abbreviated as B<i18n>); telling such an application about a particular
set of preferences is known as B<localization> (B<l10n>).
-Perl has been extended to support the locale system. This
-is controlled per application by using one pragma, one function call,
-and several environment variables.
+Perl has been extended to support certain types of locales available in
+the locale system. This is controlled per application by using one
+pragma, one function call, and several environment variables.
+
+Perl supports single-byte locales that are supersets of ASCII, such as
+the ISO 8859 ones, and one multi-byte-type locale, UTF-8 ones, described
+in the next paragraph. Perl doesn't support any other multi-byte
+locales, such as the ones for East Asian languages.
Unfortunately, there are quite a few deficiencies with the design (and
-often, the implementations) of locales, and their use for character sets
-has mostly been supplanted by Unicode (see L<perlunitut> for an
-introduction to that, and keep on reading here for how Unicode interacts
-with locales in Perl).
-
-Perl continues to support the old locale system, and starting in v5.16,
-provides a hybrid way to use the Unicode character set, along with the
-other portions of locales that may not be so problematic.
+often, the implementations) of locales. Unicode was invented (see
+L<perlunitut> for an introduction to that) in part to address these
+design deficiencies, and nowadays, there is a series of "UTF-8
+locales", based on Unicode. These are locales whose character set is
+Unicode, encoded in UTF-8. Starting in v5.20, Perl fully supports
+UTF-8 locales, except for sorting and string comparisons like C<lt> and
+C<ge>. Starting in v5.26, Perl can handle these reasonably as well,
+depending on the platform's implementation. However, for earlier
+releases or for better control, use L<Unicode::Collate>. Perl continues to
+support the old non UTF-8 locales as well. There are currently no UTF-8
+locales for EBCDIC platforms.
+
(Unicode is also creating C<CLDR>, the "Common Locale Data Repository",
L<http://cldr.unicode.org/> which includes more types of information than
are available in the POSIX locale system. At the time of this writing,
there was no CPAN module that provides access to this XML-encoded data.
-However, many of its locales have the POSIX-only data extracted, and are
-available at L<http://unicode.org/Public/cldr/latest/>.)
+However, it is possible to compute the POSIX locale data from them, and
+earlier CLDR versions had these already extracted for you as UTF-8 locales
+L<http://unicode.org/Public/cldr/2.0.1/>.)
=head1 WHAT IS A LOCALE
=over
-=item Category LC_NUMERIC: Numeric formatting
+=item Category C<LC_NUMERIC>: Numeric formatting
This indicates how numbers should be formatted for human readability,
for example the character used as the decimal point.
-=item Category LC_MONETARY: Formatting of monetary amounts
+=item Category C<LC_MONETARY>: Formatting of monetary amounts
=for comment
-The nbsp below makes this look better
+The nbsp below makes this look better (though not great)
E<160>
-=item Category LC_TIME: Date/Time formatting
+=item Category C<LC_TIME>: Date/Time formatting
=for comment
-The nbsp below makes this look better
+The nbsp below makes this look better (though not great)
E<160>
-=item Category LC_MESSAGES: Error and other messages
+=item Category C<LC_MESSAGES>: Error and other messages
This is used by Perl itself only for accessing operating system error
-messages via L<$!|perlvar/$ERRNO>.
+messages via L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>.
-=item Category LC_COLLATE: Collation
+=item Category C<LC_COLLATE>: Collation
This indicates the ordering of letters for comparison and sorting.
In Latin alphabets, for example, "b", generally follows "a".
-=item Category LC_CTYPE: Character Types
+=item Category C<LC_CTYPE>: Character Types
This indicates, for example if a character is an uppercase letter.
Some platforms have other categories, dealing with such things as
measurement units and paper sizes. None of these are used directly by
Perl, but outside operations that Perl interacts with may use
-these. See L</Not within the scope of any use locale variant> below.
+these. See L</Not within the scope of "use locale"> below.
=back
=head1 PREPARING TO USE LOCALES
-Perl itself will not use locales unless specifically requested to (but
+Perl itself (outside the L<POSIX> module) will not use locales unless
+specifically requested to (but
again note that Perl may interact with code that does use them). Even
if there is such a request, B<all> of the following must be true
for it to work properly:
If you want a Perl application to process and present your data
according to a particular locale, the application code should include
-the S<C<use locale>> pragma (see L<The use locale pragma>) where
+the S<C<use locale>> pragma (see L</The "use locale" pragma>) where
appropriate, and B<at least one> of the following must be true:
=over 4
=item 2
B<The application must set its own locale> using the method described in
-L<The setlocale function>.
+L</The setlocale function>.
=back
=head1 USING LOCALES
-=head2 The use locale pragma
-
-By default, Perl itself ignores the current locale. The S<C<use locale>>
+=head2 The C<"use locale"> pragma
+
+Starting in Perl 5.28, this pragma may be used in
+L<multi-threaded|threads> applications on systems that have thread-safe
+locale ability. Some caveats apply, see L</Multi-threaded> below. On
+systems without this capability, or in earlier Perls, do NOT use this
+pragma in scripts that have multiple L<threads|threads> active. The
+locale in these cases is not local to a single thread. Another thread
+may change the locale at any time, which could cause at a minimum that a
+given thread is operating in a locale it isn't expecting to be in. On
+some platforms, segfaults can also occur. The locale change need not be
+explicit; some operations cause perl to change the locale itself. You
+are vulnerable simply by having done a S<C<"use locale">>.
+
+By default, Perl itself (outside the L<POSIX> module)
+ignores the current locale. The S<C<use locale>>
pragma tells Perl to use the current locale for some operations.
-Starting in v5.16, there is an optional parameter to this pragma:
-
- use locale ':not_characters';
-
-This parameter allows better mixing of locales and Unicode, and is
-described fully in L</Unicode and UTF-8>, but briefly, it tells Perl to
-not use the character portions of the locale definition, that is
-the C<LC_CTYPE> and C<LC_COLLATE> categories. Instead it will use the
-native character set (extended by Unicode). When using this parameter,
-you are responsible for getting the external character set translated
-into the native/Unicode one (which it already will be if it is one of
-the increasingly popular UTF-8 locales). There are convenient ways of
-doing this, as described in L</Unicode and UTF-8>.
+Starting in v5.16, there are optional parameters to this pragma,
+described below, which restrict which operations are affected by it.
The current locale is set at execution time by
L<setlocale()|/The setlocale function> described below. If that function
hasn't yet been called in the course of the program's execution, the
current locale is that which was determined by the L</"ENVIRONMENT"> in
-effect at the start of the program, except that
-C<L<LC_NUMERIC|/Category LC_NUMERIC: Numeric Formatting>> is always
-initialized to the C locale (mentioned under L<Finding locales>).
-If there is no valid environment, the current locale is undefined. It
-is likely, but not necessarily, the "C" locale.
+effect at the start of the program.
+If there is no valid environment, the current locale is whatever the
+system default has been set to. On POSIX systems, it is likely, but
+not necessarily, the "C" locale. On Windows, the default is set via the
+computer's S<C<Control Panel-E<gt>Regional and Language Options>> (or its
+current equivalent).
The operations that are affected by locale are:
=over 4
-=item B<Not within the scope of any C<use locale> variant>
+=item B<Not within the scope of C<"use locale">>
+
+Only certain operations originating outside Perl should be affected, as
+follows:
-Only operations originating outside Perl should be affected.
+=over 4
-The variable L<$!|perlvar/$ERRNO> (and its synonyms C<$ERRNO> and
-C<$OS_ERROR>) when used as strings always are in terms of the current
-locale.
+=item *
-The current locale is also used when going outside of Perl with
+The current locale is used when going outside of Perl with
operations like L<system()|perlfunc/system LIST> or
L<qxE<sol>E<sol>|perlop/qxE<sol>STRINGE<sol>>, if those operations are
locale-sensitive.
+=item *
+
Also Perl gives access to various C library functions through the
L<POSIX> module. Some of those functions are always affected by the
current locale. For example, C<POSIX::strftime()> uses C<LC_TIME>;
C<POSIX::strtod()> uses C<LC_NUMERIC>; C<POSIX::strcoll()> and
-C<POSIX::strxfrm()> use C<LC_COLLATE>; and character classification
-functions like C<POSIX::isalnum()> use C<LC_CTYPE>. All such functions
+C<POSIX::strxfrm()> use C<LC_COLLATE>. All such functions
will behave according to the current underlying locale, even if that
-isn't exposed to Perl space.
+locale isn't exposed to Perl space.
+
+This applies as well to L<I18N::Langinfo>.
+
+=item *
-And, certain Perl operations that are set-up within the scope of a
-C<use locale> variant retain that effect even outside the scope.
+XS modules for all categories but C<LC_NUMERIC> get the underlying
+locale, and hence any C library functions they call will use that
+underlying locale. For more discussion, see L<perlxs/CAVEATS>.
+
+=back
+
+Note that all C programs (including the perl interpreter, which is
+written in C) always have an underlying locale. That locale is the "C"
+locale unless changed by a call to L<setlocale()|/The setlocale
+function>. When Perl starts up, it changes the underlying locale to the
+one which is indicated by the L</ENVIRONMENT>. When using the L<POSIX>
+module or writing XS code, it is important to keep in mind that the
+underlying locale may be something other than "C", even if the program
+hasn't explicitly changed it.
+
+=for comment
+The nbsp below makes this look better (though not great)
+
+E<160>
+
+=item B<Lingering effects of C<S<use locale>>>
+
+Certain Perl operations that are set-up within the scope of a
+C<use locale> retain that effect even outside the scope.
These include:
=over 4
The output format of a L<write()|perlfunc/write> is determined by an
earlier format declaration (L<perlfunc/format>), so whether or not the
output is affected by locale is determined by if the C<format()> is
-within the scope of a C<use locale> variant, not whether the C<write()>
+within the scope of a C<use locale>, not whether the C<write()>
is.
=item *
Regular expression patterns can be compiled using
-L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodual> with actual
+L<qrE<sol>E<sol>|perlop/qrE<sol>STRINGE<sol>msixpodualn> with actual
matching deferred to later. Again, it is whether or not the compilation
was done within the scope of C<use locale> that determines the match
behavior, not if the matches are done within such a scope or not.
=back
-=item B<Under C<use locale ':not_characters';>>
+=for comment
+The nbsp below makes this look better (though not great)
+
+
+E<160>
+
+=item B<Under C<"use locale";>>
=over 4
=item *
-All the non-Perl operations.
+All the above operations
=item *
and
C<sprintf()>.
-=back
-
-=for comment
-The nbsp below makes this look better
-
-E<160>
-
-=item B<Under just plain C<use locale;>>
-
-=over 4
-
-=item *
-
-All the above operations
-
=item *
B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
operands are char-for-char identical. If you really want to know whether
two strings--which C<eq> and C<cmp> may consider different--are equal
as far as collation in the locale is concerned, see the discussion in
-L<Category LC_COLLATE: Collation>.
+L<Category C<LC_COLLATE>: Collation>.
=item *
B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
+=item *
+
+B<The variables L<$!|perlvar/$ERRNO>> (and its synonyms C<$ERRNO> and
+C<$OS_ERROR>) B<and L<$^E|perlvar/$EXTENDED_OS_ERROR>> (and its synonym
+C<$EXTENDED_OS_ERROR>) when used as strings use C<LC_MESSAGES>.
+
=back
=back
The default behavior is restored with the S<C<no locale>> pragma, or
upon reaching the end of the block enclosing C<use locale>.
-Note that C<use locale> and C<use locale ':not_characters'> may be
+Note that C<use locale> calls may be
nested, and that what is in effect within an inner scope will revert to
the outer scope's rules at the end of the inner scope.
The string result of any operation that uses locale
information is tainted, as it is possible for a locale to be
-untrustworthy. See L<"SECURITY">.
+untrustworthy. See L</"SECURITY">.
+
+Starting in Perl v5.16 in a very limited way, and more generally in
+v5.22, you can restrict which category or categories are enabled by this
+particular instance of the pragma by adding parameters to it. For
+example,
+
+ use locale qw(:ctype :numeric);
+
+enables locale awareness within its scope of only those operations
+(listed above) that are affected by C<LC_CTYPE> and C<LC_NUMERIC>.
+
+The possible categories are: C<:collate>, C<:ctype>, C<:messages>,
+C<:monetary>, C<:numeric>, C<:time>, and the pseudo category
+C<:characters> (described below).
+
+Thus you can say
+
+ use locale ':messages';
+
+and only L<$!|perlvar/$ERRNO> and L<$^E|perlvar/$EXTENDED_OS_ERROR>
+will be locale aware. Everything else is unaffected.
+
+Since Perl doesn't currently do anything with the C<LC_MONETARY>
+category, specifying C<:monetary> does effectively nothing. Some
+systems have other categories, such as C<LC_PAPER>, but Perl
+also doesn't do anything with them, and there is no way to specify
+them in this pragma's arguments.
+
+You can also easily say to use all categories but one, by either, for
+example,
+
+ use locale ':!ctype';
+ use locale ':not_ctype';
+
+both of which mean to enable locale awarness of all categories but
+C<LC_CTYPE>. Only one category argument may be specified in a
+S<C<use locale>> if it is of the negated form.
+
+Prior to v5.22 only one form of the pragma with arguments is available:
+
+ use locale ':not_characters';
+
+(and you have to say C<not_>; you can't use the bang C<!> form). This
+pseudo category is a shorthand for specifying both C<:collate> and
+C<:ctype>. Hence, in the negated form, it is nearly the same thing as
+saying
+
+ use locale qw(:messages :monetary :numeric :time);
+
+We use the term "nearly", because C<:not_characters> also turns on
+S<C<use feature 'unicode_strings'>> within its scope. This form is
+less useful in v5.20 and later, and is described fully in
+L</Unicode and UTF-8>, but briefly, it tells Perl to not use the
+character portions of the locale definition, that is the C<LC_CTYPE> and
+C<LC_COLLATE> categories. Instead it will use the native character set
+(extended by Unicode). When using this parameter, you are responsible
+for getting the external character set translated into the
+native/Unicode one (which it already will be if it is one of the
+increasingly popular UTF-8 locales). There are convenient ways of doing
+this, as described in L</Unicode and UTF-8>.
=head2 The setlocale function
+WARNING! Prior to Perl 5.28 or on a system that does not support
+thread-safe locale operations, do NOT use this function in a
+L<thread|threads>. The locale will change in all other threads at the
+same time, and should your thread get paused by the operating system,
+and another started, that thread will not have the locale it is
+expecting. On some platforms, there can be a race leading to segfaults
+if two threads call this function nearly simultaneously.
+
You can switch locales as often as you wish at run time with the
C<POSIX::setlocale()> function:
# (Showing the testing for success/failure of operations is
# omitted in these examples to avoid distracting from the main
# point)
+
use POSIX qw(locale_h);
+ use locale;
+ my $old_locale;
# query and save the old locale
$old_locale = setlocale(LC_CTYPE);
# LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
setlocale(LC_CTYPE, "");
- # LC_CTYPE now reset to default defined by LC_ALL/LC_CTYPE/LANG
- # environment variables. See below for documentation.
+ # LC_CTYPE now reset to the default defined by the
+ # LC_ALL/LC_CTYPE/LANG environment variables, or to the system
+ # default. See below for documentation.
# restore the old locale
setlocale(LC_CTYPE, $old_locale);
example.
If no second argument is provided and the category is something other
-than LC_ALL, the function returns a string naming the current locale
+than C<LC_ALL>, the function returns a string naming the current locale
for the category. You can use this value as the second argument in a
-subsequent call to C<setlocale()>.
+subsequent call to C<setlocale()>, B<but> on some platforms the string
+is opaque, not something that most people would be able to decipher as
+to what locale it means.
-If no second argument is provided and the category is LC_ALL, the
+If no second argument is provided and the category is C<LC_ALL>, the
result is implementation-dependent. It may be a string of
concatenated locale names (separator also implementation-dependent)
or a single locale name. Please consult your L<setlocale(3)> man page for
to the environment made by the application after startup may or may not
be noticed, depending on your system's C library.
-If the second argument does not correspond to a valid locale, the locale
-for the category is not changed, and the function returns C<undef>.
+Note that when a form of C<use locale> that doesn't include all
+categories is specified, Perl ignores the excluded categories.
-Note that Perl ignores the current C<LC_CTYPE> and C<LC_COLLATE> locales
-within the scope of a C<use locale ':not_characters'>.
+If C<set_locale()> fails for some reason (for example, an attempt to set
+to a locale unknown to the system), the locale for the category is not
+changed, and the function returns C<undef>.
-If C<set_locale()> fails for some reason (for example an attempt to set
-to a locale unknown to the system), C<undef> is returned.
+Starting in Perl 5.28, on multi-threaded perls compiled on systems that
+implement POSIX 2008 thread-safe locale operations, this function
+doesn't actually call the system C<setlocale>. Instead those
+thread-safe operations are used to emulate the C<setlocale> function,
+but in a thread-safe manner.
For further information about the categories, consult L<setlocale(3)>.
+=head2 Multi-threaded operation
+
+Beginning in Perl 5.28, multi-threaded locale operation is supported on
+systems that implement either the POSIX 2008 or Windows-specific
+thread-safe locale operations. Many modern systems, such as various
+Unix variants and Darwin do have this.
+
+You can tell if using locales is safe on your system by looking at the
+read-only boolean variable C<${^SAFE_LOCALES}>. The value is 1 if the
+perl is not threaded, or if it is using thread-safe locale operations.
+
+Thread-safe operations are supported in Windows starting in Visual Studio
+2005, and in systems compatible with POSIX 2008. Some platforms claim
+to support POSIX 2008, but have buggy implementations, so that the hints
+files for compiling to run on them turn off attempting to use
+thread-safety. C<${^SAFE_LOCALES}> will be 0 on them.
+
+Be aware that writing a multi-threaded application will not be portable
+to a platform which lacks the native thread-safe locale support. On
+systems that do have it, you automatically get this behavior for
+threaded perls, without having to do anything. If for some reason, you
+don't want to use this capability (perhaps the POSIX 2008 support is
+buggy on your system), you can manually compile Perl to use the old
+non-thread-safe implementation by passing the argument
+C<-Accflags='-DNO_THREAD_SAFE_LOCALE'> to F<Configure>.
+Except on Windows, this will continue to use certain of the POSIX 2008
+functions in some situations. If these are buggy, you can pass the
+following to F<Configure> instead or additionally:
+C<-Accflags='-DNO_POSIX_2008_LOCALE'>. This will also keep the code
+from using thread-safe locales.
+C<${^SAFE_LOCALES}> will be 0 on systems that turn off the thread-safe
+operations.
+
+The initial program is started up using the locale specified from the
+environment, as currently, described in L</ENVIRONMENT>. All newly
+created threads start with C<LC_ALL> set to C<"C">>. Each thread may
+use C<POSIX::setlocale()> to query or switch its locale at any time,
+without affecting any other thread. All locale-dependent operations
+automatically use their thread's locale.
+
+This should be completely transparent to any applications written
+entirely in Perl (minus a few rarely encountered caveats given in the
+L</Multi-threaded> section). Information for XS module writers is given
+in L<perlxs/Locale-aware XS code>.
+
=head2 Finding locales
For locales available in your system, consult also L<setlocale(3)> to
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
-This means that your locale settings had LC_ALL set to "En_US" and
+This means that your locale settings had C<LC_ALL> set to "En_US" and
LANG exists but has no value. Perl tried to believe you but could not.
Instead, Perl gave up and fell back to the "C" locale, the default locale
-that is supposed to work no matter what. This usually means your locale
-settings were wrong, they mention locales your system has never heard
-of, or the locale installation in your system has problems (for example,
-some system files are broken or missing). There are quick and temporary
-fixes to these problems, as well as more thorough and lasting fixes.
+that is supposed to work no matter what. (On Windows, it first tries
+falling back to the system default locale.) This usually means your
+locale settings were wrong, they mention locales your system has never
+heard of, or the locale installation in your system has problems (for
+example, some system files are broken or missing). There are quick and
+temporary fixes to these problems, as well as more thorough and lasting
+fixes.
+
+=head2 Testing for broken locales
+
+If you are building Perl from source, the Perl test suite file
+F<lib/locale.t> can be used to test the locales on your system.
+Setting the environment variable C<PERL_DEBUG_FULL_TEST> to 1
+will cause it to output detailed results. For example, on Linux, you
+could say
+
+ PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
+
+Besides many other tests, it will test every locale it finds on your
+system to see if they conform to the POSIX standard. If any have
+errors, it will include a summary near the end of the output of which
+locales passed all its tests, and which failed, and why.
=head2 Temporarily fixing locale problems
locale inconsistencies or to run Perl under the default locale "C".
Perl's moaning about locale problems can be silenced by setting the
-environment variable PERL_BADLANG to a zero value, for example "0".
+environment variable C<PERL_BADLANG> to "0" or "".
This method really just sweeps the problem under the carpet: you tell
Perl to shut up even when Perl sees that something is wrong. Do not
be surprised if later something locale-dependent misbehaves.
Perl can be run under the "C" locale by setting the environment
-variable LC_ALL to "C". This method is perhaps a bit more civilized
-than the PERL_BADLANG approach, but setting LC_ALL (or
+variable C<LC_ALL> to "C". This method is perhaps a bit more civilized
+than the C<PERL_BADLANG> approach, but setting C<LC_ALL> (or
other locale variables) may affect other programs as well, not just
Perl. In particular, external programs run from within Perl will see
these changes. If you make the new settings permanent (read on), all
-programs you run see the changes. See L<"ENVIRONMENT"> for
-the full list of relevant environment variables and L<USING LOCALES>
+programs you run see the changes. See L</"ENVIRONMENT"> for
+the full list of relevant environment variables and L</"USING LOCALES">
for their effects in Perl. Effects in other programs are
-easily deducible. For example, the variable LC_COLLATE may well affect
+easily deducible. For example, the variable C<LC_COLLATE> may well affect
your B<sort> program (or whatever the program that arranges "records"
alphabetically in your system is called).
You can test out changing these variables temporarily, and if the
new settings seem to help, put those settings into your shell startup
-files. Consult your local documentation for the exact details. For in
+files. Consult your local documentation for the exact details. For
Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
LC_ALL=en_US.ISO8859-1
setenv LC_ALL en_US.ISO8859-1
-or if you have the "env" application you can do in any shell
+or if you have the "env" application you can do (in any shell)
env LC_ALL=en_US.ISO8859-1 perl ...
mis(sing)configuration of the whole system's locales usually requires
the help of your friendly system administrator.
-First, see earlier in this document about L<Finding locales>. That tells
+First, see earlier in this document about L</Finding locales>. That tells
how to find which locales are really supported--and more importantly,
installed--on your system. In our example error message, environment
variables affecting the locale are listed in the order of decreasing
(prefix matches do not count and case usually counts) like "En_US"
without the quotes, then you should be okay because you are using a
locale name that should be installed and available in your system.
-In this case, see L<Permanently fixing your system's locale configuration>.
+In this case, see L</Permanently fixing your system's locale configuration>.
=head2 Permanently fixing your system's locale configuration
that you can list and which somehow matches what you tried. The
rules for matching locale names are a bit vague because
standardization is weak in this area. See again the
-L<Finding locales> about general rules.
+L</Finding locales> about general rules.
=head2 Fixing system locale configuration
Contact a system administrator (preferably your own) and report the exact
error message you get, and ask them to read this same documentation you
are now reading. They should be able to check whether there is something
-wrong with the locale configuration of the system. The L<Finding locales>
+wrong with the locale configuration of the system. The L</Finding locales>
section is unfortunately a bit vague about the exact commands and places
because these things are not that standardized.
The C<POSIX::localeconv()> function allows you to get particulars of the
locale-dependent numeric formatting information specified by the current
-C<LC_NUMERIC> and C<LC_MONETARY> locales. (If you just want the name of
+underlying C<LC_NUMERIC> and C<LC_MONETARY> locales (regardless of
+whether called from within the scope of C<S<use locale>> or not). (If
+you just want the name of
the current locale for a particular category, use C<POSIX::setlocale()>
-with a single parameter--see L<The setlocale function>.)
+with a single parameter--see L</The setlocale function>.)
use POSIX qw(locale_h);
}
print "\n";
+Note that if the platform doesn't have C<LC_NUMERIC> and/or
+C<LC_MONETARY> available or enabled, the corresponding elements of the
+hash will be missing.
+
=head2 I18N::Langinfo
Another interface for querying locale-dependent information is the
The following subsections describe basic locale categories. Beyond these,
some combination categories allow manipulation of more than one
-basic category at a time. See L<"ENVIRONMENT"> for a discussion of these.
+basic category at a time. See L</"ENVIRONMENT"> for a discussion of these.
-=head2 Category LC_COLLATE: Collation
+=head2 Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting
-In the scope of S<C<use locale>> (but not a
-C<use locale ':not_characters'>), Perl looks to the C<LC_COLLATE>
+In the scope of a S<C<use locale>> form that includes collation, Perl
+looks to the C<LC_COLLATE>
environment variable to determine the application's notions on collation
(ordering) of characters. For example, "b" follows "a" in Latin
alphabets, but where do "E<aacute>" and "E<aring>" belong? And while
"color" follows "chocolate" in English, what about in traditional Spanish?
The following collations all make sense and you may meet any of them
-if you "use locale".
+if you C<"use locale">.
A B C D E a b c d e
A a B b C c D d E e
sorting raw binary data, whereas the locale-dependent collation of the
first example is useful for natural text.
-As noted in L<USING LOCALES>, C<cmp> compares according to the current
+As noted in L</USING LOCALES>, C<cmp> compares according to the current
collation locale when C<use locale> is in effect, but falls back to a
char-by-char comparison for strings that the locale says are equal. You
can use C<POSIX::strcoll()> if you don't want this fall-back:
dictionary-like ordering that ignores space characters completely and
which folds case.
+Perl uses the platform's C library collation functions C<strcoll()> and
+C<strxfrm()>. That means you get whatever they give. On some
+platforms, these functions work well on UTF-8 locales, giving
+a reasonable default collation for the code points that are important in
+that locale. (And if they aren't working well, the problem may only be
+that the locale definition is deficient, so can be fixed by using a
+better definition file. Unicode's definitions (see L</Freely available
+locale definitions>) provide reasonable UTF-8 locale collation
+definitions.) Starting in Perl v5.26, Perl's use of these functions has
+been made more seamless. This may be sufficient for your needs. For
+more control, and to make sure strings containing any code point (not
+just the ones important in the locale) collate properly, the
+L<Unicode::Collate> module is suggested.
+
+In non-UTF-8 locales (hence single byte), code points above 0xFF are
+technically invalid. But if present, again starting in v5.26, they will
+collate to the same position as the highest valid code point does. This
+generally gives good results, but the collation order may be skewed if
+the valid code point gets special treatment when it forms particular
+sequences with other characters as defined by the locale.
+When two strings collate identically, the code point order is used as a
+tie breaker.
+
+If Perl detects that there are problems with the locale collation order,
+it reverts to using non-locale collation rules for that locale.
+
If you have a single string that you want to check for "equality in
locale" against several others, you might think you could gain a little
efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
in case it's needed again. An example rewritten the easy way with
C<cmp> runs just about as fast. It also copes with null characters
embedded in strings; if you call C<strxfrm()> directly, it treats the first
-null it finds as a terminator. don't expect the transformed strings
+null it finds as a terminator. Don't expect the transformed strings
it produces to be portable across systems--or even from one revision
of your operating system to the next. In short, don't call C<strxfrm()>
directly: let Perl do it for you.
Note: C<use locale> isn't shown in some of these examples because it isn't
-needed: C<strcoll()> and C<strxfrm()> exist only to generate locale-dependent
-results, and so always obey the current C<LC_COLLATE> locale.
+needed: C<strcoll()> and C<strxfrm()> are POSIX functions
+which use the standard system-supplied C<libc> functions that
+always obey the current C<LC_COLLATE> locale.
-=head2 Category LC_CTYPE: Character Types
+=head2 Category C<LC_CTYPE>: Character Types
-In the scope of S<C<use locale>> (but not a
-C<use locale ':not_characters'>), Perl obeys the C<LC_CTYPE> locale
+In the scope of a S<C<use locale>> form that includes C<LC_CTYPE>, Perl
+obeys the C<LC_CTYPE> locale
setting. This controls the application's notion of which characters are
-alphabetic. This affects Perl's C<\w> regular expression metanotation,
+alphabetic, numeric, punctuation, I<etc>. This affects Perl's C<\w>
+regular expression metanotation,
which stands for alphanumeric characters--that is, alphabetic,
-numeric, and including other special characters such as the underscore or
-
hyphen. (Consult L<perlre> for more information about
+numeric, and the platform's native underscore.
+(Consult L<perlre> for more information about
regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale
setting, characters like "E<aelig>", "E<eth>", "E<szlig>", and
"E<oslash>" may be understood as C<\w> characters.
+It also affects things like C<\s>, C<\D>, and the POSIX character
+classes, like C<[[:graph:]]>. (See L<perlrecharclass> for more
+information on all these.)
The C<LC_CTYPE> locale also provides the map used in transliterating
characters between lower and uppercase. This affects the case-mapping
-functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>; case-mapping
+functions--C<fc()>, C<lc()>, C<lcfirst()>, C<uc()>, and C<ucfirst()>;
+case-mapping
interpolation with C<\F>, C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted
-strings and C<s///> substitutions; and case-independent regular expression
+strings and C<s///> substitutions; and case-insensitive regular expression
pattern matching using the C<i> modifier.
-Finally, C<LC_CTYPE> affects the POSIX character-class test
-functions--C<isalpha()>, C<islower()>, and so on. For example, if you move
-from the "C" locale to a 7-bit Scandinavian one, you may find--possibly
-to your surprise--that "|" moves from the C<ispunct()> class to C<isalpha()>.
-Unfortunately, this creates big problems for regular expressions. "|" still
-means alternation even though it matches C<\w>.
+Starting in v5.20, Perl supports UTF-8 locales for C<LC_CTYPE>, but
+otherwise Perl only supports single-byte locales, such as the ISO 8859
+series. This means that wide character locales, for example for Asian
+languages, are not well-supported. Use of these locales may cause core
+dumps. If the platform has the capability for Perl to detect such a
+locale, starting in Perl v5.22, L<Perl will warn, default
+enabled|warnings/Category Hierarchy>, using the C<locale> warning
+category, whenever such a locale is switched into. The UTF-8 locale
+support is actually a
+superset of POSIX locales, because it is really full Unicode behavior
+as if no C<LC_CTYPE> locale were in effect at all (except for tainting;
+see L</SECURITY>). POSIX locales, even UTF-8 ones,
+are lacking certain concepts in Unicode, such as the idea that changing
+the case of a character could expand to be more than one character.
+Perl in a UTF-8 locale, will give you that expansion. Prior to v5.20,
+Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
+with some restrictions, and on other platforms more like the "C" locale.
+For releases v5.16 and v5.18, C<S<use locale 'not_characters>> could be
+used as a workaround for this (see L</Unicode and UTF-8>).
Note that there are quite a few things that are unaffected by the
-current locale. All the escape sequences for particular characters,
+current locale. Any literal character is the native character for the
+given platform. Hence 'A' means the character at code point 65 on ASCII
+platforms, and 193 on EBCDIC. That may or may not be an 'A' in the
+current locale, if that locale even has an 'A'.
+Similarly, all the escape sequences for particular characters,
C<\n> for example, always mean the platform's native one. This means,
for example, that C<\N> in regular expressions (every character
-but new-line) work on the platform character set.
+but new-line) works on the platform character set.
+
+Starting in v5.22, Perl will by default warn when switching into a
+locale that redefines any ASCII printable character (plus C<\t> and
+C<\n>) into a different class than expected. This is likely to
+happen on modern locales only on EBCDIC platforms, where, for example,
+a CCSID 0037 locale on a CCSID 1047 machine moves C<"[">, but it can
+happen on ASCII platforms with the ISO 646 and other
+7-bit locales that are essentially obsolete. Things may still work,
+depending on what features of Perl are used by the program. For
+example, in the example from above where C<"|"> becomes a C<\w>, and
+there are no regular expressions where this matters, the program may
+still work properly. The warning lists all the characters that
+it can determine could be adversely affected.
B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
in clearly ineligible characters being considered to be alphanumeric by
your application. For strict matching of (mundane) ASCII letters and
digits--for example, in command strings--locale-aware applications
-should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">.
+should use C<\w> with the C</a> regular expression modifier. See L</"SECURITY">.
-=head2 Category LC_NUMERIC: Numeric Formatting
+=head2 Category C<LC_NUMERIC>: Numeric Formatting
-After a proper C<POSIX::setlocale()> call, and within the scope of one
-of the C<use locale> variants, Perl obeys the C<LC_NUMERIC>
-locale information, which controls an application's idea of how numbers
-should be formatted for human readability.
+After a proper C<POSIX::setlocale()> call, and within the scope of
+of a C<use locale> form that includes numerics, Perl obeys the
+C<LC_NUMERIC> locale information, which controls an application's idea
+of how numbers should be formatted for human readability.
In most implementations the only effect is to
change the character used for the decimal point--perhaps from "." to ",".
The functions aren't aware of such niceties as thousands separation and
-so on. (See L<The localeconv function> if you care about these things.)
+so on. (See L</The localeconv function> if you care about these things.)
use POSIX qw(strtod setlocale LC_NUMERIC);
use locale;
See also L<I18N::Langinfo> and C<RADIXCHAR>.
-=head2 Category LC_MONETARY: Formatting of monetary amounts
+=head2 Category C<LC_MONETARY>: Formatting of monetary amounts
The C standard defines the C<LC_MONETARY> category, but not a function
that is affected by its contents. (Those with experience of standards
committees will recognize that the working group decided to punt on the
issue.) Consequently, Perl essentially takes no notice of it. If you
really want to use C<LC_MONETARY>, you can query its contents--see
-L<The localeconv function>--and use the information that it returns in your
+L</The localeconv function>--and use the information that it returns in your
application's own formatting of currency amounts. However, you may well
find that the information, voluminous and complex though it may be, still
does not quite meet your requirements: currency formatting is a hard nut
See also L<I18N::Langinfo> and C<CRNCYSTR>.
-=head2 LC_TIME
+=head2 Category C<LC_TIME>: Respresentation of time
Output produced by C<POSIX::strftime()>, which builds a formatted
human-readable date/time string, is affected by the current C<LC_TIME>
Regular expression checks for safe file names or mail addresses using
C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
-characters such as "E<gt>" and "|" are alphanumeric.
+characters such as C<"E<gt>"> and C<"|"> are alphanumeric.
=item *
String interpolation with case-mapping, as in, say, C<$dest =
-"C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE
+"C:\U$name.$ext">, may produce dangerous results if a bogus C<LC_CTYPE>
case-mapping table is in effect.
=item *
=item *
-B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>)
+B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u>, C<\U>, or C<\F>)
-Result string containing interpolated material is tainted if
-C<use locale> (but not S<C<use locale ':not_characters'>>) is in effect.
+The result string containing interpolated material is tainted if
+a C<use locale> form that includes C<LC_CTYPE> is in effect.
=item *
Scalar true/false result never tainted.
-Subpatterns, either delivered as a list-context result or as $1 etc.
-are tainted if C<use locale> (but not S<C<use locale ':not_characters'>>)
-is in effect, and the subpattern regular
-expression contains C<\w> (to match an alphanumeric character), C<\W>
-(non-alphanumeric character), C<\s> (whitespace character), or C<\S>
-(non whitespace character). The matched-pattern variable, $&, $`
-(pre-match), $' (post-match), and $+ (last match) are also tainted if
-C<use locale> is in effect and the regular expression contains C<\w>,
-C<\W>, C<\s>, or C<\S>.
+All subpatterns, either delivered as a list-context result or as C<$1>
+I<etc>., are tainted if a C<use locale> form that includes
+C<LC_CTYPE> is in effect, and the subpattern
+regular expression contains a locale-dependent construct. These
+constructs include C<\w> (to match an alphanumeric character), C<\W>
+(non-alphanumeric character), C<\b> and C<\B> (word-boundary and
+non-boundardy, which depend on what C<\w> and C<\W> match), C<\s>
+(whitespace character), C<\S> (non whitespace character), C<\d> and
+C<\D> (digits and non-digits), and the POSIX character classes, such as
+C<[:alpha:]> (see L<perlrecharclass/POSIX Character Classes>).
+
+Tainting is also likely if the pattern is to be matched
+case-insensitively (via C</i>). The exception is if all the code points
+to be matched this way are above 255 and do not have folds under Unicode
+rules to below 256. Tainting is not done for these because Perl
+only uses Unicode rules for such code points, and those rules are the
+same no matter what the current locale.
+
+The matched-pattern variables, C<$&>, C<$`> (pre-match), C<$'>
+(post-match), and C<$+> (last match) also are tainted.
=item *
B<Substitution operator> (C<s///>):
Has the same behavior as the match operator. Also, the left
-operand of C<=~> becomes tainted when C<use locale>
-(but not S<C<use locale ':not_characters'>>) is in effect if modified as
+operand of C<=~> becomes tainted when a C<use locale>
+form that includes C<LC_CTYPE> is in effect, if modified as
a result of a substitution based on a regular
-expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of
-case-mapping with C<\l>, C<\L>,C<\u> or C<\U>.
+expression match involving any of the things mentioned in the previous
+item, or of case-mapping, such as C<\l>, C<\L>,C<\u>, C<\U>, or C<\F>.
=item *
B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
-Results are tainted if C<use locale> (but not
-S<C<use locale ':not_characters'>>) is in effect.
+Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is
+in effect.
=item *
Results are never tainted.
-=item *
-
-B<POSIX character class tests> (C<isalnum()>, C<isalpha()>, C<isdigit()>,
-C<isgraph()>, C<islower()>, C<isprint()>, C<ispunct()>, C<isspace()>, C<isupper()>,
-C<isxdigit()>):
-
-True/false results are never tainted.
-
=back
Three examples illustrate locale-dependent tainting.
open(F, ">$localized_output_file")
or warn "Open of $localized_output_file failed: $!\n";
-This third program fails to run because $& is tainted: it is the result
+This third program fails to run because C<$&> is tainted: it is the result
of a match involving C<\w> while C<use locale> is in effect.
=head1 ENVIRONMENT
=over 12
+=item PERL_SKIP_LOCALE_INIT
+
+This environment variable, available starting in Perl v5.20, if set
+(to any value), tells Perl to not use the rest of the
+environment variables to initialize with. Instead, Perl uses whatever
+the current locale settings are. This is particularly useful in
+embedded environments, see
+L<perlembed/Using embedded Perl with POSIX locales>.
+
=item PERL_BADLANG
A string that can suppress Perl's warning about failed locale settings
at startup. Failure can occur if the locale support in the operating
system is lacking (broken) in some way--or if you mistyped the name of
a locale when you set up your environment. If this environment
-variable is absent, or has a value that does not evaluate to integer
-zero--that is, "0" or ""-- Perl will complain about locale setting
-failures.
+variable is absent, or has a value other than "0" or "", Perl will
+complain about locale setting failures.
-B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message.
+B<NOTE>: C<PERL_BADLANG> only gives you a way to hide the warning message.
The message tells about some problem in your system's locale support,
and you should investigate what the problem is.
The following environment variables are not specific to Perl: They are
part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
-for controlling an application's opinion on data.
+for controlling an application's opinion on data. Windows is non-POSIX,
+but Perl arranges for the following to work as described anyway.
+If the locale given by an environment variable is not valid, Perl tries
+the next lower one in priority. If none are valid, on Windows, the
+system default locale is then tried. If all else fails, the C<"C">
+locale is used. If even that doesn't work, something is badly broken,
+but Perl tries to forge ahead with whatever the locale settings might
+be.
=over 12
-=item LC_ALL
+=item C<LC_ALL>
C<LC_ALL> is the "override-all" locale environment variable. If
set, it overrides all the rest of the locale environment variables.
-=item LANGUAGE
+=item C<LANGUAGE>
B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you
are using the GNU libc. This is the case if you are using e.g. Linux.
instead a "path" (":"-separated list) of I<languages> (not locales).
See the GNU C<gettext> library documentation for more information.
-=item LC_CTYPE
+=item C<LC_CTYPE>
In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG>
chooses the character type locale.
-=item LC_COLLATE
+=item C<LC_COLLATE>
In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation
(sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>,
C<LANG> chooses the collation locale.
-=item LC_MONETARY
+=item C<LC_MONETARY>
In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary
formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>,
C<LANG> chooses the monetary formatting locale.
-=item LC_NUMERIC
+=item C<LC_NUMERIC>
In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format
locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG>
chooses the numeric format.
-=item LC_TIME
+=item C<LC_TIME>
In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time
formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>,
C<LANG> chooses the date and time formatting locale.
-=item LANG
+=item C<LANG>
C<LANG> is the "catch-all" locale environment variable. If it is set, it
is used as the last resort after the overall C<LC_ALL> and the
-category-specific C<LC_...>.
+category-specific C<LC_I<foo>>.
=back
=head2 Examples
-The LC_NUMERIC controls the numeric output:
+The C<LC_NUMERIC> controls the numeric output:
use locale;
use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
This prints C<2.7>.
+You could also exclude C<LC_NUMERIC>, if you don't need it, by
+
+ use locale ':!numeric';
+
=head2 Backward compatibility
Versions of Perl prior to 5.004 B<mostly> ignored locale information,
generally behaving as if something similar to the C<"C"> locale were
always in force, even if the program environment suggested otherwise
-(see L<The setlocale function>). By default, Perl still behaves this
+(see L</The setlocale function>). By default, Perl still behaves this
way for backward compatibility. If you want a Perl application to pay
attention to locale information, you B<must> use the S<C<use locale>>
-pragma (see L<The use locale pragma>) or, in the unlikely event
+pragma (see L</The "use locale" pragma>) or, in the unlikely event
that you want to do so for just pattern matching, the
C</l> regular expression modifier (see L<perlre/Character set
modifiers>) to instruct it to do so.
The Unicode CLDR project extracts the POSIX portion of many of its
locales, available at
- http://unicode.org/Public/cldr/latest/
+ http://unicode.org/Public/cldr/2.0.1/
+
+(Newer versions of CLDR require you to compute the POSIX data yourself.
+See L<http://unicode.org/Public/cldr/latest/>.)
There is a large collection of locale definitions at:
=head2 An imperfect standard
Internationalization, as defined in the C and POSIX standards, can be
-criticized as incomplete, ungainly, and having too large a granularity.
-(Locales apply to a whole process, when it would arguably be more useful
-to have them apply to a single thread, window group, or whatever.) They
-also have a tendency, like standards groups, to divide the world into
-nations, when we all know that the world can equally well be divided
-into bankers, bikers, gamers, and so on.
+criticized as incomplete and ungainly. They also have a tendency, like
+standards groups, to divide the world into nations, when we all know
+that the world can equally well be divided into bankers, bikers, gamers,
+and so on.
=head1 Unicode and UTF-8
The support of Unicode is new starting from Perl version v5.6, and more fully
-implemented in version v5.8 and later. See L<perluniintro>. It is
-strongly recommended that when combining Unicode and locale (starting in
-v5.16), you use
+implemented in versions v5.8 and later. See L<perluniintro>.
+
+Starting in Perl v5.20, UTF-8 locales are supported in Perl, except
+C<LC_COLLATE> is only partially supported; collation support is improved
+in Perl v5.26 to a level that may be sufficient for your needs
+(see L</Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting>).
+
+If you have Perl v5.16 or v5.18 and can't upgrade, you can use
use locale ':not_characters';
instead use the L<PerlIO::locale> module, or the L<Encode::Locale>
module, both available from CPAN. The latter module also has methods to
ease the handling of C<ARGV> and environment variables, and can be used
-on individual strings. Also, if you know that all your locales will be
+on individual strings. If you know that all your locales will be
UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
command line switch.
This form of the pragma allows essentially seamless handling of locales
-with Unicode. The collation order will be Unicode's. It is strongly
-recommended that when you need to order and sort strings that you use
-the standard module L<Unicode::Collate> which gives much better results
-in many instances than you can get with the old-style locale handling.
-
-For pre-v5.16 Perls, or if you use the locale pragma without the
-C<:not_characters> parameter, Perl tries to work with both Unicode and
-locales--but there are problems.
-
-Perl does not handle multi-byte locales in this case, such as have been
-used for various
-Asian languages, such as Big5 or Shift JIS. However, the increasingly
-common multi-byte UTF-8 locales, if properly implemented, may work
-reasonably well (depending on your C library implementation) in this
-form of the locale pragma, simply because both
+with Unicode. The collation order will be by Unicode code point order.
+L<Unicode::Collate> can be used to get Unicode rules collation.
+
+All the modules and switches just described can be used in v5.20 with
+just plain C<use locale>, and, should the input locales not be UTF-8,
+you'll get the less than ideal behavior, described below, that you get
+with pre-v5.16 Perls, or when you use the locale pragma without the
+C<:not_characters> parameter in v5.16 and v5.18. If you are using
+exclusively UTF-8 locales in v5.20 and higher, the rest of this section
+does not apply to you.
+
+There are two cases, multi-byte and single-byte locales. First
+multi-byte:
+
+The only multi-byte (or wide character) locale that Perl is ever likely
+to support is UTF-8. This is due to the difficulty of implementation,
+the fact that high quality UTF-8 locales are now published for every
+area of the world (L<http://unicode.org/Public/cldr/2.0.1/> for
+ones that are already set-up, but from an earlier version;
+L<http://unicode.org/Public/cldr/latest/> for the most up-to-date, but
+you have to extract the POSIX information yourself), and that
+failing all that you can use the L<Encode> module to translate to/from
+your locale. So, you'll have to do one of those things if you're using
+one of these locales, such as Big5 or Shift JIS. For UTF-8 locales, in
+Perls (pre v5.20) that don't have full UTF-8 locale support, they may
+work reasonably well (depending on your C library implementation)
+simply because both
they and Perl store characters that take up multiple bytes the same way.
However, some, if not most, C library implementations may not process
the characters in the upper half of the Latin-1 range (128 - 255)
-properly under LC_CTYPE. To see if a character is a particular type
+properly under C<LC_CTYPE>. To see if a character is a particular type
under a locale, Perl uses the functions like C<isalnum()>. Your C
library may not work for UTF-8 locales with those functions, instead
-only working under the newer wide library functions like C<iswalnum()>.
-
+only working under the newer wide library functions like C<iswalnum()>,
+which Perl does not use.
+These multi-byte locales are treated like single-byte locales, and will
+have the restrictions described below. Starting in Perl v5.22 a warning
+message is raised when Perl detects a multi-byte locale that it doesn't
+fully support.
+
+For single-byte locales,
Perl generally takes the tack to use locale rules on code points that can fit
in a single byte, and Unicode rules for those that can't (though this
isn't uniformly applied, see the note at the end of this section). This
regular expression character class C<[[:alpha:]]> will magically match
0xD7 in the Greek locale but not in the Latin one.
-However, there are places where this breaks down. Certain constructs are
+However, there are places where this breaks down. Certain Perl constructs are
for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
-issue occurs with C<\N{...}>. It is therefore a bad idea to use C<\p{}> or
+issue occurs with C<\N{...}>. Prior to v5.20, it is therefore a bad
+idea to use C<\p{}> or
C<\N{}> under plain C<use locale>--I<unless> you can guarantee that the
-locale will be a ISO8859-1. Use POSIX character classes instead.
+locale will be ISO8859-1. Use POSIX character classes instead.
Another problem with this approach is that operations that cross the
single byte/multiple byte boundary are not well-defined, and so are
-disallowed. (This boundary is between the codepoints at 255/256.).
+disallowed. (This boundary is between the codepoints at 255/256.)
For example, lower casing LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178)
should return LATIN SMALL LETTER Y WITH DIAERESIS (U+00FF). But in the
Greek locale, for example, there is no character at 0xFF, and Perl
I<provided> you make certain that all locales will always and only be either
an ISO8859-1, or, if you don't have a deficient C library, a UTF-8 locale.
+Still another problem is that this approach can lead to two code
+points meaning the same character. Thus in a Greek locale, both U+03A7
+and U+00D7 are GREEK CAPITAL LETTER CHI.
+
+Because of all these problems, starting in v5.22, Perl will raise a
+warning if a multi-byte (hence Unicode) code point is used when a
+single-byte locale is in effect. (Although it doesn't check for this if
+doing so would unreasonably slow execution down.)
+
Vendor locales are notoriously buggy, and it is difficult for Perl to test
its locale-handling code because this interacts with code that Perl has no
control over; therefore the locale-handling code in Perl may be buggy as
Pre-v5.12, it was somewhat haphazard; in v5.12 it was applied fairly
consistently to regular expression matching except for bracketed
character classes; in v5.14 it was extended to all regex matches; and in
-v5.16 to the casing operations such as C<"\L"> and C<uc()>. For
-collation, in all releases, the system's C<strxfrm()> function is called,
-and whatever it does is what you get.
+v5.16 to the casing operations such as C<\L> and C<uc()>. For
+collation, in all releases so far, the system's C<strxfrm()> function is
+called, and whatever it does is what you get. Starting in v5.26, various
+bugs are fixed with the way perl uses this function.
=head1 BUGS
+=head2 Collation of strings containing embedded C<NUL> characters
+
+C<NUL> characters will sort the same as the lowest collating control
+character does, or to C<"\001"> in the unlikely event that there are no
+control characters at all in the locale. In cases where the strings
+don't contain this non-C<NUL> control, the results will be correct, and
+in many locales, this control, whatever it might be, will rarely be
+encountered. But there are cases where a C<NUL> should sort before this
+control, but doesn't. If two strings do collate identically, the one
+containing the C<NUL> will sort to earlier. Prior to 5.26, there were
+more bugs.
+
+=head2 Multi-threaded
+
+XS code or C-language libraries called from it that use the system
+L<C<setlocale(3)>> function (except on Windows) likely will not work
+from a multi-threaded application without changes. See
+L<perlxs/Locale-aware XS code>.
+
+An XS module that is locale-dependent could have been written under the
+assumption that it will never be called in a multi-threaded environment,
+and so uses other non-locale constructs that aren't multi-thread-safe.
+See L<perlxs/Thread-aware system interfaces>.
+
+POSIX does not define a way to get the name of the current per-thread
+locale. Some systems, such as Darwin and NetBSD do implement a
+function, L<querylocale(3)> to do this. On non-Windows systems without
+it, such as Linux, there are some additional caveats:
+
+=over
+
+=item *
+
+An embedded perl needs to be started up while the global locale is in
+effect. See L<perlembed/Using embedded Perl with POSIX locales>.
+
+=item *
+
+It becomes more important for perl to know about all the possible
+locale categories on the platform, even if they aren't apparently used
+in your program. Perl knows all of the Linux ones. If your platform
+has others, you can send email to L<mailto:perlbug@perl.org> for
+inclusion of it in the next release. In the meantime, it is possible to
+edit the Perl source to teach it about the category, and then recompile.
+Search for instances of, say, C<LC_PAPER> in the source, and use that as
+a template to add the omitted one.
+
+=item *
+
+It is possible, though hard to do, to call C<POSIX::setlocale> with a
+locale that it doesn't recognize as syntactically legal, but actually is
+legal on that system. This should happen only with embedded perls, or
+if you hand-craft a locale name yourself.
+
+=back
+
=head2 Broken systems
In certain systems, the operating system's locale support
please report in excruciating detail to <F<perlbug@perl.org>>, and
also contact your vendor: bug fixes may exist for these problems
in your operating system. Sometimes such bug fixes are called an
-operating system upgrade.
+operating system upgrade. If you have the source for Perl, include in
+the perlbug email the output of the test described above in L</Testing
+for broken locales>.
=head1 SEE ALSO
L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>,
-L<POSIX/isalnum>, L<POSIX/isalpha>,
-L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>,
-L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>,
-L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>,
+L<POSIX/localeconv>,
L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>,
L<POSIX/strtod>, L<POSIX/strxfrm>.
+For special considerations when Perl is embedded in a C program,
+see L<perlembed/Using embedded Perl with POSIX locales>.
+
=head1 HISTORY
Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
Dunlop, assisted by the perl5-porters. Prose worked over a bit by
-Tom Christiansen, and updated by Perl 5 porters.
+Tom Christiansen, and now maintained by Perl 5 porters.
https://perl5.git.perl.org / perl5.git / blobdiff