and cannot be fixed or used by Perl. Such deficiencies can
b4ffc3db 1496and will result in mysterious hangs and/or Perl core dumps when
2bdf8add 1497C<use locale> is in effect. When confronted with such a system,
7f2de2d2 1498please report in excruciating detail to <F<perlbug@perl.org>>, and
b4ffc3db 1499also contact your vendor: bug fixes may exist for these problems
2bdf8add 1500in your operating system. Sometimes such bug fixes are called an
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1501operating system upgrade. If you have the source for Perl, include in
1502the perlbug email the output of the test described above in L</Testing
1503for broken locales>.
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1504
1505=head1 SEE ALSO
1506
b310b053
JH
1507L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
1508L<POSIX/isalnum>, L<POSIX/isalpha>,
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1509L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>,
1510L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>,
1511L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>,
1512L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
1513L<POSIX/strtod>, L<POSIX/strxfrm>.
5f05dabc 1514
ccd65d51
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1515For special considerations when Perl is embedded in a C program,
1516see L<perlembed/Using embedded Perl with POSIX locales>.
1517
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1518=head1 HISTORY
1519
b0c42ed9 1520Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
5a964f20 1521Dunlop, assisted by the perl5-porters. Prose worked over a bit by
c052850d 1522Tom Christiansen, and updated by Perl 5 porters.