+=encoding utf8
+
=head1 NAME
perllocale - Perl locale handling (internationalization and localization)
=head1 DESCRIPTION
-Perl supports language-specific notions of data such as "is this
-a letter", "what is the uppercase equivalent of this letter", and
-"which of these letters comes first". These are important issues,
-especially for languages other than English--but also for English: it
-would be naE<iuml>ve to imagine that C<A-Za-z> defines all the "letters"
-needed to write in English. Perl is also aware that some character other
-than '.' may be preferred as a decimal point, and that output date
-representations may be language-specific. The process of making an
-application take account of its users' preferences in such matters is
-called B<internationalization> (often abbreviated as B<i18n>); telling
-such an application about a particular set of preferences is known as
-B<localization> (B<l10n>).
-
-Perl can understand language-specific data via the standardized (ISO C,
-XPG4, POSIX 1.c) method called "the locale system". The locale system is
-controlled per application using one pragma, one function call, and
-several environment variables.
-
-B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an
-application specifically requests it--see L<Backward compatibility>.
-The one exception is that write() now B<always> uses the current locale
-- see L<"NOTES">.
+In the beginning there was ASCII, the "American Standard Code for
+Information Interchange", which works quite well for Americans with
+their English alphabet and dollar-denominated currency. But it doesn't
+work so well even for other English speakers, who may use different
+currencies, such as the pound sterling (as the symbol for that currency
+is not in ASCII); and it's hopelessly inadequate for many of the
+thousands of the world's other languages.
+
+To address these deficiencies, the concept of locales was invented
+(formally the ISO C, XPG4, POSIX 1.c "locale system"). And applications
+were and are being written that use the locale mechanism. The process of
+making such an application take account of its users' preferences in
+these kinds of matters is called B<internationalization> (often
+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.
+
+Unfortunately, there are quite a few deficiencies with the design (and
+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. (Use
+L<Unicode::Collate> for these.) Perl continues to support the old
+non UTF-8 locales as well.
+
+(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/>.)
+
+=head1 WHAT IS A LOCALE
+
+A locale is a set of data that describes various aspects of how various
+communities in the world categorize their world. These categories are
+broken down into the following types (some of which include a brief
+note here):
+
+=over
+
+=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 C<LC_MONETARY>: Formatting of monetary amounts
+
+=for comment
+The nbsp below makes this look better (though not great)
+
+E<160>
+
+=item Category C<LC_TIME>: Date/Time formatting
+
+=for comment
+The nbsp below makes this look better (though not great)
+
+E<160>
+
+=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> and L<$^E|perlvar/$EXTENDED_OS_ERROR>.
+
+=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 C<LC_CTYPE>: Character Types
+
+This indicates, for example if a character is an uppercase letter.
+
+=item Other categories
+
+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 "use locale"> below.
+
+=back
+
+More details on the categories used by Perl are given below in L</LOCALE
+CATEGORIES>.
+
+Together, these categories go a long way towards being able to customize
+a single program to run in many different locations. But there are
+deficiencies, so keep reading.
=head1 PREPARING TO USE LOCALES
-If Perl applications are to understand and present your data
-correctly according a locale of your choice, B<all> of the following
-must be true:
+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:
=over 4
=item *
B<Your operating system must support the locale system>. If it does,
-you should find that the setlocale() function is a documented part of
+you should find that the C<setlocale()> function is a documented part of
its C library.
=item *
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 *
+=item 1
-B<The locale-determining environment variables (see L<"ENVIRONMENT">)
+B<The locale-determining environment variables (see L</"ENVIRONMENT">)
must be correctly set up> at the time the application is started, either
-by yourself or by whoever set up your system account.
+by yourself or by whomever set up your system account; or
-=item *
+=item 2
B<The application must set its own locale> using the method described in
L<The setlocale function>.
=head1 USING LOCALES
-=head2 The use locale pragma
+=head2 The C<"use locale"> pragma
+
+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 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.
+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 C<"use locale">>
-By default, Perl ignores the current locale. The S<C<use locale>>
-pragma tells Perl to use the current locale for some operations:
+Only certain operations originating outside Perl should be affected, as
+follows:
=over 4
=item *
-B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) and
-the POSIX string collation functions strcoll() and strxfrm() use
-C<LC_COLLATE>. sort() is also affected if used without an
+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
+will behave according to the current underlying locale, even if that
+locale isn't exposed to Perl space.
+
+=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. 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
+
+=item *
+
+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>, not whether the C<write()>
+is.
+
+=item *
+
+Regular expression patterns can be compiled using
+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>
+
+=item B<Under C<"use locale";>>
+
+=over 4
+
+=item *
+
+All the above operations
+
+=item *
+
+B<Format declarations> (L<perlfunc/format>) and hence any subsequent
+C<write()>s use C<LC_NUMERIC>.
+
+=item *
+
+B<stringification and output> use C<LC_NUMERIC>.
+These include the results of
+C<print()>,
+C<printf()>,
+C<say()>,
+and
+C<sprintf()>.
+
+=item *
+
+B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) use
+C<LC_COLLATE>. C<sort()> is also affected if used without an
explicit comparison function, because it uses C<cmp> by default.
B<Note:> C<eq> and C<ne> are unaffected by locale: they always
-perform a byte-by-byte comparison of their scalar operands. What's
+perform a char-by-char comparison of their scalar operands. What's
more, if C<cmp> finds that its operands are equal according to the
collation sequence specified by the current locale, it goes on to
-perform a byte-by-byte comparison, and only returns I<0> (equal) if the
-operands are bit-for-bit identical. If you really want to know whether
+perform a char-by-char comparison, and only returns I<0> (equal) if the
+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>.
-
-=item *
-
-B<Regular expressions and case-modification functions> (uc(), lc(),
-ucfirst(), and lcfirst()) use C<LC_CTYPE>
+L<Category C<LC_COLLATE>: Collation>.
=item *
-B<The formatting functions> (printf(), sprintf() and write()) use
-C<LC_NUMERIC>
+B<Regular expressions and case-modification functions> (C<uc()>, C<lc()>,
+C<ucfirst()>, and C<lcfirst()>) use C<LC_CTYPE>
=item *
-B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>.
+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<$EXTENDED_OS_ERROR>) when used as strings use C<LC_MESSAGES>.
=back
-C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in
-L<LOCALE CATEGORIES>.
+=back
The default behavior is restored with the S<C<no locale>> pragma, or
-upon reaching the end of block enclosing C<use locale>.
+upon reaching the end of the block enclosing C<use locale>.
+Note that C<use locale> calls may be
+nested, and that what is in effect within an inner scope will revert to
+the outer scope's rules at the end of the inner scope.
The string result of any operation that uses locale
information is tainted, as it is possible for a locale to be
untrustworthy. See L<"SECURITY">.
+Starting in Perl v5.16 in a very limited way, and more generally in
+v5.22, you can restrict which category or categories are enabled by this
+particular instance of the pragma by adding parameters to it. For
+example,
+
+ use locale qw(:ctype :numeric);
+
+enables locale awareness within its scope of only those operations
+(listed above) that are affected by C<LC_CTYPE> and C<LC_NUMERIC>.
+
+The possible categories are: C<:collate>, C<:ctype>, C<:messages>,
+C<:monetary>, C<:numeric>, C<:time>, and the pseudo category
+C<:characters> (described below).
+
+Thus you can say
+
+ use locale ':messages';
+
+and only L<$!|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_SIZE>, but Perl
+also doesn't know anything about 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
You can switch locales as often as you wish at run time with the
-POSIX::setlocale() function:
-
- # This functionality not usable prior to Perl 5.004
- require 5.004;
+C<POSIX::setlocale()> function:
# Import locale-handling tool set from POSIX module.
# This example uses: setlocale -- the function call
# LC_CTYPE -- explained below
+ # (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);
-The first argument of setlocale() gives the B<category>, the second the
+This simultaneously affects all threads of the program, so it may be
+problematic to use locales in threaded applications except where there
+is a single locale applicable to all threads.
+
+The first argument of C<setlocale()> gives the B<category>, the second the
B<locale>. The category tells in what aspect of data processing you
want to apply locale-specific rules. Category names are discussed in
-L<LOCALE CATEGORIES> and L<"ENVIRONMENT">. The locale is the name of a
+L</LOCALE CATEGORIES> and L</"ENVIRONMENT">. The locale is the name of a
collection of customization information corresponding to a particular
combination of language, country or territory, and codeset. Read on for
hints on the naming of locales: not all systems name locales as in the
example.
-If no second argument is provided and the category is something else
-than LC_ALL, the function returns a string naming the current locale
+If no second argument is provided and the category is something other
+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 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 locales names (separator also implementation-dependent)
-or a single locale name. Please consult your L<setlocale(3)> for
+concatenated locale names (separator also implementation-dependent)
+or a single locale name. Please consult your L<setlocale(3)> man page for
details.
If a second argument is given and it corresponds to a valid locale,
the locale for the category is set to that value, and the function
returns the now-current locale value. You can then use this in yet
-another call to setlocale(). (In some implementations, the return
+another call to C<setlocale()>. (In some implementations, the return
value may sometimes differ from the value you gave as the second
argument--think of it as an alias for the value you gave.)
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 I<undef>.
+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>.
+
For further information about the categories, consult L<setlocale(3)>.
english.iso88591 german.iso88591 russian.iso88595
english.roman8 russian.koi8r
-Sadly, even though the calling interface for setlocale() has been
+Sadly, even though the calling interface for C<setlocale()> has been
standardized, names of locales and the directories where the
configuration resides have not been. The basic form of the name is
I<language_territory>B<.>I<codeset>, but the latter parts after
the POSIX standard. They define the B<default locale> in which
every program starts in the absence of locale information in its
environment. (The I<default> default locale, if you will.) Its language
-is (American) English and its character codeset ASCII.
+is (American) English and its character codeset ASCII or, rarely, a
+superset thereof (such as the "DEC Multinational Character Set
+(DEC-MCS)"). B<Warning>. The C locale delivered by some vendors
+may not actually exactly match what the C standard calls for. So
+beware.
B<NOTE>: Not all systems have the "POSIX" locale (not all systems are
POSIX-conformant), so use "C" when you need explicitly to specify this
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
+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
-your B<sort> program (or whatever the program that arranges `records'
+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"
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)
+
+ env LC_ALL=en_US.ISO8859-1 perl ...
+
If you do not know what shell you have, consult your local
helpdesk or the equivalent.
the same. In this case, try running under a locale
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
+standardization is weak in this area. See again the
L<Finding locales> about general rules.
=head2 Fixing system locale configuration
=head2 The localeconv function
-The POSIX::localeconv() function allows you to get particulars of the
+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
-the current locale for a particular category, use POSIX::setlocale()
+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>.)
use POSIX qw(locale_h);
printf "%-20s = %s\n", $_, $locale_values->{$_}
}
-
localeconv() takes no arguments, and returns B<a reference to> a hash.
+
C<localeconv()> takes no arguments, and returns B<a reference to> a hash.
The keys of this hash are variable names for formatting, such as
C<decimal_point> and C<thousands_sep>. The values are the
corresponding, er, values. See L<POSIX/localeconv> for a longer
example listing the categories an implementation might be expected to
provide; some provide more and others fewer. You don't need an
-explicit C<use locale>, because localeconv() always observes the
+explicit C<use locale>, because C<localeconv()> always observes the
current locale.
Here's a simple-minded example program that rewrites its command-line
parameters as integers correctly formatted in the current locale:
- # See comments in previous example
- require 5.004;
- use POSIX qw(locale_h);
-
- # Get some of locale's numeric formatting parameters
- my ($thousands_sep, $grouping) =
- @{localeconv()}{'thousands_sep', 'grouping'};
-
- # Apply defaults if values are missing
- $thousands_sep = ',' unless $thousands_sep;
-
- # grouping and mon_grouping are packed lists
- # of small integers (characters) telling the
- # grouping (thousand_seps and mon_thousand_seps
- # being the group dividers) of numbers and
- # monetary quantities. The integers' meanings:
- # 255 means no more grouping, 0 means repeat
- # the previous grouping, 1-254 means use that
- # as the current grouping. Grouping goes from
- # right to left (low to high digits). In the
- # below we cheat slightly by never using anything
- # else than the first grouping (whatever that is).
- if ($grouping) {
- @grouping = unpack("C*", $grouping);
- } else {
- @grouping = (3);
- }
-
- # Format command line params for current locale
- for (@ARGV) {
- $_ = int; # Chop non-integer part
- 1 while
- s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
- print "$_";
- }
- print "\n";
+ use POSIX qw(locale_h);
+
+ # Get some of locale's numeric formatting parameters
+ my ($thousands_sep, $grouping) =
+ @{localeconv()}{'thousands_sep', 'grouping'};
+
+ # Apply defaults if values are missing
+ $thousands_sep = ',' unless $thousands_sep;
+
+ # grouping and mon_grouping are packed lists
+ # of small integers (characters) telling the
+ # grouping (thousand_seps and mon_thousand_seps
+ # being the group dividers) of numbers and
+ # monetary quantities. The integers' meanings:
+ # 255 means no more grouping, 0 means repeat
+ # the previous grouping, 1-254 means use that
+ # as the current grouping. Grouping goes from
+ # right to left (low to high digits). In the
+ # below we cheat slightly by never using anything
+ # else than the first grouping (whatever that is).
+ if ($grouping) {
+ @grouping = unpack("C*", $grouping);
+ } else {
+ @grouping = (3);
+ }
+
+ # Format command line params for current locale
+ for (@ARGV) {
+ $_ = int; # Chop non-integer part
+ 1 while
+ s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
+ print "$_";
+ }
+ 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
-I18N::Langinfo::langinfo() function, available at least in UNIX-like
+C<I18N::Langinfo::langinfo()> function, available at least in Unix-like
systems and VMS.
-The following example will import the langinfo() function itself and
-three constants to be used as arguments to langinfo(): a constant for
+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 abbreviated first day of the week (the numbering starts from
Sunday = 1) and two more constants for the affirmative and negative
answers for a yes/no question in the current locale.
use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR);
- my ($abday_1, $yesstr, $nostr) = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
+ my ($abday_1, $yesstr, $nostr)
+ = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
print "$abday_1? [$yesstr/$nostr] ";
In other words, in the "C" (or English) locale the above will probably
print something like:
- Sun? [yes/no]
+ Sun? [yes/no]
See L<I18N::Langinfo> for more information.
some combination categories allow manipulation of more than one
basic category at a time. See L<"ENVIRONMENT"> for a discussion of these.
-=head2 Category LC_COLLATE: Collation
+=head2 Category C<LC_COLLATE>: Collation
-In the scope of S<C<use locale>>, 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 Spanish?
+(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
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
-byte-by-byte comparison for strings that the locale says are equal. You
-can use POSIX::strcoll() if you don't want this fall-back:
+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:
use POSIX qw(strcoll);
$equal_in_locale =
!strcoll("space and case ignored", "SpaceAndCaseIgnored");
-$equal_in_locale will be true if the collation locale specifies a
+C<$equal_in_locale> will be true if the collation locale specifies a
dictionary-like ordering that ignores space characters completely and
which folds case.
+Perl currently 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.
+
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 POSIX::strxfrm() in conjunction with C<eq>:
+efficiency by using C<POSIX::strxfrm()> in conjunction with C<eq>:
use POSIX qw(strxfrm);
$xfrm_string = strxfrm("Mixed-case string");
print "locale collation ignores case\n"
if $xfrm_string eq strxfrm("mixed-case string");
-strxfrm() takes a string and maps it into a transformed string for use
-in byte-by-byte comparisons against other transformed strings during
+C<strxfrm()> takes a string and maps it into a transformed string for use
+in char-by-char comparisons against other transformed strings during
collation. "Under the hood", locale-affected Perl comparison operators
-call strxfrm() for both operands, then do a byte-by-byte
-comparison of the transformed strings. By calling strxfrm() explicitly
+call C<strxfrm()> for both operands, then do a char-by-char
+comparison of the transformed strings. By calling C<strxfrm()> explicitly
and using a non locale-affected comparison, the example attempts to save
a couple of transformations. But in fact, it doesn't save anything: Perl
magic (see L<perlguts/Magic Variables>) creates the transformed version of a
string the first time it's needed in a comparison, then keeps this version around
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 strxfrm() directly, it treats the first
+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
it produces to be portable across systems--or even from one revision
-of your operating system to the next. In short, don't call strxfrm()
+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: strcoll() and 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>>, 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.
+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--lc(), lcfirst, uc(), and ucfirst(); case-mapping
-interpolation with C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted strings
-and C<s///> substitutions; and case-independent regular expression
+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
pattern matching using the C<i> modifier.
-Finally, C<LC_CTYPE> affects the POSIX character-class test
-functions--isalpha(), 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 ispunct() class to isalpha().
+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 ISO 646 one,
+you may find--possibly to your surprise--that C<"|"> 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 v5.22, a
+warning will be raised when such a locale is switched into. More
+details are given several paragraphs further down.
+
+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. (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,
+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. 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 unlikely to
+happen on modern locales, but can happen 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) letters and
+your application. For strict matching of (mundane) ASCII letters and
digits--for example, in command strings--locale-aware applications
-should use C<\w> inside a C<no locale> block. See L<"SECURITY">.
-
-=head2 Category LC_NUMERIC: Numeric Formatting
-
-In the scope of S<C<use locale>>, Perl obeys the C<LC_NUMERIC> locale
-information, which controls an application's idea of how numbers should
-be formatted for human readability by the printf(), sprintf(), and
-write() functions. String-to-numeric conversion by the POSIX::strtod()
-function is also affected. In most implementations the only effect is to
-change the character used for the decimal point--perhaps from '.' to ','.
-These functions aren't aware of such niceties as thousands separation and
-so on. (See L<The localeconv function> if you care about these things.)
-
-Output produced by print() is also affected by the current locale: it
-depends on whether C<use locale> or C<no locale> is in effect, and
-corresponds to what you'd get from printf() in the "C" locale. The
-same is true for Perl's internal conversions between numeric and
-string formats:
-
- use POSIX qw(strtod);
- use locale;
+should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">.
+
+=head2 Category C<LC_NUMERIC>: Numeric Formatting
+
+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.)
- $n = 5/2; # Assign numeric 2.5 to $n
+ use POSIX qw(strtod setlocale LC_NUMERIC);
+ use locale;
- $a = " $n"; # Locale-dependent conversion to string
+ setlocale LC_NUMERIC, "";
- print "half five is $n\n"; # Locale-dependent output
+ $n = 5/2; # Assign numeric 2.5 to $n
- printf "half five is %g\n", $n; # Locale-dependent output
+ $a = " $n"; # Locale-dependent conversion to string
- print "DECIMAL POINT IS COMMA\n"
- if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
+ print "half five is $n\n"; # Locale-dependent output
+
+ printf "half five is %g\n", $n; # Locale-dependent output
+
+ print "DECIMAL POINT IS COMMA\n"
+ if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
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 no function
+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 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
-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
+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
+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
to crack.
See also L<I18N::Langinfo> and C<CRNCYSTR>.
-=head2 LC_TIME
+=head2 C<LC_TIME>
-Output produced by POSIX::strftime(), which builds a formatted
+Output produced by C<POSIX::strftime()>, which builds a formatted
human-readable date/time string, is affected by the current C<LC_TIME>
locale. Thus, in a French locale, the output produced by the C<%B>
format element (full month name) for the first month of the year would
strftime("%B", 0, 0, 0, 1, $_, 96);
}
-Note: C<use locale> isn't needed in this example: as a function that
-exists only to generate locale-dependent results, strftime() always
-obeys the current C<LC_TIME> locale.
+Note: C<use locale> isn't needed in this example: C<strftime()> is a POSIX
+function which uses the standard system-supplied C<libc> function that
+always obeys the current C<LC_TIME> locale.
See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
=head2 Other categories
-The remaining locale category, C<LC_MESSAGES> (possibly supplemented
-by others in particular implementations) is not currently used by
-Perl--except possibly to affect the behavior of library functions
-called by extensions outside the standard Perl distribution and by the
+The remaining locale categories are not currently used by Perl itself.
+But again note that things Perl interacts with may use these, including
+extensions outside the standard Perl distribution, and by the
operating system and its utilities. Note especially that the string
value of C<$!> and the error messages given by external utilities may
be changed by C<LC_MESSAGES>. If you want to have portable error
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 *
-The date and day names in dates formatted by strftime() could be
+The date and day names in dates formatted by C<strftime()> could be
manipulated to advantage by a malicious user able to subvert the
C<LC_DATE> locale. ("Look--it says I wasn't in the building on
Sunday.")
=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> 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> is in effect, and the subpattern regular
-expression contains C<\w> (to match an alphanumeric character), C<\W>
-(non-alphanumeric character), C<\s> (white-space character), or C<\S>
-(non white-space 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> 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>.
+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>.
=item *
-B<Output formatting functions> (printf() and write()):
+B<Output formatting functions> (C<printf()> and C<write()>):
Results are never tainted because otherwise even output from print,
for example C<print(1/7)>, should be tainted if C<use locale> is in
=item *
-B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
+B<Case-mapping functions> (C<lc()>, C<lcfirst()>, C<uc()>, C<ucfirst()>):
-Results are tainted if C<use locale> is in effect.
+Results are tainted if a C<use locale> form that includes C<LC_CTYPE> is
+in effect.
=item *
-B<POSIX locale-dependent functions> (localeconv(), strcoll(),
-strftime(), strxfrm()):
+B<POSIX locale-dependent functions> (C<localeconv()>, C<strcoll()>,
+C<strftime()>, C<strxfrm()>):
Results are never tainted.
=item *
-B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
-isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
-isxdigit()):
+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.
$tainted_output_file = shift;
open(F, ">$tainted_output_file")
- or warn "Open of $untainted_output_file failed: $!\n";
+ or warn "Open of $tainted_output_file failed: $!\n";
The program can be made to run by "laundering" the tainted value through
a regular expression: the second example--which still ignores locale
open(F, ">$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.
=back
The following environment variables are not specific to Perl: They are
-part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method
-for controlling an application's opinion on data.
+part of the standardized (ISO C, XPG4, POSIX 1.c) C<setlocale()> method
+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.
-If you are using "commercial" UNIXes you are most probably I<not>
+If you are using "commercial" Unixes you are most probably I<not>
using GNU libc and you can ignore C<LANGUAGE>.
However, in the case you are using C<LANGUAGE>: it affects the
language of informational, warning, and error messages output by
commands (in other words, it's like C<LC_MESSAGES>) but it has higher
-priority than L<LC_ALL>. Moreover, it's not a single value but
+priority than C<LC_ALL>. Moreover, it's not a single value but
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 C<LC_NUMERIC> controls the numeric output:
+
+ use locale;
+ use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants.
+ setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
+ printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23.
+
+and also how strings are parsed by C<POSIX::strtod()> as numbers:
+
+ use locale;
+ use POSIX qw(locale_h strtod);
+ setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung";
+ my $x = strtod("2,34") + 5;
+ print $x, "\n"; # Probably shows 7,34.
+
=head1 NOTES
+=head2 String C<eval> and C<LC_NUMERIC>
+
+A string L<eval|perlfunc/eval EXPR> parses its expression as standard
+Perl. It is therefore expecting the decimal point to be a dot. If
+C<LC_NUMERIC> is set to have this be a comma instead, the parsing will
+be confused, perhaps silently.
+
+ use locale;
+ use POSIX qw(locale_h);
+ setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
+ my $a = 1.2;
+ print eval "$a + 1.5";
+ print "\n";
+
+prints C<13,5>. This is because in that locale, the comma is the
+decimal point character. The C<eval> thus expands to:
+
+ eval "1,2 + 1.5"
+
+and the result is not what you likely expected. No warnings are
+generated. If you do string C<eval>'s within the scope of
+S<C<use locale>>, you should instead change the C<eval> line to do
+something like:
+
+ print eval "no locale; $a + 1.5";
+
+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,
(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>) to instruct it to do so.
+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.
Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE>
information if available; that is, C<\w> did understand what
and the locale.) These downsides are dictated more by the operating
system's implementation of the locale system than by Perl.
-=head2 write() and LC_NUMERIC
+=head2 Freely available locale definitions
-Formats are the only part of Perl that unconditionally use information
-from a program's locale; if a program's environment specifies an
-LC_NUMERIC locale, it is always used to specify the decimal point
-character in formatted output. Formatted output cannot be controlled by
-C<use locale> because the pragma is tied to the block structure of the
-program, and, for historical reasons, formats exist outside that block
-structure.
+The Unicode CLDR project extracts the POSIX portion of many of its
+locales, available at
-=head2 Freely available locale definitions
+ http://unicode.org/Public/cldr/latest/
-There is a large collection of locale definitions at
-C<ftp://dkuug.dk/i18n/WG15-collection>. You should be aware that it is
+There is a large collection of locale definitions at:
+
+ http://std.dkuug.dk/i18n/WG15-collection/locales/
+
+You should be aware that it is
unsupported, and is not claimed to be fit for any purpose. If your
system allows installation of arbitrary locales, you may find the
definitions useful as they are, or as a basis for the development of
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. But, for now, it's the only
-standard we've got. This may be construed as a bug.
+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
+
+ use locale ':not_characters';
+
+When this form of the pragma is used, only the non-character portions of
+locales are used by Perl, for example C<LC_NUMERIC>. Perl assumes that
+you have translated all the characters it is to operate on into Unicode
+(actually the platform's native character set (ASCII or EBCDIC) plus
+Unicode). For data in files, this can conveniently be done by also
+specifying
+
+ use open ':locale';
+
+This pragma arranges for all inputs from files to be translated into
+Unicode from the current locale as specified in the environment (see
+L</ENVIRONMENT>), and all outputs to files to be translated back
+into the locale. (See L<open>). On a per-filehandle basis, you can
+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. 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 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.
+
+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/latest/>), 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 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()>,
+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
+prevents many problems in locales that aren't UTF-8. Suppose the locale
+is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi. But
+in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
+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 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{...}>. 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 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.)
+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
+has no way of knowing what the character at 0xFF is really supposed to
+represent. Thus it disallows the operation. In this mode, the
+lowercase of U+0178 is itself.
+
+The same problems ensue if you enable automatic UTF-8-ification of your
+standard file handles, default C<open()> layer, and C<@ARGV> on non-ISO8859-1,
+non-UTF-8 locales (by using either the B<-C> command line switch or the
+C<PERL_UNICODE> environment variable; see L<perlrun>).
+Things are read in as UTF-8, which would normally imply a Unicode
+interpretation, but the presence of a locale causes them to be interpreted
+in that locale instead. For example, a 0xD7 code point in the Unicode
+input, which should mean the multiplication sign, won't be interpreted by
+Perl that way under the Greek locale. This is not a problem
+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
+well. (However, the Unicode-supplied locales should be better, and
+there is a feed back mechanism to correct any problems. See
+L</Freely available locale definitions>.)
+
+If you have Perl v5.16, the problems mentioned above go away if you use
+the C<:not_characters> parameter to the locale pragma (except for vendor
+bugs in the non-character portions). If you don't have v5.16, and you
+I<do> have locales that work, using them may be worthwhile for certain
+specific purposes, as long as you keep in mind the gotchas already
+mentioned. For example, if the collation for your locales works, it
+runs faster under locales than under L<Unicode::Collate>; and you gain
+access to such things as the local currency symbol and the names of the
+months and days of the week. (But to hammer home the point, in v5.16,
+you get this access without the downsides of locales by using the
+C<:not_characters> form of the pragma.)
+
+Note: The policy of using locale rules for code points that can fit in a
+byte, and Unicode rules for those that can't is not uniformly applied.
+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 so far, the system's C<strxfrm()> function is
+called, and whatever it does is what you get.
=head1 BUGS
In certain systems, the operating system's locale support
is broken and cannot be fixed or used by Perl. Such deficiencies can
-and will result in mysterious hangs and/or Perl core dumps when the
+and will result in mysterious hangs and/or Perl core dumps when
C<use locale> is in effect. When confronted with such a system,
please report in excruciating detail to <F<perlbug@perl.org>>, and
-complain to your vendor: bug fixes may exist for these problems
+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<POSIX/isalnum>, L<POSIX/isalpha>,
+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/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.
-
-Last update: Thu Jun 11 08:44:13 MDT 1998
+Tom Christiansen, and updated by Perl 5 porters.
https://perl5.git.perl.org / perl5.git / blobdiff