PERLLOCALE(1)
NNAAMMEE
perllocale - Perl locale handling (internationalization
and localization)
DDEESSCCRRIIPPTTIIOONN
Perl supports language-specific notions of data such as
"is this a letter", "what is the uppercase equivalent of
this letter", and "which of these letters comes first".
These are important issues, especially for languages other
than English - but also for English: it would be very
naieve to think that A-Za-z defines all the "letters".
Perl is also aware that some character other than '.' may
be preferred as a decimal point, and that output date
representations may be language-specific. The process of
making an application take account of its users'
preferences in such matters is called iinntteerrnnaattiioonnaalliizzaattiioonn
(often abbreviated as ii1188nn); telling such an application
about a particular set of preferences is known as
llooccaalliizzaattiioonn (ll1100nn).
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.
NNOOTTEE: This feature is new in Perl 5.004, and does not
apply unless an application specifically requests it - see
the section on Backward compatibility. The one exception
is that write() now aallwwaayyss uses the current locale - see
the section on NOTES.
PPRREEPPAARRIINNGG TTOO UUSSEE LLOOCCAALLEESS
If Perl applications are to be able to understand and
present your data correctly according a locale of your
choice, aallll of the following must be true:
+o YYoouurr ooppeerraattiinngg ssyysstteemm mmuusstt ssuuppppoorrtt tthhee llooccaallee ssyysstteemm.
If it does, you should find that the setlocale()
function is a documented part of its C library.
+o DDeeffiinniittiioonnss ffoorr tthhee llooccaalleess wwhhiicchh yyoouu uussee mmuusstt bbee
iinnssttaalllleedd. 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 which are not delivered with
your operating system.) Read your system
documentation for further illumination.
+o PPeerrll mmuusstt bbeelliieevvee tthhaatt tthhee llooccaallee ssyysstteemm iiss ssuuppppoorrtteedd.
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 section
on The use locale pragma) where appropriate, and aatt lleeaasstt
oonnee of the following must be true:
+o TThhee llooccaallee--ddeetteerrmmiinniinngg eennvviirroonnmmeenntt vvaarriiaabblleess ((sseeee tthhee
sseeccttiioonn oonn 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.
+o TThhee aapppplliiccaattiioonn mmuusstt sseett iittss oowwnn llooccaallee using the
method described in the section on The setlocale
function.
UUSSIINNGG LLOOCCAALLEESS
TThhee uussee llooccaallee pprraaggmmaa
By default, Perl ignores the current locale. The use
locale pragma tells Perl to use the current locale for
some operations:
+o TThhee ccoommppaarriissoonn ooppeerraattoorrss (lt, le, cmp, ge, and gt) and
the POSIX string collation functions strcoll() and
strxfrm() use LC_COLLATE. sort() is also affected if
it is used without an explicit comparison function
because it uses cmp by default.
NNoottee:: eq and ne are unaffected by the locale: they
always perform a byte-by-byte 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 byte-by-byte comparison, and only returns 0 (equal)
if the operands are bit-for-bit 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 the section on Category LC_COLLATE:
Collation.
+o RReegguullaarr eexxpprreessssiioonnss aanndd ccaassee--mmooddiiffiiccaattiioonn ffuunnccttiioonnss
(uc(), lc(), ucfirst(), and lcfirst()) use LC_CTYPE
+o TThhee ffoorrmmaattttiinngg ffuunnccttiioonnss (printf(), sprintf() and
write()) use LC_NUMERIC
+o TThhee PPOOSSIIXX ddaattee ffoorrmmaattttiinngg ffuunnccttiioonn (strftime()) uses
LC_TIME.
LC_COLLATE, LC_CTYPE, and so on, are discussed further in
the section on LOCALE CATEGORIES.
The default behavior returns with no locale or on reaching
the end of the enclosing block.
Note that the string result of any operation that uses
locale information is tainted, as it is possible for a
locale to be untrustworthy. See the section on SECURITY.
TThhee sseettllooccaallee ffuunnccttiioonn
You can switch locales as often as you wish at run time
with the POSIX::setlocale() function:
# This functionality not usable prior to Perl 5.004
require 5.004;
# Import locale-handling tool set from POSIX module.
# This example uses: setlocale -- the function call
# LC_CTYPE -- explained below
use POSIX qw(locale_h);
# 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 default defined by LC_ALL/LC_CTYPE/LANG
# environment variables. See below for documentation.
# restore the old locale
setlocale(LC_CTYPE, $old_locale);
The first argument of setlocale() gives the ccaatteeggoorryy, the
second the llooccaallee. The category tells in what aspect of
data processing you want to apply locale-specific rules.
Category names are discussed in the section on LOCALE
CATEGORIES and the section on ENVIRONMENT. The locale is
the name of a collection of customization information
corresponding to a particular combination of language,
country or territory, and codeset. Read on for hints on
the naming of locales: not all systems name locales as in
the example.
If no second argument is provided, the function returns a
string naming the current locale for the category. You
can use this value as the second argument in a subsequent
call to setlocale(). If a second argument is given and it
corresponds to a valid locale, the locale for the category
is set to that value, and the function returns the now-
current locale value. You can use this in a subsequent
call to setlocale(). (In some implementations, the return
value may sometimes differ from the value you gave as the
second argument - think of it as an alias for the value
that you gave.)
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 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 for the category is not changed, and
the function returns undef.
For further information about the categories, consult the
setlocale(3) manpage. For the locales available in your
system, also consult the setlocale(3) manpage and see
whether it leads you to the list of the 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
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 setlocale()
has been standardized, the names of the locales and the
directories where the configuration is, have not. The
basic form of the name is
language_country/territory..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 ddeeffaauulltt llooccaallee 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.
NNOOTTEE: 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.
TThhee llooccaalleeccoonnvv ffuunnccttiioonn
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
section on 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 aa rreeffeerreennccee
ttoo a hash. The keys of this hash are formatting variable
names such as decimal_point and thousands_sep; the values
are the corresponding values. See the localeconv entry in
the POSIX (3) manpage for a longer example, which lists
all the categories an implementation might be expected to
provide; some provide more and others fewer, however.
Note that you don't need use locale: as a function with
the job of querying the locale, localeconv() always
observes the current locale.
Here's a simple-minded example program which rewrites its
command line parameters as integers formatted correctly in
the current locale:
# See comments in previous example
require 5.004;
use POSIX qw(locale_h);
# Get some of locale's numeric formatting parameters
my ($thousands_sep, $grouping) =
@{localeconv()}{'thousands_sep', 'grouping'};
# Apply defaults if values are missing
$thousands_sep = ',' unless $thousands_sep;
$grouping = 3 unless $grouping;
# Format command line params for current locale
for (@ARGV) {
$_ = int; # Chop non-integer part
1 while
s/(\d)(\d{$grouping}($|$thousands_sep))/$1$thousands_sep$2/;
print "$_";
}
print "\n";
LLOOCCAALLEE CCAATTEEGGOORRIIEESS
The subsections which follow describe basic locale
categories. As well as these, there are some combination
categories which allow the manipulation of more than one
basic category at a time. See the section on ENVIRONMENT
for a discussion of these.
CCaatteeggoorryy LLCC__CCOOLLLLAATTEE:: CCoollllaattiioonn
When in the scope of use locale, Perl looks to the
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 'a' and 'aa' belong?)
Here is a code snippet that will tell you what are the
alphanumeric characters in the current locale, in the
locale 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 the section on USING LOCALES, cmp compares
according to the current collation locale when use locale
is in effect, but falls back to a byte-by-byte comparison
for strings which 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 which ignores space
characters completely, and 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 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 byte-by-byte comparisons against other
transformed strings during collation. "Under the hood",
locale-affected Perl comparison operators call strxfrm()
for both their operands, then do a byte-by-byte comparison
of the transformed strings. By calling strxfrm()
explicitly, 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 the
section on Magic Variables in the perlguts manpage)
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
cmp runs just about as fast. It also copes with null
characters embedded in strings; if you call strxfrm()
directly, it treats the first null it finds as a
terminator. And don't expect the transformed strings it
produces to be portable across systems - or even from one
revision 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, as
it isn't needed: strcoll() and strxfrm() exist only to
generate locale-dependent results, and so always obey the
current LC_COLLATE locale.
CCaatteeggoorryy LLCC__CCTTYYPPEE:: CChhaarraacctteerr TTyyppeess
When in the scope of use locale, Perl obeys the LC_CTYPE
locale setting. This controls the application's notion of
which characters are alphabetic. This affects Perl's \w
regular expression metanotation, which stands for
alphanumeric characters - that is, alphabetic and numeric
characters. (Consult the perlre manpage 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.
The 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 \l, \L, \u
or <\U> in double-quoted strings and in s///
substitutions; and case-independent regular expression
pattern matching using the i modifier.
Finally, 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().
NNoottee:: 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 (unaccented) letters and digits - for example,
in command strings - locale-aware applications should use
\w inside a no locale block. See the section on SECURITY.
CCaatteeggoorryy LLCC__NNUUMMEERRIICC:: NNuummeerriicc FFoorrmmaattttiinngg
When in the scope of use locale, Perl obeys the LC_NUMERIC
locale information, which controls application's idea of
how numbers should be formatted for human readability by
the printf(), sprintf(), and write() functions. String to
numeric conversion by the POSIX::strtod() function is also
affected. In most implementations the only effect is to
change the character used for the decimal point - perhaps
from '.' to ',': these functions aren't aware of such
niceties as thousands separation and so on. (See the
section on The localeconv function if you care about these
things.)
Note that output produced by print() is nneevveerr affected by
the current locale: it is independent of whether use
locale or no locale is in effect, and corresponds to what
you'd get from printf() in the "C" locale. The same is
true for Perl's internal conversions between numeric and
string formats:
use POSIX qw(strtod);
use locale;
$n = 5/2; # Assign numeric 2.5 to $n
$a = " $n"; # Locale-independent conversion to string
print "half five is $n\n"; # Locale-independent 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
CCaatteeggoorryy LLCC__MMOONNEETTAARRYY:: FFoorrmmaattttiinngg ooff mmoonneettaarryy aammoouunnttss
The C standard defines the LC_MONETARY category, but no
function that is affected by its contents. (Those with
experience of standards committees will recognize that the
working group decided to punt on the issue.)
Consequently, Perl takes no notice of it. If you really
want to use LC_MONETARY, you can query its contents - see
the section on The localeconv function - and use the
information that it returns in your application's own
formatting of currency amounts. However, you may well
find that the information, though voluminous and complex,
does not quite meet your requirements: currency formatting
is a hard nut to crack.
LLCC__TTIIMMEE
The 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 the 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: as a
function which exists only to generate locale-dependent
results, strftime() always obeys the current LC_TIME
locale.
OOtthheerr ccaatteeggoorriieess
The remaining locale category, LC_MESSAGES (possibly
supplemented by others in particular implementations) is
not currently used by Perl - except possibly to affect the
behavior of library functions called by extensions which
are not part of the standard Perl distribution.
SSEECCUURRIITTYY
While the main discussion of Perl security issues can be
found in the perlsec manpage, a discussion of Perl's
locale handling would be incomplete if it did not draw
your attention to locale-dependent security issues.
Locales - particularly on systems which allow unprivileged
users to build their own locales - are untrustworthy. A
malicious (or just plain broken) locale can make a locale-
aware application give unexpected results. Here are a few
possibilities:
+o Regular expression checks for safe file names or mail
addresses using \w may be spoofed by an LC_CTYPE
locale which claims that characters such as ">" and
"|" are alphanumeric.
+o 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.
+o If the decimal point character in the LC_NUMERIC
locale is surreptitiously changed from a dot to a
comma, sprintf("%g", 0.123456e3) produces a string
result of "123,456". Many people would interpret this
as one hundred and twenty-three thousand, four hundred
and fifty-six.
+o A sneaky LC_COLLATE locale could result in the names
of students with "D" grades appearing ahead of those
with "A"s.
+o An application which takes the trouble to use the
information in LC_MONETARY may format debits as if
they were credits and vice versa if that locale has
been subverted. Or it make may make payments in US
dollars instead of Hong Kong dollars.
+o 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
maliciously be modified presents similar challenges.
Similarly, they are not specific to Perl: any programming
language which allows you to write programs which take
account of their environment exposes you to these issues.
Perl cannot protect you from all of the possibilities
shown in the examples - there is no substitute for your
own vigilance - but, when use locale is in effect, Perl
uses the tainting mechanism (see the perlsec manpage) to
mark string results which become locale-dependent, and
which may be untrustworthy in consequence. Here is a
summary of the tainting behavior of operators and
functions which may be affected by the locale:
CCoommppaarriissoonn ooppeerraattoorrss (lt, le, ge, gt and cmp):
Scalar true/false (or less/equal/greater) result is
never tainted.
CCaassee--mmaappppiinngg iinntteerrppoollaattiioonn (with \l, \L, \u or <\U>)
Result string containing interpolated material is
tainted if use locale is in effect.
MMaattcchhiinngg ooppeerraattoorr (m//):
Scalar true/false result never tainted.
Subpatterns, either delivered as an array-context
result, or as $1 etc. are tainted if use locale is in
effect, and the subpattern regular expression contains
\w (to match an alphanumeric character), \W (non-
alphanumeric character), \s (white-space character),
or \S (non white-space character). The matched
pattern variable, $&, $` (pre-match), $' (post-match),
and $+ (last match) are also tainted if use locale is
in effect and the regular expression contains \w, \W,
\s, or \S.
SSuubbssttiittuuttiioonn ooppeerraattoorr (s///):
Has the same behavior as the match operator. Also,
the left operand of =~ becomes tainted when use locale
in effect, if it is modified as a result of a
substitution based on a regular expression match
involving \w, \W, \s, or \S; or of case-mapping with
\l, \L,\u or <\U>.
IInn--mmeemmoorryy ffoorrmmaattttiinngg ffuunnccttiioonn (sprintf()):
Result is tainted if "use locale" is in effect.
OOuuttppuutt ffoorrmmaattttiinngg ffuunnccttiioonnss (printf() and write()):
Success/failure result is never tainted.
CCaassee--mmaappppiinngg ffuunnccttiioonnss (lc(), lcfirst(), uc(), ucfirst()):
Results are tainted if use locale is in effect.
PPOOSSIIXX llooccaallee--ddeeppeennddeenntt ffuunnccttiioonnss (localeconv(), strcoll(),
strftime(), strxfrm()):
Results are never tainted.
PPOOSSIIXX cchhaarraacctteerr ccllaassss tteessttss (isalnum(), isalpha(),
isdigit(), isgraph(), islower(), isprint(), ispunct(),
isspace(), isupper(), 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 $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 very similar program which is locale-
aware:
#/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 when use locale is
in effect.
EENNVVIIRROONNMMEENNTT
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) is some
way - or if you mistyped the name of a locale
when you set up your environment. If this
environment variable is absent, or has a value
which does not evaluate to integer zero - that
is "0" or "" - Perl will complain about locale
setting failures.
NNOOTTEE: 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.
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.
LC_ALL LC_ALL is the "override-all" locale
environment variable. If it is set, it
overrides all the rest of the locale
environment variables.
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_....
NNOOTTEESS
BBaacckkwwaarrdd ccoommppaattiibbiilliittyy
Versions of Perl prior to 5.004 mmoossttllyy ignored locale
information, generally behaving as if something similar to
the "C" locale (see the section on 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 mmuusstt use the use locale pragma (see the section on The
use locale Pragma) to instruct it to do so.
Versions of Perl from 5.002 to 5.003 did use the LC_CTYPE
information if that was available, that is, \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.
II1188NN::CCoollllaattee oobbssoolleettee
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.
SSoorrtt ssppeeeedd aanndd mmeemmoorryy uussee iimmppaaccttss
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.
write() and LC_NUMERIC
Formats are the only part of Perl which unconditionally
use information from a program's locale; if a program's
environment specifies an LC_NUMERIC locale, it is always
used to specify the decimal point character in formatted
output. Formatted output cannot be controlled by use
locale because the pragma is tied to the block structure
of the program, and, for historical reasons, formats exist
outside that block structure.
FFrreeeellyy aavvaaiillaabbllee llooccaallee ddeeffiinniittiioonnss
There is a large collection of locale definitions at
ftp://dkuug.dk/i18n/WG15-collection. You should be aware
that it is unsupported, and is not claimed to be fit for
any purpose. If your system allows the installation of
arbitrary locales, you may find the definitions useful as
they are, or as a basis for the development of your own
locales.
II1188nn aanndd ll1100nn
"Internationalization" is often abbreviated as ii1188nn
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 ll1100nn.
AAnn iimmppeerrffeecctt ssttaannddaarrdd
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.
BBUUGGSS
BBrrookkeenn ssyysstteemmss
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 use locale is in
effect. When confronted with such a system, please report
in excruciating detail to lt;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.
SSEEEE AALLSSOO
the isalnum entry in the POSIX (3) manpage, the isalpha
entry in the POSIX (3) manpage, the isdigit entry in the
POSIX (3) manpage, the isgraph entry in the POSIX (3)
manpage, the islower entry in the POSIX (3) manpage, the
isprint entry in the POSIX (3) manpage, the ispunct entry
in the POSIX (3) manpage, the isspace entry in the POSIX
(3) manpage, the isupper entry in the POSIX (3) manpage,
the isxdigit entry in the POSIX (3) manpage, the
localeconv entry in the POSIX (3) manpage, the setlocale
entry in the POSIX (3) manpage, the strcoll entry in the
POSIX (3) manpage, the strftime entry in the POSIX (3)
manpage, the strtod entry in the POSIX (3) manpage, the
strxfrm entry in the POSIX (3) manpage
HHIISSTTOORRYY
Jarkko Hietaniemi's original perli18n.pod heavily hacked
by Dominic Dunlop, assisted by the perl5-porters.
Last update: Wed Jan 22 11:04:58 EST 1997