=head1 DESCRIPTION
+Locales these days have been mostly been supplanted by Unicode, but Perl
+continues to support them. See L</Unicode and UTF-8> below.
+
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
+needed to write correct 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
=over 4
-=item *
+=item 1
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 whoever 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 and the C</l> regular expression modifier tell Perl to use the
+current locale for some operations (C</l> for just pattern matching).
+
+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
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<The formatting functions> (printf(), sprintf() and write()) use
-C<LC_NUMERIC>
+B<Format declarations> (format()) use C<LC_NUMERIC>
=item *
If no second argument is provided and the category is 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 setlocale(3) man page for
details.
If a second argument is given and it corresponds to a valid locale,
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)>.
+For further information about the categories, consult setlocale(3).
=head2 Finding locales
-For locales available in your system, consult also L<setlocale(3)> to
+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:
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.
+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
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'
+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
=head2 I18N::Langinfo
Another interface for querying locale-dependent information is the
-I18N::Langinfo::langinfo() function, available at least in UNIX-like
+I18N::Langinfo::langinfo() function, available at least in Unix-like
systems and VMS.
The following example will import the langinfo() function itself and
In the scope of S<C<use locale>>, 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 Spanish?
The following collations all make sense and you may meet any of them
if you "use locale".
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
+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);
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 operands, then do a byte-by-byte
+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. But in fact, it doesn't save anything: Perl
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 transliterating
characters between lower and uppercase. This affects the case-mapping
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">.
+should use C<\w> with the C</a> regular expression modifier. 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()
+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 ','.
+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.)
+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;
+ use POSIX qw(strtod setlocale LC_NUMERIC);
+
+ setlocale LC_NUMERIC, "";
$n = 5/2; # Assign numeric 2.5 to $n
=head2 Category 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
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, $&, $`
+(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>.
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.
=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
(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
=head2 write() and LC_NUMERIC
-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.
+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
+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 5.6, and more fully
+implemented in version 5.8 and later. See L<perluniintro>. Perl tries to
+work with both Unicode and locales--but of course, there are problems.
+
+Perl does not handle multi-byte locales, 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, tend to work
+reasonably well in Perl, simply because both they and Perl store
+characters that take up multiple bytes the same way.
+
+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 wasn't
+uniformly applied prior to Perl 5.14). 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, even if the string is encoded in UTF-8, which would normally imply
+Unicode semantics. (The "U" in UTF-8 stands for Unicode.)
+
+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 C<use locale>--I<unless> you can guarantee that the locale will
+be a ISO8859-1 or UTF-8 one. Use POSIX character classes instead.
+
+
+The same problem ensues 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. Again, this is not a problem
+I<provided> you make certain that all locales will always and only be either
+an ISO8859-1 or 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. But if 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, collation runs faster under
+locales than under L<Unicode::Collate> (albeit with less flexibility), and
+you gain access to such things as the local currency symbol and the names
+of the months and days of the week.
=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.
=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>,
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