=head1 NAME
-perllocale - Perl locale handling (internationlization and localization)
+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
+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
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
+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 you want a Perl application to process and present your data
according to a particular locale, the application code should include
-the S<C<use locale>> pragma (see L<The use locale Pragma>) where
+the S<C<use locale>> pragma (see L<The use locale pragma>) where
appropriate, and B<at least one> of the following must be true:
=over 4
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
+The default behavior returns with S<C<no locale>> or on reaching the
end of the enclosing block.
Note that the string result of any operation that uses locale
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
+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.
If the second argument does not correspond to a valid locale, the 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 de_DE russian
- english.iso88591 de_DE.ISO8859-1 russian.iso88595
- en_US german ru_RU
- en_US.ISO8859-1 german.iso88591 ru_RU.ISO8859-5
+ english german russian
+ english.iso88591 german.iso88591 russian.iso88595
Sadly, even though the calling interface for 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
+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 are not always present.
Two special locales are worth particular mention: "C" and "POSIX".
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.
+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
$equal_in_locale will be true if the collation locale specifies a
dictionary-like ordering which ignores space characters completely, and
-which folds case. Alternatively, you can use this idiom:
-
- use locale;
- $s_a = "space and case ignored";
- $s_b = "SpaceAndCaseIgnored";
- $equal_in_locale = $s_a ge $s_b && $s_a le $s_b;
-
-which works because neither C<ne> nor C<ge> falls back to doing a
-byte-by-byte comparison when the operands are equal according to the
-locale. The idiom may be less efficient than using strcoll(), but,
-unlike that function, it is not confused by strings containing embedded
-nulls.
+which folds case.
If you have a single string which you want to check for "equality in
locale" against several others, you might think you could gain a little
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
-magic (see L<perlguts/Magic>) creates the transformed version of a
+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
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
+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. In short, don't call strxfrm() directly:
-let Perl do it for you.
+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
+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
needed: strcoll() and strxfrm() exist only to generate locale-dependent
setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and
'E<oslash>' may be understood as C<\w> characters.
-C<LC_CTYPE> also affects the POSIX character-class test functions -
+The C<LC_CTYPE> locale also provides the map used in translating
+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
+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().
The C standard defines the C<LC_MONETARY> category, but no function that
is affected by its contents. (Those with experience of standards
-committees will recognise that the working group decided to punt on the
+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 formating of currency amounts. However, you may well
+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.
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
+except possibly to affect the behavior of library functions called by
extensions which are not part of the standard Perl distribution.
=head1 SECURITY
=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 *
+
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
C<use locale> is in effect, Perl uses the tainting mechanism (see
L<perlsec>) to mark string results which become locale-dependent, and
which may be untrustworthy in consequence. Here is a summary of the
-tainting behaviour of operators and functions which may be affected by
+tainting behavior of operators and functions which may be affected by
the locale:
=over 4
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>)
+
+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 an array-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). The
-matched pattern variable, $&, is also tainted if C<use locale> is in
-effect, and the regular expression contains C<\w>.
+expression contains C<\w> (to match an alphanumeric character), C<\W>
+(non-alphanumeric character), C<\s> (white-space character), or C<\S>
+(non white-space character). The matched pattern variable, $&, $`
+(pre-match), $' (post-match), and $+ (last match) are also tainted if
+C<use locale> is in effect and the regular expression contains C<\w>,
+C<\W>, C<\s>, or C<\S>.
=item B<Substitution operator> (C<s///>):
-Has the same behaviour as the match operator. When C<use locale> is
-in effect, he left operand of C<=~> will become tainted if it is
-modified as a result of a substitution based on a regular expression
-match involving C<\w>.
+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
+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>.
=item B<In-memory formatting function> (sprintf()):
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
+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...
+ # Command line sanity check omitted...
$tainted_output_file = shift;
open(F, ">$tainted_output_file")
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
+information - runs, creating the file named on its command line
if it can.
#/usr/local/bin/perl -T
=item PERL_BADLANG
A string that can suppress Perl's warning about failed locale settings
-at start-up. Failure can occur if the locale support in the operating
+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
=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
+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 S<C<use locale>> Pragma>) to instruct
-it to do so.
+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.
+
+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.
+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
and the locale.) These downsides are dictated more by the operating
system's implementation of the locale system than by Perl.
-=head2 I18N:Collate
+=head2 write() and LC_NUMERIC
-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 now 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>.
+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.
=head2 Freely available locale definitions
=head2 I18n and l10n
-Internationalization is often abbreviated as B<i18n> because its first
-and last letters are separated by eighteen others. In the same way, you
-abbreviate localization to B<l10n>.
+"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 An imperfect standard
=head2 Broken systems
-In certain system environments 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.
+In certain system environments 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
+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
+in your operating system. Sometimes such bug fixes are called an
+operating system upgrade.
=head1 SEE ALSO
=head1 HISTORY
-Jarrko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
+Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic
Dunlop, assisted by the perl5-porters.
-Last update: Mon Dec 23 10:44:08 EST 1996
+Last update: Wed Jan 22 11:04:58 EST 1997
projects / p5sagit/p5-mst-13.2.git / blobdiff