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diff --git a/Master/tlpkg/tlperl.straw/lib/pods/perllocale.pod b/Master/tlpkg/tlperl.straw/lib/pods/perllocale.pod deleted file mode 100755 index 3c2b3ab8ae2..00000000000 --- a/Master/tlpkg/tlperl.straw/lib/pods/perllocale.pod +++ /dev/null @@ -1,1043 +0,0 @@ -=head1 NAME - -perllocale - Perl locale handling (internationalization and localization) - -=head1 DESCRIPTION - -Perl supports language-specific notions of data such as "is this -a letter", "what is the 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 naE<iuml>ve to imagine that C<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 B<internationalization> (often abbreviated as B<i18n>); telling -such an application about a particular set of preferences is known as -B<localization> (B<l10n>). - -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. - -B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an -application specifically requests it--see L<Backward compatibility>. -The one exception is that write() now B<always> uses the current locale -- see L<"NOTES">. - -=head1 PREPARING TO USE LOCALES - -If Perl applications are to understand and present your data -correctly according a locale of your choice, B<all> of the following -must be true: - -=over 4 - -=item * - -B<Your operating system must support the locale system>. If it does, -you should find that the setlocale() function is a documented part of -its C library. - -=item * - -B<Definitions for locales that you use must be installed>. You, or -your system administrator, must make sure that this is the case. The -available locales, the location in which they are kept, and the manner -in which they are installed all vary from system to system. Some systems -provide only a few, hard-wired locales and do not allow more to be -added. Others allow you to add "canned" locales provided by the system -supplier. Still others allow you or the system administrator to define -and add arbitrary locales. (You may have to ask your supplier to -provide canned locales that are not delivered with your operating -system.) Read your system documentation for further illumination. - -=item * - -B<Perl must believe that the locale system is supported>. If it does, -C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is -C<define>. - -=back - -If you want a Perl application to process and present your data -according to a particular locale, the application code should include -the S<C<use locale>> pragma (see L<The use locale pragma>) where -appropriate, and B<at least one> of the following must be true: - -=over 4 - -=item * - -B<The locale-determining environment variables (see L<"ENVIRONMENT">) -must be correctly set up> at the time the application is started, either -by yourself or by whoever set up your system account. - -=item * - -B<The application must set its own locale> using the method described in -L<The setlocale function>. - -=back - -=head1 USING LOCALES - -=head2 The use locale pragma - -By default, Perl ignores the current locale. The S<C<use locale>> -pragma tells Perl to use the current locale for some operations: - -=over 4 - -=item * - -B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) and -the POSIX string collation functions strcoll() and strxfrm() use -C<LC_COLLATE>. sort() is also affected if used without an -explicit comparison function, because it uses C<cmp> by default. - -B<Note:> C<eq> and C<ne> are unaffected by locale: they always -perform a char-by-char comparison of their scalar operands. What's -more, if C<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 I<0> (equal) if the -operands are char-for-char identical. If you really want to know whether -two strings--which C<eq> and C<cmp> may consider different--are equal -as far as collation in the locale is concerned, see the discussion in -L<Category LC_COLLATE: Collation>. - -=item * - -B<Regular expressions and case-modification functions> (uc(), lc(), -ucfirst(), and lcfirst()) use C<LC_CTYPE> - -=item * - -B<The formatting functions> (printf(), sprintf() and write()) use -C<LC_NUMERIC> - -=item * - -B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>. - -=back - -C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in -L<LOCALE CATEGORIES>. - -The default behavior is restored with the S<C<no locale>> pragma, or -upon reaching the end of block enclosing C<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 L<"SECURITY">. - -=head2 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 - # 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 B<category>, the second the -B<locale>. The category tells in what aspect of data processing you -want to apply locale-specific rules. Category names are discussed in -L<LOCALE CATEGORIES> and L<"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 I<undef>. - -For further information about the categories, consult setlocale(3). - -=head2 Finding locales - -For locales available in your system, consult also setlocale(3) to -see whether it leads to the list of available locales (search for the -I<SEE ALSO> section). If that fails, try the following command lines: - - locale -a - - nlsinfo - - ls /usr/lib/nls/loc - - ls /usr/lib/locale - - ls /usr/lib/nls - - ls /usr/share/locale - -and see whether they list something resembling these - - en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5 - en_US.iso88591 de_DE.iso88591 ru_RU.iso88595 - en_US de_DE ru_RU - en de ru - english german russian - english.iso88591 german.iso88591 russian.iso88595 - english.roman8 russian.koi8r - -Sadly, even though the calling interface for setlocale() has been -standardized, names of locales and the directories where the -configuration resides have not been. The basic form of the name is -I<language_territory>B<.>I<codeset>, but the latter parts after -I<language> are not always present. The I<language> and I<country> -are usually from the standards B<ISO 3166> and B<ISO 639>, the -two-letter abbreviations for the countries and the languages of the -world, respectively. The I<codeset> part often mentions some B<ISO -8859> character set, the Latin codesets. For example, C<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 B<default locale> in which -every program starts in the absence of locale information in its -environment. (The I<default> default locale, if you will.) Its language -is (American) English and its character codeset ASCII. - -B<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. - -=head2 LOCALE PROBLEMS - -You may encounter the following warning message at Perl startup: - - perl: warning: Setting locale failed. - perl: warning: Please check that your locale settings: - LC_ALL = "En_US", - LANG = (unset) - are supported and installed on your system. - perl: warning: Falling back to the standard locale ("C"). - -This means that your locale settings had LC_ALL set to "En_US" and -LANG exists but has no value. Perl tried to believe you but could not. -Instead, Perl gave up and fell back to the "C" locale, the default locale -that is supposed to work no matter what. 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. - -=head2 Temporarily fixing locale problems - -The two quickest fixes are either to render Perl silent about any -locale inconsistencies or to run Perl under the default locale "C". - -Perl's moaning about locale problems can be silenced by setting the -environment variable PERL_BADLANG to a zero value, for example "0". -This method really just sweeps the problem under the carpet: you tell -Perl to shut up even when Perl sees that something is wrong. Do not -be surprised if later something locale-dependent misbehaves. - -Perl can be run under the "C" locale by setting the environment -variable LC_ALL to "C". This method is perhaps a bit more civilized -than the PERL_BADLANG approach, but setting LC_ALL (or -other locale variables) may affect other programs as well, not just -Perl. In particular, external programs run from within Perl will see -these changes. If you make the new settings permanent (read on), all -programs you run see the changes. See L<"ENVIRONMENT"> for -the full list of relevant environment variables and L<USING LOCALES> -for their effects in Perl. Effects in other programs are -easily deducible. For example, the variable LC_COLLATE may well affect -your B<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 (B<sh>, B<ksh>, B<bash>, B<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 (B<csh>, B<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. - -=head2 Permanently fixing locale problems - -The slower but superior fixes are when you may be able to yourself -fix the misconfiguration of your own environment variables. The -mis(sing)configuration of the whole system's locales usually requires -the help of your friendly system administrator. - -First, see earlier in this document about L<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 B<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 L<Permanently fixing your system's locale configuration>. - -=head2 Permanently fixing your system's locale configuration - -This is when you see something like: - - perl: warning: Please check that your locale settings: - LC_ALL = "En_US", - LANG = (unset) - are supported and installed on your system. - -but then cannot see that "En_US" listed by the above-mentioned -commands. You may see things like "en_US.ISO8859-1", but that isn't -the same. In this case, try running under a locale -that you can list and which somehow matches what you tried. The -rules for matching locale names are a bit vague because -standardization is weak in this area. See again the -L<Finding locales> about general rules. - -=head2 Fixing system locale configuration - -Contact a system administrator (preferably your own) and report the exact -error message you get, and ask them to read this same documentation you -are now reading. They should be able to check whether there is something -wrong with the locale configuration of the system. The L<Finding locales> -section is unfortunately a bit vague about the exact commands and places -because these things are not that standardized. - -=head2 The localeconv function - -The POSIX::localeconv() function allows you to get particulars of the -locale-dependent numeric formatting information specified by the current -C<LC_NUMERIC> and C<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 L<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 B<a reference to> a hash. -The keys of this hash are variable names for formatting, such as -C<decimal_point> and C<thousands_sep>. The values are the -corresponding, er, values. See L<POSIX/localeconv> 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 C<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"; - -=head2 I18N::Langinfo - -Another interface for querying locale-dependent information is the -I18N::Langinfo::langinfo() function, available at least in UNIX-like -systems and VMS. - -The following example will import the langinfo() function itself and -three constants to be used as arguments to langinfo(): a constant for -the abbreviated first day of the week (the numbering starts from -Sunday = 1) and two more constants for the affirmative and negative -answers for a yes/no question in the current locale. - - use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR); - - my ($abday_1, $yesstr, $nostr) = map { langinfo } qw(ABDAY_1 YESSTR NOSTR); - - print "$abday_1? [$yesstr/$nostr] "; - -In other words, in the "C" (or English) locale the above will probably -print something like: - - Sun? [yes/no] - -See L<I18N::Langinfo> for more information. - -=head1 LOCALE CATEGORIES - -The following subsections describe basic locale categories. Beyond these, -some combination categories allow manipulation of more than one -basic category at a time. See L<"ENVIRONMENT"> for a discussion of these. - -=head2 Category LC_COLLATE: Collation - -In the scope of S<C<use locale>>, Perl looks to the C<LC_COLLATE> -environment variable to determine the application's notions on collation -(ordering) of characters. For example, 'b' follows 'a' in Latin -alphabets, but where do 'E<aacute>' and 'E<aring>' 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 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 S<C<use -locale>> has appeared earlier in the same block) must be used for -sorting raw binary data, whereas the locale-dependent collation of the -first example is useful for natural text. - -As noted in L<USING LOCALES>, C<cmp> compares according to the current -collation locale when C<use locale> is in effect, but falls back to a -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 C<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 L<perlguts/Magic Variables>) 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 -C<cmp> runs just about as fast. It also copes with null characters -embedded in strings; if you call strxfrm() directly, it treats the first -null it finds as a terminator. don't expect the transformed strings -it produces to be portable across systems--or even from one revision -of your operating system to the next. In short, don't call strxfrm() -directly: let Perl do it for you. - -Note: C<use locale> isn't shown in some of these examples because it isn't -needed: strcoll() and strxfrm() exist only to generate locale-dependent -results, and so always obey the current C<LC_COLLATE> locale. - -=head2 Category LC_CTYPE: Character Types - -In the scope of S<C<use locale>>, Perl obeys the C<LC_CTYPE> locale -setting. This controls the application's notion of which characters are -alphabetic. This affects Perl's C<\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 L<perlre> for more information about -regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale -setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and -'E<oslash>' may be understood as C<\w> characters. - -The C<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 C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted strings -and C<s///> substitutions; and case-independent regular expression -pattern matching using the C<i> modifier. - -Finally, C<LC_CTYPE> affects the POSIX character-class test -functions--isalpha(), islower(), and so on. For example, if you move -from the "C" locale to a 7-bit Scandinavian one, you may find--possibly -to your surprise--that "|" moves from the ispunct() class to isalpha(). - -B<Note:> A broken or malicious C<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 C<\w> inside a C<no locale> block. See L<"SECURITY">. - -=head2 Category LC_NUMERIC: Numeric Formatting - -After a proper POSIX::setlocale() call, Perl obeys the C<LC_NUMERIC> -locale information, 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() -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 L<The localeconv function> if you care about these things.) - -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 L<I18N::Langinfo> and C<RADIXCHAR>. - -=head2 Category LC_MONETARY: Formatting of monetary amounts - -The C standard defines the C<LC_MONETARY> category, but no function -that is affected by its contents. (Those with experience of standards -committees will recognize that the working group decided to punt on the -issue.) Consequently, Perl takes no notice of it. If you really want -to use C<LC_MONETARY>, you can query its contents--see -L<The localeconv function>--and use the information that it returns in your -application's own 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 L<I18N::Langinfo> and C<CRNCYSTR>. - -=head2 LC_TIME - -Output produced by POSIX::strftime(), which builds a formatted -human-readable date/time string, is affected by the current C<LC_TIME> -locale. Thus, in a French locale, the output produced by the C<%B> -format element (full month name) for the first month of the year would -be "janvier". Here's how to get a list of long month names in the -current locale: - - use POSIX qw(strftime); - for (0..11) { - $long_month_name[$_] = - strftime("%B", 0, 0, 0, 1, $_, 96); - } - -Note: C<use locale> isn't needed in this example: as a function that -exists only to generate locale-dependent results, strftime() always -obeys the current C<LC_TIME> locale. - -See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>, -C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>. - -=head2 Other categories - -The remaining locale category, C<LC_MESSAGES> (possibly supplemented -by others in particular implementations) is not currently used by -Perl--except possibly to affect the behavior of library functions -called by extensions outside the standard Perl distribution and by the -operating system and its utilities. Note especially that the string -value of C<$!> and the error messages given by external utilities may -be changed by C<LC_MESSAGES>. If you want to have portable error -codes, use C<%!>. See L<Errno>. - -=head1 SECURITY - -Although the main discussion of Perl security issues can be found in -L<perlsec>, a discussion of Perl's locale handling would be incomplete -if it did not draw your attention to locale-dependent security issues. -Locales--particularly on systems that allow unprivileged users to -build their own locales--are untrustworthy. A malicious (or just plain -broken) locale can make a locale-aware application give unexpected -results. Here are a few possibilities: - -=over 4 - -=item * - -Regular expression checks for safe file names or mail addresses using -C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that -characters such as "E<gt>" and "|" are alphanumeric. - -=item * - -String interpolation with case-mapping, as in, say, C<$dest = -"C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE -case-mapping table is in effect. - -=item * - -A sneaky C<LC_COLLATE> locale could result in the names of students with -"D" grades appearing ahead of those with "A"s. - -=item * - -An application that takes the trouble to use information in -C<LC_MONETARY> may format debits as if they were credits and vice versa -if that locale has been subverted. Or it might make payments in US -dollars instead of Hong Kong dollars. - -=item * - -The date and day names in dates formatted by strftime() could be -manipulated to advantage by a malicious user able to subvert the -C<LC_DATE> locale. ("Look--it says I wasn't in the building on -Sunday.") - -=back - -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 -C<use locale> is in effect, Perl uses the tainting mechanism (see -L<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: - -=over 4 - -=item * - -B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>): - -Scalar true/false (or less/equal/greater) result is never tainted. - -=item * - -B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>) - -Result string containing interpolated material is tainted if -C<use locale> is in effect. - -=item * - -B<Matching operator> (C<m//>): - -Scalar true/false result never tainted. - -Subpatterns, either delivered as a list-context result or as $1 etc. -are tainted if C<use locale> is in effect, and the subpattern regular -expression contains C<\w> (to match an alphanumeric character), C<\W> -(non-alphanumeric character), C<\s> (whitespace character), or C<\S> -(non whitespace character). The matched-pattern variable, $&, $` -(pre-match), $' (post-match), and $+ (last match) are also tainted if -C<use locale> is in effect and the regular expression contains C<\w>, -C<\W>, C<\s>, or C<\S>. - -=item * - -B<Substitution operator> (C<s///>): - -Has the same behavior as the match operator. Also, the left -operand of C<=~> becomes tainted when C<use locale> in effect -if modified as a result of a substitution based on a regular -expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of -case-mapping with C<\l>, C<\L>,C<\u> or C<\U>. - -=item * - -B<Output formatting functions> (printf() and write()): - -Results are never tainted because otherwise even output from print, -for example C<print(1/7)>, should be tainted if C<use locale> is in -effect. - -=item * - -B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()): - -Results are tainted if C<use locale> is in effect. - -=item * - -B<POSIX locale-dependent functions> (localeconv(), strcoll(), -strftime(), strxfrm()): - -Results are never tainted. - -=item * - -B<POSIX character class tests> (isalnum(), isalpha(), isdigit(), -isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), -isxdigit()): - -True/false results are never tainted. - -=back - -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 C<\w> while C<use locale> is in effect. - -=head1 ENVIRONMENT - -=over 12 - -=item PERL_BADLANG - -A string that can suppress Perl's warning about failed locale settings -at startup. Failure can occur if the locale support in the operating -system is lacking (broken) in some way--or if you mistyped the name of -a locale when you set up your environment. If this environment -variable is absent, or has a value that does not evaluate to integer -zero--that is, "0" or ""-- Perl will complain about locale setting -failures. - -B<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. - -=back - -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. - -=over 12 - -=item LC_ALL - -C<LC_ALL> is the "override-all" locale environment variable. If -set, it overrides all the rest of the locale environment variables. - -=item LANGUAGE - -B<NOTE>: C<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 I<not> -using GNU libc and you can ignore C<LANGUAGE>. - -However, in the case you are using C<LANGUAGE>: it affects the -language of informational, warning, and error messages output by -commands (in other words, it's like C<LC_MESSAGES>) but it has higher -priority than L<LC_ALL>. Moreover, it's not a single value but -instead a "path" (":"-separated list) of I<languages> (not locales). -See the GNU C<gettext> library documentation for more information. - -=item LC_CTYPE - -In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type -locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG> -chooses the character type locale. - -=item LC_COLLATE - -In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation -(sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>, -C<LANG> chooses the collation locale. - -=item LC_MONETARY - -In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary -formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>, -C<LANG> chooses the monetary formatting locale. - -=item LC_NUMERIC - -In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format -locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG> -chooses the numeric format. - -=item LC_TIME - -In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time -formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>, -C<LANG> chooses the date and time formatting locale. - -=item LANG - -C<LANG> is the "catch-all" locale environment variable. If it is set, it -is used as the last resort after the overall C<LC_ALL> and the -category-specific C<LC_...>. - -=back - -=head2 Examples - -The LC_NUMERIC controls the numeric output: - - use locale; - use POSIX qw(locale_h); # Imports setlocale() and the LC_ constants. - setlocale(LC_NUMERIC, "fr_FR") or die "Pardon"; - printf "%g\n", 1.23; # If the "fr_FR" succeeded, probably shows 1,23. - -and also how strings are parsed by POSIX::strtod() as numbers: - - use locale; - use POSIX qw(locale_h strtod); - setlocale(LC_NUMERIC, "de_DE") or die "Entschuldigung"; - my $x = strtod("2,34") + 5; - print $x, "\n"; # Probably shows 7,34. - -=head1 NOTES - -=head2 Backward compatibility - -Versions of Perl prior to 5.004 B<mostly> ignored locale information, -generally behaving as if something similar to the C<"C"> locale were -always in force, even if the program environment suggested otherwise -(see L<The setlocale function>). By default, Perl still behaves this -way for backward compatibility. If you want a Perl application to pay -attention to locale information, you B<must> use the S<C<use locale>> -pragma (see L<The use locale pragma>) to instruct it to do so. - -Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE> -information if available; that is, C<\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. - -=head2 I18N:Collate obsolete - -In versions of Perl prior to 5.004, per-locale collation was possible -using the C<I18N::Collate> library module. This module is now mildly -obsolete and should be avoided in new applications. The C<LC_COLLATE> -functionality is now integrated into the Perl core language: One can -use locale-specific scalar data completely normally with C<use locale>, -so there is no longer any need to juggle with the scalar references of -C<I18N::Collate>. - -=head2 Sort speed and memory use impacts - -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. - -=head2 write() and LC_NUMERIC - -Formats are the only part of Perl that unconditionally use information -from a program's locale; if a program's environment specifies an -LC_NUMERIC locale, it is always used to specify the decimal point -character in formatted output. Formatted output cannot be controlled by -C<use locale> because the pragma is tied to the block structure of the -program, and, for historical reasons, formats exist outside that block -structure. - -=head2 Freely available locale definitions - -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 -definitions useful as they are, or as a basis for the development of -your own locales. - -=head2 I18n and l10n - -"Internationalization" is often abbreviated as B<i18n> because its first -and last letters are separated by eighteen others. (You may guess why -the internalin ... internaliti ... i18n tends to get abbreviated.) In -the same way, "localization" is often abbreviated to B<l10n>. - -=head2 An imperfect standard - -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. - -=head1 Unicode and UTF-8 - -The support of Unicode is new starting from Perl version 5.6, and -more fully implemented in the version 5.8. See L<perluniintro> and -L<perlunicode> for more details. - -Usually locale settings and Unicode do not affect each other, but -there are exceptions, see L<perlunicode/Locales> for examples. - -=head1 BUGS - -=head2 Broken systems - -In certain systems, the operating system's locale support -is broken and cannot be fixed or used by Perl. Such deficiencies can -and will result in mysterious hangs and/or Perl core dumps when the -C<use locale> is in effect. When confronted with such a system, -please report in excruciating detail to <F<perlbug@perl.org>>, 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. - -=head1 SEE ALSO - -L<I18N::Langinfo>, L<perluniintro>, L<perlunicode>, L<open>, -L<POSIX/isalnum>, L<POSIX/isalpha>, -L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>, -L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>, -L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>, -L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>, -L<POSIX/strtod>, L<POSIX/strxfrm>. - -=head1 HISTORY - -Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic -Dunlop, assisted by the perl5-porters. Prose worked over a bit by -Tom Christiansen. - -Last update: Thu Jun 11 08:44:13 MDT 1998 |