=head1 NAME
-perllocale - Perl locale handling (internationlization)
+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 upper-case 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 naÔve 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.
-
-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 a pragma, one
-function call, and several environment variables.
+Locales these days have been mostly been supplanted by Unicode, but Perl
+continues to support them. See L</Unicode and UTF-8> below.
-B<NOTE>: This feature is new in Perl 5.004, and does not apply unless
-an application specifically requests it - see L<Backward
-compatibility>.
+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 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
+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">.
=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
+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:
=over 4
=item *
B<Your operating system must support the locale system>. If it does,
-you should find that the C<setlocale> function is a documented part of
+you should find that the setlocale() function is a documented part of
its C library.
=item *
-B<Definitions for the locales which 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 and add arbitrary locales. (You may have to ask your
-supplier to provide canned locales whch are not delivered with your
-operating system.) Read your system documentation for further
-illumination.
+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 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 that are not delivered with your operating
+system.) Read your system documentation for further illumination.
=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 (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>) 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 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 C<setlocale> function>.
+B<The application must set its own locale> using the method described in
+L<The setlocale function>.
=back
=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:
-
-=over 4
-
-=item *
+By default, Perl ignores the current locale. The S<C<use locale>>
+pragma and the C</l> regular expression modifier tell Perl to use the
+current locale for some operations (C</l> for just pattern matching).
-B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>)
-use C<LC_COLLATE>. The C<sort> function is also affected if it is
-used without an explicit comparison function because it uses C<cmp> by
-default.
+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.
-B<Note:> The C<eq> and C<ne> operators are unaffected by the locale:
-they always perform a byte-by-byte comparison of their scalar
-arguments. If you really want to know if two strings - which C<eq>
-may consider different - are equal as far as collation is concerned,
-use something like
+The operations that are affected by locale are:
- !("space and case ignored" cmp "SpaceAndCaseIgnored")
+=over 4
-(which would be true if the collation locale specified a
-dictionary-like ordering).
+=item *
-I<Editor's note:> I am right about C<eq> and C<ne>, aren't I?
+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
+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 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 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> (C<uc>,
-C<lc>, C<ucfirst>, and C<lcfirst>) use C<LC_CTYPE>
+B<Regular expressions and case-modification functions> (uc(), lc(),
+ucfirst(), and lcfirst()) use C<LC_CTYPE>
=item *
-B<The formatting functions> (C<printf> and C<sprintf>) use
-C<LC_NUMERIC>
+B<Format declarations> (format()) use C<LC_NUMERIC>
=item *
-B<The POSIX date formatting function> (C<strftime>) uses C<LC_TIME>.
+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
+C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in
L<LOCALE CATEGORIES>.
-The default behaviour 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 block enclosing C<use locale>.
-Note that the result of any operation that uses locale information is
-tainted (see L<perlsec.pod>), since locales can be created by
-unprivileged users on some systems.
+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">.
=head2 The setlocale function
-You can switch locales as often as you wish at runtime with the
-C<POSIX::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;
# LC_CTYPE -- explained below
use POSIX qw(locale_h);
- # query and save the old locale.
+ # query and save the old locale
$old_locale = setlocale(LC_CTYPE);
setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
# restore the old locale
setlocale(LC_CTYPE, $old_locale);
-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 collection of customization information corresponding to a paricular
-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 C<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
-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 that you gave.)
+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
+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
+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
-to the environment made by the application after start-up may or may
-not be noticed, depending on the implementation of your system's C
-library.
+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 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>.
-If the second argument does not correspond to a valid locale, the
-locale for the category is not changed, and the function returns
-C<undef>.
+For further information about the categories, consult setlocale(3).
-For further information about the categories, consult
-L<setlocale(3)>. 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 C<SEE ALSO>
-section). If that fails, try the following command lines:
+=head2 Finding locales
+
+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 de_DE ru_RU
- en de ru
- english german russian
- english.iso88591 german.iso88591 russian.iso88595
-
-Sadly, even though the calling interface for C<setlocale> has been
-standardized, the names of the locales have not. The form of the name
-is usually I<language_country>B</>I<territory>B<.>I<codeset>, but the
-latter parts are not always present.
-
-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 every program starts in the absence of
-locale information in its environment. (The default default locale,
-if you will.) Its language is (American) English and its character
-codeset ASCII.
-
-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 default locale.
+ 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, 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, 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 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
+default locale.
+
+=head2 LOCALE PROBLEMS
+
+You may encounter the following warning message at Perl startup:
+
+ perl: warning: Setting locale failed.
+ perl: warning: Please check that your locale settings:
+ LC_ALL = "En_US",
+ LANG = (unset)
+ 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
+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 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 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 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
+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 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
+
+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
+
+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
+
+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 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 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 Permanently fixing your system's locale configuration
+
+This is when you see something like:
+
+ perl: warning: Please check that your locale settings:
+ LC_ALL = "En_US",
+ LANG = (unset)
+ 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 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
+standardization is weak in this area. See again the
+L<Finding locales> about general rules.
+
+=head2 Fixing system locale configuration
+
+Contact a system administrator (preferably your own) and report the exact
+error message you get, and ask them to read this same documentation you
+are now reading. They should be able to check whether there is something
+wrong with the locale configuration of the system. The L<Finding locales>
+section is unfortunately a bit vague about the exact commands and places
+because these things are not that standardized.
=head2 The localeconv function
-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
-C<POSIX::setlocale> with a single parameter - see L<The setlocale
-function>.)
+The 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()
+with a single parameter--see L<The setlocale function>.)
use POSIX qw(locale_h);
- use locale;
# Get a reference to a hash of locale-dependent info
$locale_values = localeconv();
# Output sorted list of the values
for (sort keys %$locale_values) {
- printf "%-20s = %s\n", $_, $locale_values->{$_}
+ printf "%-20s = %s\n", $_, $locale_values->{$_}
}
-C<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.
-
-I<Editor's note:> I can't work out whether C<POSIX::localeconv>
-correctly obeys C<use locale> and C<no locale>. In my opinion, it
-should, if only to be consistent with other locale stuff - although
-it's hardly a show-stopper if it doesn't. Could someone check,
-please?
+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
+current locale.
-Here's a simple-minded example program which rewrites its command line
-parameters as integers formatted correctly in 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);
- use locale;
# Get some of locale's numeric formatting parameters
my ($thousands_sep, $grouping) =
- @{localeconv()}{'thousands_sep', 'grouping'};
+ @{localeconv()}{'thousands_sep', 'grouping'};
# Apply defaults if values are missing
$thousands_sep = ',' unless $thousands_sep;
- $grouping = 3 unless $grouping;
+
+ # grouping and mon_grouping are packed lists
+ # of small integers (characters) telling the
+ # grouping (thousand_seps and mon_thousand_seps
+ # being the group dividers) of numbers and
+ # monetary quantities. The integers' meanings:
+ # 255 means no more grouping, 0 means repeat
+ # the previous grouping, 1-254 means use that
+ # as the current grouping. Grouping goes from
+ # right to left (low to high digits). In the
+ # below we cheat slightly by never using anything
+ # else than the first grouping (whatever that is).
+ if ($grouping) {
+ @grouping = unpack("C*", $grouping);
+ } else {
+ @grouping = (3);
+ }
# Format command line params for current locale
- for (@ARGV)
- {
- $_ = int; # Chop non-integer part
+ for (@ARGV) {
+ $_ = int; # Chop non-integer part
1 while
- s/(\d)(\d{$grouping}($|$thousands_sep))/$1$thousands_sep$2/;
- print "$_ ";
+ s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
+ print "$_";
}
print "\n";
-I<Editor's note:> Like all the examples, this needs testing on systems
-which, unlike mine, have non-toy implementations of locale handling.
+=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 descibe basic locale categories. As well
-as these, there are some combination categories which allow the
-manipulation of of more than one basic category at a time. See
-L<ENVIRONMENT VARIABLES> 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 B<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 '¡' and '\9f' belong?)
+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?
-Here is a code snippet that will tell you what are the alphanumeric
-characters in the current locale, in the locale order:
+The following collations all make sense and you may meet any of them
+if you "use locale".
- use locale;
- print +(sort grep /\w/, map { chr() } 0..255), "\n";
+ 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 to tell what "word"
+characters are in the current locale, in that locale's order:
-I<Editor's note:> The original example had C<setlocale(LC_COLLATE, "")>
-prior to C<print ...>. I think this is wrong: as soon as you utter
-S<C<use locale>>, the default behaviour of C<sort> (well, C<cmp>, really)
-becomes locale-aware. The locale it's aware of is the current locale
-which, unless you've changed it yourself, is the default locale
-defined by your environment.
+ use locale;
+ 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:
+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
sorting raw binary data, whereas the locale-dependent collation of the
-first example is useful for written text.
-
-B<NOTE>: In some locales some characters may have no collation value
-at all - for example, if '-' is such a character, 'relocate' and
-'re-locate' may be considered to be equal to each other, and so sort
-to the same position.
+first example is useful for natural text.
+
+As noted in L<USING LOCALES>, C<cmp> compares according to the current
+collation locale when C<use locale> is in effect, but falls back to a
+char-by-char comparison for strings that the locale says are equal. You
+can use 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
+dictionary-like ordering that ignores space characters completely and
+which folds case.
+
+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>:
+
+ use POSIX qw(strxfrm);
+ $xfrm_string = strxfrm("Mixed-case string");
+ print "locale collation ignores spaces\n"
+ if $xfrm_string eq strxfrm("Mixed-casestring");
+ print "locale collation ignores hyphens\n"
+ if $xfrm_string eq strxfrm("Mixedcase 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 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 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
+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
+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 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
-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 regular expressions.) Thanks to C<LC_CTYPE>,
-depending on your locale setting, characters like '\90', '\8a',
-'þ', and '¯' may be understood as C<\w> characters.
-
-C<LC_CTYPE> also affects the POSIX character-class test functions -
-C<isalpha>, C<islower> and so on. For example, if you move from the
-"C" locale to a 7-bit Scandinavian one, you may find - possibly to
-your surprise -that "|" moves from the C<ispunct> class to C<isalpha>.
-
-I<Editor's note:> I can't work out whether the C<POSIX::is...> stuff
-correctly obeys C<use locale> and C<no locale>. In my opinion, they
-should. Could someone check, please?
-
-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.
+In the scope of S<C<use locale>>, 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,
+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.
+
+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
+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().
+
+B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result
+in clearly ineligible characters being considered to be alphanumeric by
+your application. For strict matching of (mundane) ASCII letters and
+digits--for example, in command strings--locale-aware applications
+should use C<\w> with the C</a> regular expression modifier. See L<"SECURITY">.
=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 C<printf>, C<fprintf>,
-and C<write> functions. String to numeric conversion by the
-C<POSIX::strtod> function is also affected. In most impementations
-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.)
-
-I<Editor's note:> I can't work out whether C<POSIX::strtod> correctly
-obeys C<use locale> and C<no locale>. In my opinion, it should -
-although it's hardly a show-stopper if it doesn't. Could someone
-check, please?
-
-Note that output produced by C<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 C<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" # Locale-dependent conversion
- if $n == (strtod("2,5"))[0];
+ 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
+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 recognise 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 formating 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.
+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
+to crack.
+
+See also L<I18N::Langinfo> and C<CRNCYSTR>.
=head2 LC_TIME
-The output produced by C<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);
- use locale;
- for (0..11)
- {
- $long_month_name[$_] = strftime("%B", 0, 0, 0, 1, $_, 96);
+ for (0..11) {
+ $long_month_name[$_] =
+ strftime("%B", 0, 0, 0, 1, $_, 96);
}
-I<Editor's note:> Unchecked in "alien" locales: my system can't do
-French...
+Note: C<use locale> isn't needed in this example: as a function that
+exists only to generate locale-dependent results, strftime() always
+obeys the current C<LC_TIME> locale.
+
+See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>,
+C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>.
=head2 Other categories
-The remaining locale category, C<LC_MESSAGES> (possibly supplemented by
-others in particular implementations) is not currently used by Perl -
-except possibly to affect the behaviour of library functions called
-by extensions which are not part of the standard Perl distribution.
+The remaining locale category, C<LC_MESSAGES> (possibly supplemented
+by others in particular implementations) is not currently used by
+Perl--except possibly to affect the behavior of library functions
+called by extensions outside the standard Perl distribution and by the
+operating system and its utilities. Note especially that the string
+value of C<$!> 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
+
+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 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:
+
+=over 4
+
+=item *
+
+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.
+
+=item *
+
+String interpolation with case-mapping, as in, say, C<$dest =
+"C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE
+case-mapping table is in effect.
+
+=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 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 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
+Sunday.")
+
+=back
+
+Such dangers are not peculiar to the locale system: any aspect of an
+application's environment which may be modified maliciously presents
+similar challenges. Similarly, they are not specific to Perl: any
+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 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 that become locale-dependent, and
+which may be untrustworthy in consequence. Here is a summary of the
+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>):
+
+Scalar true/false (or less/equal/greater) result is never tainted.
+
+=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.
+
+=item *
+
+B<Matching operator> (C<m//>):
+
+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> (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///>):
+
+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>.
+
+=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.
+
+=item *
+
+B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()):
+
+Results are tainted if C<use locale> is in effect.
+
+=item *
+
+B<POSIX locale-dependent functions> (localeconv(), strcoll(),
+strftime(), strxfrm()):
+
+Results are never tainted.
+
+=item *
+
+B<POSIX character class tests> (isalnum(), isalpha(), isdigit(),
+isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(),
+isxdigit()):
+
+True/false results are never tainted.
+
+=back
+
+Three examples illustrate locale-dependent tainting.
+The first program, which ignores its locale, won't run: a value taken
+directly from the command line may not be used to name an output file
+when taint checks are enabled.
+
+ #/usr/local/bin/perl -T
+ # Run with taint checking
+
+ # Command line sanity check omitted...
+ $tainted_output_file = shift;
+
+ open(F, ">$tainted_output_file")
+ or warn "Open of $untainted_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
+if it can.
+
+ #/usr/local/bin/perl -T
+
+ $tainted_output_file = shift;
+ $tainted_output_file =~ m%[\w/]+%;
+ $untainted_output_file = $&;
+
+ open(F, ">$untainted_output_file")
+ or warn "Open of $untainted_output_file failed: $!\n";
+
+Compare this with a similar but locale-aware program:
+
+ #/usr/local/bin/perl -T
+
+ $tainted_output_file = shift;
+ use locale;
+ $tainted_output_file =~ m%[\w/]+%;
+ $localized_output_file = $&;
+
+ open(F, ">$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
+of a match involving C<\w> while C<use locale> is in effect.
=head1 ENVIRONMENT
=item PERL_BADLANG
-A string that controls whether Perl warns in its startup about failed
-locale settings. This can happen if the locale support in the
-operating system is lacking (broken) is some way. If this string has
-an integer value differing from zero, Perl will not complain.
+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.
-B<NOTE>: This is just hiding the warning message. The message tells
-about some problem in your system's locale support and you should
-investigate what the problem is.
+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,
+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 to
-control an application's opinion on data.
+part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method
+for controlling an application's opinion on data.
=over 12
=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
=item 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.
+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
-In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the montary formatting
-locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>, C<LANG>
-chooses the monetary formatting locale.
+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 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.
+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
-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
+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_...>.
=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 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 S<C<use locale>> Pragma>) to
-instruct it to do so.
-
-=head2 Sort speed
+Versions of Perl prior to 5.004 B<mostly> ignored locale information,
+generally behaving as if something similar to the C<"C"> locale were
+always in force, even if the program environment suggested otherwise
+(see L<The setlocale function>). By default, Perl still behaves this
+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 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
+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
+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
+use locale-specific scalar data completely normally with C<use locale>,
+so there is no longer any need to juggle with the scalar references of
+C<I18N::Collate>.
+
+=head2 Sort speed and memory use impacts
Comparing and sorting by locale is usually slower than the default
-sorting; factors of 2 to 4 have been observed. It will also consume
-more memory: while a Perl scalar variable is participating in any
-string comparison or sorting operation and obeying the locale
-collation rules it will take about 3-15 (the exact value depends on
-the operating system and the locale) times more memory than normally.
-These downsides are dictated more by the operating system
-implementation of the locale system than by Perl.
-
-=head2 I18N:Collate
-
-In Perl 5.003 (and later development releases prior to 5.003_06),
-per-locale collation was possible using the C<I18N::Collate> library
-module. This is now mildly obsolete and should be avoided in new
-applications. The C<LC_COLLATE> functionality is integrated into the
-Perl core language and one can use locale-specific scalar data
-completely normally - there is no need to juggle with the scalar
-references of C<I18N::Collate>.
+sorting; slow-downs of two to four times have been observed. It will
+also consume more memory: once a Perl scalar variable has participated
+in any string comparison or sorting operation obeying the locale
+collation rules, it will take 3-15 times more memory than before. (The
+exact multiplier depends on the string's contents, the operating system
+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
+
+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 An imperfect standard
+=head2 Freely available locale definitions
-Internationalization, as defined in the C and POSIX standards, can be
-criticized as incomplete, ungainly, and having too large a
-granularity. (Locales apply to a whole process, when it would
-arguably be more useful to have them apply to a single thread, window
-group, or whatever.) They also have a tendency, like standards
-groups, to divide the world into nations, when we all know that the
-world can equally well be divided into bankers, bikers, gamers, and so
-on. But, for now, it's the only standard we've got. This may be
-construed as a bug.
+There is a large collection of locale definitions at:
-=head2 Freely available locale definitions
+ 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
+your own locales.
+
+=head2 I18n and l10n
-There is a large collection of locale definitions at
-C<ftp://dkuug.dk/i18n/WG15-collection>. You should be aware that they
-are unsupported, and are not claimed to be fit for any purpose. If
-your system allows the installation of arbitrary locales, you may find
-them useful as they are, or as a basis for the development of your own
-locales.
+"Internationalization" is often abbreviated as B<i18n> because its first
+and last letters are separated by eighteen others. (You may guess why
+the internalin ... internaliti ... i18n tends to get abbreviated.) In
+the same way, "localization" is often abbreviated to B<l10n>.
-=head2 i18n and l10n
+=head2 An imperfect standard
-Internationalization is often abbreviated as B<i18n> because its first
-and last letters are separated by eighteen others. You can also talk of
-localization (B<l10n>), the process of tailoring an
-internationalizated application for use in a particular locale.
+Internationalization, as defined in the C and POSIX standards, can be
+criticized as incomplete, ungainly, and having too large a granularity.
+(Locales apply to a whole process, when it would arguably be more useful
+to have them apply to a single thread, window group, or whatever.) They
+also have a tendency, like standards groups, to divide the world into
+nations, when we all know that the world can equally well be divided
+into bankers, bikers, gamers, and so on.
+
+=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
=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. One
-example is IRIX before release 6.2, in which the C<LC_COLLATE> support
-simply does not work. When confronted with such a system, please
-report in excruciating detail to C<perlbug@perl.com>, and complain to
-your vendor: maybe some bug fixes exist for these problems in your
-operating system. Sometimes such bug fixes are called an operating
-system upgrade.
-
-=head2 Rendering of this documentation
-
-This manual page contains non-ASCII characters, which should all be
-rendered as accented letters, and which should make some sort of sense
-in context. If this is not the case, your system is probably not
-using the ISO 8859-1 character set which was used to write them,
-and/or your formatting, display, and printing software are not
-correctly mapping them to your host's character set. If this annoys
-you, and if you can convince yourself that it is due to a bug in one
-of Perl's various C<pod2>... utilities, by all means report it as a
-Perl bug. Otherwise, pausing only to curse anyone who ever invented
-yet another character set, see if you can make it handle ISO 8859-1
-sensibly.
+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
+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)/strtod>
-
-I<Editor's note:> That looks horrible after going through C<pod2man>.
-But I do want to call out all thse sectins by name. What should I
-have done?
+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
-Perl 5.003's F<perli18n.pod> heavily hacked by Dominic Dunlop.
-
-Last update:
-Mon Dec 16 14:13:10 WET 1996
+Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
+Dunlop, assisted by the perl5-porters. Prose worked over a bit by
+Tom Christiansen, and updated by Perl 5 porters.
https://perl5.git.perl.org / perl5.git / blobdiff