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PERLLOCALE(1) Perl Programmers Reference Guide PERLLOCALE(1)

NAME

perllocale - Perl locale handling (internationalization and localiza-

tion)

DESCRIPTION

Perl supports language-specific notions of data such as "is this a let-

ter", "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 naieve

to imagine that "A-Za-z" defines all the "letters" needed to write in

English. Perl is also aware that some character other than '.' may be preferred as a decimal point, and that output date representations may

be language-specific. The process of making an application take

account of its users' preferences in such matters is called iinntteerrnnaa-

ttiioonnaalliizzaattiioonn (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 "Backward compatibility".

The one exception is that write() now aallwwaayyss uses the current locale -

see "NOTES".

PPRREEPPAARRIINNGG TTOO UUSSEE LLOOCCAALLEESS If Perl applications are 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 llooccaalleess tthhaatt 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 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 documenta-

tion for further illumination. +o PPeerrll mmuusstt bbeelliieevvee tthhaatt tthhee llooccaallee ssyysstteemm iiss ssuuppppoorrtteedd. If it does,

"perl -V:dsetlocale" will say that the value for "dsetlocale" is

"define".

If you want a Perl application to process and present your data accord-

ing to a particular locale, the application code should include the "use locale" pragma (see "The use locale pragma") where appropriate, and aatt lleeaasstt oonnee of the following must be true: o The localedetermining environment variables (see "ENVIRONMENT") mmuusstt bbee ccoorrrreeccttllyy sseett uupp at the time the application is started, either by yourself or by whoever set up your system account. o The application must set its own locale sn te ehd ecie in "The setlocale function". UUSSIINNGG LLOOCCAALLEESS The use locale pragma By default, Perl ignores the current locale. The "use locale" pragma tells Perl to use the current locale for some operations: o The comparison operators "t, l" "m" "e, n "t) n the POSIX string collation functions strcoll() and strxfrm() use "LCCOLLATE". sort() is also affected if used without an explicit comparison function, because it uses "cmp" by default. NNoottee:: "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 LCCOLLATE: Collation".

+o RReegguullaarr eexxpprreessssiioonnss aanndd ccaassee-mmooddiiffiiccaattiioonn ffuunnccttiioonnss (uc(), lc(),

ucfirst(), and lcfirst()) use "LCCTYPE" o The formatting functions pit(, pit( ad rt() s "LCNUMERIC" o The POSIX date formatting function srtm() ss LTM" "LCCOLLATE", "LCCTYPE", and so on, are discussed further in "LOCALE CATEGORIES". The default behavior is restored with the "no locale" pragma, or upon reaching the end of block enclosing "use locale". 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:

# 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

# LCCTYPE - explained below

use POSIX qw(localeh);

# query and save the old locale

$oldlocale = setlocale(LCCTYPE);

setlocale(LCCTYPE, "frCA.ISO8859-1");

# LCCTYPE now in locale "French, Canada, codeset ISO 8859-1"

setlocale(LCCTYPE, "");

# LCCTYPE now reset to default defined by LCALL/LCCTYPE/LANG

# environment variables. See below for documentation.

# restore the old locale

setlocale(LCCTYPE, $oldlocale);

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

"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 else than LCALL, the function returns a string naming the current locale for the category. You can use this value as the second argument in a subsequent call to setlocale(). If no second argument is provided and the category is LCALL, the

result is implementation-dependent. It may be a string of concatenated

locales names (separator also implementation-dependent) or a single

locale name. Please consult your setlocale(3) 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 corre-

sponding 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. 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 setlocale(3). FFiinnddiinngg llooccaalleess 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

enUS.ISO8859-1 deDE.ISO8859-1 ruRU.ISO8859-5

enUS.iso88591 deDE.iso88591 ruRU.iso88595 enUS deDE ruRU 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 stan-

dardized, names of locales and the directories where the configuration

resides have not been. The basic form of the name is languageterri-

tory..codeset, but the latter parts after language are not always present. The language and country are usually from the standards IISSOO

33116666 and IISSOO 663399, the two-letter abbreviations for the countries and

the languages of the world, respectively. The codeset part often men-

tions some IISSOO 88885599 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 ddeeffaauulltt llooccaallee in which every pro-

gram 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. LLOOCCAALLEE PPRROOBBLLEEMMSS You may encounter the following warning message at Perl startup: perl: warning: Setting locale failed. perl: warning: Please check that your locale settings: LCALL = "EnUS", 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 LCALL set to "EnUS" and LANG exists but has no value. Perl tried to believe you but could not. Instead, Perl gave up and fell back to the "C" locale, the default locale that is supposed to work no matter what. This usually means your locale settings were wrong, they mention locales your system has never heard of, or the locale installation in your system has problems (for example, some system files are broken or missing). There are quick and temporary fixes to these problems, as well as more thorough and lasting fixes. TTeemmppoorraarriillyy ffiixxiinngg llooccaallee pprroobblleemmss 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 PERLBADLANG 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 vari-

able LCALL to "C". This method is perhaps a bit more civilized than

the PERLBADLANG approach, but setting LCALL (or other locale vari-

ables) may affect other programs as well, not just Perl. In particu-

lar, 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 LCCOL-

LATE may well affect your ssoorrtt program (or whatever the program that arranges `records' alphabetically in your system is called). You can test out changing these variables temporarily, and if the new settings seem to help, put those settings into your shell startup files. Consult your local documentation for the exact details. For in

Bourne-like shells (sshh, kksshh, bbaasshh, zzsshh):

LCALL=enUS.ISO8859-1

export LCALL

This assumes that we saw the locale "enUS.ISO8859-1" using the com-

mands discussed above. We decided to try that instead of the above

faulty locale "EnUS"-and in Cshish shells (ccsshh, ttccsshh)

setenv LCALL enUS.ISO8859-1

or if you have the "env" application you can do in any shell

env LCALL=enUS.ISO8859-1 perl ...

If you do not know what shell you have, consult your local helpdesk or the equivalent. PPeerrmmaanneennttllyy ffiixxiinngg llooccaallee pprroobblleemmss 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 impor-

tantly, installed-on your system. In our example error message, envi-

ronment variables affecting the locale are listed in the order of decreasing importance (and unset variables do not matter). Therefore, having LCALL set to "EnUS" 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 eexxaaccttllyy (prefix matches do not count and case usually counts) like "EnUS" 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". PPeerrmmaanneennttllyy ffiixxiinngg yyoouurr ssyysstteemm''ss llooccaallee ccoonnffiigguurraattiioonn This is when you see something like: perl: warning: Please check that your locale settings: LCALL = "EnUS", LANG = (unset) are supported and installed on your system.

but then cannot see that "EnUS" listed by the above-mentioned com-

mands. You may see things like "enUS.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. FFiixxiinngg ssyysstteemm llooccaallee ccoonnffiigguurraattiioonn Contact a system administrator (preferably your own) and report the

exact error message you get, and ask them to read this same documenta-

tion 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 cur-

rent "LCNUMERIC" and "LCMONETARY" locales. (If you just want the

name of the current locale for a particular category, use POSIX::setlo-

cale() with a single parameter-see "The setlocale function".)

use POSIX qw(localeh);

# Get a reference to a hash of locale-dependent info

$localevalues = localeconv();

# Output sorted list of the values

for (sort keys %$localevalues) {

printf "%-20s = %s\n", $, $localevalues->{$}

} localeconv() takes no arguments, and returns aa rreeffeerreennccee ttoo a hash.

The keys of this hash are variable names for formatting, such as "deci-

malpoint" and "thousandssep". 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:

# See comments in previous example

require 5.004; use POSIX qw(localeh);

# Get some of locale's numeric formatting parameters

my ($thousandssep, $grouping) =

@{localeconv()}{'thousandssep', 'grouping'};

# Apply defaults if values are missing

$thousandssep = ',' unless $thousandssep;

# grouping and mongrouping are packed lists

# of small integers (characters) telling the

# grouping (thousandseps and monthousandseps

# 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{$grouping[0]}($|$thousandssep))/$1$thousandssep$2/;

print "$";

} print "\n"; II1188NN::::LLaannggiinnffoo

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 ABDAY1 YESSTR NOSTR);

my ($abday1, $yesstr, $nostr) = map { langinfo } qw(ABDAY1 YESSTR NOSTR);

print "$abday1? [$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. LLOOCCAALLEE CCAATTEEGGOORRIIEESS 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. CCaatteeggoorryy LLCCCCOOLLLLAATTEE:: CCoollllaattiioonn

In the scope of "use locale", Perl looks to the "LCCOLLATE" environ-

ment variable to determine the application's notions on collation

(ordering) of characters. For example, 'b' follows 'a' in Latin alpha-

bets, but where do 'a' and 'aa' belong? And while 'color' follows 'chocolate' in English, what about in Spanish? The following collations all make sense and you may meet any of them if you "use locale". 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 cur-

rent 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);

$equalinlocale =

!strcoll("space and case ignored", "SpaceAndCaseIgnored");

$equalinlocale will be true if the collation locale specifies a dic-

tionary-like ordering that ignores space characters completely and

which folds case. If you have a single string that you want to check for "equality in locale" against several others, you might think you could gain a little efficiency by using POSIX::strxfrm() in conjunction with "eq": use POSIX qw(strxfrm);

$xfrmstring = strxfrm("Mixed-case string");

print "locale collation ignores spaces\n"

if $xfrmstring eq strxfrm("Mixed-casestring");

print "locale collation ignores hyphens\n"

if $xfrmstring eq strxfrm("Mixedcase string");

print "locale collation ignores case\n"

if $xfrmstring 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() exist only to generate locale-

dependent results, and so always obey the current "LCCOLLATE" locale. CCaatteeggoorryy LLCCCCTTYYPPEE:: CChhaarraacctteerr TTyyppeess In the scope of "use locale", Perl obeys the "LCCTYPE" locale setting.

This controls the application's notion of which characters are alpha-

betic. This affects Perl's "\w" regular expression metanotation, which

stands for alphanumeric characters-that is, alphabetic, numeric, and

including other special characters such as the underscore or hyphen. (Consult perlre for more information about regular expressions.) Thanks to "LCCTYPE", depending on your locale setting, characters like 'ae', 'd`', 'ss', and 'o' may be understood as "\w" characters. The "LCCTYPE" locale also provides the map used in transliterating

characters between lower and uppercase. This affects the case-mapping

functions-lc(), lcfirst, uc(), and ucfirst(); case-mapping interpola-

tion with "\l", "\L", "\u", or "\U" in double-quoted strings and "s///"

substitutions; and case-independent regular expression pattern matching

using the "i" modifier.

Finally, "LCCTYPE" affects the POSIX character-class test func-

tions-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 "LCCTYPE" locale definition may result in clearly ineligible characters being considered to be alphanumeric by

your application. For strict matching of (mundane) letters and dig-

its-for example, in command strings-locale-aware applications should

use "\w" inside a "no locale" block. See "SECURITY". CCaatteeggoorryy LLCCNNUUMMEERRIICC:: NNuummeerriicc FFoorrmmaattttiinngg

In the scope of "use locale", Perl obeys the "LCNUMERIC" locale infor-

mation, which controls an application's idea of how numbers should be formatted for human readability by the printf(), sprintf(), and write()

functions. String-to-numeric conversion by the POSIX::strtod() func-

tion 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 sepa-

ration and so on. (See "The localeconv function" if you care about these things.) Output produced by print() is also affected by the current locale: it

depends on whether "use locale" or "no locale" is in effect, and corre-

sponds to what you'd get from printf() in the "C" locale. The same is

true for Perl's internal conversions between numeric and string for-

mats: use POSIX qw(strtod); use locale;

$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". CCaatteeggoorryy LLCCMMOONNEETTAARRYY:: FFoorrmmaattttiinngg ooff mmoonneettaarryy aammoouunnttss The C standard defines the "LCMONETARY" category, but no function that

is affected by its contents. (Those with experience of standards com-

mittees 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 "LCMONETARY", you can query its contents-see "The localeconv

function"-and use the information that it returns in your applica-

tion'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". LLCCTTIIMMEE

Output produced by POSIX::strftime(), which builds a formatted human-

readable date/time string, is affected by the current "LCTIME" 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) {

$longmonthname[$] =

strftime("%B", 0, 0, 0, 1, $, 96);

} Note: "use locale" isn't needed in this example: as a function that

exists only to generate locale-dependent results, strftime() always

obeys the current "LCTIME" locale. See also I18N::Langinfo and "ABDAY1".."ABDAY7", "DAY1".."DAY7", "ABMON1".."ABMON12", and "ABMON1".."ABMON12". OOtthheerr ccaatteeggoorriieess The remaining locale category, "LCMESSAGES" (possibly supplemented by others in particular implementations) is not currently used by

Perl-except possibly to affect the behavior of library functions

called by extensions outside the standard Perl distribution and by the operating system and its utilities. Note especially that the string

value of $! and the error messages given by external utilities may be

changed by "LCMESSAGES". If you want to have portable error codes,

use "%!". See Errno.

SSEECCUURRIITTYY 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 bro-

ken) 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 "LCCTYPE" locale that 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

LCCTYPE case-mapping table is in effect.

+o A sneaky "LCCOLLATE" locale could result in the names of students with "D" grades appearing ahead of those with "A"s. +o An application that takes the trouble to use information in "LCMONETARY" 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. +o The date and day names in dates formatted by strftime() could be manipulated to advantage by a malicious user able to subvert the

"LCDATE" locale. ("Look-it says I wasn't in the building on Sun-

day.") 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 pro-

gramming 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 exam-

ples-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 behav-

ior of operators and functions that may be affected by the locale: +o CCoommppaarriissoonn ooppeerraattoorrss ("lt", "le", "ge", "gt" and "cmp"): Scalar true/false (or less/equal/greater) result is never tainted.

+o CCaassee-mmaappppiinngg iinntteerrppoollaattiioonn (with "\l", "\L", "\u" or "\U")

Result string containing interpolated material is tainted if "use locale" is in effect. +o MMaattcchhiinngg ooppeerraattoorr ("m//"): Scalar true/false result never tainted.

Subpatterns, either delivered as a list-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 charac-

ter), "\W" (non-alphanumeric character), "\s" (white-space charac-

ter), 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". +o SSuubbssttiittuuttiioonn ooppeerraattoorr ("s///"):

Has the same behavior as the match operator. Also, the left oper-

and of "=~" becomes tainted when "use locale" in effect if 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". +o OOuuttppuutt ffoorrmmaattttiinngg ffuunnccttiioonnss (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.

+o CCaassee-mmaappppiinngg ffuunnccttiioonnss (lc(), lcfirst(), uc(), ucfirst()):

Results are tainted if "use locale" is in effect.

+o PPOOSSIIXX llooccaallee-ddeeppeennddeenntt ffuunnccttiioonnss (localeconv(), strcoll(), strf-

time(), strxfrm()): Results are never tainted. +o 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 pro-

gram, 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...

$taintedoutputfile = shift;

open(F, ">$taintedoutputfile")

or warn "Open of $untaintedoutputfile 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

$taintedoutputfile = shift;

$taintedoutputfile =~ m%[\w/]+%;

$untaintedoutputfile = $&;

open(F, ">$untaintedoutputfile")

or warn "Open of $untaintedoutputfile failed: $!\n";

Compare this with a similar but locale-aware program:

#/usr/local/bin/perl -T

$taintedoutputfile = shift;

use locale;

$taintedoutputfile =~ m%[\w/]+%;

$localizedoutputfile = $&;

open(F, ">$localizedoutputfile")

or warn "Open of $localizedoutputfile 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 PERLBADLANG 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. NNOOTTEE: PERLBADLANG only gives you a way to hide the warning

message. The message tells about some problem in your sys-

tem'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.

LCALL "LCALL" is the "override-all" locale environment variable.

If set, it overrides all the rest of the locale environment variables. LANGUAGE NNOOTTEE: "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 "LCMES-

SAGES") but it has higher priority than LCALL. 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.

LCCTYPE In the absence of "LCALL", "LCCTYPE" chooses the charac-

ter type locale. In the absence of both "LCALL" and "LCCTYPE", "LANG" chooses the character type locale.

LCCOLLATE In the absence of "LCALL", "LCCOLLATE" chooses the colla-

tion (sorting) locale. In the absence of both "LCALL" and "LCCOLLATE", "LANG" chooses the collation locale.

LCMONETARY In the absence of "LCALL", "LCMONETARY" chooses the mone-

tary formatting locale. In the absence of both "LCALL" and "LCMONETARY", "LANG" chooses the monetary formatting locale. LCNUMERIC In the absence of "LCALL", "LCNUMERIC" chooses the numeric format locale. In the absence of both "LCALL" and "LCNUMERIC", "LANG" chooses the numeric format. LCTIME In the absence of "LCALL", "LCTIME" chooses the date and time formatting locale. In the absence of both "LCALL" and "LCTIME", "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

"LCALL" and the category-specific "LC...".

NNOOTTEESS BBaacckkwwaarrdd ccoommppaattiibbiilliittyy

Versions of Perl prior to 5.004 mmoossttllyy ignored locale information, gen-

erally 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 atten-

tion to locale information, you mmuusstt use the "use locale" pragma (see "The use locale pragma") to instruct it to do so. Versions of Perl from 5.002 to 5.003 did use the "LCCTYPE" 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. 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 "LCCOLLATE" 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 colla-

tion 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() aanndd LLCCNNUUMMEERRIICC Formats are the only part of Perl that unconditionally use information from a program's locale; if a program's environment specifies an

LCNUMERIC locale, it is always used to specify the decimal point char-

acter 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 installation of arbitrary locales, you may find the defi-

nitions 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 use-

ful 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.

UUnniiccooddee aanndd UUTTFF-88

The support of Unicode is new starting from Perl version 5.6, and more fully implemented in the version 5.8. See perluniintro and perlunicode for more details. Usually locale settings and Unicode do not affect each other, but there are exceptions, see "Locales" in perlunicode for examples.

BUGS

BBrrookkeenn ssyysstteemmss In certain systems, the operating system's locale support is broken and cannot be fixed or used by Perl. Such deficiencies can and will result in mysterious hangs and/or Perl core dumps when the "use locale" is in

effect. When confronted with such a system, please report in excruci-

ating detail to , and complain to your vendor: bug fixes may exist for these problems in your operating system. Sometimes such bug fixes are called an operating system upgrade.