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16
17 <H1><A NAME="SEC39" HREF="gettext_toc.html#TOC39">The Programmer's View</A></H1>
18
19 <P>
20 One aim of the current message catalog implementation provided by
21 GNU <CODE>gettext</CODE> was to use the systems message catalog handling, if the
22 installer wishes to do so. So we perhaps should first take a look at
23 the solutions we know about. The people in the POSIX committee does not
24 manage to agree on one of the semi-official standards which we'll
25 describe below. In fact they couldn't agree on anything, so nothing
26 decide only to include an example of an interface. The major Unix vendors
27 are split in the usage of the two most important specifications: X/Opens
28 catgets vs. Uniforums gettext interface. We'll describe them both and
29 later explain our solution of this dilemma.
30
31 </P>
32
33
34
35 <H2><A NAME="SEC40" HREF="gettext_toc.html#TOC40">About <CODE>catgets</CODE></A></H2>
36
37 <P>
38 The <CODE>catgets</CODE> implementation is defined in the X/Open Portability
39 Guide, Volume 3, XSI Supplementary Definitions, Chapter 5. But the
40 process of creating this standard seemed to be too slow for some of
41 the Unix vendors so they created their implementations on preliminary
42 versions of the standard. Of course this leads again to problems while
43 writing platform independent programs: even the usage of <CODE>catgets</CODE>
44 does not guarantee a unique interface.
45
46 </P>
47 <P>
48 Another, personal comment on this that only a bunch of committee members
49 could have made this interface. They never really tried to program
50 using this interface. It is a fast, memory-saving implementation, an
51 user can happily live with it. But programmers hate it (at least me and
52 some others do...)
53
54 </P>
55 <P>
56 But we must not forget one point: after all the trouble with transfering
57 the rights on Unix(tm) they at last came to X/Open, the very same who
58 published this specifications. This leads me to making the prediction
59 that this interface will be in future Unix standards (e.g. Spec1170) and
60 therefore part of all Unix implementation (implementations, which are
61 <EM>allowed</EM> to wear this name).
62
63 </P>
64
65
66
67 <H3><A NAME="SEC41" HREF="gettext_toc.html#TOC41">The Interface</A></H3>
68
69 <P>
70 The interface to the <CODE>catgets</CODE> implementation consists of three
71 functions which correspond to those used in file access: <CODE>catopen</CODE>
72 to open the catalog for using, <CODE>catgets</CODE> for accessing the message
73 tables, and <CODE>catclose</CODE> for closing after work is done. Prototypes
74 for the functions and the needed definitions are in the
75 <CODE>&#60;nl_types.h&#62;</CODE> header file.
76
77 </P>
78 <P>
79 <CODE>catopen</CODE> is used like in this:
80
81 </P>
82
83 <PRE>
84 nl_catd catd = catopen ("catalog_name", 0);
85 </PRE>
86
87 <P>
88 The function takes as the argument the name of the catalog. This usual
89 refers to the name of the program or the package. The second parameter
90 is not further specified in the standard. I don't even know whether it
91 is implemented consistently among various systems. So the common advice
92 is to use <CODE>0</CODE> as the value. The return value is a handle to the
93 message catalog, equivalent to handles to file returned by <CODE>open</CODE>.
94
95 </P>
96 <P>
97 This handle is of course used in the <CODE>catgets</CODE> function which can
98 be used like this:
99
100 </P>
101
102 <PRE>
103 char *translation = catgets (catd, set_no, msg_id, "original string");
104 </PRE>
105
106 <P>
107 The first parameter is this catalog descriptor. The second parameter
108 specifies the set of messages in this catalog, in which the message
109 described by <CODE>msg_id</CODE> is obtained. <CODE>catgets</CODE> therefore uses a
110 three-stage addressing:
111
112 </P>
113
114 <PRE>
115 catalog name => set number => message ID => translation
116 </PRE>
117
118 <P>
119 The fourth argument is not used to address the translation. It is given
120 as a default value in case when one of the addressing stages fail. One
121 important thing to remember is that although the return type of catgets
122 is <CODE>char *</CODE> the resulting string <EM>must not</EM> be changed. It
123 should better <CODE>const char *</CODE>, but the standard is published in
124 1988, one year before ANSI C.
125
126 </P>
127 <P>
128 The last of these function functions is used and behaves as expected:
129
130 </P>
131
132 <PRE>
133 catclose (catd);
134 </PRE>
135
136 <P>
137 After this no <CODE>catgets</CODE> call using the descriptor is legal anymore.
138
139 </P>
140
141
142 <H3><A NAME="SEC42" HREF="gettext_toc.html#TOC42">Problems with the <CODE>catgets</CODE> Interface?!</A></H3>
143
144 <P>
145 Now that this descriptions seemed to be really easy where are the
146 problem we speak of. In fact the interface could be used in a
147 reasonable way, but constructing the message catalogs is a pain. The
148 reason for this lies in the third argument of <CODE>catgets</CODE>: the unique
149 message ID. This has to be a numeric value for all messages in a single
150 set. Perhaps you could imagine the problems keeping such list while
151 changing the source code. Add a new message here, remove one there. Of
152 course there have been developed a lot of tools helping to organize this
153 chaos but one as the other fails in one aspect or the other. We don't
154 want to say that the other approach has no problems but they are far
155 more easily to manage.
156
157 </P>
158
159
160 <H2><A NAME="SEC43" HREF="gettext_toc.html#TOC43">About <CODE>gettext</CODE></A></H2>
161
162 <P>
163 The definition of the <CODE>gettext</CODE> interface comes from a Uniforum
164 proposal and it is followed by at least one major Unix vendor
165 (Sun) in its last developments. It is not specified in any official
166 standard, though.
167
168 </P>
169 <P>
170 The main points about this solution is that it does not follow the
171 method of normal file handling (open-use-close) and that it does not
172 burden the programmer so many task, especially the unique key handling.
173 Of course here is also a unique key needed, but this key is the
174 message itself (how long or short it is). See section <A HREF="gettext_8.html#SEC48">Comparing the Two Interfaces</A> for a
175 more detailed comparison of the two methods.
176
177 </P>
178 <P>
179 The following section contains a rather detailed description of the
180 interface. We make it that detailed because this is the interface
181 we chose for the GNU <CODE>gettext</CODE> Library. Programmers interested
182 in using this library will be interested in this description.
183
184 </P>
185
186
187
188 <H3><A NAME="SEC44" HREF="gettext_toc.html#TOC44">The Interface</A></H3>
189
190 <P>
191 The minimal functionality an interface must have is a) to select a
192 domain the strings are coming from (a single domain for all programs is
193 not reasonable because its construction and maintenance is difficult,
194 perhaps impossible) and b) to access a string in a selected domain.
195
196 </P>
197 <P>
198 This is principally the description of the <CODE>gettext</CODE> interface. It
199 has an global domain which unqualified usages reference. Of course this
200 domain is selectable by the user.
201
202 </P>
203
204 <PRE>
205 char *textdomain (const char *domain_name);
206 </PRE>
207
208 <P>
209 This provides the possibility to change or query the current status of
210 the current global domain of the <CODE>LC_MESSAGE</CODE> category. The
211 argument is a null-terminated string, whose characters must be legal in
212 the use in filenames. If the <VAR>domain_name</VAR> argument is <CODE>NULL</CODE>,
213 the function return the current value. If no value has been set
214 before, the name of the default domain is returned: <EM>messages</EM>.
215 Please note that although the return value of <CODE>textdomain</CODE> is of
216 type <CODE>char *</CODE> no changing is allowed. It is also important to know
217 that no checks of the availability are made. If the name is not
218 available you will see this by the fact that no translations are provided.
219
220 </P>
221 <P>
222 To use a domain set by <CODE>textdomain</CODE> the function
223
224 </P>
225
226 <PRE>
227 char *gettext (const char *msgid);
228 </PRE>
229
230 <P>
231 is to be used. This is the simplest reasonable form one can imagine.
232 The translation of the string <VAR>msgid</VAR> is returned if it is available
233 in the current domain. If not available the argument itself is
234 returned. If the argument is <CODE>NULL</CODE> the result is undefined.
235
236 </P>
237 <P>
238 One things which should come into mind is that no explicit dependency to
239 the used domain is given. The current value of the domain for the
240 <CODE>LC_MESSAGES</CODE> locale is used. If this changes between two
241 executions of the same <CODE>gettext</CODE> call in the program, both calls
242 reference a different message catalog.
243
244 </P>
245 <P>
246 For the easiest case, which is normally used in internationalized
247 packages, once at the beginning of execution a call to <CODE>textdomain</CODE>
248 is issued, setting the domain to a unique name, normally the package
249 name. In the following code all strings which have to be translated are
250 filtered through the gettext function. That's all, the package speaks
251 your language.
252
253 </P>
254
255
256 <H3><A NAME="SEC45" HREF="gettext_toc.html#TOC45">Solving Ambiguities</A></H3>
257
258 <P>
259 While this single name domain work good for most applications there
260 might be the need to get translations from more than one domain. Of
261 course one could switch between different domains with calls to
262 <CODE>textdomain</CODE>, but this is really not convenient nor is it fast. A
263 possible situation could be one case discussing while this writing: all
264 error messages of functions in the set of common used functions should
265 go into a separate domain <CODE>error</CODE>. By this mean we would only need
266 to translate them once.
267
268 </P>
269 <P>
270 For this reasons there are two more functions to retrieve strings:
271
272 </P>
273
274 <PRE>
275 char *dgettext (const char *domain_name, const char *msgid);
276 char *dcgettext (const char *domain_name, const char *msgid,
277 int category);
278 </PRE>
279
280 <P>
281 Both take an additional argument at the first place, which corresponds
282 to the argument of <CODE>textdomain</CODE>. The third argument of
283 <CODE>dcgettext</CODE> allows to use another locale but <CODE>LC_MESSAGES</CODE>.
284 But I really don't know where this can be useful. If the
285 <VAR>domain_name</VAR> is <CODE>NULL</CODE> or <VAR>category</VAR> has an value beside
286 the known ones, the result is undefined. It should also be noted that
287 this function is not part of the second known implementation of this
288 function family, the one found in Solaris.
289
290 </P>
291 <P>
292 A second ambiguity can arise by the fact, that perhaps more than one
293 domain has the same name. This can be solved by specifying where the
294 needed message catalog files can be found.
295
296 </P>
297
298 <PRE>
299 char *bindtextdomain (const char *domain_name,
300 const char *dir_name);
301 </PRE>
302
303 <P>
304 Calling this function binds the given domain to a file in the specified
305 directory (how this file is determined follows below). Especially a
306 file in the systems default place is not favored against the specified
307 file anymore (as it would be by solely using <CODE>textdomain</CODE>). A
308 <CODE>NULL</CODE> pointer for the <VAR>dir_name</VAR> parameter returns the binding
309 associated with <VAR>domain_name</VAR>. If <VAR>domain_name</VAR> itself is
310 <CODE>NULL</CODE> nothing happens and a <CODE>NULL</CODE> pointer is returned. Here
311 again as for all the other functions is true that none of the return
312 value must be changed!
313
314 </P>
315 <P>
316 It is important to remember that relative path names for the
317 <VAR>dir_name</VAR> parameter can be trouble. Since the path is always
318 computed relative to the current directory different results will be
319 achieved when the program executes a <CODE>chdir</CODE> command. Relative
320 paths should always be avoided to avoid dependencies and
321 unreliabilities.
322
323 </P>
324
325
326 <H3><A NAME="SEC46" HREF="gettext_toc.html#TOC46">Locating Message Catalog Files</A></H3>
327
328 <P>
329 Because many different languages for many different packages have to be
330 stored we need some way to add these information to file message catalog
331 files. The way usually used in Unix environments is have this encoding
332 in the file name. This is also done here. The directory name given in
333 <CODE>bindtextdomain</CODE>s second argument (or the default directory),
334 followed by the value and name of the locale and the domain name are
335 concatenated:
336
337 </P>
338
339 <PRE>
340 <VAR>dir_name</VAR>/<VAR>locale</VAR>/LC_<VAR>category</VAR>/<VAR>domain_name</VAR>.mo
341 </PRE>
342
343 <P>
344 The default value for <VAR>dir_name</VAR> is system specific. For the GNU
345 library, and for packages adhering to its conventions, it's:
346
347 <PRE>
348 /usr/local/share/locale
349 </PRE>
350
351 <P>
352 <VAR>locale</VAR> is the value of the locale whose name is this
353 <CODE>LC_<VAR>category</VAR></CODE>. For <CODE>gettext</CODE> and <CODE>dgettext</CODE> this
354 locale is always <CODE>LC_MESSAGES</CODE>. <CODE>dcgettext</CODE> specifies the
355 locale by the third argument.<A NAME="DOCF2" HREF="gettext_foot.html#FOOT2">(2)</A> <A NAME="DOCF3" HREF="gettext_foot.html#FOOT3">(3)</A>
356
357 </P>
358
359
360 <H3><A NAME="SEC47" HREF="gettext_toc.html#TOC47">Optimization of the *gettext functions</A></H3>
361
362 <P>
363 At this point of the discussion we should talk about an advantage of the
364 GNU <CODE>gettext</CODE> implementation. Some readers might have pointed out
365 that an internationalized program might have a poor performance if some
366 string has to be translated in an inner loop. While this is unavoidable
367 when the string varies from one run of the loop to the other it is
368 simply a waste of time when the string is always the same. Take the
369 following example:
370
371 </P>
372
373 <PRE>
374 {
375 while (...)
376 {
377 puts (gettext ("Hello world"));
378 }
379 }
380 </PRE>
381
382 <P>
383 When the locale selection does not change between two runs the resulting
384 string is always the same. One way to use this is:
385
386 </P>
387
388 <PRE>
389 {
390 str = gettext ("Hello world");
391 while (...)
392 {
393 puts (str);
394 }
395 }
396 </PRE>
397
398 <P>
399 But this solution is not usable in all situation (e.g. when the locale
400 selection changes) nor is it good readable.
401
402 </P>
403 <P>
404 The GNU C compiler, version 2.7 and above, provide another solution for
405 this. To describe this we show here some lines of the
406 <TT>`intl/libgettext.h'</TT> file. For an explanation of the expression
407 command block see section `Statements and Declarations in Expressions' in <CITE>The GNU CC Manual</CITE>.
408
409 </P>
410
411 <PRE>
412 # if defined __GNUC__ &#38;&#38; __GNUC__ == 2 &#38;&#38; __GNUC_MINOR__ &#62;= 7
413 extern int _nl_msg_cat_cntr;
414 # define dcgettext(domainname, msgid, category) \
415 (__extension__ \
416 ({ \
417 char *result; \
418 if (__builtin_constant_p (msgid)) \
419 { \
420 static char *__translation__; \
421 static int __catalog_counter__; \
422 if (! __translation__ \
423 || __catalog_counter__ != _nl_msg_cat_cntr) \
424 { \
425 __translation__ = \
426 dcgettext__ ((domainname), (msgid), (category)); \
427 __catalog_counter__ = _nl_msg_cat_cntr; \
428 } \
429 result = __translation__; \
430 } \
431 else \
432 result = dcgettext__ ((domainname), (msgid), (category)); \
433 result; \
434 }))
435 # endif
436 </PRE>
437
438 <P>
439 The interesting thing here is the <CODE>__builtin_constant_p</CODE> predicate.
440 This is evaluated at compile time and so optimization can take place
441 immediately. Here two cases are distinguished: the argument to
442 <CODE>gettext</CODE> is not a constant value in which case simply the function
443 <CODE>dcgettext__</CODE> is called, the real implementation of the
444 <CODE>dcgettext</CODE> function.
445
446 </P>
447 <P>
448 If the string argument <EM>is</EM> constant we can reuse the once gained
449 translation when the locale selection has not changed. This is exactly
450 what is done here. The <CODE>_nl_msg_cat_cntr</CODE> variable is defined in
451 the <TT>`loadmsgcat.c'</TT> which is available in <TT>`libintl.a'</TT> and is
452 changed whenever a new message catalog is loaded.
453
454 </P>
455
456
457 <H2><A NAME="SEC48" HREF="gettext_toc.html#TOC48">Comparing the Two Interfaces</A></H2>
458
459 <P>
460 The following discussion is perhaps a little bit colored. As said
461 above we implemented GNU <CODE>gettext</CODE> following the Uniforum
462 proposal and this surely has its reasons. But it should show how we
463 came to this decision.
464
465 </P>
466 <P>
467 First we take a look at the developing process. When we write an
468 application using NLS provided by <CODE>gettext</CODE> we proceed as always.
469 Only when we come to a string which might be seen by the users and thus
470 has to be translated we use <CODE>gettext("...")</CODE> instead of
471 <CODE>"..."</CODE>. At the beginning of each source file (or in a central
472 header file) we define
473
474 </P>
475
476 <PRE>
477 #define gettext(String) (String)
478 </PRE>
479
480 <P>
481 Even this definition can be avoided when the system supports the
482 <CODE>gettext</CODE> function in its C library. When we compile this code the
483 result is the same as if no NLS code is used. When you take a look at
484 the GNU <CODE>gettext</CODE> code you will see that we use <CODE>_("...")</CODE>
485 instead of <CODE>gettext("...")</CODE>. This reduces the number of
486 additional characters per translatable string to <EM>3</EM> (in words:
487 three).
488
489 </P>
490 <P>
491 When now a production version of the program is needed we simply replace
492 the definition
493
494 </P>
495
496 <PRE>
497 #define _(String) (String)
498 </PRE>
499
500 <P>
501 by
502
503 </P>
504
505 <PRE>
506 #include &#60;libintl.h&#62;
507 #define _(String) gettext (String)
508 </PRE>
509
510 <P>
511 Additionally we run the program <TT>`xgettext'</TT> on all source code file
512 which contain translatable strings and that's it: we have a running
513 program which does not depend on translations to be available, but which
514 can use any that becomes available.
515
516 </P>
517 <P>
518 The same procedure can be done for the <CODE>gettext_noop</CODE> invocations
519 (see section <A HREF="gettext_3.html#SEC18">Special Cases of Translatable Strings</A>). First you can define <CODE>gettext_noop</CODE> to a
520 no-op macro and later use the definition from <TT>`libintl.h'</TT>. Because
521 this name is not used in Suns implementation of <TT>`libintl.h'</TT>,
522 you should consider the following code for your project:
523
524 </P>
525
526 <PRE>
527 #ifdef gettext_noop
528 # define N_(String) gettext_noop (String)
529 #else
530 # define N_(String) (String)
531 #endif
532 </PRE>
533
534 <P>
535 <CODE>N_</CODE> is a short form similar to <CODE>_</CODE>. The <TT>`Makefile'</TT> in
536 the <TT>`po/'</TT> directory of GNU gettext knows by default both of the
537 mentioned short forms so you are invited to follow this proposal for
538 your own ease.
539
540 </P>
541 <P>
542 Now to <CODE>catgets</CODE>. The main problem is the work for the
543 programmer. Every time he comes to a translatable string he has to
544 define a number (or a symbolic constant) which has also be defined in
545 the message catalog file. He also has to take care for duplicate
546 entries, duplicate message IDs etc. If he wants to have the same
547 quality in the message catalog as the GNU <CODE>gettext</CODE> program
548 provides he also has to put the descriptive comments for the strings and
549 the location in all source code files in the message catalog. This is
550 nearly a Mission: Impossible.
551
552 </P>
553 <P>
554 But there are also some points people might call advantages speaking for
555 <CODE>catgets</CODE>. If you have a single word in a string and this string
556 is used in different contexts it is likely that in one or the other
557 language the word has different translations. Example:
558
559 </P>
560
561 <PRE>
562 printf ("%s: %d", gettext ("number"), number_of_errors)
563
564 printf ("you should see %d %s", number_count,
565 number_count == 1 ? gettext ("number") : gettext ("numbers"))
566 </PRE>
567
568 <P>
569 Here we have to translate two times the string <CODE>"number"</CODE>. Even
570 if you do not speak a language beside English it might be possible to
571 recognize that the two words have a different meaning. In German the
572 first appearance has to be translated to <CODE>"Anzahl"</CODE> and the second
573 to <CODE>"Zahl"</CODE>.
574
575 </P>
576 <P>
577 Now you can say that this example is really esoteric. And you are
578 right! This is exactly how we felt about this problem and decide that
579 it does not weight that much. The solution for the above problem could
580 be very easy:
581
582 </P>
583
584 <PRE>
585 printf ("%s %d", gettext ("number:"), number_of_errors)
586
587 printf (number_count == 1 ? gettext ("you should see %d number")
588 : gettext ("you should see %d numbers"),
589 number_count)
590 </PRE>
591
592 <P>
593 We believe that we can solve all conflicts with this method. If it is
594 difficult one can also consider changing one of the conflicting string a
595 little bit. But it is not impossible to overcome.
596
597 </P>
598 <P>
599 Translator note: It is perhaps appropriate here to tell those English
600 speaking programmers that the plural form of a noun cannot be formed by
601 appending a single `s'. Most other languages use different methods.
602 Even the above form is not general enough to cope with all languages.
603 Rafal Maszkowski &#60;rzm@mat.uni.torun.pl&#62; reports:
604
605 </P>
606
607 <BLOCKQUOTE>
608 <P>
609 In Polish we use e.g. plik (file) this way:
610
611 <PRE>
612 1 plik
613 2,3,4 pliki
614 5-21 pliko'w
615 22-24 pliki
616 25-31 pliko'w
617 </PRE>
618
619 <P>
620 and so on (o' means 8859-2 oacute which should be rather okreska,
621 similar to aogonek).
622 </BLOCKQUOTE>
623
624 <P>
625 A workable approach might be to consider methods like the one used for
626 <CODE>LC_TIME</CODE> in the POSIX.2 standard. The value of the
627 <CODE>alt_digits</CODE> field can be up to 100 strings which represent the
628 numbers 1 to 100. Using this in a situation of an internationalized
629 program means that an array of translatable strings should be indexed by
630 the number which should represent. A small example:
631
632 </P>
633
634 <PRE>
635 void
636 print_month_info (int month)
637 {
638 const char *month_pos[12] =
639 { N_("first"), N_("second"), N_("third"), N_("fourth"),
640 N_("fifth"), N_("sixth"), N_("seventh"), N_("eighth"),
641 N_("ninth"), N_("tenth"), N_("eleventh"), N_("twelfth") };
642 printf (_("%s is the %s month\n"), nl_langinfo (MON_1 + month),
643 _(month_pos[month]));
644 }
645 </PRE>
646
647 <P>
648 It should be obvious that this method is only reasonable for small
649 ranges of numbers.
650
651 </P>
652
653
654
655 <H2><A NAME="SEC49" HREF="gettext_toc.html#TOC49">Using libintl.a in own programs</A></H2>
656
657 <P>
658 Starting with version 0.9.4 the library <CODE>libintl.h</CODE> should be
659 self-contained. I.e., you can use it in your own programs without
660 providing additional functions. The <TT>`Makefile'</TT> will put the header
661 and the library in directories selected using the <CODE>$(prefix)</CODE>.
662
663 </P>
664 <P>
665 One exception of the above is found on HP-UX systems. Here the C library
666 does not contain the <CODE>alloca</CODE> function (and the HP compiler does
667 not generate it inlined). But it is not intended to rewrite the whole
668 library just because of this dumb system. Instead include the
669 <CODE>alloca</CODE> function in all package you use the <CODE>libintl.a</CODE> in.
670
671 </P>
672
673
674 <H2><A NAME="SEC50" HREF="gettext_toc.html#TOC50">Being a <CODE>gettext</CODE> grok</A></H2>
675
676 <P>
677 To fully exploit the functionality of the GNU <CODE>gettext</CODE> library it
678 is surely helpful to read the source code. But for those who don't want
679 to spend that much time in reading the (sometimes complicated) code here
680 is a list comments:
681
682 </P>
683
684 <UL>
685 <LI>Changing the language at runtime
686
687 For interactive programs it might be useful to offer a selection of the
688 used language at runtime. To understand how to do this one need to know
689 how the used language is determined while executing the <CODE>gettext</CODE>
690 function. The method which is presented here only works correctly
691 with the GNU implementation of the <CODE>gettext</CODE> functions. It is not
692 possible with underlying <CODE>catgets</CODE> functions or <CODE>gettext</CODE>
693 functions from the systems C library. The exception is of course the
694 GNU C Library which uses the GNU <CODE>gettext</CODE> Library for message handling.
695
696 In the function <CODE>dcgettext</CODE> at every call the current setting of
697 the highest priority environment variable is determined and used.
698 Highest priority means here the following list with decreasing
699 priority:
700
701
702 <OL>
703 <LI><CODE>LANGUAGE</CODE>
704
705 <LI><CODE>LC_ALL</CODE>
706
707 <LI><CODE>LC_xxx</CODE>, according to selected locale
708
709 <LI><CODE>LANG</CODE>
710
711 </OL>
712
713 Afterwards the path is constructed using the found value and the
714 translation file is loaded if available.
715
716 What is now when the value for, say, <CODE>LANGUAGE</CODE> changes. According
717 to the process explained above the new value of this variable is found
718 as soon as the <CODE>dcgettext</CODE> function is called. But this also means
719 the (perhaps) different message catalog file is loaded. In other
720 words: the used language is changed.
721
722 But there is one little hook. The code for gcc-2.7.0 and up provides
723 some optimization. This optimization normally prevents the calling of
724 the <CODE>dcgettext</CODE> function as long as no new catalog is loaded. But
725 if <CODE>dcgettext</CODE> is not called the program also cannot find the
726 <CODE>LANGUAGE</CODE> variable be changed (see section <A HREF="gettext_8.html#SEC47">Optimization of the *gettext functions</A>). A
727 solution for this is very easy. Include the following code in the
728 language switching function.
729
730
731 <PRE>
732 /* Change language. */
733 setenv ("LANGUAGE", "fr", 1);
734
735 /* Make change known. */
736 {
737 extern int _nl_msg_cat_cntr;
738 ++_nl_msg_cat_cntr;
739 }
740 </PRE>
741
742 The variable <CODE>_nl_msg_cat_cntr</CODE> is defined in <TT>`loadmsgcat.c'</TT>.
743 The programmer will find himself in need for a construct like this only
744 when developing programs which do run longer and provide the user to
745 select the language at runtime. Non-interactive programs (like all
746 these little Unix tools) should never need this.
747
748 </UL>
749
750
751
752 <H2><A NAME="SEC51" HREF="gettext_toc.html#TOC51">Temporary Notes for the Programmers Chapter</A></H2>
753
754
755
756 <H3><A NAME="SEC52" HREF="gettext_toc.html#TOC52">Temporary - Two Possible Implementations</A></H3>
757
758 <P>
759 There are two competing methods for language independent messages:
760 the X/Open <CODE>catgets</CODE> method, and the Uniforum <CODE>gettext</CODE>
761 method. The <CODE>catgets</CODE> method indexes messages by integers; the
762 <CODE>gettext</CODE> method indexes them by their English translations.
763 The <CODE>catgets</CODE> method has been around longer and is supported
764 by more vendors. The <CODE>gettext</CODE> method is supported by Sun,
765 and it has been heard that the COSE multi-vendor initiative is
766 supporting it. Neither method is a POSIX standard; the POSIX.1
767 committee had a lot of disagreement in this area.
768
769 </P>
770 <P>
771 Neither one is in the POSIX standard. There was much disagreement
772 in the POSIX.1 committee about using the <CODE>gettext</CODE> routines
773 vs. <CODE>catgets</CODE> (XPG). In the end the committee couldn't
774 agree on anything, so no messaging system was included as part
775 of the standard. I believe the informative annex of the standard
776 includes the XPG3 messaging interfaces, "...as an example of
777 a messaging system that has been implemented..."
778
779 </P>
780 <P>
781 They were very careful not to say anywhere that you should use one
782 set of interfaces over the other. For more on this topic please
783 see the Programming for Internationalization FAQ.
784
785 </P>
786
787
788 <H3><A NAME="SEC53" HREF="gettext_toc.html#TOC53">Temporary - About <CODE>catgets</CODE></A></H3>
789
790 <P>
791 There have been a few discussions of late on the use of
792 <CODE>catgets</CODE> as a base. I think it important to present both
793 sides of the argument and hence am opting to play devil's advocate
794 for a little bit.
795
796 </P>
797 <P>
798 I'll not deny the fact that <CODE>catgets</CODE> could have been designed
799 a lot better. It currently has quite a number of limitations and
800 these have already been pointed out.
801
802 </P>
803 <P>
804 However there is a great deal to be said for consistency and
805 standardization. A common recurring problem when writing Unix
806 software is the myriad portability problems across Unix platforms.
807 It seems as if every Unix vendor had a look at the operating system
808 and found parts they could improve upon. Undoubtedly, these
809 modifications are probably innovative and solve real problems.
810 However, software developers have a hard time keeping up with all
811 these changes across so many platforms.
812
813 </P>
814 <P>
815 And this has prompted the Unix vendors to begin to standardize their
816 systems. Hence the impetus for Spec1170. Every major Unix vendor
817 has committed to supporting this standard and every Unix software
818 developer waits with glee the day they can write software to this
819 standard and simply recompile (without having to use autoconf)
820 across different platforms.
821
822 </P>
823 <P>
824 As I understand it, Spec1170 is roughly based upon version 4 of the
825 X/Open Portability Guidelines (XPG4). Because <CODE>catgets</CODE> and
826 friends are defined in XPG4, I'm led to believe that <CODE>catgets</CODE>
827 is a part of Spec1170 and hence will become a standardized component
828 of all Unix systems.
829
830 </P>
831
832
833 <H3><A NAME="SEC54" HREF="gettext_toc.html#TOC54">Temporary - Why a single implementation</A></H3>
834
835 <P>
836 Now it seems kind of wasteful to me to have two different systems
837 installed for accessing message catalogs. If we do want to remedy
838 <CODE>catgets</CODE> deficiencies why don't we try to expand <CODE>catgets</CODE>
839 (in a compatible manner) rather than implement an entirely new system.
840 Otherwise, we'll end up with two message catalog access systems installed
841 with an operating system - one set of routines for packages using GNU
842 <CODE>gettext</CODE> for their internationalization, and another set of routines
843 (catgets) for all other software. Bloated?
844
845 </P>
846 <P>
847 Supposing another catalog access system is implemented. Which do
848 we recommend? At least for Linux, we need to attract as many
849 software developers as possible. Hence we need to make it as easy
850 for them to port their software as possible. Which means supporting
851 <CODE>catgets</CODE>. We will be implementing the <CODE>glocale</CODE> code
852 within our <CODE>libc</CODE>, but does this mean we also have to incorporate
853 another message catalog access scheme within our <CODE>libc</CODE> as well?
854 And what about people who are going to be using the <CODE>glocale</CODE>
855 + non-<CODE>catgets</CODE> routines. When they port their software to
856 other platforms, they're now going to have to include the front-end
857 (<CODE>glocale</CODE>) code plus the back-end code (the non-<CODE>catgets</CODE>
858 access routines) with their software instead of just including the
859 <CODE>glocale</CODE> code with their software.
860
861 </P>
862 <P>
863 Message catalog support is however only the tip of the iceberg.
864 What about the data for the other locale categories. They also have
865 a number of deficiencies. Are we going to abandon them as well and
866 develop another duplicate set of routines (should <CODE>glocale</CODE>
867 expand beyond message catalog support)?
868
869 </P>
870 <P>
871 Like many parts of Unix that can be improved upon, we're stuck with balancing
872 compatibility with the past with useful improvements and innovations for
873 the future.
874
875 </P>
876
877
878
879 <H3><A NAME="SEC55" HREF="gettext_toc.html#TOC55">Temporary - Notes</A></H3>
880
881 <P>
882 X/Open agreed very late on the standard form so that many
883 implementations differ from the final form. Both of my system (old
884 Linux catgets and Ultrix-4) have a strange variation.
885
886 </P>
887 <P>
888 OK. After incorporating the last changes I have to spend some time on
889 making the GNU/Linux <CODE>libc</CODE> <CODE>gettext</CODE> functions. So in future
890 Solaris is not the only system having <CODE>gettext</CODE>.
891
892 </P>
893 <P><HR><P>
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