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. Unicode was invented (see
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 comparisions. (Use
-L<Unicode::Collate> for these.) Perl continues to support the old
-non UTF-8 locales as well.
+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>. There are
+actually two slightly different types of UTF-8 locales: one for Turkic
+languages and one for everything else.
+
+Starting in Perl v5.30, Perl detects Turkic locales by their
+behaviour, and seamlessly handles both types; previously only the
+non-Turkic one was supported. The name of the locale is ignored, if
+your system has a C<tr_TR.UTF-8> locale and it doesn't behave like a
+Turkic locale, perl will treat it like a non-Turkic locale.
+
+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 as UTF-8 locales 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
=item Category C<LC_MONETARY>: Formatting of monetary amounts
-=for comment
-The nbsp below makes this look better (though not great)
-
-E<160>
+Z<>
=item Category C<LC_TIME>: Date/Time formatting
-=for comment
-The nbsp below makes this look better (though not great)
-
-E<160>
+Z<>
=item Category C<LC_MESSAGES>: Error and other messages
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 (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>.
+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
=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 operations originating outside Perl should be affected, as follows:
+Only certain operations (all originating outside Perl) should be
+affected, as follows:
=over 4
=item *
-The variables L<$!|perlvar/$ERRNO> (and its synonyms C<$ERRNO> and
-C<$OS_ERROR>) and L<$^E|perlvar/$EXTENDED_OS_ERROR> (and its synonym
-C<$EXTENDED_OS_ERROR>) when used as strings always are in terms of the
-current locale and as if within the scope of L<"use bytes"|bytes>. This is
-likely to change in Perl v5.22.
-
-=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.
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
locale isn't exposed to Perl space.
+This applies as well to L<I18N::Langinfo>.
+
=item *
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. Perl always initializes C<LC_NUMERIC> to C<"C">
-because too many modules are unable to cope with the decimal point in a
-floating point number not being a dot (it's a comma in many locales).
-But note that these modules are vulnerable because C<LC_NUMERIC>
-currently can be changed at any time by a call to the C C<set_locale()>
-by XS code or by something XS code calls, or by C<POSIX::setlocale()> by
-Perl code. This is true also for the Perl-provided lite wrappers for XS
-modules to use some C library C<printf> functions:
-C<Gconvert>,
-L<my_sprintf|perlapi/my_sprintf>,
-L<my_snprintf|perlapi/my_snprintf>,
-and
-L<my_vsnprintf|perlapi/my_vsnprintf>.
+underlying locale. For more discussion, see L<perlxs/CAVEATS>.
=back
-=for comment
-The nbsp below makes this look better (though not great)
+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.
-E<160>
+Z<>
=item B<Lingering effects of C<S<use locale>>>
Certain Perl operations that are set-up within the scope of a
-C<use locale> variant retain that effect even outside the scope.
+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
-=for comment
-The nbsp below makes this look better (though not great)
-
-E<160>
+Z<>
-=item B<Under C<"use locale ':not_characters';">>
+=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 (though not great)
-
-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 C<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:
to the environment made by the application after startup may or may not
be noticed, depending on your system's C library.
-Note that Perl ignores the current C<LC_CTYPE> and C<LC_COLLATE> locales
-within the scope of a C<use locale ':not_characters'>.
+Note that when a form of C<use locale> that doesn't include all
+categories is specified, Perl ignores the excluded categories.
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>.
+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.
+
+You can force the thread-safe locale operations to always be used (if
+available) by recompiling perl with
+
+ -Accflags='-DUSE_THREAD_SAFE_LOCALE'
+
+added to your call to F<Configure>.
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.
+
+Normally on unthreaded builds, the traditional C<setlocale()> is used
+and not the thread-safe locale functions. You can force the use of these
+on systems that have them by adding the
+C<-Accflags='-DUSE_THREAD_SAFE_LOCALE'> to F<Configure>.
+
+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
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 C<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.
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 C<LC_COLLATE> may well affect
your B<sort> program (or whatever the program that arranges "records"
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.
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
-C<I18N::Langinfo::langinfo()> function, available at least in Unix-like
-systems and VMS.
+C<I18N::Langinfo::langinfo()> function.
The following example will import the C<langinfo()> function itself and
three constants to be used as arguments to C<langinfo()>: a constant for
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 C<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 only supports single-byte locales for C<LC_COLLATE>. This means
-that a UTF-8 locale likely will just give you machine-native ordering.
-Use L<Unicode::Collate> for the full implementation of the Unicode
-Collation Algorithm.
+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
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.
=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, numeric, punctuation, I<etc>. This affects Perl's C<\w>
regular expression metanotation,
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 (deprecated) POSIX character-class test
-functions--C<POSIX::isalpha()>, C<POSIX::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<POSIX::ispunct()> class to C<POSIX::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 supported. The UTF-8 locale support is actually a
+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 locale were in effect at all (except for tainting; see
-L</SECURITY>). POSIX locales, even UTF-8 ones,
+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,
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) 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;
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 C<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 *
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.
All subpatterns, either delivered as a list-context result or as C<$1>
-I<etc>., are tainted if C<use locale> (but not
-S<C<use locale ':not_characters'>>) is in effect, and the subpattern
+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
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 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>.
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<POSIX::isalnum()>,
-C<POSIX::isalpha()>, C<POSIX::isdigit()>, C<POSIX::isgraph()>,
-C<POSIX::islower()>, C<POSIX::isprint()>, C<POSIX::ispunct()>,
-C<POSIX::isspace()>, C<POSIX::isupper()>, C<POSIX::isxdigit()>):
-
-True/false results are never tainted.
-
=back
Three examples illustrate locale-dependent tainting.
=item PERL_SKIP_LOCALE_INIT
-This environment variable, available starting in Perl v5.20, and if it
-evaluates to a TRUE value, tells Perl to not use the rest of the
+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
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>: 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,
instead a "path" (":"-separated list) of I<languages> (not locales).
See the GNU C<gettext> library documentation for more information.
-=item C<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>
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_I<foo>>
+category-specific C<LC_I<foo>>.
=back
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 versions v5.8 and later. See L<perluniintro>.
-Starting in Perl v5.20, UTF-8 locales are supported in Perl, except for
-C<LC_COLLATE> (use L<Unicode::Collate> instead). If you have Perl v5.16
-or v5.18 and can't upgrade, you can use
+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';
This form of the pragma allows essentially seamless handling of locales
with Unicode. The collation order will be by Unicode code point order.
-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.
+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,
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/latest/>), and that
+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
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()>.
-However, they are treated like single-byte locales, and will have the
-restrictions described below.
+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
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{...}>. Prior to v5.20, It is therefore a bad
+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
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
=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>.
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