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.
NOTE: 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 always uses the current locale - see ``NOTES''.
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:
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''.
"LC_COLLATE", "LC_CTYPE", 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''.
# 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 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 else than LC_ALL, the function returns a string naming the current locale for the category. You can use this value as the second argument in a subsequent call to setlocale().
If no second argument is provided and the category is LC_ALL, the result is implementation-dependent. It may be a string of concatenated locales 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.
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).
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.
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.
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LC_ALL = "En_US",
LANG = (unset)
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
This means that your locale settings had LC_ALL set to ``En_US'' and LANG exists but has no value. Perl tried to believe you but could not. Instead, Perl gave up and fell back to the ``C'' locale, the default locale that is supposed to work no matter what. This usually means your locale settings were wrong, they mention locales your system has never heard of, or the locale installation in your system has problems (for example, some system files are broken or missing). There are quick and temporary fixes to these problems, as well as more thorough and lasting fixes.
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 in 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.
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''.
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.
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:
# 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 $thousands_sep;
# grouping and mon_grouping are packed lists
# of small integers (characters) telling the
# grouping (thousand_seps and mon_thousand_seps
# being the group dividers) of numbers and
# monetary quantities. The integers' meanings:
# 255 means no more grouping, 0 means repeat
# the previous grouping, 1-254 means use that
# as the current grouping. Grouping goes from
# right to left (low to high digits). In the
# below we cheat slightly by never using anything
# else than the first grouping (whatever that is).
if ($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";
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.
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.
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() exist only to generate locale-dependent results, and so always obey the current "LC_COLLATE" locale.
The "LC_CTYPE" locale also provides the map used in transliterating characters between lower and uppercase. This affects the case-mapping functions---lc(), lcfirst, uc(), and ucfirst(); case-mapping interpolation with "\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 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().
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) letters and digits---for example, in command strings---locale-aware applications should use "\w" inside a "no locale" block. See ``SECURITY''.
Output produced by print() is also affected by the current locale: it corresponds to what you'd get from printf() in the ``C'' locale. The same is true for Perl's internal conversions between numeric and string formats:
use POSIX qw(strtod setlocale LC_NUMERIC);
setlocale LC_NUMERIC, "";
$n = 5/2; # Assign numeric 2.5 to $n
$a = " $n"; # Locale-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".
See also I18N::Langinfo and "CRNCYSTR".
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 that exists only to generate locale-dependent results, strftime() 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".
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:
Scalar true/false (or less/equal/greater) result is never tainted.
Result string containing interpolated material is tainted if "use locale" is in effect.
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 character), "\W" (non-alphanumeric character), "\s" (whitespace character), or "\S" (non whitespace 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".
Has the same behavior as the match operator. Also, the left operand 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".
Results are never tainted because otherwise even output from print, for example "print(1/7)", should be tainted if "use locale" is in effect.
Results are tainted if "use locale" is in effect.
Results are never tainted.
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 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.
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.
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.
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.
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.
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.
Usually locale settings and Unicode do not affect each other, but there are exceptions, see ``Locales'' in perlunicode for examples.
Last update: Thu Jun 11 08:44:13 MDT 1998