+=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
-very naE<iuml>ve to think that C<A-Za-z> defines all the "letters". 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 was 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, and their use for character sets
+has mostly been supplanted by Unicode (see L<perlunitut> for an
+introduction to that, and keep on reading here for how Unicode interacts
+with locales in Perl).
+
+Perl continues to support the old locale system, and starting in v5.16,
+provides a hybrid way to use the Unicode character set, along with the
+other portions of locales that may not be so problematic.
+(Unicode is also creating C<CLDR>, the "Common Locale Data Repository",
+L<http://cldr.unicode.org/> which includes more types of information than
+are available in the POSIX locale system. At the time of this writing,
+there was no CPAN module that provides access to this XML-encoded data.
+However, many of its locales have the POSIX-only data extracted, and are
+available at L<http://unicode.org/Public/cldr/latest/>.)
+
+=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 LC_NUMERIC: Numeric formatting
+
+This indicates how numbers should be formatted for human readability,
+for example the character used as the decimal point.
+
+=item Category LC_MONETARY: Formatting of monetary amounts
+
+=for comment
+The nbsp below makes this look better
+
+E<160>
+
+=item Category LC_TIME: Date/Time formatting
+
+=for comment
+The nbsp below makes this look better
+
+E<160>
+
+=item Category LC_MESSAGES: Error and other messages
+
+This for the most part is beyond the scope of Perl
+
+=item Category LC_COLLATE: Collation
+
+This indicates the ordering of letters for comparision and sorting.
+In Latin alphabets, for example, "b", generally follows "a".
+
+=item Category LC_CTYPE: Character Types
+
+This indicates, for example if a character is an uppercase letter.
+
+=back
+
+More details on the categories 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 be able to understand and present your data
-correctly according a locale of your choice, B<all> of the following
-must be true:
+Perl will not use locales unless specifically requested to (see L</NOTES> below
+for the partial exception of C<write()>). But even if there is such a
+request, B<all> of the following must be true for it to work properly:
=over 4
=item *
-B<Definitions for the locales which you use must be installed>. You, or
+B<Definitions for locales that you use must be installed>. You, or
your system administrator, must make sure that this is the case. The
available locales, the location in which they are kept, and the manner
-in which they are installed, vary from system to system. Some systems
-provide only a few, hard-wired, locales, and do not allow more to be
-added; others allow you to add "canned" locales provided by the system
-supplier; still others allow you or the system administrator to define
+in which they are installed all vary from system to system. Some systems
+provide only a few, hard-wired locales and do not allow more to be
+added. Others allow you to add "canned" locales provided by the system
+supplier. Still others allow you or the system administrator to define
and add arbitrary locales. (You may have to ask your supplier to
-provide canned locales which are not delivered with your operating
+provide canned locales that are not delivered with your operating
system.) Read your system documentation for further illumination.
=item *
=over 4
-=item *
+=item 1
-B<The locale-determining environment variables (see L<"ENVIRONMENT">)
-must be correctly set up>, either by yourself, or by the person who set
-up your system account, at the time the application is started.
+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 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>.
=head2 The use locale pragma
By default, Perl ignores the current locale. The S<C<use locale>>
-pragma tells Perl to use the current locale for some operations:
+pragma tells Perl to use the current locale for some operations.
+Starting in v5.16, there is an optional parameter to this pragma:
+
+ use locale ':not_characters';
+
+This parameter allows better mixing of locales and Unicode, and is
+described fully in L</Unicode and UTF-8>, but briefly, it tells Perl to
+not use the character portions of the locale definition, that is
+the C<LC_CTYPE> and C<LC_COLLATE> categories. Instead it will use the
+native (extended by Unicode) character set. 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>.
+
+The current locale is set at execution time by
+L<setlocale()|/The setlocale function> described below. If that function
+hasn't yet been called in the course of the program's execution, the
+current locale is that which was determined by the L</"ENVIRONMENT"> in
+effect at the start of the program, except that
+C<L<LC_NUMERIC|/Category LC_NUMERIC: Numeric Formatting>> is always
+initialized to the C locale (mentioned under L<Finding locales>).
+If there is no valid environment, the current locale is undefined. It
+is likely, but not necessarily, the "C" locale.
+
+The operations that are affected by locale are:
+
+=over 4
+
+=item B<Under C<use locale ':not_characters';>>
+
+=over 4
+
+=item *
+
+B<Format declarations> (format()) use C<LC_NUMERIC>
+
+=item *
+
+B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>.
+
+=back
+
+=for comment
+The nbsp below makes this look better
+
+E<160>
+
+=item B<Under just plain C<use locale;>>
+
+The above operations are affected, as well as the following:
=over 4
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 it is used without an
-explicit comparison function because it uses C<cmp> by default.
+C<LC_COLLATE>. 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 the locale: they always
-perform a byte-by-byte comparison of their scalar operands. What's
+B<Note:> C<eq> and C<ne> are unaffected by locale: they always
+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
-two strings - which C<eq> and C<cmp> may consider different - are equal
+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>.
B<Regular expressions and case-modification functions> (uc(), lc(),
ucfirst(), and lcfirst()) use C<LC_CTYPE>
-=item *
-
-B<The formatting functions> (printf(), sprintf() and write()) use
-C<LC_NUMERIC>
-
-=item *
-
-B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>.
-
=back
-C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in L<LOCALE
-CATEGORIES>.
+=back
-The default behavior returns with S<C<no locale>> or on reaching the
-end of the enclosing block.
+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
+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.
-Note that the string result of any operation that uses locale
+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">.
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;
-
# Import locale-handling tool set from POSIX module.
# This example uses: setlocale -- the function call
# LC_CTYPE -- explained below
The first argument of 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, 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(). 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 use this in a subsequent call to
-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 that you gave.)
+If no second argument is provided and the category is something else
+than 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().
+
+If no second argument is provided and the category is LC_ALL, the
+result is implementation-dependent. It may be a string of
+concatenated locale names (separator also implementation-dependent)
+or a single locale name. Please consult your 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
+value may sometimes differ from the value you gave as the second
+argument--think of it as an alias for the value you gave.)
As the example shows, if the second argument is an empty string, the
category's locale is returned to the default specified by the
corresponding environment variables. Generally, this results in a
-return to the default which was in force when Perl started up: changes
+return to the default that was in force when Perl started up: changes
to the environment made by the application after startup may or may not
-be noticed, depending on the implementation of your system's C library.
+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>.
-For further information about the categories, consult L<setlocale(3)>.
+Note that Perl ignores the current C<LC_CTYPE> and C<LC_COLLATE> locales
+within the scope of a C<use locale ':not_characters'>.
+
+For further information about the categories, consult setlocale(3).
=head2 Finding locales
-For the locales available in your system, also consult L<setlocale(3)>
-and see whether it leads you to the list of the available locales
-(search for the I<SEE ALSO> section). If that fails, try the following
-command lines:
+For locales available in your system, consult also setlocale(3) to
+see whether it leads to the list of available locales (search for the
+I<SEE ALSO> section). If that fails, try the following command lines:
locale -a
ls /usr/lib/nls
+ ls /usr/share/locale
+
and see whether they list something resembling these
en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
+ en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
en_US de_DE ru_RU
en de ru
english german russian
english.iso88591 german.iso88591 russian.iso88595
+ english.roman8 russian.koi8r
Sadly, even though the calling interface for setlocale() has been
-standardized, the names of the locales and the directories where the
-configuration is, have not. The basic form of the name is
-I<language_country/territory>B<.>I<codeset>, but the latter parts
-after the I<language> are not always present. The I<language> and the
-I<country> are usually from the standards B<ISO 3166> and B<ISO 639>,
-respectively, the two-letter abbreviations for the countries and the
-languages of the world. The I<codeset> part often mentions some B<ISO
-8859> character set, the Latin codesets. For example the C<ISO
-8859-1> is the so-called "Western codeset" that can be used to encode
-most of the Western European languages. Again, sadly, as you can see,
-there are several ways to write even the name of that one standard.
+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
+I<language> are not always present. The I<language> and I<country>
+are usually from the standards B<ISO 3166> and B<ISO 639>, the
+two-letter abbreviations for the countries and the languages of the
+world, respectively. The I<codeset> part often mentions some B<ISO
+8859> character set, the Latin codesets. For example, C<ISO 8859-1>
+is the so-called "Western European codeset" that can be used to encode
+most Western European languages adequately. Again, there are several
+ways to write even the name of that one standard. Lamentably.
Two special locales are worth particular mention: "C" and "POSIX".
Currently these are effectively the same locale: the difference is
-mainly that the first one is defined by the C standard and the second by
-the POSIX standard. What they define is the B<default locale> in which
+mainly that the first one is defined by the C standard, the second by
+the POSIX standard. They define the B<default locale> in which
every program starts in the absence of locale information in its
-environment. (The default default locale, if you will.) Its language
+environment. (The I<default> default locale, if you will.) Its language
is (American) English and its character codeset ASCII.
+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
=head2 LOCALE PROBLEMS
-You may meet the following warning message at Perl startup:
+You may encounter the following warning message at Perl startup:
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
-This means that your locale settings were that LC_ALL equals "En_US"
-and LANG exists but has no value. Perl tried to believe you but it
-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 either or both of the two problems: either your locale settings
-were wrong, they talk of locales your system has never heard of, or
-that the locale installation in your system has problems, for example
-some system files are broken or missing. For the problems there are
-quick and temporary fixes and more thorough and lasting fixes.
+This means that your locale settings had 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.
=head2 Temporarily fixing locale problems
-The two quickest fixes are either to make Perl be silent about any
+The two quickest fixes are either to render Perl silent about any
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 non-zero value, for example
-"1". 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 works funny.
+environment variable PERL_BADLANG to a zero value, for example "0".
+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 civilised
-than the PERL_BADLANG one but please note that setting the LC_ALL (or
-the other locale variables) may affect also other programs, not just
-Perl. Especially external programs run from within Perl will see
+variable LC_ALL to "C". This method is perhaps a bit more civilized
+than the PERL_BADLANG approach, but setting 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
-the programs you run will see the changes. See L<ENVIRONMENT> for for
-the full list of all the environment variables and L<USING LOCALES>
-for their effects in Perl. The effects in other programs are quite
-easily deducible: for example the variable LC_COLLATE may well affect
-your "sort" program (or whatever the program that arranges `records'
+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"
alphabetically in your system is called).
-You can first try out changing these variables temporarily and if the
-new settings seem to help then put the settings into the startup files
-of your environment. Please consult your local documentation for the
-exact details but very shortly for UNIXish systems: in Bourneish
-shells (sh, ksh, bash, zsh) for example
+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
+Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>):
LC_ALL=en_US.ISO8859-1
export LC_ALL
-We assume here that we saw with the above discussed commands the
-locale "en_US.ISO8859-1" and decided to try that instead of the above
-faulty locale "En_US" -- and in Cshish shells (csh, tcsh)
+This assumes that we saw the locale "en_US.ISO8859-1" using the commands
+discussed above. We decided to try that instead of the above faulty
+locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>)
setenv LC_ALL en_US.ISO8859-1
-
-If you do not know what shell you have, please consult your local
+
+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.
=head2 Permanently fixing locale problems
-Then the slower but better fixes: the misconfiguration of your own
-environment variables you may be able to fix yourself; the
+The slower but superior fixes are when you may be able to yourself
+fix the misconfiguration of your own environment variables. The
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 how you can find which locales really are supported and more
-importantly, installed, in your system. In our example error message
-the environment variables affecting the locale are listed in the order
-of decreasing importance and unset variables do not matter, therefore
-in the above error message the LC_ALL being "En_US" must have been the
-bad choice. Always try fixing first the locale settings listed first.
+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
+importance (and unset variables do not matter). Therefore, having
+LC_ALL set to "En_US" must have been the bad choice, as shown by the
+error message. First try fixing locale settings listed first.
-Second, if you see with the listed commands something B<exactly> (for
-example prefix matches do not count and case usually matters) 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 skip forward to L<Fixing the system locale
-configuration>.
+Second, if using the listed commands you see something B<exactly>
+(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>.
-=head2 Permantently fixing your locale configuration
+=head2 Permanently fixing your system's locale configuration
-This is the case when for example you see
+This is when you see something like:
perl: warning: Please check that your locale settings:
LC_ALL = "En_US",
are supported and installed on your system.
but then cannot see that "En_US" listed by the above-mentioned
-commands. You may see things like "en_US.ISO8859-1" but that is not
-the same thing. In this case you might try running under a locale
-that you could list and somehow matches with what you tried. The
+commands. You may see things like "en_US.ISO8859-1", but that isn't
+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
-standardisation is weak in this area. See again the L<Finding
-locales> about the general rules.
+standardization is weak in this area. See again the
+L<Finding locales> about general rules.
-=head2 Permanently fixing the system locale configuration
+=head2 Fixing system locale configuration
-Please contact your system administrator and tell her the exact error
-message you get and ask her to read this same documentation you are
-now reading. She should be able to check whether there is something
-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 standardised.
+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>
+section is unfortunately a bit vague about the exact commands and places
+because these things are not that standardized.
=head2 The localeconv function
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()
-with a single parameter - see L<The setlocale function>.)
+with a single parameter--see L<The setlocale function>.)
use POSIX qw(locale_h);
}
localeconv() takes no arguments, and returns B<a reference to> a hash.
-The keys of this hash are formatting variable names such as
-C<decimal_point> and C<thousands_sep>; the values are the corresponding
-values. See L<POSIX (3)/localeconv> for a longer example, which lists
-all the categories an implementation might be expected to provide; some
-provide more and others fewer, however. Note that you don't need C<use
-locale>: as a function with the job of querying the locale, localeconv()
-always observes the current locale.
-
-Here's a simple-minded example program which rewrites its command line
-parameters as integers formatted correctly 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 = 3 unless $grouping;
-
- # Format command line params for current locale
- for (@ARGV) {
- $_ = int; # Chop non-integer part
- 1 while
- s/(\d)(\d{$grouping}($|$thousands_sep))/$1$thousands_sep$2/;
- print "$_";
- }
- print "\n";
+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
+current locale.
+
+Here's a simple-minded example program that rewrites its command-line
+parameters as integers correctly formatted in the current locale:
+
+ 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";
+
+=head2 I18N::Langinfo
+
+Another interface for querying locale-dependent information is the
+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 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, $nostr)
+ = map { langinfo } qw(ABDAY_1 YESSTR NOSTR);
+
+ print "$abday_1? [$yesstr/$nostr] ";
+
+In other words, in the "C" (or English) locale the above will probably
+print something like:
+
+ Sun? [yes/no]
+
+See L<I18N::Langinfo> for more information.
=head1 LOCALE CATEGORIES
-The subsections which follow describe basic locale categories. As well
-as these, there are some combination categories which allow the
-manipulation of more than one basic category at a time. See
-L<"ENVIRONMENT"> for a discussion of these.
+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.
=head2 Category LC_COLLATE: Collation
-When in the scope of S<C<use locale>>, Perl looks to the C<LC_COLLATE>
-environment variable to determine the application's notions on the
-collation (ordering) of characters. ('b' follows 'a' in Latin
-alphabets, but where do 'E<aacute>' and 'E<aring>' belong?)
+In the scope of S<C<use locale>> (but not a
+C<use locale ':not_characters'>), 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".
+
+ A B C D E a b c d e
+ A a B b C c D d E e
+ a A b B c C d D e E
+ a b c d e A B C D E
-Here is a code snippet that will tell you what are the alphanumeric
-characters in the current locale, in the locale order:
+Here is a code snippet to tell what "word"
+characters are in the current locale, in that locale's order:
use locale;
- print +(sort grep /\w/, map { chr() } 0..255), "\n";
+ print +(sort grep /\w/, map { chr } 0..255), "\n";
Compare this with the characters that you see and their order if you
state explicitly that the locale should be ignored:
no locale;
- print +(sort grep /\w/, map { chr() } 0..255), "\n";
+ print +(sort grep /\w/, map { chr } 0..255), "\n";
This machine-native collation (which is what you get unless S<C<use
locale>> has appeared earlier in the same block) must be used for
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 which the locale says are equal. You
+char-by-char comparison for strings that the locale says are equal. You
can use POSIX::strcoll() if you don't want this fall-back:
use POSIX qw(strcoll);
!strcoll("space and case ignored", "SpaceAndCaseIgnored");
$equal_in_locale will be true if the collation locale specifies a
-dictionary-like ordering which ignores space characters completely, and
+dictionary-like ordering that ignores space characters completely and
which folds case.
-If you have a single string which you want to check for "equality in
+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>:
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
+in char-by-char comparisons against other transformed strings during
collation. "Under the hood", locale-affected Perl comparison operators
-call strxfrm() for both their operands, then do a byte-by-byte
-comparison of the transformed strings. By calling strxfrm() explicitly,
+call strxfrm() for both operands, then do a char-by-char
+comparison of the transformed strings. By calling strxfrm() explicitly
and using a non locale-affected comparison, the example attempts to save
-a couple of transformations. In fact, it doesn't save anything: Perl
+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 it around
+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
-null it finds as a terminator. And don't expect the transformed strings
-it produces to be portable across systems - or even from one revision
+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()
directly: let Perl do it for you.
-Note: C<use locale> isn't shown in some of these examples, as it isn't
+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.
=head2 Category LC_CTYPE: Character Types
-When in the scope of S<C<use locale>>, Perl obeys the C<LC_CTYPE> locale
+In the scope of S<C<use locale>> (but not a
+C<use locale ':not_characters'>), 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,
-which stands for alphanumeric characters - that is, alphabetic and
-numeric characters. (Consult L<perlre> for more information about
+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
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.
-The C<LC_CTYPE> locale also provides the map used in translating
+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 <\U> in double-quoted strings
-and in C<s///> substitutions; and case-independent regular expression
+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
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 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().
+Unfortunately, this creates big problems for regular expressions. "|" still
+means alternation even though it matches C<\w>.
+
+Note that there are quite a few things that are unaffected by the
+current locale. All the escape sequences for particular characters,
+C<\n> for example, always mean the platform's native one. This means,
+for example, that C<\N> in regular expressions (every character
+but new-line) work on the platform character set.
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 (unaccented) letters and
-digits - for example, in command strings - locale-aware applications
-should use C<\w> inside a C<no locale> block. See L<"SECURITY">.
+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">.
=head2 Category LC_NUMERIC: Numeric Formatting
-When in the scope of S<C<use locale>>, Perl obeys the C<LC_NUMERIC>
-locale information, which controls 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.)
-
-Note that output produced by print() is B<never> affected by the
-current locale: it is independent of 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;
+After a proper POSIX::setlocale() call, 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
+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 setlocale LC_NUMERIC);
+
+ setlocale LC_NUMERIC, "";
$n = 5/2; # Assign numeric 2.5 to $n
- $a = " $n"; # Locale-independent conversion to string
+ $a = " $n"; # Locale-dependent conversion to string
- print "half five is $n\n"; # Locale-independent output
+ 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
-The C standard defines the C<LC_MONETARY> category, but no function that
-is affected by its contents. (Those with experience of standards
+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
+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, though voluminous and complex, does not quite
-meet your requirements: currency formatting is a hard nut to crack.
+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
-The output produced by POSIX::strftime(), which builds a formatted
+Output produced by 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
-be "janvier". Here's how to get a list of the long month names in the
+be "janvier". Here's how to get a list of long month names in the
current locale:
use POSIX qw(strftime);
strftime("%B", 0, 0, 0, 1, $_, 96);
}
-Note: C<use locale> isn't needed in this example: as a function which
+Note: C<use locale> isn't needed in this example: as a function that
exists only to generate locale-dependent results, strftime() always
obeys the current C<LC_TIME> locale.
+See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
+C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
+
=head2 Other categories
-The remaining locale category, C<LC_MESSAGES> (possibly supplemented by
-others in particular implementations) is not currently used by Perl -
-except possibly to affect the behavior of library functions called by
-extensions which are not part of the standard Perl distribution.
+The remaining locale category, C<LC_MESSAGES> (possibly supplemented
+by others in particular implementations) is not currently used by
+Perl--except possibly to affect the behavior of library functions
+called by extensions outside the standard Perl distribution and by the
+operating system and its utilities. Note especially that the string
+value of C<$!> and the error messages given by external utilities may
+be changed by C<LC_MESSAGES>. If you want to have portable error
+codes, use C<%!>. See L<Errno>.
=head1 SECURITY
-While the main discussion of Perl security issues can be found in
+Although the main discussion of Perl security issues can be found in
L<perlsec>, a discussion of Perl's locale handling would be incomplete
if it did not draw your attention to locale-dependent security issues.
-Locales - particularly on systems which allow unprivileged users to
-build their own locales - are untrustworthy. A malicious (or just plain
+Locales--particularly on systems that allow unprivileged users to
+build their own locales--are untrustworthy. A malicious (or just plain
broken) locale can make a locale-aware application give unexpected
results. Here are a few possibilities:
=item *
Regular expression checks for safe file names or mail addresses using
-C<\w> may be spoofed by an C<LC_CTYPE> locale which claims that
+C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that
characters such as "E<gt>" and "|" are alphanumeric.
=item *
=item *
-If the decimal point character in the C<LC_NUMERIC> locale is
-surreptitiously changed from a dot to a comma, C<sprintf("%g",
-0.123456e3)> produces a string result of "123,456". Many people would
-interpret this as one hundred and twenty-three thousand, four hundred
-and fifty-six.
-
-=item *
-
A sneaky C<LC_COLLATE> locale could result in the names of students with
"D" grades appearing ahead of those with "A"s.
=item *
-An application which takes the trouble to use the information in
+An application that takes the trouble to use information in
C<LC_MONETARY> may format debits as if they were credits and vice versa
-if that locale has been subverted. Or it make may make payments in US
+if that locale has been subverted. Or it might make payments in US
dollars instead of Hong Kong dollars.
=item *
The date and day names in dates formatted by 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
+C<LC_DATE> locale. ("Look--it says I wasn't in the building on
Sunday.")
=back
Such dangers are not peculiar to the locale system: any aspect of an
-application's environment which may maliciously be modified presents
+application's environment which may be modified maliciously presents
similar challenges. Similarly, they are not specific to Perl: any
-programming language which allows you to write programs which take
+programming language that allows you to write programs that take
account of their environment exposes you to these issues.
-Perl cannot protect you from all of the possibilities shown in the
-examples - there is no substitute for your own vigilance - but, when
+Perl cannot protect you from all possibilities shown in the
+examples--there is no substitute for your own vigilance--but, when
C<use locale> is in effect, Perl uses the tainting mechanism (see
-L<perlsec>) to mark string results which become locale-dependent, and
+L<perlsec>) to mark string results that become locale-dependent, and
which may be untrustworthy in consequence. Here is a summary of the
-tainting behavior of operators and functions which may be affected by
+tainting behavior of operators and functions that may be affected by
the locale:
=over 4
-=item B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
+=item *
+
+B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>):
Scalar true/false (or less/equal/greater) result is never tainted.
-=item B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or <\U>)
+=item *
+
+B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>)
Result string containing interpolated material is tainted if
-C<use locale> is in effect.
+C<use locale> (but not S<C<use locale ':not_characters'>>) is in effect.
-=item B<Matching operator> (C<m//>):
+=item *
+
+B<Matching operator> (C<m//>):
Scalar true/false result never tainted.
-Subpatterns, either delivered as an array-context result, or as $1 etc.
-are tainted if C<use locale> is in effect, and the subpattern regular
+Subpatterns, either delivered as a list-context result or as $1 etc.
+are tainted if C<use locale> (but not S<C<use locale ':not_characters'>>)
+is in effect, and the subpattern regular
expression contains C<\w> (to match an alphanumeric character), C<\W>
-(non-alphanumeric character), C<\s> (white-space character), or C<\S>
-(non white-space character). The matched pattern variable, $&, $`
+(non-alphanumeric character), C<\s> (whitespace character), or C<\S>
+(non whitespace character). The matched-pattern variable, $&, $`
(pre-match), $' (post-match), and $+ (last match) are also tainted if
C<use locale> is in effect and the regular expression contains C<\w>,
C<\W>, C<\s>, or C<\S>.
-=item B<Substitution operator> (C<s///>):
+=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 it is modified as a result of a substitution based on a regular
+operand of C<=~> becomes tainted when C<use locale>
+(but not S<C<use locale ':not_characters'>>) is in effect if modified as
+a result of a substitution based on a regular
expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of
-case-mapping with C<\l>, C<\L>,C<\u> or <\U>.
+case-mapping with C<\l>, C<\L>,C<\u> or C<\U>.
-=item B<In-memory formatting function> (sprintf()):
+=item *
-Result is tainted if "use locale" is in effect.
+B<Output formatting functions> (printf() and write()):
-=item B<Output formatting functions> (printf() and 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
+effect.
-Success/failure result is never tainted.
+=item *
+
+B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
-=item B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
+Results are tainted if C<use locale> (but not
+S<C<use locale ':not_characters'>>) is in effect.
-Results are tainted if C<use locale> is in effect.
+=item *
-
=item B<POSIX locale-dependent functions> (localeconv(), strcoll(),
+B<POSIX locale-dependent functions> (localeconv(), strcoll(),
strftime(), strxfrm()):
Results are never tainted.
-=item B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
+=item *
+
+B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
isxdigit()):
$tainted_output_file = shift;
open(F, ">$tainted_output_file")
- or warn "Open of $untainted_output_file failed: $!\n";
+ or warn "Open of $tainted_output_file failed: $!\n";
The program can be made to run by "laundering" the tainted value through
-a regular expression: the second example - which still ignores locale
-information - runs, creating the file named on its command line
+a regular expression: the second example--which still ignores locale
+information--runs, creating the file named on its command line
if it can.
#/usr/local/bin/perl -T
open(F, ">$untainted_output_file")
or warn "Open of $untainted_output_file failed: $!\n";
-Compare this with a very similar program which is locale-aware:
+Compare this with a similar but locale-aware program:
#/usr/local/bin/perl -T
or warn "Open of $localized_output_file failed: $!\n";
This third program fails to run because $& is tainted: it is the result
-of a match involving C<\w> when C<use locale> is in effect.
+of a match involving C<\w> while C<use locale> is in effect.
=head1 ENVIRONMENT
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) is 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 which does not evaluate to integer zero - that
-is "0" or "" - Perl will complain about locale setting failures.
+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.
B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message.
The message tells about some problem in your system's locale support,
=item LC_ALL
-C<LC_ALL> is the "override-all" locale environment variable. If it is
+C<LC_ALL> is the "override-all" locale environment variable. If
set, it overrides all the rest of the locale environment variables.
+=item 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>
+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 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
In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type
=back
+=head2 Examples
+
+The 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 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 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 (see
-L<The setlocale function>) was always in force, even if the program
-environment suggested otherwise. By default, Perl still behaves this
-way so as to maintain 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.
+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
+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
+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 that was available, that is, C<\w> did understand what
-are the letters according to the locale environment variables.
+information if available; that is, C<\w> did understand what
+were the letters according to the locale environment variables.
The problem was that the user had no control over the feature:
if the C library supported locales, Perl used them.
=head2 I18N:Collate obsolete
-In versions of Perl prior to 5.004 per-locale collation was possible
+In versions of Perl prior to 5.004, per-locale collation was possible
using the C<I18N::Collate> library module. This module is now mildly
obsolete and should be avoided in new applications. The C<LC_COLLATE>
functionality is now integrated into the Perl core language: One can
=head2 write() and LC_NUMERIC
-Formats are the only part of Perl which 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.
+If a program's environment specifies an LC_NUMERIC locale and C<use
+locale> is in effect when the format is declared, the locale is used
+to specify the decimal point character in formatted output. Formatted
+output cannot be controlled by C<use locale> at the time when write()
+is called.
=head2 Freely available locale definitions
-There is a large collection of locale definitions at
-C<ftp://dkuug.dk/i18n/WG15-collection>. You should be aware that it is
+The Unicode CLDR project extracts the POSIX portion of many of its
+locales, available at
+
+ http://unicode.org/Public/cldr/latest/
+
+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 the installation of arbitrary locales, you may find the
+system allows installation of arbitrary locales, you may find the
definitions useful as they are, or as a basis for the development of
your own locales.
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 version v5.8 and later. See L<perluniintro>. It is
+strongly recommended that when combining Unicode and locale (starting in
+v5.16), you 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. Also, if you know that all your locales will be
+UTF-8, as many are these days, you can use the L<B<-C>|perlrun/-C>
+command line switch.
+
+This form of the pragma allows essentially seamless handling of locales
+with Unicode. The collation order will be Unicode's. It is strongly
+recommended that when you need to order and sort strings that you use
+the standard module L<Unicode::Collate> which gives much better results
+in many instances than you can get with the old-style locale handling.
+
+For pre-v5.16 Perls, or if you use the locale pragma without the
+C<:not_characters> parameter, Perl tries to work with both Unicode and
+locales--but there are problems.
+
+Perl does not handle multi-byte locales in this case, such as have been
+used for various
+Asian languages, such as Big5 or Shift JIS. However, the increasingly
+common multi-byte UTF-8 locales, if properly implemented, may work
+reasonably well (depending on your C library implementation) in this
+form of the locale pragma, simply because both
+they and Perl store characters that take up multiple bytes the same way.
+However, some, if not most, C library implementations may not process
+the characters in the upper half of the Latin-1 range (128 - 255)
+properly under LC_CTYPE. To see if a character is a particular type
+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()>.
+
+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 constructs are
+for Unicode only, such as C<\p{Alpha}>. They assume that 0xD7 always has its
+Unicode meaning (or the equivalent on EBCDIC platforms). Since Latin1 is a
+subset of Unicode and 0xD7 is the multiplication sign in both Latin1 and
+Unicode, C<\p{Alpha}> will never match it, regardless of locale. A similar
+issue occurs with C<\N{...}>. It is therefore a bad idea to use C<\p{}> or
+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.
+
+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.
+
+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, the system's C<strxfrm()> function is called,
+and whatever it does is what you get.
=head1 BUGS
=head2 Broken systems
-In certain system environments the operating system's locale support
+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.com>>, and
-complain to your vendor: maybe some bug fixes exist for these problems
+please report in excruciating detail to <F<perlbug@perl.org>>, and
+also contact your vendor: bug fixes may exist for these problems
in your operating system. Sometimes such bug fixes are called an
operating system upgrade.
=head1 SEE ALSO
-L<POSIX (3)/isalnum>, L<POSIX (3)/isalpha>, L<POSIX (3)/isdigit>,
-L<POSIX (3)/isgraph>, L<POSIX (3)/islower>, L<POSIX (3)/isprint>,
-L<POSIX (3)/ispunct>, L<POSIX (3)/isspace>, L<POSIX (3)/isupper>,
-L<POSIX (3)/isxdigit>, L<POSIX (3)/localeconv>, L<POSIX (3)/setlocale>,
-L<POSIX (3)/strcoll>, L<POSIX (3)/strftime>, L<POSIX (3)/strtod>,
-L<POSIX (3)/strxfrm>
+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>.
=head1 HISTORY
Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
-Dunlop, assisted by the perl5-porters.
-
-Last update: Mon Nov 17 22:48:48 EET 1997
+Dunlop, assisted by the perl5-porters. Prose worked over a bit by
+Tom Christiansen, and updated by Perl 5 porters.
https://perl5.git.perl.org / perl5.git / blobdiff