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1 | =head1 NAME |
2 | |
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3 | perllocale - Perl locale handling (internationalization and localization) |
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4 | |
5 | =head1 DESCRIPTION |
6 | |
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7 | Perl supports language-specific notions of data such as "is this |
8 | a letter", "what is the uppercase equivalent of this letter", and |
9 | "which of these letters comes first". These are important issues, |
10 | especially for languages other than English--but also for English: it |
11 | would be naE<iuml>ve to imagine that C<A-Za-z> defines all the "letters" |
12 | needed to write in English. Perl is also aware that some character other |
13 | than '.' may be preferred as a decimal point, and that output date |
14 | representations may be language-specific. The process of making an |
15 | application take account of its users' preferences in such matters is |
16 | called B<internationalization> (often abbreviated as B<i18n>); telling |
17 | such an application about a particular set of preferences is known as |
18 | B<localization> (B<l10n>). |
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19 | |
20 | Perl can understand language-specific data via the standardized (ISO C, |
21 | XPG4, POSIX 1.c) method called "the locale system". The locale system is |
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22 | controlled per application using one pragma, one function call, and |
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23 | several environment variables. |
24 | |
25 | B<NOTE>: This feature is new in Perl 5.004, and does not apply unless an |
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26 | application specifically requests it--see L<Backward compatibility>. |
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27 | The one exception is that write() now B<always> uses the current locale |
28 | - see L<"NOTES">. |
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29 | |
30 | =head1 PREPARING TO USE LOCALES |
31 | |
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32 | If Perl applications are to understand and present your data |
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33 | correctly according a locale of your choice, B<all> of the following |
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34 | must be true: |
35 | |
36 | =over 4 |
37 | |
38 | =item * |
39 | |
40 | B<Your operating system must support the locale system>. If it does, |
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41 | you should find that the setlocale() function is a documented part of |
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42 | its C library. |
43 | |
44 | =item * |
45 | |
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46 | B<Definitions for locales that you use must be installed>. You, or |
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47 | your system administrator, must make sure that this is the case. The |
48 | available locales, the location in which they are kept, and the manner |
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49 | in which they are installed all vary from system to system. Some systems |
50 | provide only a few, hard-wired locales and do not allow more to be |
51 | added. Others allow you to add "canned" locales provided by the system |
52 | supplier. Still others allow you or the system administrator to define |
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53 | and add arbitrary locales. (You may have to ask your supplier to |
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54 | provide canned locales that are not delivered with your operating |
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55 | system.) Read your system documentation for further illumination. |
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56 | |
57 | =item * |
58 | |
59 | B<Perl must believe that the locale system is supported>. If it does, |
60 | C<perl -V:d_setlocale> will say that the value for C<d_setlocale> is |
61 | C<define>. |
62 | |
63 | =back |
64 | |
65 | If you want a Perl application to process and present your data |
66 | according to a particular locale, the application code should include |
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67 | the S<C<use locale>> pragma (see L<The use locale pragma>) where |
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68 | appropriate, and B<at least one> of the following must be true: |
69 | |
70 | =over 4 |
71 | |
72 | =item * |
73 | |
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74 | B<The locale-determining environment variables (see L<"ENVIRONMENT">) |
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75 | must be correctly set up> at the time the application is started, either |
76 | by yourself or by whoever set up your system account. |
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77 | |
78 | =item * |
79 | |
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80 | B<The application must set its own locale> using the method described in |
81 | L<The setlocale function>. |
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82 | |
83 | =back |
84 | |
85 | =head1 USING LOCALES |
86 | |
87 | =head2 The use locale pragma |
88 | |
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89 | By default, Perl ignores the current locale. The S<C<use locale>> |
90 | pragma tells Perl to use the current locale for some operations: |
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91 | |
92 | =over 4 |
93 | |
94 | =item * |
95 | |
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96 | B<The comparison operators> (C<lt>, C<le>, C<cmp>, C<ge>, and C<gt>) and |
97 | the POSIX string collation functions strcoll() and strxfrm() use |
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98 | C<LC_COLLATE>. sort() is also affected if used without an |
99 | explicit comparison function, because it uses C<cmp> by default. |
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100 | |
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101 | B<Note:> C<eq> and C<ne> are unaffected by locale: they always |
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102 | perform a byte-by-byte comparison of their scalar operands. What's |
103 | more, if C<cmp> finds that its operands are equal according to the |
104 | collation sequence specified by the current locale, it goes on to |
105 | perform a byte-by-byte comparison, and only returns I<0> (equal) if the |
106 | operands are bit-for-bit identical. If you really want to know whether |
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107 | two strings--which C<eq> and C<cmp> may consider different--are equal |
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108 | as far as collation in the locale is concerned, see the discussion in |
109 | L<Category LC_COLLATE: Collation>. |
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110 | |
111 | =item * |
112 | |
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113 | B<Regular expressions and case-modification functions> (uc(), lc(), |
114 | ucfirst(), and lcfirst()) use C<LC_CTYPE> |
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115 | |
116 | =item * |
117 | |
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118 | B<The formatting functions> (printf(), sprintf() and write()) use |
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119 | C<LC_NUMERIC> |
120 | |
121 | =item * |
122 | |
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123 | B<The POSIX date formatting function> (strftime()) uses C<LC_TIME>. |
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124 | |
125 | =back |
126 | |
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127 | C<LC_COLLATE>, C<LC_CTYPE>, and so on, are discussed further in |
128 | L<LOCALE CATEGORIES>. |
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129 | |
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130 | The default behavior is restored with the S<C<no locale>> pragma, or |
131 | upon reaching the end of block enclosing C<use locale>. |
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132 | |
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133 | The string result of any operation that uses locale |
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134 | information is tainted, as it is possible for a locale to be |
135 | untrustworthy. See L<"SECURITY">. |
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136 | |
137 | =head2 The setlocale function |
138 | |
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139 | You can switch locales as often as you wish at run time with the |
140 | POSIX::setlocale() function: |
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141 | |
142 | # This functionality not usable prior to Perl 5.004 |
143 | require 5.004; |
144 | |
145 | # Import locale-handling tool set from POSIX module. |
146 | # This example uses: setlocale -- the function call |
147 | # LC_CTYPE -- explained below |
148 | use POSIX qw(locale_h); |
149 | |
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150 | # query and save the old locale |
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151 | $old_locale = setlocale(LC_CTYPE); |
152 | |
153 | setlocale(LC_CTYPE, "fr_CA.ISO8859-1"); |
154 | # LC_CTYPE now in locale "French, Canada, codeset ISO 8859-1" |
155 | |
156 | setlocale(LC_CTYPE, ""); |
157 | # LC_CTYPE now reset to default defined by LC_ALL/LC_CTYPE/LANG |
158 | # environment variables. See below for documentation. |
159 | |
160 | # restore the old locale |
161 | setlocale(LC_CTYPE, $old_locale); |
162 | |
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163 | The first argument of setlocale() gives the B<category>, the second the |
164 | B<locale>. The category tells in what aspect of data processing you |
165 | want to apply locale-specific rules. Category names are discussed in |
166 | L<LOCALE CATEGORIES> and L<"ENVIRONMENT">. The locale is the name of a |
167 | collection of customization information corresponding to a particular |
168 | combination of language, country or territory, and codeset. Read on for |
169 | hints on the naming of locales: not all systems name locales as in the |
170 | example. |
171 | |
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172 | If no second argument is provided and the category is something else |
173 | than LC_ALL, the function returns a string naming the current locale |
174 | for the category. You can use this value as the second argument in a |
175 | subsequent call to setlocale(). |
176 | |
177 | If no second argument is provided and the category is LC_ALL, the |
178 | result is implementation-dependent. It may be a string of |
179 | concatenated locales names (separator also implementation-dependent) |
180 | or a single locale name. Please consult your L<setlocale(3)> for |
181 | details. |
182 | |
183 | If a second argument is given and it corresponds to a valid locale, |
184 | the locale for the category is set to that value, and the function |
185 | returns the now-current locale value. You can then use this in yet |
186 | another call to setlocale(). (In some implementations, the return |
187 | value may sometimes differ from the value you gave as the second |
188 | argument--think of it as an alias for the value you gave.) |
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189 | |
190 | As the example shows, if the second argument is an empty string, the |
191 | category's locale is returned to the default specified by the |
192 | corresponding environment variables. Generally, this results in a |
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193 | return to the default that was in force when Perl started up: changes |
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194 | to the environment made by the application after startup may or may not |
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195 | be noticed, depending on your system's C library. |
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196 | |
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197 | If the second argument does not correspond to a valid locale, the locale |
198 | for the category is not changed, and the function returns I<undef>. |
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199 | |
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200 | For further information about the categories, consult L<setlocale(3)>. |
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201 | |
202 | =head2 Finding locales |
203 | |
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204 | For locales available in your system, consult also L<setlocale(3)> to |
205 | see whether it leads to the list of available locales (search for the |
206 | I<SEE ALSO> section). If that fails, try the following command lines: |
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207 | |
208 | locale -a |
209 | |
210 | nlsinfo |
211 | |
212 | ls /usr/lib/nls/loc |
213 | |
214 | ls /usr/lib/locale |
215 | |
216 | ls /usr/lib/nls |
217 | |
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218 | ls /usr/share/locale |
219 | |
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220 | and see whether they list something resembling these |
221 | |
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222 | en_US.ISO8859-1 de_DE.ISO8859-1 ru_RU.ISO8859-5 |
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223 | en_US.iso88591 de_DE.iso88591 ru_RU.iso88595 |
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224 | en_US de_DE ru_RU |
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225 | en de ru |
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226 | english german russian |
227 | english.iso88591 german.iso88591 russian.iso88595 |
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228 | english.roman8 russian.koi8r |
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229 | |
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230 | Sadly, even though the calling interface for setlocale() has been |
231 | standardized, names of locales and the directories where the |
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232 | configuration resides have not been. The basic form of the name is |
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233 | I<language_territory>B<.>I<codeset>, but the latter parts after |
234 | I<language> are not always present. The I<language> and I<country> |
235 | are usually from the standards B<ISO 3166> and B<ISO 639>, the |
236 | two-letter abbreviations for the countries and the languages of the |
237 | world, respectively. The I<codeset> part often mentions some B<ISO |
238 | 8859> character set, the Latin codesets. For example, C<ISO 8859-1> |
239 | is the so-called "Western European codeset" that can be used to encode |
240 | most Western European languages adequately. Again, there are several |
241 | ways to write even the name of that one standard. Lamentably. |
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242 | |
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243 | Two special locales are worth particular mention: "C" and "POSIX". |
244 | Currently these are effectively the same locale: the difference is |
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245 | mainly that the first one is defined by the C standard, the second by |
246 | the POSIX standard. They define the B<default locale> in which |
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247 | every program starts in the absence of locale information in its |
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248 | environment. (The I<default> default locale, if you will.) Its language |
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249 | is (American) English and its character codeset ASCII. |
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250 | |
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251 | B<NOTE>: Not all systems have the "POSIX" locale (not all systems are |
252 | POSIX-conformant), so use "C" when you need explicitly to specify this |
253 | default locale. |
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254 | |
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255 | =head2 LOCALE PROBLEMS |
256 | |
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257 | You may encounter the following warning message at Perl startup: |
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258 | |
259 | perl: warning: Setting locale failed. |
260 | perl: warning: Please check that your locale settings: |
261 | LC_ALL = "En_US", |
262 | LANG = (unset) |
263 | are supported and installed on your system. |
264 | perl: warning: Falling back to the standard locale ("C"). |
265 | |
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266 | This means that your locale settings had LC_ALL set to "En_US" and |
267 | LANG exists but has no value. Perl tried to believe you but could not. |
268 | Instead, Perl gave up and fell back to the "C" locale, the default locale |
269 | that is supposed to work no matter what. This usually means your locale |
270 | settings were wrong, they mention locales your system has never heard |
271 | of, or the locale installation in your system has problems (for example, |
272 | some system files are broken or missing). There are quick and temporary |
273 | fixes to these problems, as well as more thorough and lasting fixes. |
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274 | |
275 | =head2 Temporarily fixing locale problems |
276 | |
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277 | The two quickest fixes are either to render Perl silent about any |
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278 | locale inconsistencies or to run Perl under the default locale "C". |
279 | |
280 | Perl's moaning about locale problems can be silenced by setting the |
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281 | environment variable PERL_BADLANG to a zero value, for example "0". |
282 | This method really just sweeps the problem under the carpet: you tell |
283 | Perl to shut up even when Perl sees that something is wrong. Do not |
284 | be surprised if later something locale-dependent misbehaves. |
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285 | |
286 | Perl can be run under the "C" locale by setting the environment |
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287 | variable LC_ALL to "C". This method is perhaps a bit more civilized |
288 | than the PERL_BADLANG approach, but setting LC_ALL (or |
289 | other locale variables) may affect other programs as well, not just |
290 | Perl. In particular, external programs run from within Perl will see |
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291 | these changes. If you make the new settings permanent (read on), all |
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292 | programs you run see the changes. See L<ENVIRONMENT> for |
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293 | the full list of relevant environment variables and L<USING LOCALES> |
294 | for their effects in Perl. Effects in other programs are |
295 | easily deducible. For example, the variable LC_COLLATE may well affect |
296 | your B<sort> program (or whatever the program that arranges `records' |
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297 | alphabetically in your system is called). |
298 | |
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299 | You can test out changing these variables temporarily, and if the |
300 | new settings seem to help, put those settings into your shell startup |
301 | files. Consult your local documentation for the exact details. For in |
302 | Bourne-like shells (B<sh>, B<ksh>, B<bash>, B<zsh>): |
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303 | |
304 | LC_ALL=en_US.ISO8859-1 |
305 | export LC_ALL |
306 | |
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307 | This assumes that we saw the locale "en_US.ISO8859-1" using the commands |
308 | discussed above. We decided to try that instead of the above faulty |
309 | locale "En_US"--and in Cshish shells (B<csh>, B<tcsh>) |
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310 | |
311 | setenv LC_ALL en_US.ISO8859-1 |
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312 | |
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313 | If you do not know what shell you have, consult your local |
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314 | helpdesk or the equivalent. |
315 | |
316 | =head2 Permanently fixing locale problems |
317 | |
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318 | The slower but superior fixes are when you may be able to yourself |
319 | fix the misconfiguration of your own environment variables. The |
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320 | mis(sing)configuration of the whole system's locales usually requires |
321 | the help of your friendly system administrator. |
322 | |
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323 | First, see earlier in this document about L<Finding locales>. That tells |
324 | how to find which locales are really supported--and more importantly, |
325 | installed--on your system. In our example error message, environment |
326 | variables affecting the locale are listed in the order of decreasing |
327 | importance (and unset variables do not matter). Therefore, having |
328 | LC_ALL set to "En_US" must have been the bad choice, as shown by the |
329 | error message. First try fixing locale settings listed first. |
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330 | |
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331 | Second, if using the listed commands you see something B<exactly> |
332 | (prefix matches do not count and case usually counts) like "En_US" |
333 | without the quotes, then you should be okay because you are using a |
334 | locale name that should be installed and available in your system. |
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335 | In this case, see L<Permanently fixing your system's locale configuration>. |
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336 | |
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337 | =head2 Permanently fixing your system's locale configuration |
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338 | |
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339 | This is when you see something like: |
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340 | |
341 | perl: warning: Please check that your locale settings: |
342 | LC_ALL = "En_US", |
343 | LANG = (unset) |
344 | are supported and installed on your system. |
345 | |
346 | but then cannot see that "En_US" listed by the above-mentioned |
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347 | commands. You may see things like "en_US.ISO8859-1", but that isn't |
348 | the same. In this case, try running under a locale |
349 | that you can list and which somehow matches what you tried. The |
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350 | rules for matching locale names are a bit vague because |
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351 | standardization is weak in this area. See again the |
352 | L<Finding locales> about general rules. |
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353 | |
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354 | =head2 Fixing system locale configuration |
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355 | |
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356 | Contact a system administrator (preferably your own) and report the exact |
357 | error message you get, and ask them to read this same documentation you |
358 | are now reading. They should be able to check whether there is something |
359 | wrong with the locale configuration of the system. The L<Finding locales> |
360 | section is unfortunately a bit vague about the exact commands and places |
361 | because these things are not that standardized. |
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362 | |
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363 | =head2 The localeconv function |
364 | |
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365 | The POSIX::localeconv() function allows you to get particulars of the |
366 | locale-dependent numeric formatting information specified by the current |
367 | C<LC_NUMERIC> and C<LC_MONETARY> locales. (If you just want the name of |
368 | the current locale for a particular category, use POSIX::setlocale() |
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369 | with a single parameter--see L<The setlocale function>.) |
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370 | |
371 | use POSIX qw(locale_h); |
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372 | |
373 | # Get a reference to a hash of locale-dependent info |
374 | $locale_values = localeconv(); |
375 | |
376 | # Output sorted list of the values |
377 | for (sort keys %$locale_values) { |
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378 | printf "%-20s = %s\n", $_, $locale_values->{$_} |
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379 | } |
380 | |
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381 | localeconv() takes no arguments, and returns B<a reference to> a hash. |
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382 | The keys of this hash are variable names for formatting, such as |
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383 | C<decimal_point> and C<thousands_sep>. The values are the |
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384 | corresponding, er, values. See L<POSIX/localeconv> for a longer |
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385 | example listing the categories an implementation might be expected to |
386 | provide; some provide more and others fewer. You don't need an |
387 | explicit C<use locale>, because localeconv() always observes the |
388 | current locale. |
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389 | |
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390 | Here's a simple-minded example program that rewrites its command-line |
391 | parameters as integers correctly formatted in the current locale: |
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392 | |
393 | # See comments in previous example |
394 | require 5.004; |
395 | use POSIX qw(locale_h); |
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396 | |
397 | # Get some of locale's numeric formatting parameters |
398 | my ($thousands_sep, $grouping) = |
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399 | @{localeconv()}{'thousands_sep', 'grouping'}; |
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400 | |
401 | # Apply defaults if values are missing |
402 | $thousands_sep = ',' unless $thousands_sep; |
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403 | |
404 | # grouping and mon_grouping are packed lists |
405 | # of small integers (characters) telling the |
406 | # grouping (thousand_seps and mon_thousand_seps |
407 | # being the group dividers) of numbers and |
408 | # monetary quantities. The integers' meanings: |
409 | # 255 means no more grouping, 0 means repeat |
410 | # the previous grouping, 1-254 means use that |
411 | # as the current grouping. Grouping goes from |
412 | # right to left (low to high digits). In the |
413 | # below we cheat slightly by never using anything |
414 | # else than the first grouping (whatever that is). |
415 | if ($grouping) { |
416 | @grouping = unpack("C*", $grouping); |
417 | } else { |
418 | @grouping = (3); |
419 | } |
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420 | |
421 | # Format command line params for current locale |
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422 | for (@ARGV) { |
423 | $_ = int; # Chop non-integer part |
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424 | 1 while |
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425 | s/(\d)(\d{$grouping[0]}($|$thousands_sep))/$1$thousands_sep$2/; |
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426 | print "$_"; |
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427 | } |
428 | print "\n"; |
429 | |
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430 | =head2 I18N::Langinfo |
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431 | |
432 | Another interface for querying locale-dependent information is the |
433 | I18N::Langinfo::langinfo() function, available at least in UNIX-like |
434 | systems and VMS. |
435 | |
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436 | The following example will import the langinfo() function itself and |
437 | three constants to be used as arguments to langinfo(): a constant for |
438 | the abbreviated first day of the week (the numbering starts from |
439 | Sunday = 1) and two more constants for the affirmative and negative |
440 | answers for a yes/no question in the current locale. |
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441 | |
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442 | use I18N::Langinfo qw(langinfo ABDAY_1 YESSTR NOSTR); |
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443 | |
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444 | my ($abday_1, $yesstr, $nostr) = map { langinfo } qw(ABDAY_1 YESSTR NOSTR); |
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445 | |
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446 | print "$abday_1? [$yesstr/$nostr] "; |
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447 | |
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448 | In other words, in the "C" (or English) locale the above will probably |
449 | print something like: |
450 | |
451 | Sun? [yes/no] |
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452 | |
453 | See L<I18N::Langinfo> for more information. |
454 | |
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455 | =head1 LOCALE CATEGORIES |
456 | |
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457 | The following subsections describe basic locale categories. Beyond these, |
458 | some combination categories allow manipulation of more than one |
459 | basic category at a time. See L<"ENVIRONMENT"> for a discussion of these. |
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460 | |
461 | =head2 Category LC_COLLATE: Collation |
462 | |
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463 | In the scope of S<C<use locale>>, Perl looks to the C<LC_COLLATE> |
464 | environment variable to determine the application's notions on collation |
465 | (ordering) of characters. For example, 'b' follows 'a' in Latin |
466 | alphabets, but where do 'E<aacute>' and 'E<aring>' belong? And while |
467 | 'color' follows 'chocolate' in English, what about in Spanish? |
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468 | |
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469 | The following collations all make sense and you may meet any of them |
470 | if you "use locale". |
471 | |
472 | A B C D E a b c d e |
35316ca3 |
473 | A a B b C c D d E e |
60f0fa02 |
474 | a A b B c C d D e E |
475 | a b c d e A B C D E |
476 | |
f1cbbd6e |
477 | Here is a code snippet to tell what "word" |
5a964f20 |
478 | characters are in the current locale, in that locale's order: |
5f05dabc |
479 | |
480 | use locale; |
35316ca3 |
481 | print +(sort grep /\w/, map { chr } 0..255), "\n"; |
5f05dabc |
482 | |
14280422 |
483 | Compare this with the characters that you see and their order if you |
484 | state explicitly that the locale should be ignored: |
5f05dabc |
485 | |
486 | no locale; |
35316ca3 |
487 | print +(sort grep /\w/, map { chr } 0..255), "\n"; |
5f05dabc |
488 | |
489 | This machine-native collation (which is what you get unless S<C<use |
490 | locale>> has appeared earlier in the same block) must be used for |
491 | sorting raw binary data, whereas the locale-dependent collation of the |
b0c42ed9 |
492 | first example is useful for natural text. |
5f05dabc |
493 | |
14280422 |
494 | As noted in L<USING LOCALES>, C<cmp> compares according to the current |
495 | collation locale when C<use locale> is in effect, but falls back to a |
5a964f20 |
496 | byte-by-byte comparison for strings that the locale says are equal. You |
14280422 |
497 | can use POSIX::strcoll() if you don't want this fall-back: |
498 | |
499 | use POSIX qw(strcoll); |
500 | $equal_in_locale = |
501 | !strcoll("space and case ignored", "SpaceAndCaseIgnored"); |
502 | |
503 | $equal_in_locale will be true if the collation locale specifies a |
5a964f20 |
504 | dictionary-like ordering that ignores space characters completely and |
9e3a2af8 |
505 | which folds case. |
14280422 |
506 | |
5a964f20 |
507 | If you have a single string that you want to check for "equality in |
14280422 |
508 | locale" against several others, you might think you could gain a little |
509 | efficiency by using POSIX::strxfrm() in conjunction with C<eq>: |
510 | |
511 | use POSIX qw(strxfrm); |
512 | $xfrm_string = strxfrm("Mixed-case string"); |
513 | print "locale collation ignores spaces\n" |
514 | if $xfrm_string eq strxfrm("Mixed-casestring"); |
515 | print "locale collation ignores hyphens\n" |
516 | if $xfrm_string eq strxfrm("Mixedcase string"); |
517 | print "locale collation ignores case\n" |
518 | if $xfrm_string eq strxfrm("mixed-case string"); |
519 | |
520 | strxfrm() takes a string and maps it into a transformed string for use |
521 | in byte-by-byte comparisons against other transformed strings during |
522 | collation. "Under the hood", locale-affected Perl comparison operators |
5a964f20 |
523 | call strxfrm() for both operands, then do a byte-by-byte |
524 | comparison of the transformed strings. By calling strxfrm() explicitly |
14280422 |
525 | and using a non locale-affected comparison, the example attempts to save |
5a964f20 |
526 | a couple of transformations. But in fact, it doesn't save anything: Perl |
2ae324a7 |
527 | magic (see L<perlguts/Magic Variables>) creates the transformed version of a |
5a964f20 |
528 | string the first time it's needed in a comparison, then keeps this version around |
14280422 |
529 | in case it's needed again. An example rewritten the easy way with |
e38874e2 |
530 | C<cmp> runs just about as fast. It also copes with null characters |
14280422 |
531 | embedded in strings; if you call strxfrm() directly, it treats the first |
5a964f20 |
532 | null it finds as a terminator. don't expect the transformed strings |
533 | it produces to be portable across systems--or even from one revision |
e38874e2 |
534 | of your operating system to the next. In short, don't call strxfrm() |
535 | directly: let Perl do it for you. |
14280422 |
536 | |
5a964f20 |
537 | Note: C<use locale> isn't shown in some of these examples because it isn't |
14280422 |
538 | needed: strcoll() and strxfrm() exist only to generate locale-dependent |
539 | results, and so always obey the current C<LC_COLLATE> locale. |
5f05dabc |
540 | |
541 | =head2 Category LC_CTYPE: Character Types |
542 | |
5a964f20 |
543 | In the scope of S<C<use locale>>, Perl obeys the C<LC_CTYPE> locale |
14280422 |
544 | setting. This controls the application's notion of which characters are |
545 | alphabetic. This affects Perl's C<\w> regular expression metanotation, |
f1cbbd6e |
546 | which stands for alphanumeric characters--that is, alphabetic, |
547 | numeric, and including other special characters such as the underscore or |
548 | hyphen. (Consult L<perlre> for more information about |
14280422 |
549 | regular expressions.) Thanks to C<LC_CTYPE>, depending on your locale |
550 | setting, characters like 'E<aelig>', 'E<eth>', 'E<szlig>', and |
551 | 'E<oslash>' may be understood as C<\w> characters. |
5f05dabc |
552 | |
2c268ad5 |
553 | The C<LC_CTYPE> locale also provides the map used in transliterating |
68dc0745 |
554 | characters between lower and uppercase. This affects the case-mapping |
5a964f20 |
555 | functions--lc(), lcfirst, uc(), and ucfirst(); case-mapping |
556 | interpolation with C<\l>, C<\L>, C<\u>, or C<\U> in double-quoted strings |
557 | and C<s///> substitutions; and case-independent regular expression |
e38874e2 |
558 | pattern matching using the C<i> modifier. |
559 | |
5a964f20 |
560 | Finally, C<LC_CTYPE> affects the POSIX character-class test |
561 | functions--isalpha(), islower(), and so on. For example, if you move |
562 | from the "C" locale to a 7-bit Scandinavian one, you may find--possibly |
563 | to your surprise--that "|" moves from the ispunct() class to isalpha(). |
5f05dabc |
564 | |
14280422 |
565 | B<Note:> A broken or malicious C<LC_CTYPE> locale definition may result |
566 | in clearly ineligible characters being considered to be alphanumeric by |
5a964f20 |
567 | your application. For strict matching of (mundane) letters and |
568 | digits--for example, in command strings--locale-aware applications |
14280422 |
569 | should use C<\w> inside a C<no locale> block. See L<"SECURITY">. |
5f05dabc |
570 | |
571 | =head2 Category LC_NUMERIC: Numeric Formatting |
572 | |
5a964f20 |
573 | In the scope of S<C<use locale>>, Perl obeys the C<LC_NUMERIC> locale |
574 | information, which controls an application's idea of how numbers should |
575 | be formatted for human readability by the printf(), sprintf(), and |
576 | write() functions. String-to-numeric conversion by the POSIX::strtod() |
577 | function is also affected. In most implementations the only effect is to |
578 | change the character used for the decimal point--perhaps from '.' to ','. |
579 | These functions aren't aware of such niceties as thousands separation and |
580 | so on. (See L<The localeconv function> if you care about these things.) |
581 | |
3cf03d68 |
582 | Output produced by print() is also affected by the current locale: it |
583 | depends on whether C<use locale> or C<no locale> is in effect, and |
584 | corresponds to what you'd get from printf() in the "C" locale. The |
585 | same is true for Perl's internal conversions between numeric and |
586 | string formats: |
5f05dabc |
587 | |
588 | use POSIX qw(strtod); |
589 | use locale; |
14280422 |
590 | |
5f05dabc |
591 | $n = 5/2; # Assign numeric 2.5 to $n |
592 | |
35316ca3 |
593 | $a = " $n"; # Locale-dependent conversion to string |
5f05dabc |
594 | |
35316ca3 |
595 | print "half five is $n\n"; # Locale-dependent output |
5f05dabc |
596 | |
597 | printf "half five is %g\n", $n; # Locale-dependent output |
598 | |
14280422 |
599 | print "DECIMAL POINT IS COMMA\n" |
600 | if $n == (strtod("2,5"))[0]; # Locale-dependent conversion |
5f05dabc |
601 | |
4bbcc6e8 |
602 | See also L<I18N::Langinfo> and C<RADIXCHAR>. |
603 | |
5f05dabc |
604 | =head2 Category LC_MONETARY: Formatting of monetary amounts |
605 | |
5a964f20 |
606 | The C standard defines the C<LC_MONETARY> category, but no function |
607 | that is affected by its contents. (Those with experience of standards |
b0c42ed9 |
608 | committees will recognize that the working group decided to punt on the |
14280422 |
609 | issue.) Consequently, Perl takes no notice of it. If you really want |
13a2d996 |
610 | to use C<LC_MONETARY>, you can query its contents--see |
611 | L<The localeconv function>--and use the information that it returns in your |
612 | application's own formatting of currency amounts. However, you may well |
613 | find that the information, voluminous and complex though it may be, still |
614 | does not quite meet your requirements: currency formatting is a hard nut |
615 | to crack. |
5f05dabc |
616 | |
4bbcc6e8 |
617 | See also L<I18N::Langinfo> and C<CRNCYSTR>. |
618 | |
5f05dabc |
619 | =head2 LC_TIME |
620 | |
5a964f20 |
621 | Output produced by POSIX::strftime(), which builds a formatted |
5f05dabc |
622 | human-readable date/time string, is affected by the current C<LC_TIME> |
623 | locale. Thus, in a French locale, the output produced by the C<%B> |
624 | format element (full month name) for the first month of the year would |
5a964f20 |
625 | be "janvier". Here's how to get a list of long month names in the |
5f05dabc |
626 | current locale: |
627 | |
628 | use POSIX qw(strftime); |
14280422 |
629 | for (0..11) { |
630 | $long_month_name[$_] = |
631 | strftime("%B", 0, 0, 0, 1, $_, 96); |
5f05dabc |
632 | } |
633 | |
5a964f20 |
634 | Note: C<use locale> isn't needed in this example: as a function that |
14280422 |
635 | exists only to generate locale-dependent results, strftime() always |
636 | obeys the current C<LC_TIME> locale. |
5f05dabc |
637 | |
4bbcc6e8 |
638 | See also L<I18N::Langinfo> and C<ABDAY_1>..C<ABDAY_7>, C<DAY_1>..C<DAY_7>, |
2a2bf5f4 |
639 | C<ABMON_1>..C<ABMON_12>, and C<ABMON_1>..C<ABMON_12>. |
4bbcc6e8 |
640 | |
5f05dabc |
641 | =head2 Other categories |
642 | |
5a964f20 |
643 | The remaining locale category, C<LC_MESSAGES> (possibly supplemented |
644 | by others in particular implementations) is not currently used by |
98a6f11e |
645 | Perl--except possibly to affect the behavior of library functions |
646 | called by extensions outside the standard Perl distribution and by the |
647 | operating system and its utilities. Note especially that the string |
648 | value of C<$!> and the error messages given by external utilities may |
649 | be changed by C<LC_MESSAGES>. If you want to have portable error |
265f5c4a |
650 | codes, use C<%!>. See L<Errno>. |
14280422 |
651 | |
652 | =head1 SECURITY |
653 | |
5a964f20 |
654 | Although the main discussion of Perl security issues can be found in |
14280422 |
655 | L<perlsec>, a discussion of Perl's locale handling would be incomplete |
656 | if it did not draw your attention to locale-dependent security issues. |
5a964f20 |
657 | Locales--particularly on systems that allow unprivileged users to |
658 | build their own locales--are untrustworthy. A malicious (or just plain |
14280422 |
659 | broken) locale can make a locale-aware application give unexpected |
660 | results. Here are a few possibilities: |
661 | |
662 | =over 4 |
663 | |
664 | =item * |
665 | |
666 | Regular expression checks for safe file names or mail addresses using |
5a964f20 |
667 | C<\w> may be spoofed by an C<LC_CTYPE> locale that claims that |
14280422 |
668 | characters such as "E<gt>" and "|" are alphanumeric. |
669 | |
670 | =item * |
671 | |
e38874e2 |
672 | String interpolation with case-mapping, as in, say, C<$dest = |
673 | "C:\U$name.$ext">, may produce dangerous results if a bogus LC_CTYPE |
674 | case-mapping table is in effect. |
675 | |
676 | =item * |
677 | |
14280422 |
678 | A sneaky C<LC_COLLATE> locale could result in the names of students with |
679 | "D" grades appearing ahead of those with "A"s. |
680 | |
681 | =item * |
682 | |
5a964f20 |
683 | An application that takes the trouble to use information in |
14280422 |
684 | C<LC_MONETARY> may format debits as if they were credits and vice versa |
5a964f20 |
685 | if that locale has been subverted. Or it might make payments in US |
14280422 |
686 | dollars instead of Hong Kong dollars. |
687 | |
688 | =item * |
689 | |
690 | The date and day names in dates formatted by strftime() could be |
691 | manipulated to advantage by a malicious user able to subvert the |
5a964f20 |
692 | C<LC_DATE> locale. ("Look--it says I wasn't in the building on |
14280422 |
693 | Sunday.") |
694 | |
695 | =back |
696 | |
697 | Such dangers are not peculiar to the locale system: any aspect of an |
5a964f20 |
698 | application's environment which may be modified maliciously presents |
14280422 |
699 | similar challenges. Similarly, they are not specific to Perl: any |
5a964f20 |
700 | programming language that allows you to write programs that take |
14280422 |
701 | account of their environment exposes you to these issues. |
702 | |
5a964f20 |
703 | Perl cannot protect you from all possibilities shown in the |
704 | examples--there is no substitute for your own vigilance--but, when |
14280422 |
705 | C<use locale> is in effect, Perl uses the tainting mechanism (see |
5a964f20 |
706 | L<perlsec>) to mark string results that become locale-dependent, and |
14280422 |
707 | which may be untrustworthy in consequence. Here is a summary of the |
5a964f20 |
708 | tainting behavior of operators and functions that may be affected by |
14280422 |
709 | the locale: |
710 | |
711 | =over 4 |
712 | |
551e1d92 |
713 | =item * |
714 | |
715 | B<Comparison operators> (C<lt>, C<le>, C<ge>, C<gt> and C<cmp>): |
14280422 |
716 | |
717 | Scalar true/false (or less/equal/greater) result is never tainted. |
718 | |
551e1d92 |
719 | =item * |
720 | |
721 | B<Case-mapping interpolation> (with C<\l>, C<\L>, C<\u> or C<\U>) |
e38874e2 |
722 | |
723 | Result string containing interpolated material is tainted if |
724 | C<use locale> is in effect. |
725 | |
551e1d92 |
726 | =item * |
727 | |
728 | B<Matching operator> (C<m//>): |
14280422 |
729 | |
730 | Scalar true/false result never tainted. |
731 | |
5a964f20 |
732 | Subpatterns, either delivered as a list-context result or as $1 etc. |
14280422 |
733 | are tainted if C<use locale> is in effect, and the subpattern regular |
e38874e2 |
734 | expression contains C<\w> (to match an alphanumeric character), C<\W> |
735 | (non-alphanumeric character), C<\s> (white-space character), or C<\S> |
5a964f20 |
736 | (non white-space character). The matched-pattern variable, $&, $` |
e38874e2 |
737 | (pre-match), $' (post-match), and $+ (last match) are also tainted if |
738 | C<use locale> is in effect and the regular expression contains C<\w>, |
739 | C<\W>, C<\s>, or C<\S>. |
14280422 |
740 | |
551e1d92 |
741 | =item * |
742 | |
743 | B<Substitution operator> (C<s///>): |
14280422 |
744 | |
e38874e2 |
745 | Has the same behavior as the match operator. Also, the left |
5a964f20 |
746 | operand of C<=~> becomes tainted when C<use locale> in effect |
747 | if modified as a result of a substitution based on a regular |
e38874e2 |
748 | expression match involving C<\w>, C<\W>, C<\s>, or C<\S>; or of |
7b8d334a |
749 | case-mapping with C<\l>, C<\L>,C<\u> or C<\U>. |
14280422 |
750 | |
551e1d92 |
751 | =item * |
752 | |
753 | B<Output formatting functions> (printf() and write()): |
14280422 |
754 | |
3cf03d68 |
755 | Results are never tainted because otherwise even output from print, |
756 | for example C<print(1/7)>, should be tainted if C<use locale> is in |
757 | effect. |
14280422 |
758 | |
551e1d92 |
759 | =item * |
760 | |
761 | B<Case-mapping functions> (lc(), lcfirst(), uc(), ucfirst()): |
14280422 |
762 | |
763 | Results are tainted if C<use locale> is in effect. |
764 | |
551e1d92 |
765 | =item * |
766 | |
767 | B<POSIX locale-dependent functions> (localeconv(), strcoll(), |
14280422 |
768 | strftime(), strxfrm()): |
769 | |
770 | Results are never tainted. |
771 | |
551e1d92 |
772 | =item * |
773 | |
774 | B<POSIX character class tests> (isalnum(), isalpha(), isdigit(), |
14280422 |
775 | isgraph(), islower(), isprint(), ispunct(), isspace(), isupper(), |
776 | isxdigit()): |
777 | |
778 | True/false results are never tainted. |
779 | |
780 | =back |
781 | |
782 | Three examples illustrate locale-dependent tainting. |
783 | The first program, which ignores its locale, won't run: a value taken |
54310121 |
784 | directly from the command line may not be used to name an output file |
14280422 |
785 | when taint checks are enabled. |
786 | |
787 | #/usr/local/bin/perl -T |
788 | # Run with taint checking |
789 | |
54310121 |
790 | # Command line sanity check omitted... |
14280422 |
791 | $tainted_output_file = shift; |
792 | |
793 | open(F, ">$tainted_output_file") |
794 | or warn "Open of $untainted_output_file failed: $!\n"; |
795 | |
796 | The program can be made to run by "laundering" the tainted value through |
5a964f20 |
797 | a regular expression: the second example--which still ignores locale |
798 | information--runs, creating the file named on its command line |
14280422 |
799 | if it can. |
800 | |
801 | #/usr/local/bin/perl -T |
802 | |
803 | $tainted_output_file = shift; |
804 | $tainted_output_file =~ m%[\w/]+%; |
805 | $untainted_output_file = $&; |
806 | |
807 | open(F, ">$untainted_output_file") |
808 | or warn "Open of $untainted_output_file failed: $!\n"; |
809 | |
5a964f20 |
810 | Compare this with a similar but locale-aware program: |
14280422 |
811 | |
812 | #/usr/local/bin/perl -T |
813 | |
814 | $tainted_output_file = shift; |
815 | use locale; |
816 | $tainted_output_file =~ m%[\w/]+%; |
817 | $localized_output_file = $&; |
818 | |
819 | open(F, ">$localized_output_file") |
820 | or warn "Open of $localized_output_file failed: $!\n"; |
821 | |
822 | This third program fails to run because $& is tainted: it is the result |
5a964f20 |
823 | of a match involving C<\w> while C<use locale> is in effect. |
5f05dabc |
824 | |
825 | =head1 ENVIRONMENT |
826 | |
827 | =over 12 |
828 | |
829 | =item PERL_BADLANG |
830 | |
14280422 |
831 | A string that can suppress Perl's warning about failed locale settings |
54310121 |
832 | at startup. Failure can occur if the locale support in the operating |
5a964f20 |
833 | system is lacking (broken) in some way--or if you mistyped the name of |
900bd440 |
834 | a locale when you set up your environment. If this environment |
835 | variable is absent, or has a value that does not evaluate to integer |
836 | zero--that is, "0" or ""-- Perl will complain about locale setting |
837 | failures. |
5f05dabc |
838 | |
14280422 |
839 | B<NOTE>: PERL_BADLANG only gives you a way to hide the warning message. |
840 | The message tells about some problem in your system's locale support, |
841 | and you should investigate what the problem is. |
5f05dabc |
842 | |
843 | =back |
844 | |
845 | The following environment variables are not specific to Perl: They are |
14280422 |
846 | part of the standardized (ISO C, XPG4, POSIX 1.c) setlocale() method |
847 | for controlling an application's opinion on data. |
5f05dabc |
848 | |
849 | =over 12 |
850 | |
851 | =item LC_ALL |
852 | |
5a964f20 |
853 | C<LC_ALL> is the "override-all" locale environment variable. If |
5f05dabc |
854 | set, it overrides all the rest of the locale environment variables. |
855 | |
528d65ad |
856 | =item LANGUAGE |
857 | |
858 | B<NOTE>: C<LANGUAGE> is a GNU extension, it affects you only if you |
859 | are using the GNU libc. This is the case if you are using e.g. Linux. |
860 | If you are using "commercial" UNIXes you are most probably I<not> |
22b6f60d |
861 | using GNU libc and you can ignore C<LANGUAGE>. |
862 | |
863 | However, in the case you are using C<LANGUAGE>: it affects the |
864 | language of informational, warning, and error messages output by |
865 | commands (in other words, it's like C<LC_MESSAGES>) but it has higher |
866 | priority than L<LC_ALL>. Moreover, it's not a single value but |
867 | instead a "path" (":"-separated list) of I<languages> (not locales). |
868 | See the GNU C<gettext> library documentation for more information. |
528d65ad |
869 | |
5f05dabc |
870 | =item LC_CTYPE |
871 | |
872 | In the absence of C<LC_ALL>, C<LC_CTYPE> chooses the character type |
873 | locale. In the absence of both C<LC_ALL> and C<LC_CTYPE>, C<LANG> |
874 | chooses the character type locale. |
875 | |
876 | =item LC_COLLATE |
877 | |
14280422 |
878 | In the absence of C<LC_ALL>, C<LC_COLLATE> chooses the collation |
879 | (sorting) locale. In the absence of both C<LC_ALL> and C<LC_COLLATE>, |
880 | C<LANG> chooses the collation locale. |
5f05dabc |
881 | |
882 | =item LC_MONETARY |
883 | |
14280422 |
884 | In the absence of C<LC_ALL>, C<LC_MONETARY> chooses the monetary |
885 | formatting locale. In the absence of both C<LC_ALL> and C<LC_MONETARY>, |
886 | C<LANG> chooses the monetary formatting locale. |
5f05dabc |
887 | |
888 | =item LC_NUMERIC |
889 | |
890 | In the absence of C<LC_ALL>, C<LC_NUMERIC> chooses the numeric format |
891 | locale. In the absence of both C<LC_ALL> and C<LC_NUMERIC>, C<LANG> |
892 | chooses the numeric format. |
893 | |
894 | =item LC_TIME |
895 | |
14280422 |
896 | In the absence of C<LC_ALL>, C<LC_TIME> chooses the date and time |
897 | formatting locale. In the absence of both C<LC_ALL> and C<LC_TIME>, |
898 | C<LANG> chooses the date and time formatting locale. |
5f05dabc |
899 | |
900 | =item LANG |
901 | |
14280422 |
902 | C<LANG> is the "catch-all" locale environment variable. If it is set, it |
903 | is used as the last resort after the overall C<LC_ALL> and the |
5f05dabc |
904 | category-specific C<LC_...>. |
905 | |
906 | =back |
907 | |
908 | =head1 NOTES |
909 | |
910 | =head2 Backward compatibility |
911 | |
b0c42ed9 |
912 | Versions of Perl prior to 5.004 B<mostly> ignored locale information, |
5a964f20 |
913 | generally behaving as if something similar to the C<"C"> locale were |
914 | always in force, even if the program environment suggested otherwise |
915 | (see L<The setlocale function>). By default, Perl still behaves this |
916 | way for backward compatibility. If you want a Perl application to pay |
917 | attention to locale information, you B<must> use the S<C<use locale>> |
b687b08b |
918 | pragma (see L<The use locale pragma>) to instruct it to do so. |
b0c42ed9 |
919 | |
920 | Versions of Perl from 5.002 to 5.003 did use the C<LC_CTYPE> |
5a964f20 |
921 | information if available; that is, C<\w> did understand what |
922 | were the letters according to the locale environment variables. |
b0c42ed9 |
923 | The problem was that the user had no control over the feature: |
924 | if the C library supported locales, Perl used them. |
925 | |
926 | =head2 I18N:Collate obsolete |
927 | |
5a964f20 |
928 | In versions of Perl prior to 5.004, per-locale collation was possible |
b0c42ed9 |
929 | using the C<I18N::Collate> library module. This module is now mildly |
930 | obsolete and should be avoided in new applications. The C<LC_COLLATE> |
931 | functionality is now integrated into the Perl core language: One can |
932 | use locale-specific scalar data completely normally with C<use locale>, |
933 | so there is no longer any need to juggle with the scalar references of |
934 | C<I18N::Collate>. |
5f05dabc |
935 | |
14280422 |
936 | =head2 Sort speed and memory use impacts |
5f05dabc |
937 | |
938 | Comparing and sorting by locale is usually slower than the default |
14280422 |
939 | sorting; slow-downs of two to four times have been observed. It will |
940 | also consume more memory: once a Perl scalar variable has participated |
941 | in any string comparison or sorting operation obeying the locale |
942 | collation rules, it will take 3-15 times more memory than before. (The |
943 | exact multiplier depends on the string's contents, the operating system |
944 | and the locale.) These downsides are dictated more by the operating |
945 | system's implementation of the locale system than by Perl. |
5f05dabc |
946 | |
e38874e2 |
947 | =head2 write() and LC_NUMERIC |
948 | |
5a964f20 |
949 | Formats are the only part of Perl that unconditionally use information |
e38874e2 |
950 | from a program's locale; if a program's environment specifies an |
951 | LC_NUMERIC locale, it is always used to specify the decimal point |
952 | character in formatted output. Formatted output cannot be controlled by |
953 | C<use locale> because the pragma is tied to the block structure of the |
954 | program, and, for historical reasons, formats exist outside that block |
955 | structure. |
956 | |
5f05dabc |
957 | =head2 Freely available locale definitions |
958 | |
959 | There is a large collection of locale definitions at |
14280422 |
960 | C<ftp://dkuug.dk/i18n/WG15-collection>. You should be aware that it is |
961 | unsupported, and is not claimed to be fit for any purpose. If your |
5a964f20 |
962 | system allows installation of arbitrary locales, you may find the |
14280422 |
963 | definitions useful as they are, or as a basis for the development of |
964 | your own locales. |
5f05dabc |
965 | |
14280422 |
966 | =head2 I18n and l10n |
5f05dabc |
967 | |
b0c42ed9 |
968 | "Internationalization" is often abbreviated as B<i18n> because its first |
969 | and last letters are separated by eighteen others. (You may guess why |
970 | the internalin ... internaliti ... i18n tends to get abbreviated.) In |
971 | the same way, "localization" is often abbreviated to B<l10n>. |
14280422 |
972 | |
973 | =head2 An imperfect standard |
974 | |
975 | Internationalization, as defined in the C and POSIX standards, can be |
976 | criticized as incomplete, ungainly, and having too large a granularity. |
977 | (Locales apply to a whole process, when it would arguably be more useful |
978 | to have them apply to a single thread, window group, or whatever.) They |
979 | also have a tendency, like standards groups, to divide the world into |
980 | nations, when we all know that the world can equally well be divided |
981 | into bankers, bikers, gamers, and so on. But, for now, it's the only |
982 | standard we've got. This may be construed as a bug. |
5f05dabc |
983 | |
984 | =head1 BUGS |
985 | |
986 | =head2 Broken systems |
987 | |
5a964f20 |
988 | In certain systems, the operating system's locale support |
2bdf8add |
989 | is broken and cannot be fixed or used by Perl. Such deficiencies can |
990 | and will result in mysterious hangs and/or Perl core dumps when the |
991 | C<use locale> is in effect. When confronted with such a system, |
7f2de2d2 |
992 | please report in excruciating detail to <F<perlbug@perl.org>>, and |
5a964f20 |
993 | complain to your vendor: bug fixes may exist for these problems |
2bdf8add |
994 | in your operating system. Sometimes such bug fixes are called an |
995 | operating system upgrade. |
5f05dabc |
996 | |
997 | =head1 SEE ALSO |
998 | |
4bbcc6e8 |
999 | L<I18N::Langinfo>, L<POSIX/isalnum>, L<POSIX/isalpha>, |
1000 | L<POSIX/isdigit>, L<POSIX/isgraph>, L<POSIX/islower>, |
1001 | L<POSIX/isprint>, L<POSIX/ispunct>, L<POSIX/isspace>, |
1002 | L<POSIX/isupper>, L<POSIX/isxdigit>, L<POSIX/localeconv>, |
1003 | L<POSIX/setlocale>, L<POSIX/strcoll>, L<POSIX/strftime>, |
1004 | L<POSIX/strtod>, L<POSIX/strxfrm>. |
5f05dabc |
1005 | |
1006 | =head1 HISTORY |
1007 | |
b0c42ed9 |
1008 | Jarkko Hietaniemi's original F<perli18n.pod> heavily hacked by Dominic |
5a964f20 |
1009 | Dunlop, assisted by the perl5-porters. Prose worked over a bit by |
1010 | Tom Christiansen. |
5f05dabc |
1011 | |
5a964f20 |
1012 | Last update: Thu Jun 11 08:44:13 MDT 1998 |