NAME¶
perllocale - Perl locale handling (internationalization and localization)
DESCRIPTION¶
In the beginning there was ASCII, the "American Standard Code for
Information Interchange", which works quite well for Americans with their
English alphabet and dollar-denominated currency. But it doesn't work so well
even for other English speakers, who may use different currencies, such as the
pound sterling (as the symbol for that currency is not in ASCII); and it's
hopelessly inadequate for many of the thousands of the world's other
languages.
To address these deficiencies, the concept of locales was invented (formally the
ISO C, XPG4, POSIX 1.c "locale system"). And applications were and
are being written that use the locale mechanism. The process of making such an
application take account of its users' preferences in these kinds of matters
is called
internationalization (often abbreviated as
i18n);
telling such an application about a particular set of preferences is known as
localization (
l10n).
Perl has been extended to support the locale system. This is controlled per
application by using one pragma, one function call, and several environment
variables.
Unfortunately, there are quite a few deficiencies with the design (and often,
the implementations) of locales. Unicode was invented (see perlunitut for an
introduction to that) in part to address these design deficiencies, and
nowadays, there is a series of "UTF-8 locales", based on Unicode.
These are locales whose character set is Unicode, encoded in UTF-8. Starting
in v5.20, Perl fully supports UTF-8 locales, except for sorting and string
comparisions. (Use Unicode::Collate for these.) Perl continues to support the
old non UTF-8 locales as well.
(Unicode is also creating "CLDR", the "Common Locale Data
Repository", <
http://cldr.unicode.org/> which includes more types
of information than are available in the POSIX locale system. At the time of
this writing, there was no CPAN module that provides access to this
XML-encoded data. However, many of its locales have the POSIX-only data
extracted, and are available as UTF-8 locales at
<
http://unicode.org/Public/cldr/latest/>.)
WHAT IS A LOCALE¶
A locale is a set of data that describes various aspects of how various
communities in the world categorize their world. These categories are broken
down into the following types (some of which include a brief note here):
- Category "LC_NUMERIC": Numeric formatting
- This indicates how numbers should be formatted for human readability, for
example the character used as the decimal point.
- Category "LC_MONETARY": Formatting of monetary amounts
-
- Category "LC_TIME": Date/Time formatting
-
- Category "LC_MESSAGES": Error and other messages
- This is used by Perl itself only for accessing operating system error
messages via $! and $^E.
- Category "LC_COLLATE": Collation
- This indicates the ordering of letters for comparison and sorting. In
Latin alphabets, for example, "b", generally follows
"a".
- Category "LC_CTYPE": Character Types
- This indicates, for example if a character is an uppercase letter.
- Other categories
- Some platforms have other categories, dealing with such things as
measurement units and paper sizes. None of these are used directly by
Perl, but outside operations that Perl interacts with may use these. See
"Not within the scope of any "use locale" variant"
below.
More details on the categories used by Perl are given below in "LOCALE
CATEGORIES".
Together, these categories go a long way towards being able to customize a
single program to run in many different locations. But there are deficiencies,
so keep reading.
PREPARING TO USE LOCALES¶
Perl itself will not use locales unless specifically requested to (but again
note that Perl may interact with code that does use them). Even if there is
such a request,
all of the following must be true for it to work
properly:
- •
- Your operating system must support the locale system. If it does,
you should find that the "setlocale()" function is a documented
part of its C library.
- •
- 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.
- •
- Perl must believe that the locale system is supported. If it does,
"perl -V:d_setlocale" will say that the value for
"d_setlocale" is "define".
If you want a Perl application to process and present your data according to a
particular locale, the application code should include the
"use locale" pragma (see "The use locale pragma")
where appropriate, and
at least one of the following must be true:
- 1.
- The locale-determining environment variables (see
"ENVIRONMENT") must be correctly set up at the time
the application is started, either by yourself or by whomever set up your
system account; or
- 2.
- The application must set its own locale using the method described
in "The setlocale function".
USING LOCALES¶
The use locale pragma¶
By default, Perl itself ignores the current locale. The
"use locale" pragma tells Perl to use the current locale for
some operations. Starting in v5.16, there is an optional parameter to this
pragma:
use locale ':not_characters';
This parameter allows better mixing of locales and Unicode (less useful in v5.20
and later), and is described fully in "Unicode and UTF-8", but
briefly, it tells Perl to not use the character portions of the locale
definition, that is the "LC_CTYPE" and "LC_COLLATE"
categories. Instead it will use the native character set (extended by
Unicode). When using this parameter, you are responsible for getting the
external character set translated into the native/Unicode one (which it
already will be if it is one of the increasingly popular UTF-8 locales). There
are convenient ways of doing this, as described in "Unicode and
UTF-8".
The current locale is set at execution time by
setlocale() 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
"ENVIRONMENT" in effect at the start of the program. If there is no
valid environment, the current locale is whatever the system default has been
set to. On POSIX systems, it is likely, but not necessarily, the "C"
locale. On Windows, the default is set via the computer's
"Control Panel->Regional and Language Options"
(or its current equivalent).
The operations that are affected by locale are:
- Not within the scope of any "use locale"
variant
- Only operations originating outside Perl should be affected, as
follows:
- •
- The variables $! (and its synonyms $ERRNO and $OS_ERROR) and $^E (and its
synonym $EXTENDED_OS_ERROR) when used as strings always are in terms of
the current locale and as if within the scope of "use bytes".
This is likely to change in Perl v5.22.
- •
- The current locale is also used when going outside of Perl with operations
like system() or qx//, if those operations are
locale-sensitive.
- •
- Also Perl gives access to various C library functions through the POSIX
module. Some of those functions are always affected by the current locale.
For example, "POSIX::strftime()" uses "LC_TIME";
"POSIX::strtod()" uses "LC_NUMERIC";
"POSIX::strcoll()" and "POSIX::strxfrm()" use
"LC_COLLATE"; and character classification functions like
"POSIX::isalnum()" use "LC_CTYPE". All such functions
will behave according to the current underlying locale, even if that
locale isn't exposed to Perl space.
- •
- XS modules for all categories but "LC_NUMERIC" get the
underlying locale, and hence any C library functions they call will use
that underlying locale. For more discussion, see "CAVEATS" in
perlxs.
- Lingering effects of
"use locale"
- Certain Perl operations that are set-up within the scope of a "use
locale" variant retain that effect even outside the scope. These
include:
- •
- The output format of a write() is determined by an earlier format
declaration ("format" in perlfunc), so whether or not the output
is affected by locale is determined by if the "format()" is
within the scope of a "use locale" variant, not whether the
"write()" is.
- •
- Regular expression patterns can be compiled using qr// with actual
matching deferred to later. Again, it is whether or not the compilation
was done within the scope of "use locale" that determines the
match behavior, not if the matches are done within such a scope or
not.
- Under "use locale ':not_characters';"
- •
- All the non-Perl operations.
- •
- Format declarations ("format" in perlfunc) and hence any
subsequent "write()"s use "LC_NUMERIC".
- •
- stringification and output use "LC_NUMERIC". These
include the results of "print()", "printf()",
"say()", and "sprintf()".
- Under just plain ""use
locale";"
- •
- All the above operations
- •
- The comparison operators ("lt", "le",
"cmp", "ge", and "gt") use
"LC_COLLATE". "sort()" is also affected if used
without an explicit comparison function, because it uses "cmp"
by default.
Note: "eq" and "ne" are unaffected by locale:
they always perform a char-by-char comparison of their scalar operands.
What's more, if "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 0
(equal) if the operands are char-for-char identical. If you really want to
know whether two strings--which "eq" and "cmp" may
consider different--are equal as far as collation in the locale is
concerned, see the discussion in "Category "LC_COLLATE":
Collation".
- •
- Regular expressions and case-modification functions
("uc()", "lc()", "ucfirst()", and
"lcfirst()") use "LC_CTYPE"
The default behavior is restored with the "no locale" pragma,
or upon reaching the end of the block enclosing "use locale". Note
that "use locale" and "use locale ':not_characters'" may
be nested, and that what is in effect within an inner scope will revert to the
outer scope's rules at the end of the inner scope.
The string result of any operation that uses locale information is tainted, as
it is possible for a locale to be untrustworthy. See "SECURITY".
The setlocale function¶
You can switch locales as often as you wish at run time with the
"POSIX::setlocale()" function:
# Import locale-handling tool set from POSIX module.
# This example uses: setlocale -- the function call
# LC_CTYPE -- explained below
# (Showing the testing for success/failure of operations is
# omitted in these examples to avoid distracting from the main
# point)
use POSIX qw(locale_h);
use locale;
my $old_locale;
# query and save the old locale
$old_locale = setlocale(LC_CTYPE);
setlocale(LC_CTYPE, "fr_CA.ISO8859-1");
# LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1"
setlocale(LC_CTYPE, "");
# LC_CTYPE now reset to the default defined by the
# LC_ALL/LC_CTYPE/LANG environment variables, or to the system
# default. See below for documentation.
# restore the old locale
setlocale(LC_CTYPE, $old_locale);
This simultaneously affects all threads of the program, so it may be problematic
to use locales in threaded applications except where there is a single locale
applicable to all threads.
The first argument of "setlocale()" gives the
category, the
second the
locale. The category tells in what aspect of data processing
you want to apply locale-specific rules. Category names are discussed in
"LOCALE CATEGORIES" and "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 other 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()",
but on some platforms the
string is opaque, not something that most people would be able to decipher as
to what locale it means.
If no second argument is provided and the category is "LC_ALL", the
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 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.
Note that Perl ignores the current "LC_CTYPE" and
"LC_COLLATE" locales within the scope of a "use locale
':not_characters'".
If "set_locale()" fails for some reason (for example, an attempt to
set to a locale unknown to the system), the locale for the category is not
changed, and the function returns "undef".
For further information about the categories, consult
setlocale(3).
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
SEE
ALSO section). If that fails, try the following command lines:
locale -a
nlsinfo
ls /usr/lib/nls/loc
ls /usr/lib/locale
ls /usr/lib/nls
ls /usr/share/locale
and see whether they list something resembling these
en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5
en_US.iso88591 de_DE.iso88591 ru_RU.iso88595
en_US de_DE ru_RU
en de ru
english german russian
english.iso88591 german.iso88591 russian.iso88595
english.roman8 russian.koi8r
Sadly, even though the calling interface for "setlocale()" has been
standardized, names of locales and the directories where the configuration
resides have not been. The basic form of the name is
language_territory.codeset, but the latter parts after
language are not always present. The
language and
country
are usually from the standards
ISO 3166 and
ISO 639, the
two-letter abbreviations for the countries and the languages of the world,
respectively. The
codeset part often mentions some
ISO
8859 character set, the Latin codesets. For example, "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
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 or, rarely, a superset thereof (such
as the "DEC Multinational Character Set (DEC-MCS)").
Warning.
The C locale delivered by some vendors may not actually exactly match what the
C standard calls for. So beware.
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.
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. (On
Windows, it first tries falling back to the system default locale.) This
usually means your locale settings were wrong, they mention locales your
system has never heard of, or the locale installation in your system has
problems (for example, some system files are broken or missing). There are
quick and temporary fixes to these problems, as well as more thorough and
lasting fixes.
Testing for broken locales¶
If you are building Perl from source, the Perl test suite file
lib/locale.t can be used to test the locales on your system. Setting
the environment variable "PERL_DEBUG_FULL_TEST" to 1 will cause it
to output detailed results. For example, on Linux, you could say
PERL_DEBUG_FULL_TEST=1 ./perl -T -Ilib lib/locale.t > locale.log 2>&1
Besides many other tests, it will test every locale it finds on your system to
see if they conform to the POSIX standard. If any have errors, it will include
a summary near the end of the output of which locales passed all its tests,
and which failed, and why.
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 "ENVIRONMENT" for the full
list of relevant environment variables and "USING LOCALES" for their
effects in Perl. Effects in other programs are easily deducible. For example,
the variable "LC_COLLATE" may well affect your
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 Bourne-like shells (
sh,
ksh,
bash,
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 (
csh,
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.
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 "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
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
"Permanently fixing your system's locale configuration".
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
"Finding locales" about general rules.
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 "Finding locales"
section is unfortunately a bit vague about the exact commands and places
because these things are not that standardized.
The localeconv function¶
The "POSIX::localeconv()" function allows you to get particulars of
the locale-dependent numeric formatting information specified by the current
"LC_NUMERIC" and "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 "The
setlocale function".)
use POSIX qw(locale_h);
# 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", $_, $locale_values->{$_}
}
"localeconv()" takes no arguments, and returns
a reference to a
hash. The keys of this hash are variable names for formatting, such as
"decimal_point" and "thousands_sep". The values are the
corresponding, er, values. See "localeconv" in POSIX 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 "use
locale", because "localeconv()" always observes the current
locale.
Here's a simple-minded example program that rewrites its command-line parameters
as integers correctly formatted in the current locale:
use POSIX qw(locale_h);
# Get some of locale's numeric formatting parameters
my ($thousands_sep, $grouping) =
@{localeconv()}{'thousands_sep', 'grouping'};
# Apply defaults if values are missing
$thousands_sep = ',' unless $thousands_sep;
# grouping and mon_grouping are packed lists
# of small integers (characters) telling the
# grouping (thousand_seps and mon_thousand_seps
# being the group dividers) of numbers and
# monetary quantities. The integers' meanings:
# 255 means no more grouping, 0 means repeat
# the previous grouping, 1-254 means use that
# as the current grouping. Grouping goes from
# right to left (low to high digits). In the
# below we cheat slightly by never using anything
# else than the first grouping (whatever that is).
if ($grouping) {
@grouping = unpack("C*", $grouping);
} else {
@grouping = (3);
}
# Format command line params for current locale
for (@ARGV) {
$_ = int; # Chop non-integer part
1 while
s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/;
print "$_";
}
print "\n";
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 I18N::Langinfo for more information.
LOCALE CATEGORIES¶
The following subsections describe basic locale categories. Beyond these, some
combination categories allow manipulation of more than one basic category at a
time. See "ENVIRONMENT" for a discussion of these.
Category "LC_COLLATE": Collation¶
In the scope of "use locale" (but not a "use locale
':not_characters'"), Perl looks to the "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 "a" and "aa" belong? And while
"color" follows "chocolate" in English, what about in
traditional Spanish?
The following collations all make sense and you may meet any of them if you
"use locale".
A B C D E a b c d e
A a B b C c D d E e
a A b B c C d D e E
a b c d e A B C D E
Here is a code snippet to tell what "word" characters are in the
current locale, in that locale's order:
use locale;
print +(sort grep /\w/, map { chr } 0..255), "\n";
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";
This machine-native collation (which is what you get unless
"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 natural text.
As noted in "USING LOCALES", "cmp" compares according to the
current collation locale when "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.
Perl currently only supports single-byte locales for "LC_COLLATE".
This means that a UTF-8 locale likely will just give you machine-native
ordering. Use Unicode::Collate for the full implementation of the Unicode
Collation Algorithm.
If you have a single string that you want to check for "equality in
locale" against several others, you might think you could gain a little
efficiency by using "POSIX::strxfrm()" in conjunction with
"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 "Magic Variables" in perlguts) 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 "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: "use locale" isn't shown in some of these examples because it
isn't needed: "strcoll()" and "strxfrm()" are POSIX
functions which use the standard system-supplied "libc" functions
that always obey the current "LC_COLLATE" locale.
Category "LC_CTYPE": Character Types¶
In the scope of "use locale" (but not a "use locale
':not_characters'"), Perl obeys the "LC_CTYPE" locale setting.
This controls the application's notion of which characters are alphabetic,
numeric, punctuation,
etc. This affects Perl's "\w" regular
expression metanotation, which stands for alphanumeric characters--that is,
alphabetic, numeric, and the platform's native underscore. (Consult perlre for
more information about regular expressions.) Thanks to "LC_CTYPE",
depending on your locale setting, characters like "ae",
"d`", "ss", and "o" may be understood as
"\w" characters. It also affects things like "\s",
"\D", and the POSIX character classes, like "[[:graph:]]".
(See perlrecharclass for more information on all these.)
The "LC_CTYPE" locale also provides the map used in transliterating
characters between lower and uppercase. This affects the case-mapping
functions--"fc()", "lc()", "lcfirst()",
"uc()", and "ucfirst()"; case-mapping interpolation with
"\F", "\l", "\L", "\u", or
"\U" in double-quoted strings and "s///" substitutions;
and case-independent regular expression pattern matching using the
"i" modifier.
Finally, "LC_CTYPE" affects the (deprecated) POSIX character-class
test functions--"POSIX::isalpha()", "POSIX::islower()",
and so on. For example, if you move from the "C" locale to a 7-bit
ISO 646 one, you may find--possibly to your surprise--that "|" moves
from the "POSIX::ispunct()" class to "POSIX::isalpha()".
Unfortunately, this creates big problems for regular expressions.
"|" still means alternation even though it matches "\w".
Starting in v5.20, Perl supports UTF-8 locales for "LC_CTYPE", but
otherwise Perl only supports single-byte locales, such as the ISO 8859 series.
This means that wide character locales, for example for Asian languages, are
not well-supported. The UTF-8 locale support is actually a superset of POSIX
locales, because it is really full Unicode behavior as if no locale were in
effect at all (except for tainting; see "SECURITY"). POSIX locales,
even UTF-8 ones, are lacking certain concepts in Unicode, such as the idea
that changing the case of a character could expand to be more than one
character. Perl in a UTF-8 locale, will give you that expansion. Prior to
v5.20, Perl treated a UTF-8 locale on some platforms like an ISO 8859-1 one,
with some restrictions, and on other platforms more like the "C"
locale. For releases v5.16 and v5.18,
"use locale 'not_characters" could be used as a
workaround for this (see "Unicode and UTF-8").
Note that there are quite a few things that are unaffected by the current
locale. Any literal character is the native character for the given platform.
Hence 'A' means the character at code point 65 on ASCII platforms, and 193 on
EBCDIC. That may or may not be an 'A' in the current locale, if that locale
even has an 'A'. Similarly, all the escape sequences for particular
characters, "\n" for example, always mean the platform's native one.
This means, for example, that "\N" in regular expressions (every
character but new-line) works on the platform character set.
Note: A broken or malicious "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
"\w" with the "/a" regular expression modifier. See
"SECURITY".
After a proper "POSIX::setlocale()" call, and within the scope of one
of the "use locale" variants, Perl obeys the "LC_NUMERIC"
locale information, which controls an application's idea of how numbers should
be formatted for human readability. In most implementations the only effect is
to change the character used for the decimal point--perhaps from "."
to ",". The functions aren't aware of such niceties as thousands
separation and so on. (See "The localeconv function" if you care
about these things.)
use POSIX qw(strtod setlocale LC_NUMERIC);
use locale;
setlocale LC_NUMERIC, "";
$n = 5/2; # Assign numeric 2.5 to $n
$a = " $n"; # Locale-dependent conversion to string
print "half five is $n\n"; # Locale-dependent output
printf "half five is %g\n", $n; # Locale-dependent output
print "DECIMAL POINT IS COMMA\n"
if $n == (strtod("2,5"))[0]; # Locale-dependent conversion
See also I18N::Langinfo and "RADIXCHAR".
The C standard defines the "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 essentially takes no notice of it. If you really
want to use "LC_MONETARY", you can query its contents--see "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 I18N::Langinfo and "CRNCYSTR".
"LC_TIME"¶
Output produced by "POSIX::strftime()", which builds a formatted
human-readable date/time string, is affected by the current
"LC_TIME" locale. Thus, in a French locale, the output produced by
the %B format element (full month name) for the first month of the year would
be "janvier". Here's how to get a list of long month names in the
current locale:
use POSIX qw(strftime);
for (0..11) {
$long_month_name[$_] =
strftime("%B", 0, 0, 0, 1, $_, 96);
}
Note: "use locale" isn't needed in this example:
"strftime()" is a POSIX function which uses the standard
system-supplied "libc" function that always obeys the current
"LC_TIME" locale.
See also I18N::Langinfo and "ABDAY_1".."ABDAY_7",
"DAY_1".."DAY_7",
"ABMON_1".."ABMON_12", and
"ABMON_1".."ABMON_12".
Other categories¶
The remaining locale categories are not currently used by Perl itself. But again
note that things Perl interacts with may use these, including extensions
outside the standard Perl distribution, and by the operating system and its
utilities. Note especially that the string value of $! and the error messages
given by external utilities may be changed by "LC_MESSAGES". If you
want to have portable error codes, use "%!". See Errno.
SECURITY¶
Although the main discussion of Perl security issues can be found in perlsec, a
discussion of Perl's locale handling would be incomplete if it did not draw
your attention to locale-dependent security issues. Locales--particularly on
systems that allow unprivileged users to build their own locales--are
untrustworthy. A malicious (or just plain broken) locale can make a
locale-aware application give unexpected results. Here are a few
possibilities:
- •
- Regular expression checks for safe file names or mail addresses using
"\w" may be spoofed by an "LC_CTYPE" locale that
claims that characters such as ">" and "|" are
alphanumeric.
- •
- String interpolation with case-mapping, as in, say, "$dest =
"C:\U$name.$ext"", may produce dangerous results if a bogus
"LC_CTYPE" case-mapping table is in effect.
- •
- A sneaky "LC_COLLATE" locale could result in the names of
students with "D" grades appearing ahead of those with
"A"s.
- •
- An application that takes the trouble to use information in
"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.
- •
- The date and day names in dates formatted by "strftime()" could
be manipulated to advantage by a malicious user able to subvert the
"LC_DATE" locale. ("Look--it says I wasn't in the building
on Sunday.")
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 "use locale" is in
effect, Perl uses the tainting mechanism (see 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:
- •
- Comparison operators ("lt", "le",
"ge", "gt" and "cmp"):
Scalar true/false (or less/equal/greater) result is never tainted.
- •
- Case-mapping interpolation (with "\l", "\L",
"\u", "\U", or "\F")
Result string containing interpolated material is tainted if "use
locale" (but not
"use locale ':not_characters'") is in effect.
- •
- Matching operator ("m//"):
Scalar true/false result never tainted.
All subpatterns, either delivered as a list-context result or as $1
etc., are tainted if "use locale" (but not
"use locale ':not_characters'") is in effect, and
the subpattern regular expression contains a locale-dependent construct.
These constructs include "\w" (to match an alphanumeric
character), "\W" (non-alphanumeric character), "\b"
and "\B" (word-boundary and non-boundardy, which depend on what
"\w" and "\W" match), "\s" (whitespace
character), "\S" (non whitespace character), "\d" and
"\D" (digits and non-digits), and the POSIX character classes,
such as "[:alpha:]" (see "POSIX Character Classes" in
perlrecharclass).
Tainting is also likely if the pattern is to be matched case-insensitively
(via "/i"). The exception is if all the code points to be
matched this way are above 255 and do not have folds under Unicode rules
to below 256. Tainting is not done for these because Perl only uses
Unicode rules for such code points, and those rules are the same no matter
what the current locale.
The matched-pattern variables, $&, "$`" (pre-match),
"$'" (post-match), and $+ (last match) also are tainted.
- •
- Substitution operator ("s///"):
Has the same behavior as the match operator. Also, the left operand of
"=~" becomes tainted when "use locale" (but not
"use locale ':not_characters'") is in effect if
modified as a result of a substitution based on a regular expression match
involving any of the things mentioned in the previous item, or of
case-mapping, such as "\l", "\L","\u",
"\U", or "\F".
- •
- Output formatting functions ("printf()" and
"write()"):
Results are never tainted because otherwise even output from print, for
example "print(1/7)", should be tainted if "use
locale" is in effect.
- •
- Case-mapping functions ("lc()", "lcfirst()",
"uc()", "ucfirst()"):
Results are tainted if "use locale" (but not
"use locale ':not_characters'") is in effect.
- •
- POSIX locale-dependent functions ("localeconv()",
"strcoll()", "strftime()", "strxfrm()"):
Results are never tainted.
- •
- POSIX character class tests ("POSIX::isalnum()",
"POSIX::isalpha()", "POSIX::isdigit()",
"POSIX::isgraph()", "POSIX::islower()",
"POSIX::isprint()", "POSIX::ispunct()",
"POSIX::isspace()", "POSIX::isupper()",
"POSIX::isxdigit()"):
True/false results are never tainted.
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 $tainted_output_file failed: $!\n";
The program can be made to run by "laundering" the tainted value
through a regular expression: the second example--which still ignores locale
information--runs, creating the file named on its command line 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 "\w" while "use locale" is in effect.
ENVIRONMENT¶
- PERL_SKIP_LOCALE_INIT
- This environment variable, available starting in Perl v5.20, and if it
evaluates to a TRUE value, tells Perl to not use the rest of the
environment variables to initialize with. Instead, Perl uses whatever the
current locale settings are. This is particularly useful in embedded
environments, see "Using embedded Perl with POSIX locales" in
perlembed.
- PERL_BADLANG
- A string that can suppress Perl's warning about failed locale settings at
startup. Failure can occur if the locale support in the operating system
is lacking (broken) in some way--or if you mistyped the name of a locale
when you set up your environment. If this environment variable is absent,
or has a value that does not evaluate to integer zero--that is,
"0" or ""-- Perl will complain about locale setting
failures.
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.
- DPKG_RUNNING_VERSION
- On Debian systems, if the DPKG_RUNNING_VERSION environment variable is set
(to any value), the locale failure warnings will be suppressed just like
with a zero PERL_BADLANG setting. This is done to avoid floods of spurious
warnings during system upgrades. See
<http://bugs.debian.org/508764>.
The following environment variables are not specific to Perl: They are part of
the standardized (ISO C, XPG4, POSIX 1.c) "setlocale()" method for
controlling an application's opinion on data. Windows is non-POSIX, but Perl
arranges for the following to work as described anyway. If the locale given by
an environment variable is not valid, Perl tries the next lower one in
priority. If none are valid, on Windows, the system default locale is then
tried. If all else fails, the "C" locale is used. If even that
doesn't work, something is badly broken, but Perl tries to forge ahead with
whatever the locale settings might be.
- "LC_ALL"
- "LC_ALL" is the "override-all" locale environment
variable. If set, it overrides all the rest of the locale environment
variables.
- "LANGUAGE"
- NOTE: "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 not using GNU libc and you can ignore
"LANGUAGE".
However, in the case you are using "LANGUAGE": it affects the
language of informational, warning, and error messages output by commands
(in other words, it's like "LC_MESSAGES") but it has higher
priority than "LC_ALL". Moreover, it's not a single value but
instead a "path" (":"-separated list) of
languages (not locales). See the GNU "gettext" library
documentation for more information.
- "LC_CTYPE".
- In the absence of "LC_ALL", "LC_CTYPE" chooses the
character type locale. In the absence of both "LC_ALL" and
"LC_CTYPE", "LANG" chooses the character type
locale.
- "LC_COLLATE"
- In the absence of "LC_ALL", "LC_COLLATE" chooses the
collation (sorting) locale. In the absence of both "LC_ALL" and
"LC_COLLATE", "LANG" chooses the collation
locale.
- "LC_MONETARY"
- In the absence of "LC_ALL", "LC_MONETARY" chooses the
monetary formatting locale. In the absence of both "LC_ALL" and
"LC_MONETARY", "LANG" chooses the monetary formatting
locale.
- "LC_NUMERIC"
- In the absence of "LC_ALL", "LC_NUMERIC" chooses the
numeric format locale. In the absence of both "LC_ALL" and
"LC_NUMERIC", "LANG" chooses the numeric format.
- "LC_TIME"
- In the absence of "LC_ALL", "LC_TIME" chooses the date
and time formatting locale. In the absence of both "LC_ALL" and
"LC_TIME", "LANG" chooses the date and time formatting
locale.
- "LANG"
- "LANG" is the "catch-all" locale environment variable.
If it is set, it is used as the last resort after the overall
"LC_ALL" and the category-specific "LC_
foo"
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.
NOTES¶
String "eval" and "LC_NUMERIC"¶
A string eval parses its expression as standard Perl. It is therefore expecting
the decimal point to be a dot. If "LC_NUMERIC" is set to have this
be a comma instead, the parsing will be confused, perhaps silently.
use locale;
use POSIX qw(locale_h);
setlocale(LC_NUMERIC, "fr_FR") or die "Pardon";
my $a = 1.2;
print eval "$a + 1.5";
print "\n";
prints "13,5". This is because in that locale, the comma is the
decimal point character. The "eval" thus expands to:
eval "1,2 + 1.5"
and the result is not what you likely expected. No warnings are generated. If
you do string "eval"'s within the scope of
"use locale", you should instead change the "eval"
line to do something like:
print eval "no locale; $a + 1.5";
This prints 2.7.
Backward compatibility¶
Versions of Perl prior to 5.004
mostly ignored locale information,
generally behaving as if something similar to the "C" locale were
always in force, even if the program environment suggested otherwise (see
"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
must use the "use locale"
pragma (see "The use locale pragma") or, in the unlikely event that
you want to do so for just pattern matching, the "/l" regular
expression modifier (see "Character set modifiers" in perlre) to
instruct it to do so.
Versions of Perl from 5.002 to 5.003 did use the "LC_CTYPE"
information if available; that is, "\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.
I18N:Collate obsolete¶
In versions of Perl prior to 5.004, per-locale collation was possible using the
"I18N::Collate" library module. This module is now mildly obsolete
and should be avoided in new applications. The "LC_COLLATE"
functionality is now integrated into the Perl core language: One can use
locale-specific scalar data completely normally with "use locale",
so there is no longer any need to juggle with the scalar references of
"I18N::Collate".
Sort speed and memory use impacts¶
Comparing and sorting by locale is usually slower than the default 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.
Freely available locale definitions¶
The Unicode CLDR project extracts the POSIX portion of many of its locales,
available at
http://unicode.org/Public/cldr/latest/
There is a large collection of locale definitions at:
http://std.dkuug.dk/i18n/WG15-collection/locales/
You should be aware that it is unsupported, and is not claimed to be fit for any
purpose. If your system allows installation of arbitrary locales, you may find
the definitions useful as they are, or as a basis for the development of your
own locales.
I18n and l10n¶
"Internationalization" is often abbreviated as
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
l10n.
An imperfect standard¶
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.
Unicode and UTF-8¶
The support of Unicode is new starting from Perl version v5.6, and more fully
implemented in versions v5.8 and later. See perluniintro.
Starting in Perl v5.20, UTF-8 locales are supported in Perl, except for
"LC_COLLATE" (use Unicode::Collate instead). If you have Perl v5.16
or v5.18 and can't upgrade, you can use
use locale ':not_characters';
When this form of the pragma is used, only the non-character portions of locales
are used by Perl, for example "LC_NUMERIC". Perl assumes that you
have translated all the characters it is to operate on into Unicode (actually
the platform's native character set (ASCII or EBCDIC) plus Unicode). For data
in files, this can conveniently be done by also specifying
use open ':locale';
This pragma arranges for all inputs from files to be translated into Unicode
from the current locale as specified in the environment (see
"ENVIRONMENT"), and all outputs to files to be translated back into
the locale. (See open). On a per-filehandle basis, you can instead use the
PerlIO::locale module, or the Encode::Locale module, both available from CPAN.
The latter module also has methods to ease the handling of "ARGV"
and environment variables, and can be used on individual strings. If you know
that all your locales will be UTF-8, as many are these days, you can use the
-C command line switch.
This form of the pragma allows essentially seamless handling of locales with
Unicode. The collation order will be by Unicode code point order. It is
strongly recommended that when you need to order and sort strings that you use
the standard module Unicode::Collate which gives much better results in many
instances than you can get with the old-style locale handling.
All the modules and switches just described can be used in v5.20 with just plain
"use locale", and, should the input locales not be UTF-8, you'll get
the less than ideal behavior, described below, that you get with pre-v5.16
Perls, or when you use the locale pragma without the
":not_characters" parameter in v5.16 and v5.18. If you are using
exclusively UTF-8 locales in v5.20 and higher, the rest of this section does
not apply to you.
There are two cases, multi-byte and single-byte locales. First multi-byte:
The only multi-byte (or wide character) locale that Perl is ever likely to
support is UTF-8. This is due to the difficulty of implementation, the fact
that high quality UTF-8 locales are now published for every area of the world
(<
http://unicode.org/Public/cldr/latest/>), and that failing all that
you can use the Encode module to translate to/from your locale. So, you'll
have to do one of those things if you're using one of these locales, such as
Big5 or Shift JIS. For UTF-8 locales, in Perls (pre v5.20) that don't have
full UTF-8 locale support, they may work reasonably well (depending on your C
library implementation) simply because both they and Perl store characters
that take up multiple bytes the same way. However, some, if not most, C
library implementations may not process the characters in the upper half of
the Latin-1 range (128 - 255) properly under "LC_CTYPE". To see if a
character is a particular type under a locale, Perl uses the functions like
"isalnum()". Your C library may not work for UTF-8 locales with
those functions, instead only working under the newer wide library functions
like "iswalnum()", which Perl does not use. These multi-byte locales
are treated like single-byte locales, and will have the restrictions described
below.
For single-byte locales, Perl generally takes the tack to use locale rules on
code points that can fit in a single byte, and Unicode rules for those that
can't (though this isn't uniformly applied, see the note at the end of this
section). This prevents many problems in locales that aren't UTF-8. Suppose
the locale is ISO8859-7, Greek. The character at 0xD7 there is a capital Chi.
But in the ISO8859-1 locale, Latin1, it is a multiplication sign. The POSIX
regular expression character class "[[:alpha:]]" will magically
match 0xD7 in the Greek locale but not in the Latin one.
However, there are places where this breaks down. Certain Perl constructs are
for Unicode only, such as "\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, "\p{Alpha}" will never match it, regardless of locale. A
similar issue occurs with "\N{...}". Prior to v5.20, It is therefore
a bad idea to use "\p{}" or "\N{}" under plain "use
locale"--
unless you can guarantee that the locale will be
ISO8859-1. Use POSIX character classes instead.
Another problem with this approach is that operations that cross the single
byte/multiple byte boundary are not well-defined, and so are disallowed. (This
boundary is between the codepoints at 255/256.) For example, lower casing
LATIN CAPITAL LETTER Y WITH DIAERESIS (U+0178) should return LATIN SMALL
LETTER Y WITH DIAERESIS (U+00FF). But in the Greek locale, for example, there
is no character at 0xFF, and Perl has no way of knowing what the character at
0xFF is really supposed to represent. Thus it disallows the operation. In this
mode, the lowercase of U+0178 is itself.
The same problems ensue if you enable automatic UTF-8-ification of your standard
file handles, default "open()" layer, and @ARGV on non-ISO8859-1,
non-UTF-8 locales (by using either the
-C command line switch or the
"PERL_UNICODE" environment variable; see perlrun). Things are read
in as UTF-8, which would normally imply a Unicode interpretation, but the
presence of a locale causes them to be interpreted in that locale instead. For
example, a 0xD7 code point in the Unicode input, which should mean the
multiplication sign, won't be interpreted by Perl that way under the Greek
locale. This is not a problem
provided you make certain that all
locales will always and only be either an ISO8859-1, or, if you don't have a
deficient C library, a UTF-8 locale.
Still another problem is that this approach can lead to two code points meaning
the same character. Thus in a Greek locale, both U+03A7 and U+00D7 are GREEK
CAPITAL LETTER CHI.
Vendor locales are notoriously buggy, and it is difficult for Perl to test its
locale-handling code because this interacts with code that Perl has no control
over; therefore the locale-handling code in Perl may be buggy as well.
(However, the Unicode-supplied locales should be better, and there is a feed
back mechanism to correct any problems. See "Freely available locale
definitions".)
If you have Perl v5.16, the problems mentioned above go away if you use the
":not_characters" parameter to the locale pragma (except for vendor
bugs in the non-character portions). If you don't have v5.16, and you
do have locales that work, using them may be worthwhile for certain
specific purposes, as long as you keep in mind the gotchas already mentioned.
For example, if the collation for your locales works, it runs faster under
locales than under Unicode::Collate; and you gain access to such things as the
local currency symbol and the names of the months and days of the week. (But
to hammer home the point, in v5.16, you get this access without the downsides
of locales by using the ":not_characters" form of the pragma.)
Note: The policy of using locale rules for code points that can fit in a byte,
and Unicode rules for those that can't is not uniformly applied. Pre-v5.12, it
was somewhat haphazard; in v5.12 it was applied fairly consistently to regular
expression matching except for bracketed character classes; in v5.14 it was
extended to all regex matches; and in v5.16 to the casing operations such as
"\L" and "uc()". For collation, in all releases so far,
the system's "strxfrm()" function is called, and whatever it does is
what you get.
BUGS¶
Broken systems¶
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 "use locale" is in effect. When
confronted with such a system, please report in excruciating detail to <
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. If you have the source for Perl, include
in the perlbug email the output of the test described above in "Testing
for broken locales".
SEE ALSO¶
I18N::Langinfo, perluniintro, perlunicode, open, "isalnum" in POSIX,
"isalpha" in POSIX, "isdigit" in POSIX,
"isgraph" in POSIX, "islower" in POSIX,
"isprint" in POSIX, "ispunct" in POSIX,
"isspace" in POSIX, "isupper" in POSIX,
"isxdigit" in POSIX, "localeconv" in POSIX,
"setlocale" in POSIX, "strcoll" in POSIX,
"strftime" in POSIX, "strtod" in POSIX,
"strxfrm" in POSIX.
For special considerations when Perl is embedded in a C program, see "Using
embedded Perl with POSIX locales" in perlembed.
HISTORY¶
Jarkko Hietaniemi's original
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.