IRIX Base Documentation 1998 November/IRIX 6.5.2 Base Documentation November 1998.img/usr/share/catman/u_man/cat1/perllocale.z/perllocale

Text File | 1998-10-30 | 49KB | 991 lines

PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



NNNNAAAAMMMMEEEE
     perllocale - Perl locale handling (internationalization and localization)

DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
     Perl supports language-specific notions of data such as "is this a
     letter", "what is the uppercase equivalent of this letter", and "which of
     these letters comes first".  These are important issues, especially for
     languages other than English - but also for English: it would be very
     naieve to think that A-Za-z defines all the "letters". Perl is also aware
     that some character other than '.' may be preferred as a decimal point,
     and that output date representations may be language-specific.  The
     process of making an application take account of its users' preferences
     in such matters is called iiiinnnntttteeeerrrrnnnnaaaattttiiiioooonnnnaaaalllliiiizzzzaaaattttiiiioooonnnn (often abbreviated as
     iiii11118888nnnn); telling such an application about a particular set of preferences
     is known as llllooooccccaaaalllliiiizzzzaaaattttiiiioooonnnn (llll11110000nnnn).

     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.

     NNNNOOOOTTTTEEEE: This feature is new in Perl 5.004, and does not apply unless an
     application specifically requests it - see the section on _B_a_c_k_w_a_r_d
     _c_o_m_p_a_t_i_b_i_l_i_t_y.  The one exception is that _w_r_i_t_e() now aaaallllwwwwaaaayyyyssss uses the
     current locale - see the section on _N_O_T_E_S.

PPPPRRRREEEEPPPPAAAARRRRIIIINNNNGGGG TTTTOOOO UUUUSSSSEEEE LLLLOOOOCCCCAAAALLLLEEEESSSS
     If Perl applications are to be able to understand and present your data
     correctly according a locale of your choice, aaaallllllll of the following must be
     true:

     +o   YYYYoooouuuurrrr ooooppppeeeerrrraaaattttiiiinnnngggg ssssyyyysssstttteeeemmmm mmmmuuuusssstttt ssssuuuuppppppppoooorrrrtttt tttthhhheeee llllooooccccaaaalllleeee ssssyyyysssstttteeeemmmm.  If it does,
         you should find that the _s_e_t_l_o_c_a_l_e() function is a documented part of
         its C library.

     +o   DDDDeeeeffffiiiinnnniiiittttiiiioooonnnnssss ffffoooorrrr tttthhhheeee llllooooccccaaaalllleeeessss wwwwhhhhiiiicccchhhh yyyyoooouuuu uuuusssseeee mmmmuuuusssstttt bbbbeeee iiiinnnnssssttttaaaalllllllleeeedddd.  You, or
         your system administrator, must make sure that this is the case. The
         available locales, the location in which they are kept, and the
         manner in which they are installed, vary from system to system.  Some
         systems provide only a few, hard-wired, locales, and do not allow
         more to be added; others allow you to add "canned" locales provided
         by the system supplier; still others allow you or the system
         administrator to define and add arbitrary locales.  (You may have to
         ask your supplier to provide canned locales which are not delivered
         with your operating system.)  Read your system documentation for
         further illumination.

     +o   PPPPeeeerrrrllll mmmmuuuusssstttt bbbbeeeelllliiiieeeevvvveeee tttthhhhaaaatttt tttthhhheeee llllooooccccaaaalllleeee ssssyyyysssstttteeeemmmm iiiissss ssssuuuuppppppppoooorrrrtttteeeedddd.  If it does,
         perl -V:d_setlocale will say that the value for d_setlocale is
         define.





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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     If you want a Perl application to process and present your data according
     to a particular locale, the application code should include the use
     locale pragma (see the section on _T_h_e _u_s_e _l_o_c_a_l_e _p_r_a_g_m_a) where
     appropriate, and aaaatttt lllleeeeaaaasssstttt oooonnnneeee of the following must be true:

     +o   TTTThhhheeee llllooooccccaaaalllleeee----ddddeeeetttteeeerrrrmmmmiiiinnnniiiinnnngggg eeeennnnvvvviiiirrrroooonnnnmmmmeeeennnntttt vvvvaaaarrrriiiiaaaabbbblllleeeessss ((((sssseeeeeeee tttthhhheeee sssseeeeccccttttiiiioooonnnn oooonnnn
         _E_N_V_I_R_O_N_M_E_N_T) must be correctly set up, either by yourself, or by the
         person who set up your system account, at the time the application is
         started.

     +o   TTTThhhheeee aaaapppppppplllliiiiccccaaaattttiiiioooonnnn mmmmuuuusssstttt sssseeeetttt iiiittttssss oooowwwwnnnn llllooooccccaaaalllleeee using the method described in
         the section on _T_h_e _s_e_t_l_o_c_a_l_e _f_u_n_c_t_i_o_n.

UUUUSSSSIIIINNNNGGGG LLLLOOOOCCCCAAAALLLLEEEESSSS
     TTTThhhheeee uuuusssseeee llllooooccccaaaalllleeee pppprrrraaaaggggmmmmaaaa

     By default, Perl ignores the current locale.  The use locale pragma tells
     Perl to use the current locale for some operations:

     +o   TTTThhhheeee ccccoooommmmppppaaaarrrriiiissssoooonnnn ooooppppeeeerrrraaaattttoooorrrrssss (lt, le, cmp, ge, and gt) and the POSIX
         string collation functions _s_t_r_c_o_l_l() and _s_t_r_x_f_r_m() use LC_COLLATE.
         _s_o_r_t() is also affected if it is used without an explicit comparison
         function because it uses cmp by default.

         NNNNooootttteeee:::: eq and ne are unaffected by the locale: they always perform a
         byte-by-byte comparison of their scalar operands.  What's more, if
         cmp finds that its operands are equal according to the collation
         sequence specified by the current locale, it goes on to perform a
         byte-by-byte comparison, and only returns _0 (equal) if the operands
         are bit-for-bit identical.  If you really want to know whether two
         strings - which eq and cmp may consider different - are equal as far
         as collation in the locale is concerned, see the discussion in the
         section on _C_a_t_e_g_o_r_y _L_C__C_O_L_L_A_T_E: _C_o_l_l_a_t_i_o_n.

     +o   RRRReeeegggguuuullllaaaarrrr eeeexxxxpppprrrreeeessssssssiiiioooonnnnssss aaaannnndddd ccccaaaasssseeee----mmmmooooddddiiiiffffiiiiccccaaaattttiiiioooonnnn ffffuuuunnnnccccttttiiiioooonnnnssss (_u_c(), _l_c(),
         _u_c_f_i_r_s_t(), and _l_c_f_i_r_s_t()) use LC_CTYPE

     +o   TTTThhhheeee ffffoooorrrrmmmmaaaattttttttiiiinnnngggg ffffuuuunnnnccccttttiiiioooonnnnssss (_p_r_i_n_t_f(), _s_p_r_i_n_t_f() and _w_r_i_t_e()) use
         LC_NUMERIC

     +o   TTTThhhheeee PPPPOOOOSSSSIIIIXXXX ddddaaaatttteeee ffffoooorrrrmmmmaaaattttttttiiiinnnngggg ffffuuuunnnnccccttttiiiioooonnnn (_s_t_r_f_t_i_m_e()) uses LC_TIME.

     LC_COLLATE, LC_CTYPE, and so on, are discussed further in the section on
     _L_O_C_A_L_E _C_A_T_E_G_O_R_I_E_S.

     The default behavior returns with no locale or on reaching the end of the
     enclosing block.

     Note that the string result of any operation that uses locale information
     is tainted, as it is possible for a locale to be untrustworthy.  See the
     section on _S_E_C_U_R_I_T_Y.




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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     TTTThhhheeee sssseeeettttllllooooccccaaaalllleeee ffffuuuunnnnccccttttiiiioooonnnn

     You can switch locales as often as you wish at run time with the
     _P_O_S_I_X::_s_e_t_l_o_c_a_l_e() 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 _s_e_t_l_o_c_a_l_e() gives the ccccaaaatttteeeeggggoooorrrryyyy, the second the
     llllooooccccaaaalllleeee.  The category tells in what aspect of data processing you want to
     apply locale-specific rules.  Category names are discussed in the section
     on _L_O_C_A_L_E _C_A_T_E_G_O_R_I_E_S and the section on _E_N_V_I_R_O_N_M_E_N_T.  The locale is the
     name of a collection of customization information corresponding to a
     particular combination of language, country or territory, and codeset.
     Read on for hints on the naming of locales: not all systems name locales
     as in the example.

     If no second argument is provided, the function returns a string naming
     the current locale for the category.  You can use this value as the
     second argument in a subsequent call to _s_e_t_l_o_c_a_l_e().  If a second
     argument is given and it corresponds to a valid locale, the locale for
     the category is set to that value, and the function returns the now-
     current locale value.  You can use this in a subsequent call to
     _s_e_t_l_o_c_a_l_e().  (In some implementations, the return value may sometimes
     differ from the value you gave as the second argument - think of it as an
     alias for the value that you gave.)

     As the example shows, if the second argument is an empty string, the
     category's locale is returned to the default specified by the
     corresponding environment variables.  Generally, this results in a return
     to the default which was in force when Perl started up: changes to the
     environment made by the application after startup may or may not be
     noticed, depending on the implementation of your system's C library.




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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     If the second argument does not correspond to a valid locale, the locale
     for the category is not changed, and the function returns _u_n_d_e_f.

     For further information about the categories, consult the _s_e_t_l_o_c_a_l_e(_3)
     manpage.  For the locales available in your system, also consult the
     _s_e_t_l_o_c_a_l_e(_3) manpage and see whether it leads you to the list of the
     available locales (search for the _S_E_E _A_L_S_O section).  If that fails, try
     the following command lines:

             locale -a

             nlsinfo

             ls /usr/lib/nls/loc

             ls /usr/lib/locale

             ls /usr/lib/nls

     and see whether they list something resembling these

             en_US.ISO8859-1     de_DE.ISO8859-1     ru_RU.ISO8859-5
             en_US               de_DE               ru_RU
             en                  de                  ru
             english             german              russian
             english.iso88591    german.iso88591     russian.iso88595

     Sadly, even though the calling interface for _s_e_t_l_o_c_a_l_e() has been
     standardized, the names of the locales and the directories where the
     configuration is, have not.  The basic form of the name is
     _l_a_n_g_u_a_g_e__c_o_u_n_t_r_y/_t_e_r_r_i_t_o_r_y...._c_o_d_e_s_e_t, but the latter parts are not always
     present.

     Two special locales are worth particular mention: "C" and "POSIX".
     Currently these are effectively the same locale: the difference is mainly
     that the first one is defined by the C standard and the second by the
     POSIX standard.  What they define is the ddddeeeeffffaaaauuuulllltttt llllooooccccaaaalllleeee 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.

     NNNNOOOOTTTTEEEE: 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.

     TTTThhhheeee llllooooccccaaaalllleeeeccccoooonnnnvvvv ffffuuuunnnnccccttttiiiioooonnnn

     The _P_O_S_I_X::_l_o_c_a_l_e_c_o_n_v() function allows you to get particulars of the
     locale-dependent numeric formatting information specified by the current
     LC_NUMERIC and LC_MONETARY locales.  (If you just want the name of the
     current locale for a particular category, use _P_O_S_I_X::_s_e_t_l_o_c_a_l_e() with a
     single parameter - see the section on _T_h_e _s_e_t_l_o_c_a_l_e _f_u_n_c_t_i_o_n.)



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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



             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", $_, $locale_values->{$_}
             }

     _l_o_c_a_l_e_c_o_n_v() takes no arguments, and returns aaaa rrrreeeeffffeeeerrrreeeennnncccceeee ttttoooo a hash.  The
     keys of this hash are formatting variable names such as decimal_point and
     thousands_sep; the values are the corresponding values.  See the
     localeconv entry in the _P_O_S_I_X (_3) manpage for a longer example, which
     lists all the categories an implementation might be expected to provide;
     some provide more and others fewer, however.  Note that you don't need
     use locale: as a function with the job of querying the locale,
     _l_o_c_a_l_e_c_o_n_v() always observes the current locale.

     Here's a simple-minded example program which rewrites its command line
     parameters as integers formatted correctly in the current locale:

             # See comments in previous example
             require 5.004;
             use POSIX qw(locale_h);

             # Get some of locale's numeric formatting parameters
             my ($thousands_sep, $grouping) =
                  @{localeconv()}{'thousands_sep', 'grouping'};

             # Apply defaults if values are missing
             $thousands_sep = ',' unless $thousands_sep;
             $grouping = 3 unless $grouping;

             # Format command line params for current locale
             for (@ARGV) {
                 $_ = int;    # Chop non-integer part
                 1 while
                 s/(\d)(\d{$grouping}($|$thousands_sep))/$1$thousands_sep$2/;
                 print "$_";
             }
             print "\n";


LLLLOOOOCCCCAAAALLLLEEEE CCCCAAAATTTTEEEEGGGGOOOORRRRIIIIEEEESSSS
     The subsections which follow describe basic locale categories.  As well
     as these, there are some combination categories which allow the
     manipulation of more than one basic category at a time.  See the section
     on _E_N_V_I_R_O_N_M_E_N_T for a discussion of these.






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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     CCCCaaaatttteeeeggggoooorrrryyyy LLLLCCCC____CCCCOOOOLLLLLLLLAAAATTTTEEEE:::: CCCCoooollllllllaaaattttiiiioooonnnn

     When in the scope of use locale, Perl looks to the LC_COLLATE environment
     variable to determine the application's notions on the collation
     (ordering) of characters.  ('b' follows 'a' in Latin alphabets, but where
     do 'a' and 'aa' belong?)

     Here is a code snippet that will tell you what are the alphanumeric
     characters in the current locale, in the locale order:

             use locale;
             print +(sort grep /\w/, map { chr() } 0..255), "\n";

     Compare this with the characters that you see and their order if you
     state explicitly that the locale should be ignored:

             no locale;
             print +(sort grep /\w/, map { chr() } 0..255), "\n";

     This machine-native collation (which is what you get unless use locale
     has appeared earlier in the same block) must be used for sorting raw
     binary data, whereas the locale-dependent collation of the first example
     is useful for natural text.

     As noted in the section on _U_S_I_N_G _L_O_C_A_L_E_S, cmp compares according to the
     current collation locale when use locale is in effect, but falls back to
     a byte-by-byte comparison for strings which the locale says are equal.
     You can use _P_O_S_I_X::_s_t_r_c_o_l_l() if you don't want this fall-back:

             use POSIX qw(strcoll);
             $equal_in_locale =
                 !strcoll("space and case ignored", "SpaceAndCaseIgnored");

     $equal_in_locale will be true if the collation locale specifies a
     dictionary-like ordering which ignores space characters completely, and
     which folds case.

     If you have a single string which you want to check for "equality in
     locale" against several others, you might think you could gain a little
     efficiency by using _P_O_S_I_X::_s_t_r_x_f_r_m() 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");

     _s_t_r_x_f_r_m() takes a string and maps it into a transformed string for use in
     byte-by-byte comparisons against other transformed strings during



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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     collation.  "Under the hood", locale-affected Perl comparison operators
     call _s_t_r_x_f_r_m() for both their operands, then do a byte-by-byte comparison
     of the transformed strings.  By calling _s_t_r_x_f_r_m() explicitly, and using a
     non locale-affected comparison, the example attempts to save a couple of
     transformations.  In fact, it doesn't save anything: Perl magic (see the
     section on _M_a_g_i_c _V_a_r_i_a_b_l_e_s in the _p_e_r_l_g_u_t_s manpage) creates the
     transformed version of a string the first time it's needed in a
     comparison, then keeps it around in case it's needed again.  An example
     rewritten the easy way with cmp runs just about as fast.  It also copes
     with null characters embedded in strings; if you call _s_t_r_x_f_r_m() directly,
     it treats the first null it finds as a terminator.  And don't expect the
     transformed strings it produces to be portable across systems - or even
     from one revision of your operating system to the next.  In short, don't
     call _s_t_r_x_f_r_m() directly: let Perl do it for you.

     Note: use locale isn't shown in some of these examples, as it isn't
     needed: _s_t_r_c_o_l_l() and _s_t_r_x_f_r_m() exist only to generate locale-dependent
     results, and so always obey the current LC_COLLATE locale.

     CCCCaaaatttteeeeggggoooorrrryyyy LLLLCCCC____CCCCTTTTYYYYPPPPEEEE:::: CCCChhhhaaaarrrraaaacccctttteeeerrrr TTTTyyyyppppeeeessss

     When in the scope of use locale, Perl obeys the LC_CTYPE locale setting.
     This controls the application's notion of which characters are
     alphabetic.  This affects Perl's \w regular expression metanotation,
     which stands for alphanumeric characters - that is, alphabetic and
     numeric characters.  (Consult the _p_e_r_l_r_e manpage for more information
     about regular expressions.)  Thanks to LC_CTYPE, depending on your locale
     setting, characters like 'ae', 'd`', 'ss', and 'o' may be understood as \w
     characters.

     The LC_CTYPE locale also provides the map used in translating characters
     between lower and uppercase.  This affects the case-mapping functions -
     _l_c(), lcfirst, _u_c() and _u_c_f_i_r_s_t(); case-mapping interpolation with \l,
     \L, \u or <\U> in double-quoted strings and in s/// substitutions; and
     case-independent regular expression pattern matching using the i
     modifier.

     Finally, LC_CTYPE affects the POSIX character-class test functions -
     _i_s_a_l_p_h_a(), _i_s_l_o_w_e_r() 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 _i_s_p_u_n_c_t() class to _i_s_a_l_p_h_a().

     NNNNooootttteeee:::: A broken or malicious LC_CTYPE locale definition may result in
     clearly ineligible characters being considered to be alphanumeric by your
     application.  For strict matching of (unaccented) letters and digits -
     for example, in command strings - locale-aware applications should use \w
     inside a no locale block.  See the section on _S_E_C_U_R_I_T_Y.

     CCCCaaaatttteeeeggggoooorrrryyyy LLLLCCCC____NNNNUUUUMMMMEEEERRRRIIIICCCC:::: NNNNuuuummmmeeeerrrriiiicccc FFFFoooorrrrmmmmaaaattttttttiiiinnnngggg






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PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     When in the scope of use locale, Perl obeys the LC_NUMERIC locale
     information, which controls application's idea of how numbers should be
     formatted for human readability by the _p_r_i_n_t_f(), _s_p_r_i_n_t_f(), and _w_r_i_t_e()
     functions.  String to numeric conversion by the _P_O_S_I_X::_s_t_r_t_o_d() function
     is also affected.  In most implementations the only effect is to change
     the character used for the decimal point - perhaps from '.'  to ',':
     these functions aren't aware of such niceties as thousands separation and
     so on.  (See the section on _T_h_e _l_o_c_a_l_e_c_o_n_v _f_u_n_c_t_i_o_n if you care about
     these things.)

     Note that output produced by _p_r_i_n_t() is nnnneeeevvvveeeerrrr affected by the current
     locale: it is independent of whether use locale or no locale is in
     effect, and corresponds to what you'd get from _p_r_i_n_t_f() in the "C"
     locale.  The same is true for Perl's internal conversions between numeric
     and string formats:

             use POSIX qw(strtod);
             use locale;

             $n = 5/2;   # Assign numeric 2.5 to $n

             $a = " $n"; # Locale-independent conversion to string

             print "half five is $n\n";       # Locale-independent output

             printf "half five is %g\n", $n;  # Locale-dependent output

             print "DECIMAL POINT IS COMMA\n"
                 if $n == (strtod("2,5"))[0]; # Locale-dependent conversion


     CCCCaaaatttteeeeggggoooorrrryyyy LLLLCCCC____MMMMOOOONNNNEEEETTTTAAAARRRRYYYY:::: FFFFoooorrrrmmmmaaaattttttttiiiinnnngggg ooooffff mmmmoooonnnneeeettttaaaarrrryyyy aaaammmmoooouuuunnnnttttssss

     The C standard defines the LC_MONETARY category, but no function that is
     affected by its contents.  (Those with experience of standards committees
     will recognize that the working group decided to punt on the issue.)
     Consequently, Perl takes no notice of it.  If you really want to use
     LC_MONETARY, you can query its contents - see the section on _T_h_e
     _l_o_c_a_l_e_c_o_n_v _f_u_n_c_t_i_o_n - and use the information that it returns in your
     application's own formatting of currency amounts.  However, you may well
     find that the information, though voluminous and complex, does not quite
     meet your requirements: currency formatting is a hard nut to crack.

     LLLLCCCC____TTTTIIIIMMMMEEEE

     The output produced by _P_O_S_I_X::_s_t_r_f_t_i_m_e(), which builds a formatted
     human-readable date/time string, is affected by the current LC_TIME
     locale.  Thus, in a French locale, the output produced by the %B format
     element (full month name) for the first month of the year would be
     "janvier".  Here's how to get a list of the long month names in the
     current locale:




                                                                        PPPPaaaaggggeeee 8888






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



             use POSIX qw(strftime);
             for (0..11) {
                 $long_month_name[$_] =
                     strftime("%B", 0, 0, 0, 1, $_, 96);
             }

     Note: use locale isn't needed in this example: as a function which exists
     only to generate locale-dependent results, _s_t_r_f_t_i_m_e() always obeys the
     current LC_TIME locale.

     OOOOtttthhhheeeerrrr ccccaaaatttteeeeggggoooorrrriiiieeeessss

     The remaining locale category, LC_MESSAGES (possibly supplemented by
     others in particular implementations) is not currently used by Perl -
     except possibly to affect the behavior of library functions called by
     extensions which are not part of the standard Perl distribution.

SSSSEEEECCCCUUUURRRRIIIITTTTYYYY
     While the main discussion of Perl security issues can be found in the
     _p_e_r_l_s_e_c manpage, a discussion of Perl's locale handling would be
     incomplete if it did not draw your attention to locale-dependent security
     issues.  Locales - particularly on systems which allow unprivileged users
     to build their own locales - are untrustworthy.  A malicious (or just
     plain broken) locale can make a locale-aware application give unexpected
     results.  Here are a few possibilities:

     +o   Regular expression checks for safe file names or mail addresses using
         \w may be spoofed by an LC_CTYPE locale which claims that characters
         such as ">" and "|" are alphanumeric.

     +o   String interpolation with case-mapping, as in, say, $dest =
         "C:\U$name.$ext", may produce dangerous results if a bogus LC_CTYPE
         case-mapping table is in effect.

     +o   If the decimal point character in the LC_NUMERIC locale is
         surreptitiously changed from a dot to a comma, sprintf("%g",
         0.123456e3) produces a string result of "123,456". Many people would
         interpret this as one hundred and twenty-three thousand, four hundred
         and fifty-six.

     +o   A sneaky LC_COLLATE locale could result in the names of students with
         "D" grades appearing ahead of those with "A"s.

     +o   An application which takes the trouble to use the information in
         LC_MONETARY may format debits as if they were credits and vice versa
         if that locale has been subverted.  Or it make may make payments in
         US dollars instead of Hong Kong dollars.

     +o   The date and day names in dates formatted by _s_t_r_f_t_i_m_e() could be
         manipulated to advantage by a malicious user able to subvert the
         LC_DATE locale.  ("Look - it says I wasn't in the building on
         Sunday.")



                                                                        PPPPaaaaggggeeee 9999






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     Such dangers are not peculiar to the locale system: any aspect of an
     application's environment which may maliciously be modified presents
     similar challenges.  Similarly, they are not specific to Perl: any
     programming language which allows you to write programs which take
     account of their environment exposes you to these issues.

     Perl cannot protect you from all of the possibilities shown in the
     examples - there is no substitute for your own vigilance - but, when use
     locale is in effect, Perl uses the tainting mechanism (see the _p_e_r_l_s_e_c
     manpage) to mark string results which become locale-dependent, and which
     may be untrustworthy in consequence.  Here is a summary of the tainting
     behavior of operators and functions which may be affected by the locale:

     CCCCoooommmmppppaaaarrrriiiissssoooonnnn ooooppppeeeerrrraaaattttoooorrrrssss (lt, le, ge, gt and cmp):
         Scalar true/false (or less/equal/greater) result is never tainted.

     CCCCaaaasssseeee----mmmmaaaappppppppiiiinnnngggg iiiinnnntttteeeerrrrppppoooollllaaaattttiiiioooonnnn (with \l, \L, \u or <\U>)
         Result string containing interpolated material is tainted if use
         locale is in effect.

     MMMMaaaattttcccchhhhiiiinnnngggg ooooppppeeeerrrraaaattttoooorrrr (m//):
         Scalar true/false result never tainted.

         Subpatterns, either delivered as an array-context result, or as $1
         etc.  are tainted if use locale is in effect, and the subpattern
         regular expression contains \w (to match an alphanumeric character),
         \W (non-alphanumeric character), \s (white-space character), or \S
         (non white-space character).  The matched pattern variable, $&, $`
         (pre-match), $' (post-match), and $+ (last match) are also tainted if
         use locale is in effect and the regular expression contains \w, \W,
         \s, or \S.

     SSSSuuuubbbbssssttttiiiittttuuuuttttiiiioooonnnn ooooppppeeeerrrraaaattttoooorrrr (s///):
         Has the same behavior as the match operator.  Also, the left operand
         of =~ becomes tainted when use locale in effect, if it is modified as
         a result of a substitution based on a regular expression match
         involving \w, \W, \s, or \S; or of case-mapping with \l, \L,\u or
         <\U>.

     IIIInnnn----mmmmeeeemmmmoooorrrryyyy ffffoooorrrrmmmmaaaattttttttiiiinnnngggg ffffuuuunnnnccccttttiiiioooonnnn (sprintf()):
         Result is tainted if "use locale" is in effect.

     OOOOuuuuttttppppuuuutttt ffffoooorrrrmmmmaaaattttttttiiiinnnngggg ffffuuuunnnnccccttttiiiioooonnnnssss (printf() and write()):
         Success/failure result is never tainted.

     CCCCaaaasssseeee----mmmmaaaappppppppiiiinnnngggg ffffuuuunnnnccccttttiiiioooonnnnssss (lc(), lcfirst(), uc(), ucfirst()):
         Results are tainted if use locale is in effect.

strxfrm()):
     PPPPOOOOSSSSIIIIXXXX llllooooccccaaaalllleeee----ddddeeeeppppeeeennnnddddeeeennnntttt ffffuuuunnnnccccttttiiiioooonnnnssss (localeconv(), strcoll(), strftime(),
         Results are never tainted.




                                                                       PPPPaaaaggggeeee 11110000






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



islower(), isprint(), ispunct(), isspace(), isupper(), isxdigit()):
     PPPPOOOOSSSSIIIIXXXX cccchhhhaaaarrrraaaacccctttteeeerrrr ccccllllaaaassssssss tttteeeessssttttssss (isalnum(), isalpha(), isdigit(), isgraph(),
         True/false results are never tainted.

     Three examples illustrate locale-dependent tainting.  The first program,
     which ignores its locale, won't run: a value taken directly from the
     command line may not be used to name an output file when taint checks are
     enabled.

             #/usr/local/bin/perl -T
             # Run with taint checking

             # Command line sanity check omitted...
             $tainted_output_file = shift;

             open(F, ">$tainted_output_file")
                 or warn "Open of $untainted_output_file failed: $!\n";

     The program can be made to run by "laundering" the tainted value through
     a regular expression: the second example - which still ignores locale
     information - runs, creating the file named on its command line if it
     can.

             #/usr/local/bin/perl -T

             $tainted_output_file = shift;
             $tainted_output_file =~ m%[\w/]+%;
             $untainted_output_file = $&;

             open(F, ">$untainted_output_file")
                 or warn "Open of $untainted_output_file failed: $!\n";

     Compare this with a very similar program which is locale-aware:

             #/usr/local/bin/perl -T

             $tainted_output_file = shift;
             use locale;
             $tainted_output_file =~ m%[\w/]+%;
             $localized_output_file = $&;

             open(F, ">$localized_output_file")
                 or warn "Open of $localized_output_file failed: $!\n";

     This third program fails to run because $& is tainted: it is the result
     of a match involving \w when use locale is in effect.

EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT
     PERL_BADLANG
                 A string that can suppress Perl's warning about failed locale
                 settings at startup.  Failure can occur if the locale support
                 in the operating system is lacking (broken) is some way - or



                                                                       PPPPaaaaggggeeee 11111111






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



                 if you mistyped the name of a locale when you set up your
                 environment.  If this environment variable is absent, or has
                 a value which does not evaluate to integer zero - that is "0"
                 or "" - Perl will complain about locale setting failures.

                 NNNNOOOOTTTTEEEE: 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) _s_e_t_l_o_c_a_l_e() method for
     controlling an application's opinion on data.

     LC_ALL      LC_ALL is the "override-all" locale environment variable. If
                 it is set, it overrides all the rest of the locale
                 environment variables.

     LC_CTYPE    In the absence of LC_ALL, LC_CTYPE chooses the character type
                 locale.  In the absence of both LC_ALL and LC_CTYPE, LANG
                 chooses the character type locale.

     LC_COLLATE  In the absence of LC_ALL, LC_COLLATE chooses the collation
                 (sorting) locale.  In the absence of both LC_ALL and
                 LC_COLLATE, LANG chooses the collation locale.

     LC_MONETARY In the absence of LC_ALL, LC_MONETARY chooses the monetary
                 formatting locale.  In the absence of both LC_ALL and
                 LC_MONETARY, LANG chooses the monetary formatting locale.

     LC_NUMERIC  In the absence of LC_ALL, LC_NUMERIC chooses the numeric
                 format locale.  In the absence of both LC_ALL and LC_NUMERIC,
                 LANG chooses the numeric format.

     LC_TIME     In the absence of LC_ALL, LC_TIME chooses the date and time
                 formatting locale.  In the absence of both LC_ALL and
                 LC_TIME, LANG chooses the date and time formatting locale.

     LANG        LANG is the "catch-all" locale environment variable. If it is
                 set, it is used as the last resort after the overall LC_ALL
                 and the category-specific LC_....

NNNNOOOOTTTTEEEESSSS
     BBBBaaaacccckkkkwwwwaaaarrrrdddd ccccoooommmmppppaaaattttiiiibbbbiiiilllliiiittttyyyy

     Versions of Perl prior to 5.004 mmmmoooossssttttllllyyyy ignored locale information,
     generally behaving as if something similar to the "C" locale (see the
     section on _T_h_e _s_e_t_l_o_c_a_l_e _f_u_n_c_t_i_o_n) was always in force, even if the
     program environment suggested otherwise.  By default, Perl still behaves
     this way so as to maintain backward compatibility.  If you want a Perl
     application to pay attention to locale information, you mmmmuuuusssstttt use the use
     locale pragma (see the section on _T_h_e _u_s_e _l_o_c_a_l_e _P_r_a_g_m_a) to instruct it



                                                                       PPPPaaaaggggeeee 11112222






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     to do so.

     Versions of Perl from 5.002 to 5.003 did use the LC_CTYPE information if
     that was available, that is, \w did understand what are the letters
     according to the locale environment variables.  The problem was that the
     user had no control over the feature:  if the C library supported
     locales, Perl used them.

     IIII11118888NNNN::::CCCCoooollllllllaaaatttteeee oooobbbbssssoooolllleeeetttteeee

     In versions of Perl prior to 5.004 per-locale collation was possible
     using the I18N::Collate library module.  This module is now mildly
     obsolete and should be avoided in new applications.  The LC_COLLATE
     functionality is now integrated into the Perl core language: One can use
     locale-specific scalar data completely normally with use locale, so there
     is no longer any need to juggle with the scalar references of
     I18N::Collate.

     SSSSoooorrrrtttt ssssppppeeeeeeeedddd aaaannnndddd mmmmeeeemmmmoooorrrryyyy uuuusssseeee iiiimmmmppppaaaaccccttttssss

     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.

     _w_r_i_t_e() and LC_NUMERIC

     Formats are the only part of Perl which unconditionally use information
     from a program's locale; if a program's environment specifies an
     LC_NUMERIC locale, it is always used to specify the decimal point
     character in formatted output.  Formatted output cannot be controlled by
     use locale because the pragma is tied to the block structure of the
     program, and, for historical reasons, formats exist outside that block
     structure.

     FFFFrrrreeeeeeeellllyyyy aaaavvvvaaaaiiiillllaaaabbbblllleeee llllooooccccaaaalllleeee ddddeeeeffffiiiinnnniiiittttiiiioooonnnnssss

     There is a large collection of locale definitions at
     ftp://dkuug.dk/i18n/WG15-collection.  You should be aware that it is
     unsupported, and is not claimed to be fit for any purpose.  If your
     system allows the installation of arbitrary locales, you may find the
     definitions useful as they are, or as a basis for the development of your
     own locales.

     IIII11118888nnnn aaaannnndddd llll11110000nnnn






                                                                       PPPPaaaaggggeeee 11113333






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))



     "Internationalization" is often abbreviated as iiii11118888nnnn 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 llll11110000nnnn.

     AAAAnnnn iiiimmmmppppeeeerrrrffffeeeecccctttt ssssttttaaaannnnddddaaaarrrrdddd

     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.

BBBBUUUUGGGGSSSS
     BBBBrrrrooookkkkeeeennnn ssssyyyysssstttteeeemmmmssss

     In certain system environments the operating system's locale support is
     broken and cannot be fixed or used by Perl.  Such deficiencies can and
     will result in mysterious hangs and/or Perl core dumps when the use
     locale is in effect.  When confronted with such a system, please report
     in excruciating detail to <_p_e_r_l_b_u_g@_p_e_r_l._c_o_m>, and complain to your
     vendor: maybe some bug fixes exist for these problems in your operating
     system.  Sometimes such bug fixes are called an operating system upgrade.

SSSSEEEEEEEE AAAALLLLSSSSOOOO
     the isalnum entry in the _P_O_S_I_X (_3) manpage, the isalpha entry in the
     _P_O_S_I_X (_3) manpage, the isdigit entry in the _P_O_S_I_X (_3) manpage, the
     isgraph entry in the _P_O_S_I_X (_3) manpage, the islower entry in the _P_O_S_I_X
     (_3) manpage, the isprint entry in the _P_O_S_I_X (_3) manpage, the ispunct
     entry in the _P_O_S_I_X (_3) manpage, the isspace entry in the _P_O_S_I_X (_3)
     manpage, the isupper entry in the _P_O_S_I_X (_3) manpage, the isxdigit entry
     in the _P_O_S_I_X (_3) manpage, the localeconv entry in the _P_O_S_I_X (_3) manpage,
     the setlocale entry in the _P_O_S_I_X (_3) manpage, the strcoll entry in the
     _P_O_S_I_X (_3) manpage, the strftime entry in the _P_O_S_I_X (_3) manpage, the
     strtod entry in the _P_O_S_I_X (_3) manpage, the strxfrm entry in the _P_O_S_I_X (_3)
     manpage

HHHHIIIISSSSTTTTOOOORRRRYYYY
     Jarkko Hietaniemi's original _p_e_r_l_i_1_8_n._p_o_d heavily hacked by Dominic
     Dunlop, assisted by the perl5-porters.

     Last update: Wed Jan 22 11:04:58 EST 1997










                                                                       PPPPaaaaggggeeee 11114444






PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))                                                    PPPPEEEERRRRLLLLLLLLOOOOCCCCAAAALLLLEEEE((((1111))))























































                                                                       PPPPaaaaggggeeee 11115555