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jpayne@68	13 <head>
jpayne@68	14 <title>GNU gettext utilities: 11. The Programmer's View</title>
jpayne@68	15
jpayne@68	16 <meta name="description" content="GNU gettext utilities: 11. The Programmer's View">
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jpayne@68	44 <table cellpadding="1" cellspacing="1" border="0">
jpayne@68	45 <tr><td valign="middle" align="left">[<a href="gettext_10.html#SEC173" title="Beginning of this chapter or previous chapter"> << </a>]</td>
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jpayne@68	52 <td valign="middle" align="left">[<a href="gettext_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
jpayne@68	53 <td valign="middle" align="left">[<a href="gettext_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
jpayne@68	54 <td valign="middle" align="left">[<a href="gettext_21.html#SEC389" title="Index">Index</a>]</td>
jpayne@68	55 <td valign="middle" align="left">[<a href="gettext_abt.html#SEC_About" title="About (help)"> ? </a>]</td>
jpayne@68	56 </tr></table>
jpayne@68	57
jpayne@68	58 <hr size="2">
jpayne@68	59 <a name="Programmers"></a>
jpayne@68	60 <a name="SEC197"></a>
jpayne@68	61 <h1 class="chapter"> <a href="gettext_toc.html#TOC190">11. The Programmer's View</a> </h1>
jpayne@68	62
jpayne@68	63
jpayne@68	64 <p>One aim of the current message catalog implementation provided by
jpayne@68	65 GNU <code>gettext</code> was to use the system's message catalog handling, if the
jpayne@68	66 installer wishes to do so. So we perhaps should first take a look at
jpayne@68	67 the solutions we know about. The people in the POSIX committee did not
jpayne@68	68 manage to agree on one of the semi-official standards which we'll
jpayne@68	69 describe below. In fact they couldn't agree on anything, so they decided
jpayne@68	70 only to include an example of an interface. The major Unix vendors
jpayne@68	71 are split in the usage of the two most important specifications: X/Open's
jpayne@68	72 catgets vs. Uniforum's gettext interface. We'll describe them both and
jpayne@68	73 later explain our solution of this dilemma.
jpayne@68	74 </p>
jpayne@68	75
jpayne@68	76
jpayne@68	77 <a name="catgets"></a>
jpayne@68	78 <a name="SEC198"></a>
jpayne@68	79 <h2 class="section"> <a href="gettext_toc.html#TOC191">11.1 About <code>catgets</code></a> </h2>
jpayne@68	80
jpayne@68	81 <p>The <code>catgets</code> implementation is defined in the X/Open Portability
jpayne@68	82 Guide, Volume 3, XSI Supplementary Definitions, Chapter 5. But the
jpayne@68	83 process of creating this standard seemed to be too slow for some of
jpayne@68	84 the Unix vendors so they created their implementations on preliminary
jpayne@68	85 versions of the standard. Of course this leads again to problems while
jpayne@68	86 writing platform independent programs: even the usage of <code>catgets</code>
jpayne@68	87 does not guarantee a unique interface.
jpayne@68	88 </p>
jpayne@68	89 <p>Another, personal comment on this that only a bunch of committee members
jpayne@68	90 could have made this interface. They never really tried to program
jpayne@68	91 using this interface. It is a fast, memory-saving implementation, an
jpayne@68	92 user can happily live with it. But programmers hate it (at least I and
jpayne@68	93 some others do…)
jpayne@68	94 </p>
jpayne@68	95 <p>But we must not forget one point: after all the trouble with transferring
jpayne@68	96 the rights on Unix they at last came to X/Open, the very same who
jpayne@68	97 published this specification. This leads me to making the prediction
jpayne@68	98 that this interface will be in future Unix standards (e.g. Spec1170) and
jpayne@68	99 therefore part of all Unix implementation (implementations, which are
jpayne@68	100 <em>allowed</em> to wear this name).
jpayne@68	101 </p>
jpayne@68	102
jpayne@68	103
jpayne@68	104 <a name="Interface-to-catgets"></a>
jpayne@68	105 <a name="SEC199"></a>
jpayne@68	106 <h3 class="subsection"> <a href="gettext_toc.html#TOC192">11.1.1 The Interface</a> </h3>
jpayne@68	107
jpayne@68	108 <p>The interface to the <code>catgets</code> implementation consists of three
jpayne@68	109 functions which correspond to those used in file access: <code>catopen</code>
jpayne@68	110 to open the catalog for using, <code>catgets</code> for accessing the message
jpayne@68	111 tables, and <code>catclose</code> for closing after work is done. Prototypes
jpayne@68	112 for the functions and the needed definitions are in the
jpayne@68	113 <code><nl_types.h></code> header file.
jpayne@68	114 </p>
jpayne@68	115 <a name="IDX1059"></a>
jpayne@68	116 <p><code>catopen</code> is used like in this:
jpayne@68	117 </p>
jpayne@68	118 <table><tr><td> </td><td><pre class="example">nl_catd catd = catopen ("catalog_name", 0);
jpayne@68	119 </pre></td></tr></table>
jpayne@68	120
jpayne@68	121 <p>The function takes as the argument the name of the catalog. This usual
jpayne@68	122 refers to the name of the program or the package. The second parameter
jpayne@68	123 is not further specified in the standard. I don't even know whether it
jpayne@68	124 is implemented consistently among various systems. So the common advice
jpayne@68	125 is to use <code>0</code> as the value. The return value is a handle to the
jpayne@68	126 message catalog, equivalent to handles to file returned by <code>open</code>.
jpayne@68	127 </p>
jpayne@68	128 <a name="IDX1060"></a>
jpayne@68	129 <p>This handle is of course used in the <code>catgets</code> function which can
jpayne@68	130 be used like this:
jpayne@68	131 </p>
jpayne@68	132 <table><tr><td> </td><td><pre class="example">char *translation = catgets (catd, set_no, msg_id, "original string");
jpayne@68	133 </pre></td></tr></table>
jpayne@68	134
jpayne@68	135 <p>The first parameter is this catalog descriptor. The second parameter
jpayne@68	136 specifies the set of messages in this catalog, in which the message
jpayne@68	137 described by <code>msg_id</code> is obtained. <code>catgets</code> therefore uses a
jpayne@68	138 three-stage addressing:
jpayne@68	139 </p>
jpayne@68	140 <table><tr><td> </td><td><pre class="display">catalog name ⇒ set number ⇒ message ID ⇒ translation
jpayne@68	141 </pre></td></tr></table>
jpayne@68	142
jpayne@68	143
jpayne@68	144 <p>The fourth argument is not used to address the translation. It is given
jpayne@68	145 as a default value in case when one of the addressing stages fail. One
jpayne@68	146 important thing to remember is that although the return type of catgets
jpayne@68	147 is <code>char *</code> the resulting string <em>must not</em> be changed. It
jpayne@68	148 should better be <code>const char *</code>, but the standard is published in
jpayne@68	149 1988, one year before ANSI C.
jpayne@68	150 </p>
jpayne@68	151 <a name="IDX1061"></a>
jpayne@68	152 <p>The last of these functions is used and behaves as expected:
jpayne@68	153 </p>
jpayne@68	154 <table><tr><td> </td><td><pre class="example">catclose (catd);
jpayne@68	155 </pre></td></tr></table>
jpayne@68	156
jpayne@68	157 <p>After this no <code>catgets</code> call using the descriptor is legal anymore.
jpayne@68	158 </p>
jpayne@68	159
jpayne@68	160 <a name="Problems-with-catgets"></a>
jpayne@68	161 <a name="SEC200"></a>
jpayne@68	162 <h3 class="subsection"> <a href="gettext_toc.html#TOC193">11.1.2 Problems with the <code>catgets</code> Interface?!</a> </h3>
jpayne@68	163
jpayne@68	164 <p>Now that this description seemed to be really easy — where are the
jpayne@68	165 problems we speak of? In fact the interface could be used in a
jpayne@68	166 reasonable way, but constructing the message catalogs is a pain. The
jpayne@68	167 reason for this lies in the third argument of <code>catgets</code>: the unique
jpayne@68	168 message ID. This has to be a numeric value for all messages in a single
jpayne@68	169 set. Perhaps you could imagine the problems keeping such a list while
jpayne@68	170 changing the source code. Add a new message here, remove one there. Of
jpayne@68	171 course there have been developed a lot of tools helping to organize this
jpayne@68	172 chaos but one as the other fails in one aspect or the other. We don't
jpayne@68	173 want to say that the other approach has no problems but they are far
jpayne@68	174 more easy to manage.
jpayne@68	175 </p>
jpayne@68	176
jpayne@68	177 <a name="gettext"></a>
jpayne@68	178 <a name="SEC201"></a>
jpayne@68	179 <h2 class="section"> <a href="gettext_toc.html#TOC194">11.2 About <code>gettext</code></a> </h2>
jpayne@68	180
jpayne@68	181 <p>The definition of the <code>gettext</code> interface comes from a Uniforum
jpayne@68	182 proposal. It was submitted there by Sun, who had implemented the
jpayne@68	183 <code>gettext</code> function in SunOS 4, around 1990. Nowadays, the
jpayne@68	184 <code>gettext</code> interface is specified by the OpenI18N standard.
jpayne@68	185 </p>
jpayne@68	186 <p>The main point about this solution is that it does not follow the
jpayne@68	187 method of normal file handling (open-use-close) and that it does not
jpayne@68	188 burden the programmer with so many tasks, especially the unique key handling.
jpayne@68	189 Of course here also a unique key is needed, but this key is the message
jpayne@68	190 itself (how long or short it is). See <a href="#SEC209">Comparing the Two Interfaces</a> for a more
jpayne@68	191 detailed comparison of the two methods.
jpayne@68	192 </p>
jpayne@68	193 <p>The following section contains a rather detailed description of the
jpayne@68	194 interface. We make it that detailed because this is the interface
jpayne@68	195 we chose for the GNU <code>gettext</code> Library. Programmers interested
jpayne@68	196 in using this library will be interested in this description.
jpayne@68	197 </p>
jpayne@68	198
jpayne@68	199
jpayne@68	200 <a name="Interface-to-gettext"></a>
jpayne@68	201 <a name="SEC202"></a>
jpayne@68	202 <h3 class="subsection"> <a href="gettext_toc.html#TOC195">11.2.1 The Interface</a> </h3>
jpayne@68	203
jpayne@68	204 <p>The minimal functionality an interface must have is a) to select a
jpayne@68	205 domain the strings are coming from (a single domain for all programs is
jpayne@68	206 not reasonable because its construction and maintenance is difficult,
jpayne@68	207 perhaps impossible) and b) to access a string in a selected domain.
jpayne@68	208 </p>
jpayne@68	209 <p>This is principally the description of the <code>gettext</code> interface. It
jpayne@68	210 has a global domain which unqualified usages reference. Of course this
jpayne@68	211 domain is selectable by the user.
jpayne@68	212 </p>
jpayne@68	213 <table><tr><td> </td><td><pre class="example">char textdomain (const char domain_name);
jpayne@68	214 </pre></td></tr></table>
jpayne@68	215
jpayne@68	216 <p>This provides the possibility to change or query the current status of
jpayne@68	217 the current global domain of the <code>LC_MESSAGE</code> category. The
jpayne@68	218 argument is a null-terminated string, whose characters must be legal in
jpayne@68	219 the use in filenames. If the <var>domain_name</var> argument is <code>NULL</code>,
jpayne@68	220 the function returns the current value. If no value has been set
jpayne@68	221 before, the name of the default domain is returned: <em>messages</em>.
jpayne@68	222 Please note that although the return value of <code>textdomain</code> is of
jpayne@68	223 type <code>char *</code> no changing is allowed. It is also important to know
jpayne@68	224 that no checks of the availability are made. If the name is not
jpayne@68	225 available you will see this by the fact that no translations are provided.
jpayne@68	226 </p>
jpayne@68	227 <p>To use a domain set by <code>textdomain</code> the function
jpayne@68	228 </p>
jpayne@68	229 <table><tr><td> </td><td><pre class="example">char gettext (const char msgid);
jpayne@68	230 </pre></td></tr></table>
jpayne@68	231
jpayne@68	232 <p>is to be used. This is the simplest reasonable form one can imagine.
jpayne@68	233 The translation of the string <var>msgid</var> is returned if it is available
jpayne@68	234 in the current domain. If it is not available, the argument itself is
jpayne@68	235 returned. If the argument is <code>NULL</code> the result is undefined.
jpayne@68	236 </p>
jpayne@68	237 <p>One thing which should come into mind is that no explicit dependency to
jpayne@68	238 the used domain is given. The current value of the domain is used.
jpayne@68	239 If this changes between two
jpayne@68	240 executions of the same <code>gettext</code> call in the program, both calls
jpayne@68	241 reference a different message catalog.
jpayne@68	242 </p>
jpayne@68	243 <p>For the easiest case, which is normally used in internationalized
jpayne@68	244 packages, once at the beginning of execution a call to <code>textdomain</code>
jpayne@68	245 is issued, setting the domain to a unique name, normally the package
jpayne@68	246 name. In the following code all strings which have to be translated are
jpayne@68	247 filtered through the gettext function. That's all, the package speaks
jpayne@68	248 your language.
jpayne@68	249 </p>
jpayne@68	250
jpayne@68	251 <a name="Ambiguities"></a>
jpayne@68	252 <a name="SEC203"></a>
jpayne@68	253 <h3 class="subsection"> <a href="gettext_toc.html#TOC196">11.2.2 Solving Ambiguities</a> </h3>
jpayne@68	254
jpayne@68	255 <p>While this single name domain works well for most applications there
jpayne@68	256 might be the need to get translations from more than one domain. Of
jpayne@68	257 course one could switch between different domains with calls to
jpayne@68	258 <code>textdomain</code>, but this is really not convenient nor is it fast. A
jpayne@68	259 possible situation could be one case subject to discussion during this
jpayne@68	260 writing: all
jpayne@68	261 error messages of functions in the set of common used functions should
jpayne@68	262 go into a separate domain <code>error</code>. By this mean we would only need
jpayne@68	263 to translate them once.
jpayne@68	264 Another case are messages from a library, as these <em>have</em> to be
jpayne@68	265 independent of the current domain set by the application.
jpayne@68	266 </p>
jpayne@68	267 <p>For this reasons there are two more functions to retrieve strings:
jpayne@68	268 </p>
jpayne@68	269 <table><tr><td> </td><td><pre class="example">char dgettext (const char domain_name, const char *msgid);
jpayne@68	270 char dcgettext (const char domain_name, const char *msgid,
jpayne@68	271 int category);
jpayne@68	272 </pre></td></tr></table>
jpayne@68	273
jpayne@68	274 <p>Both take an additional argument at the first place, which corresponds
jpayne@68	275 to the argument of <code>textdomain</code>. The third argument of
jpayne@68	276 <code>dcgettext</code> allows to use another locale category but <code>LC_MESSAGES</code>.
jpayne@68	277 But I really don't know where this can be useful. If the
jpayne@68	278 <var>domain_name</var> is <code>NULL</code> or <var>category</var> has an value beside
jpayne@68	279 the known ones, the result is undefined. It should also be noted that
jpayne@68	280 this function is not part of the second known implementation of this
jpayne@68	281 function family, the one found in Solaris.
jpayne@68	282 </p>
jpayne@68	283 <p>A second ambiguity can arise by the fact, that perhaps more than one
jpayne@68	284 domain has the same name. This can be solved by specifying where the
jpayne@68	285 needed message catalog files can be found.
jpayne@68	286 </p>
jpayne@68	287 <table><tr><td> </td><td><pre class="example">char bindtextdomain (const char domain_name,
jpayne@68	288 const char *dir_name);
jpayne@68	289 </pre></td></tr></table>
jpayne@68	290
jpayne@68	291 <p>Calling this function binds the given domain to a file in the specified
jpayne@68	292 directory (how this file is determined follows below). Especially a
jpayne@68	293 file in the systems default place is not favored against the specified
jpayne@68	294 file anymore (as it would be by solely using <code>textdomain</code>). A
jpayne@68	295 <code>NULL</code> pointer for the <var>dir_name</var> parameter returns the binding
jpayne@68	296 associated with <var>domain_name</var>. If <var>domain_name</var> itself is
jpayne@68	297 <code>NULL</code> nothing happens and a <code>NULL</code> pointer is returned. Here
jpayne@68	298 again as for all the other functions is true that none of the return
jpayne@68	299 value must be changed!
jpayne@68	300 </p>
jpayne@68	301 <p>It is important to remember that relative path names for the
jpayne@68	302 <var>dir_name</var> parameter can be trouble. Since the path is always
jpayne@68	303 computed relative to the current directory different results will be
jpayne@68	304 achieved when the program executes a <code>chdir</code> command. Relative
jpayne@68	305 paths should always be avoided to avoid dependencies and
jpayne@68	306 unreliabilities.
jpayne@68	307 </p>
jpayne@68	308 <table><tr><td> </td><td><pre class="example">wchar_t wbindtextdomain (const char domain_name,
jpayne@68	309 const wchar_t *dir_name);
jpayne@68	310 </pre></td></tr></table>
jpayne@68	311
jpayne@68	312 <p>This function is provided only on native Windows platforms. It is like
jpayne@68	313 <code>bindtextdomain</code>, except that the <var>dir_name</var> parameter is a
jpayne@68	314 wide string (in UTF-16 encoding, as usual on Windows).
jpayne@68	315 </p>
jpayne@68	316
jpayne@68	317 <a name="Locating-Catalogs"></a>
jpayne@68	318 <a name="SEC204"></a>
jpayne@68	319 <h3 class="subsection"> <a href="gettext_toc.html#TOC197">11.2.3 Locating Message Catalog Files</a> </h3>
jpayne@68	320
jpayne@68	321 <p>Because many different languages for many different packages have to be
jpayne@68	322 stored we need some way to add these information to file message catalog
jpayne@68	323 files. The way usually used in Unix environments is have this encoding
jpayne@68	324 in the file name. This is also done here. The directory name given in
jpayne@68	325 <code>bindtextdomain</code>s second argument (or the default directory),
jpayne@68	326 followed by the name of the locale, the locale category, and the domain name
jpayne@68	327 are concatenated:
jpayne@68	328 </p>
jpayne@68	329 <table><tr><td> </td><td><pre class="example"><var>dir_name</var>/<var>locale</var>/LC_<var>category</var>/<var>domain_name</var>.mo
jpayne@68	330 </pre></td></tr></table>
jpayne@68	331
jpayne@68	332 <p>The default value for <var>dir_name</var> is system specific. For the GNU
jpayne@68	333 library, and for packages adhering to its conventions, it's:
jpayne@68	334 </p><table><tr><td> </td><td><pre class="example">/usr/local/share/locale
jpayne@68	335 </pre></td></tr></table>
jpayne@68	336
jpayne@68	337 <p><var>locale</var> is the name of the locale category which is designated by
jpayne@68	338 <code>LC_<var>category</var></code>. For <code>gettext</code> and <code>dgettext</code> this
jpayne@68	339 <code>LC_<var>category</var></code> is always <code>LC_MESSAGES</code>.<a name="DOCF3" href="gettext_fot.html#FOOT3">(3)</a>
jpayne@68	340 The name of the locale category is determined through
jpayne@68	341 <code>setlocale (LC_<var>category</var>, NULL)</code>.
jpayne@68	342 <a name="DOCF4" href="gettext_fot.html#FOOT4">(4)</a>
jpayne@68	343 When using the function <code>dcgettext</code>, you can specify the locale category
jpayne@68	344 through the third argument.
jpayne@68	345 </p>
jpayne@68	346
jpayne@68	347 <a name="Charset-conversion"></a>
jpayne@68	348 <a name="SEC205"></a>
jpayne@68	349 <h3 class="subsection"> <a href="gettext_toc.html#TOC198">11.2.4 How to specify the output character set <code>gettext</code> uses</a> </h3>
jpayne@68	350
jpayne@68	351 <p><code>gettext</code> not only looks up a translation in a message catalog. It
jpayne@68	352 also converts the translation on the fly to the desired output character
jpayne@68	353 set. This is useful if the user is working in a different character set
jpayne@68	354 than the translator who created the message catalog, because it avoids
jpayne@68	355 distributing variants of message catalogs which differ only in the
jpayne@68	356 character set.
jpayne@68	357 </p>
jpayne@68	358 <p>The output character set is, by default, the value of <code>nl_langinfo
jpayne@68	359 (CODESET)</code>, which depends on the <code>LC_CTYPE</code> part of the current
jpayne@68	360 locale. But programs which store strings in a locale independent way
jpayne@68	361 (e.g. UTF-8) can request that <code>gettext</code> and related functions
jpayne@68	362 return the translations in that encoding, by use of the
jpayne@68	363 <code>bind_textdomain_codeset</code> function.
jpayne@68	364 </p>
jpayne@68	365 <p>Note that the <var>msgid</var> argument to <code>gettext</code> is not subject to
jpayne@68	366 character set conversion. Also, when <code>gettext</code> does not find a
jpayne@68	367 translation for <var>msgid</var>, it returns <var>msgid</var> unchanged –
jpayne@68	368 independently of the current output character set. It is therefore
jpayne@68	369 recommended that all <var>msgid</var>s be US-ASCII strings.
jpayne@68	370 </p>
jpayne@68	371 <dl>
jpayne@68	372 <dt><u>Function:</u> char * <b>bind_textdomain_codeset</b><i> (const char <var>domainname</var>, const char <var>codeset</var>)</i>
jpayne@68	373 <a name="IDX1062"></a>
jpayne@68	374 </dt>
jpayne@68	375 <dd><p>The <code>bind_textdomain_codeset</code> function can be used to specify the
jpayne@68	376 output character set for message catalogs for domain <var>domainname</var>.
jpayne@68	377 The <var>codeset</var> argument must be a valid codeset name which can be used
jpayne@68	378 for the <code>iconv_open</code> function, or a null pointer.
jpayne@68	379 </p>
jpayne@68	380 <p>If the <var>codeset</var> parameter is the null pointer,
jpayne@68	381 <code>bind_textdomain_codeset</code> returns the currently selected codeset
jpayne@68	382 for the domain with the name <var>domainname</var>. It returns <code>NULL</code> if
jpayne@68	383 no codeset has yet been selected.
jpayne@68	384 </p>
jpayne@68	385 <p>The <code>bind_textdomain_codeset</code> function can be used several times.
jpayne@68	386 If used multiple times with the same <var>domainname</var> argument, the
jpayne@68	387 later call overrides the settings made by the earlier one.
jpayne@68	388 </p>
jpayne@68	389 <p>The <code>bind_textdomain_codeset</code> function returns a pointer to a
jpayne@68	390 string containing the name of the selected codeset. The string is
jpayne@68	391 allocated internally in the function and must not be changed by the
jpayne@68	392 user. If the system went out of core during the execution of
jpayne@68	393 <code>bind_textdomain_codeset</code>, the return value is <code>NULL</code> and the
jpayne@68	394 global variable <var>errno</var> is set accordingly.
jpayne@68	395 </p></dd></dl>
jpayne@68	396
jpayne@68	397
jpayne@68	398 <a name="Contexts"></a>
jpayne@68	399 <a name="SEC206"></a>
jpayne@68	400 <h3 class="subsection"> <a href="gettext_toc.html#TOC199">11.2.5 Using contexts for solving ambiguities</a> </h3>
jpayne@68	401
jpayne@68	402 <p>One place where the <code>gettext</code> functions, if used normally, have big
jpayne@68	403 problems is within programs with graphical user interfaces (GUIs). The
jpayne@68	404 problem is that many of the strings which have to be translated are very
jpayne@68	405 short. They have to appear in pull-down menus which restricts the
jpayne@68	406 length. But strings which are not containing entire sentences or at
jpayne@68	407 least large fragments of a sentence may appear in more than one
jpayne@68	408 situation in the program but might have different translations. This is
jpayne@68	409 especially true for the one-word strings which are frequently used in
jpayne@68	410 GUI programs.
jpayne@68	411 </p>
jpayne@68	412 <p>As a consequence many people say that the <code>gettext</code> approach is
jpayne@68	413 wrong and instead <code>catgets</code> should be used which indeed does not
jpayne@68	414 have this problem. But there is a very simple and powerful method to
jpayne@68	415 handle this kind of problems with the <code>gettext</code> functions.
jpayne@68	416 </p>
jpayne@68	417 <p>Contexts can be added to strings to be translated. A context dependent
jpayne@68	418 translation lookup is when a translation for a given string is searched,
jpayne@68	419 that is limited to a given context. The translation for the same string
jpayne@68	420 in a different context can be different. The different translations of
jpayne@68	421 the same string in different contexts can be stored in the in the same
jpayne@68	422 MO file, and can be edited by the translator in the same PO file.
jpayne@68	423 </p>
jpayne@68	424 <p>The ‘<tt>gettext.h</tt>’ include file contains the lookup macros for strings
jpayne@68	425 with contexts. They are implemented as thin macros and inline functions
jpayne@68	426 over the functions from <code><libintl.h></code>.
jpayne@68	427 </p>
jpayne@68	428 <a name="IDX1063"></a>
jpayne@68	429 <table><tr><td> </td><td><pre class="example">const char pgettext (const char msgctxt, const char *msgid);
jpayne@68	430 </pre></td></tr></table>
jpayne@68	431
jpayne@68	432 <p>In a call of this macro, <var>msgctxt</var> and <var>msgid</var> must be string
jpayne@68	433 literals. The macro returns the translation of <var>msgid</var>, restricted
jpayne@68	434 to the context given by <var>msgctxt</var>.
jpayne@68	435 </p>
jpayne@68	436 <p>The <var>msgctxt</var> string is visible in the PO file to the translator.
jpayne@68	437 You should try to make it somehow canonical and never changing. Because
jpayne@68	438 every time you change an <var>msgctxt</var>, the translator will have to review
jpayne@68	439 the translation of <var>msgid</var>.
jpayne@68	440 </p>
jpayne@68	441 <p>Finding a canonical <var>msgctxt</var> string that doesn't change over time can
jpayne@68	442 be hard. But you shouldn't use the file name or class name containing the
jpayne@68	443 <code>pgettext</code> call – because it is a common development task to rename
jpayne@68	444 a file or a class, and it shouldn't cause translator work. Also you shouldn't
jpayne@68	445 use a comment in the form of a complete English sentence as <var>msgctxt</var> –
jpayne@68	446 because orthography or grammar changes are often applied to such sentences,
jpayne@68	447 and again, it shouldn't force the translator to do a review.
jpayne@68	448 </p>
jpayne@68	449 <p>The ‘<samp>p</samp>’ in ‘<samp>pgettext</samp>’ stands for “particular”: <code>pgettext</code>
jpayne@68	450 fetches a particular translation of the <var>msgid</var>.
jpayne@68	451 </p>
jpayne@68	452 <a name="IDX1064"></a>
jpayne@68	453 <a name="IDX1065"></a>
jpayne@68	454 <table><tr><td> </td><td><pre class="example">const char dpgettext (const char domain_name,
jpayne@68	455 const char msgctxt, const char msgid);
jpayne@68	456 const char dcpgettext (const char domain_name,
jpayne@68	457 const char msgctxt, const char msgid,
jpayne@68	458 int category);
jpayne@68	459 </pre></td></tr></table>
jpayne@68	460
jpayne@68	461 <p>These are generalizations of <code>pgettext</code>. They behave similarly to
jpayne@68	462 <code>dgettext</code> and <code>dcgettext</code>, respectively. The <var>domain_name</var>
jpayne@68	463 argument defines the translation domain. The <var>category</var> argument
jpayne@68	464 allows to use another locale category than <code>LC_MESSAGES</code>.
jpayne@68	465 </p>
jpayne@68	466 <p>As as example consider the following fictional situation. A GUI program
jpayne@68	467 has a menu bar with the following entries:
jpayne@68	468 </p>
jpayne@68	469 <table><tr><td> </td><td><pre class="smallexample">+------------+------------+--------------------------------------+
jpayne@68	470 \| File \| Printer \| \|
jpayne@68	471 +------------+------------+--------------------------------------+
jpayne@68	472 \| Open \| \| Select \|
jpayne@68	473 \| New \| \| Open \|
jpayne@68	474 +----------+ \| Connect \|
jpayne@68	475 +----------+
jpayne@68	476 </pre></td></tr></table>
jpayne@68	477
jpayne@68	478 <p>To have the strings <code>File</code>, <code>Printer</code>, <code>Open</code>,
jpayne@68	479 <code>New</code>, <code>Select</code>, and <code>Connect</code> translated there has to be
jpayne@68	480 at some point in the code a call to a function of the <code>gettext</code>
jpayne@68	481 family. But in two places the string passed into the function would be
jpayne@68	482 <code>Open</code>. The translations might not be the same and therefore we
jpayne@68	483 are in the dilemma described above.
jpayne@68	484 </p>
jpayne@68	485 <p>What distinguishes the two places is the menu path from the menu root to
jpayne@68	486 the particular menu entries:
jpayne@68	487 </p>
jpayne@68	488 <table><tr><td> </td><td><pre class="smallexample">Menu\|File
jpayne@68	489 Menu\|Printer
jpayne@68	490 Menu\|File\|Open
jpayne@68	491 Menu\|File\|New
jpayne@68	492 Menu\|Printer\|Select
jpayne@68	493 Menu\|Printer\|Open
jpayne@68	494 Menu\|Printer\|Connect
jpayne@68	495 </pre></td></tr></table>
jpayne@68	496
jpayne@68	497 <p>The context is thus the menu path without its last part. So, the calls
jpayne@68	498 look like this:
jpayne@68	499 </p>
jpayne@68	500 <table><tr><td> </td><td><pre class="smallexample">pgettext ("Menu\|", "File")
jpayne@68	501 pgettext ("Menu\|", "Printer")
jpayne@68	502 pgettext ("Menu\|File\|", "Open")
jpayne@68	503 pgettext ("Menu\|File\|", "New")
jpayne@68	504 pgettext ("Menu\|Printer\|", "Select")
jpayne@68	505 pgettext ("Menu\|Printer\|", "Open")
jpayne@68	506 pgettext ("Menu\|Printer\|", "Connect")
jpayne@68	507 </pre></td></tr></table>
jpayne@68	508
jpayne@68	509 <p>Whether or not to use the ‘<samp>\|</samp>’ character at the end of the context is a
jpayne@68	510 matter of style.
jpayne@68	511 </p>
jpayne@68	512 <p>For more complex cases, where the <var>msgctxt</var> or <var>msgid</var> are not
jpayne@68	513 string literals, more general macros are available:
jpayne@68	514 </p>
jpayne@68	515 <a name="IDX1066"></a>
jpayne@68	516 <a name="IDX1067"></a>
jpayne@68	517 <a name="IDX1068"></a>
jpayne@68	518 <table><tr><td> </td><td><pre class="example">const char pgettext_expr (const char msgctxt, const char *msgid);
jpayne@68	519 const char dpgettext_expr (const char domain_name,
jpayne@68	520 const char msgctxt, const char msgid);
jpayne@68	521 const char dcpgettext_expr (const char domain_name,
jpayne@68	522 const char msgctxt, const char msgid,
jpayne@68	523 int category);
jpayne@68	524 </pre></td></tr></table>
jpayne@68	525
jpayne@68	526 <p>Here <var>msgctxt</var> and <var>msgid</var> can be arbitrary string-valued expressions.
jpayne@68	527 These macros are more general. But in the case that both argument expressions
jpayne@68	528 are string literals, the macros without the ‘<samp>_expr</samp>’ suffix are more
jpayne@68	529 efficient.
jpayne@68	530 </p>
jpayne@68	531
jpayne@68	532 <a name="Plural-forms"></a>
jpayne@68	533 <a name="SEC207"></a>
jpayne@68	534 <h3 class="subsection"> <a href="gettext_toc.html#TOC200">11.2.6 Additional functions for plural forms</a> </h3>
jpayne@68	535
jpayne@68	536 <p>The functions of the <code>gettext</code> family described so far (and all the
jpayne@68	537 <code>catgets</code> functions as well) have one problem in the real world
jpayne@68	538 which have been neglected completely in all existing approaches. What
jpayne@68	539 is meant here is the handling of plural forms.
jpayne@68	540 </p>
jpayne@68	541 <p>Looking through Unix source code before the time anybody thought about
jpayne@68	542 internationalization (and, sadly, even afterwards) one can often find
jpayne@68	543 code similar to the following:
jpayne@68	544 </p>
jpayne@68	545 <table><tr><td> </td><td><pre class="smallexample"> printf ("%d file%s deleted", n, n == 1 ? "" : "s");
jpayne@68	546 </pre></td></tr></table>
jpayne@68	547
jpayne@68	548 <p>After the first complaints from people internationalizing the code people
jpayne@68	549 either completely avoided formulations like this or used strings like
jpayne@68	550 <code>"file(s)"</code>. Both look unnatural and should be avoided. First
jpayne@68	551 tries to solve the problem correctly looked like this:
jpayne@68	552 </p>
jpayne@68	553 <table><tr><td> </td><td><pre class="smallexample"> if (n == 1)
jpayne@68	554 printf ("%d file deleted", n);
jpayne@68	555 else
jpayne@68	556 printf ("%d files deleted", n);
jpayne@68	557 </pre></td></tr></table>
jpayne@68	558
jpayne@68	559 <p>But this does not solve the problem. It helps languages where the
jpayne@68	560 plural form of a noun is not simply constructed by adding an
jpayne@68	561 ‘s’
jpayne@68	562 but that is all. Once again people fell into the trap of believing the
jpayne@68	563 rules their language is using are universal. But the handling of plural
jpayne@68	564 forms differs widely between the language families. For example,
jpayne@68	565 Rafal Maszkowski <code><rzm@mat.uni.torun.pl></code> reports:
jpayne@68	566 </p>
jpayne@68	567 <blockquote><p>In Polish we use e.g. plik (file) this way:
jpayne@68	568 </p><table><tr><td> </td><td><pre class="example">1 plik
jpayne@68	569 2,3,4 pliki
jpayne@68	570 5-21 pliko'w
jpayne@68	571 22-24 pliki
jpayne@68	572 25-31 pliko'w
jpayne@68	573 </pre></td></tr></table>
jpayne@68	574 <p>and so on (o' means 8859-2 oacute which should be rather okreska,
jpayne@68	575 similar to aogonek).
jpayne@68	576 </p></blockquote>
jpayne@68	577
jpayne@68	578 <p>There are two things which can differ between languages (and even inside
jpayne@68	579 language families);
jpayne@68	580 </p>
jpayne@68	581 <ul>
jpayne@68	582 <li>
jpayne@68	583 The form how plural forms are built differs. This is a problem with
jpayne@68	584 languages which have many irregularities. German, for instance, is a
jpayne@68	585 drastic case. Though English and German are part of the same language
jpayne@68	586 family (Germanic), the almost regular forming of plural noun forms
jpayne@68	587 (appending an
jpayne@68	588 ‘s’)
jpayne@68	589 is hardly found in German.
jpayne@68	590
jpayne@68	591 </li><li>
jpayne@68	592 The number of plural forms differ. This is somewhat surprising for
jpayne@68	593 those who only have experiences with Romanic and Germanic languages
jpayne@68	594 since here the number is the same (there are two).
jpayne@68	595
jpayne@68	596 <p>But other language families have only one form or many forms. More
jpayne@68	597 information on this in an extra section.
jpayne@68	598 </p></li></ul>
jpayne@68	599
jpayne@68	600 <p>The consequence of this is that application writers should not try to
jpayne@68	601 solve the problem in their code. This would be localization since it is
jpayne@68	602 only usable for certain, hardcoded language environments. Instead the
jpayne@68	603 extended <code>gettext</code> interface should be used.
jpayne@68	604 </p>
jpayne@68	605 <p>These extra functions are taking instead of the one key string two
jpayne@68	606 strings and a numerical argument. The idea behind this is that using
jpayne@68	607 the numerical argument and the first string as a key, the implementation
jpayne@68	608 can select using rules specified by the translator the right plural
jpayne@68	609 form. The two string arguments then will be used to provide a return
jpayne@68	610 value in case no message catalog is found (similar to the normal
jpayne@68	611 <code>gettext</code> behavior). In this case the rules for Germanic language
jpayne@68	612 is used and it is assumed that the first string argument is the singular
jpayne@68	613 form, the second the plural form.
jpayne@68	614 </p>
jpayne@68	615 <p>This has the consequence that programs without language catalogs can
jpayne@68	616 display the correct strings only if the program itself is written using
jpayne@68	617 a Germanic language. This is a limitation but since the GNU C library
jpayne@68	618 (as well as the GNU <code>gettext</code> package) are written as part of the
jpayne@68	619 GNU package and the coding standards for the GNU project require program
jpayne@68	620 being written in English, this solution nevertheless fulfills its
jpayne@68	621 purpose.
jpayne@68	622 </p>
jpayne@68	623 <dl>
jpayne@68	624 <dt><u>Function:</u> char * <b>ngettext</b><i> (const char <var>msgid1</var>, const char <var>msgid2</var>, unsigned long int <var>n</var>)</i>
jpayne@68	625 <a name="IDX1069"></a>
jpayne@68	626 </dt>
jpayne@68	627 <dd><p>The <code>ngettext</code> function is similar to the <code>gettext</code> function
jpayne@68	628 as it finds the message catalogs in the same way. But it takes two
jpayne@68	629 extra arguments. The <var>msgid1</var> parameter must contain the singular
jpayne@68	630 form of the string to be converted. It is also used as the key for the
jpayne@68	631 search in the catalog. The <var>msgid2</var> parameter is the plural form.
jpayne@68	632 The parameter <var>n</var> is used to determine the plural form. If no
jpayne@68	633 message catalog is found <var>msgid1</var> is returned if <code>n == 1</code>,
jpayne@68	634 otherwise <code>msgid2</code>.
jpayne@68	635 </p>
jpayne@68	636 <p>An example for the use of this function is:
jpayne@68	637 </p>
jpayne@68	638 <table><tr><td> </td><td><pre class="smallexample">printf (ngettext ("%d file removed", "%d files removed", n), n);
jpayne@68	639 </pre></td></tr></table>
jpayne@68	640
jpayne@68	641 <p>Please note that the numeric value <var>n</var> has to be passed to the
jpayne@68	642 <code>printf</code> function as well. It is not sufficient to pass it only to
jpayne@68	643 <code>ngettext</code>.
jpayne@68	644 </p>
jpayne@68	645 <p>In the English singular case, the number – always 1 – can be replaced with
jpayne@68	646 "one":
jpayne@68	647 </p>
jpayne@68	648 <table><tr><td> </td><td><pre class="smallexample">printf (ngettext ("One file removed", "%d files removed", n), n);
jpayne@68	649 </pre></td></tr></table>
jpayne@68	650
jpayne@68	651 <p>This works because the ‘<samp>printf</samp>’ function discards excess arguments that
jpayne@68	652 are not consumed by the format string.
jpayne@68	653 </p>
jpayne@68	654 <p>If this function is meant to yield a format string that takes two or more
jpayne@68	655 arguments, you can not use it like this:
jpayne@68	656 </p>
jpayne@68	657 <table><tr><td> </td><td><pre class="smallexample">printf (ngettext ("%d file removed from directory %s",
jpayne@68	658 "%d files removed from directory %s",
jpayne@68	659 n),
jpayne@68	660 n, dir);
jpayne@68	661 </pre></td></tr></table>
jpayne@68	662
jpayne@68	663 <p>because in many languages the translators want to replace the ‘<samp>%d</samp>’
jpayne@68	664 with an explicit word in the singular case, just like “one” in English,
jpayne@68	665 and C format strings cannot consume the second argument but skip the first
jpayne@68	666 argument. Instead, you have to reorder the arguments so that ‘<samp>n</samp>’
jpayne@68	667 comes last:
jpayne@68	668 </p>
jpayne@68	669 <table><tr><td> </td><td><pre class="smallexample">printf (ngettext ("%2$d file removed from directory %1$s",
jpayne@68	670 "%2$d files removed from directory %1$s",
jpayne@68	671 n),
jpayne@68	672 dir, n);
jpayne@68	673 </pre></td></tr></table>
jpayne@68	674
jpayne@68	675 <p>See <a href="gettext_15.html#SEC267">C Format Strings</a> for details about this argument reordering syntax.
jpayne@68	676 </p>
jpayne@68	677 <p>When you know that the value of <code>n</code> is within a given range, you can
jpayne@68	678 specify it as a comment directed to the <code>xgettext</code> tool. This
jpayne@68	679 information may help translators to use more adequate translations. Like
jpayne@68	680 this:
jpayne@68	681 </p>
jpayne@68	682 <table><tr><td> </td><td><pre class="smallexample">if (days > 7 && days < 14)
jpayne@68	683 /* xgettext: range: 1..6 */
jpayne@68	684 printf (ngettext ("one week and one day", "one week and %d days",
jpayne@68	685 days - 7),
jpayne@68	686 days - 7);
jpayne@68	687 </pre></td></tr></table>
jpayne@68	688
jpayne@68	689 <p>It is also possible to use this function when the strings don't contain a
jpayne@68	690 cardinal number:
jpayne@68	691 </p>
jpayne@68	692 <table><tr><td> </td><td><pre class="smallexample">puts (ngettext ("Delete the selected file?",
jpayne@68	693 "Delete the selected files?",
jpayne@68	694 n));
jpayne@68	695 </pre></td></tr></table>
jpayne@68	696
jpayne@68	697 <p>In this case the number <var>n</var> is only used to choose the plural form.
jpayne@68	698 </p></dd></dl>
jpayne@68	699
jpayne@68	700 <dl>
jpayne@68	701 <dt><u>Function:</u> char * <b>dngettext</b><i> (const char <var>domain</var>, const char <var>msgid1</var>, const char *<var>msgid2</var>, unsigned long int <var>n</var>)</i>
jpayne@68	702 <a name="IDX1070"></a>
jpayne@68	703 </dt>
jpayne@68	704 <dd><p>The <code>dngettext</code> is similar to the <code>dgettext</code> function in the
jpayne@68	705 way the message catalog is selected. The difference is that it takes
jpayne@68	706 two extra parameter to provide the correct plural form. These two
jpayne@68	707 parameters are handled in the same way <code>ngettext</code> handles them.
jpayne@68	708 </p></dd></dl>
jpayne@68	709
jpayne@68	710 <dl>
jpayne@68	711 <dt><u>Function:</u> char * <b>dcngettext</b><i> (const char <var>domain</var>, const char <var>msgid1</var>, const char *<var>msgid2</var>, unsigned long int <var>n</var>, int <var>category</var>)</i>
jpayne@68	712 <a name="IDX1071"></a>
jpayne@68	713 </dt>
jpayne@68	714 <dd><p>The <code>dcngettext</code> is similar to the <code>dcgettext</code> function in the
jpayne@68	715 way the message catalog is selected. The difference is that it takes
jpayne@68	716 two extra parameter to provide the correct plural form. These two
jpayne@68	717 parameters are handled in the same way <code>ngettext</code> handles them.
jpayne@68	718 </p></dd></dl>
jpayne@68	719
jpayne@68	720 <p>Now, how do these functions solve the problem of the plural forms?
jpayne@68	721 Without the input of linguists (which was not available) it was not
jpayne@68	722 possible to determine whether there are only a few different forms in
jpayne@68	723 which plural forms are formed or whether the number can increase with
jpayne@68	724 every new supported language.
jpayne@68	725 </p>
jpayne@68	726 <p>Therefore the solution implemented is to allow the translator to specify
jpayne@68	727 the rules of how to select the plural form. Since the formula varies
jpayne@68	728 with every language this is the only viable solution except for
jpayne@68	729 hardcoding the information in the code (which still would require the
jpayne@68	730 possibility of extensions to not prevent the use of new languages).
jpayne@68	731 </p>
jpayne@68	732 <a name="IDX1072"></a>
jpayne@68	733 <a name="IDX1073"></a>
jpayne@68	734 <a name="IDX1074"></a>
jpayne@68	735 <p>The information about the plural form selection has to be stored in the
jpayne@68	736 header entry of the PO file (the one with the empty <code>msgid</code> string).
jpayne@68	737 The plural form information looks like this:
jpayne@68	738 </p>
jpayne@68	739 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=2; plural=n == 1 ? 0 : 1;
jpayne@68	740 </pre></td></tr></table>
jpayne@68	741
jpayne@68	742 <p>The <code>nplurals</code> value must be a decimal number which specifies how
jpayne@68	743 many different plural forms exist for this language. The string
jpayne@68	744 following <code>plural</code> is an expression which is using the C language
jpayne@68	745 syntax. Exceptions are that no negative numbers are allowed, numbers
jpayne@68	746 must be decimal, and the only variable allowed is <code>n</code>. Spaces are
jpayne@68	747 allowed in the expression, but backslash-newlines are not; in the
jpayne@68	748 examples below the backslash-newlines are present for formatting purposes
jpayne@68	749 only. This expression will be evaluated whenever one of the functions
jpayne@68	750 <code>ngettext</code>, <code>dngettext</code>, or <code>dcngettext</code> is called. The
jpayne@68	751 numeric value passed to these functions is then substituted for all uses
jpayne@68	752 of the variable <code>n</code> in the expression. The resulting value then
jpayne@68	753 must be greater or equal to zero and smaller than the value given as the
jpayne@68	754 value of <code>nplurals</code>.
jpayne@68	755 </p>
jpayne@68	756 <a name="IDX1075"></a>
jpayne@68	757 <p>The following rules are known at this point. The language with families
jpayne@68	758 are listed. But this does not necessarily mean the information can be
jpayne@68	759 generalized for the whole family (as can be easily seen in the table
jpayne@68	760 below).<a name="DOCF5" href="gettext_fot.html#FOOT5">(5)</a>
jpayne@68	761 </p>
jpayne@68	762 <dl compact="compact">
jpayne@68	763 <dt> Only one form:</dt>
jpayne@68	764 <dd><p>Some languages only require one single form. There is no distinction
jpayne@68	765 between the singular and plural form. An appropriate header entry
jpayne@68	766 would look like this:
jpayne@68	767 </p>
jpayne@68	768 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=1; plural=0;
jpayne@68	769 </pre></td></tr></table>
jpayne@68	770
jpayne@68	771 <p>Languages with this property include:
jpayne@68	772 </p>
jpayne@68	773 <dl compact="compact">
jpayne@68	774 <dt> Asian family</dt>
jpayne@68	775 <dd><p>Japanese, Vietnamese, Korean </p></dd>
jpayne@68	776 <dt> Tai-Kadai family</dt>
jpayne@68	777 <dd><p>Thai </p></dd>
jpayne@68	778 </dl>
jpayne@68	779
jpayne@68	780 </dd>
jpayne@68	781 <dt> Two forms, singular used for one only</dt>
jpayne@68	782 <dd><p>This is the form used in most existing programs since it is what English
jpayne@68	783 is using. A header entry would look like this:
jpayne@68	784 </p>
jpayne@68	785 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=2; plural=n != 1;
jpayne@68	786 </pre></td></tr></table>
jpayne@68	787
jpayne@68	788 <p>(Note: this uses the feature of C expressions that boolean expressions
jpayne@68	789 have to value zero or one.)
jpayne@68	790 </p>
jpayne@68	791 <p>Languages with this property include:
jpayne@68	792 </p>
jpayne@68	793 <dl compact="compact">
jpayne@68	794 <dt> Germanic family</dt>
jpayne@68	795 <dd><p>English, German, Dutch, Swedish, Danish, Norwegian, Faroese </p></dd>
jpayne@68	796 <dt> Romanic family</dt>
jpayne@68	797 <dd><p>Spanish, Portuguese, Italian </p></dd>
jpayne@68	798 <dt> Latin/Greek family</dt>
jpayne@68	799 <dd><p>Greek </p></dd>
jpayne@68	800 <dt> Slavic family</dt>
jpayne@68	801 <dd><p>Bulgarian </p></dd>
jpayne@68	802 <dt> Finno-Ugric family</dt>
jpayne@68	803 <dd><p>Finnish, Estonian </p></dd>
jpayne@68	804 <dt> Semitic family</dt>
jpayne@68	805 <dd><p>Hebrew </p></dd>
jpayne@68	806 <dt> Austronesian family</dt>
jpayne@68	807 <dd><p>Bahasa Indonesian </p></dd>
jpayne@68	808 <dt> Artificial</dt>
jpayne@68	809 <dd><p>Esperanto </p></dd>
jpayne@68	810 </dl>
jpayne@68	811
jpayne@68	812 <p>Other languages using the same header entry are:
jpayne@68	813 </p>
jpayne@68	814 <dl compact="compact">
jpayne@68	815 <dt> Finno-Ugric family</dt>
jpayne@68	816 <dd><p>Hungarian </p></dd>
jpayne@68	817 <dt> Turkic/Altaic family</dt>
jpayne@68	818 <dd><p>Turkish </p></dd>
jpayne@68	819 </dl>
jpayne@68	820
jpayne@68	821 <p>Hungarian does not appear to have a plural if you look at sentences involving
jpayne@68	822 cardinal numbers. For example, “1 apple” is “1 alma”, and “123 apples” is
jpayne@68	823 “123 alma”. But when the number is not explicit, the distinction between
jpayne@68	824 singular and plural exists: “the apple” is “az alma”, and “the apples” is
jpayne@68	825 “az almák”. Since <code>ngettext</code> has to support both types of sentences,
jpayne@68	826 it is classified here, under “two forms”.
jpayne@68	827 </p>
jpayne@68	828 <p>The same holds for Turkish: “1 apple” is “1 elma”, and “123 apples” is
jpayne@68	829 “123 elma”. But when the number is omitted, the distinction between singular
jpayne@68	830 and plural exists: “the apple” is “elma”, and “the apples” is
jpayne@68	831 “elmalar”.
jpayne@68	832 </p>
jpayne@68	833 </dd>
jpayne@68	834 <dt> Two forms, singular used for zero and one</dt>
jpayne@68	835 <dd><p>Exceptional case in the language family. The header entry would be:
jpayne@68	836 </p>
jpayne@68	837 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=2; plural=n>1;
jpayne@68	838 </pre></td></tr></table>
jpayne@68	839
jpayne@68	840 <p>Languages with this property include:
jpayne@68	841 </p>
jpayne@68	842 <dl compact="compact">
jpayne@68	843 <dt> Romanic family</dt>
jpayne@68	844 <dd><p>Brazilian Portuguese, French </p></dd>
jpayne@68	845 </dl>
jpayne@68	846
jpayne@68	847 </dd>
jpayne@68	848 <dt> Three forms, special case for zero</dt>
jpayne@68	849 <dd><p>The header entry would be:
jpayne@68	850 </p>
jpayne@68	851 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; plural=n%10==1 && n%100!=11 ? 0 : n != 0 ? 1 : 2;
jpayne@68	852 </pre></td></tr></table>
jpayne@68	853
jpayne@68	854 <p>Languages with this property include:
jpayne@68	855 </p>
jpayne@68	856 <dl compact="compact">
jpayne@68	857 <dt> Baltic family</dt>
jpayne@68	858 <dd><p>Latvian </p></dd>
jpayne@68	859 </dl>
jpayne@68	860
jpayne@68	861 </dd>
jpayne@68	862 <dt> Three forms, special cases for one and two</dt>
jpayne@68	863 <dd><p>The header entry would be:
jpayne@68	864 </p>
jpayne@68	865 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; plural=n==1 ? 0 : n==2 ? 1 : 2;
jpayne@68	866 </pre></td></tr></table>
jpayne@68	867
jpayne@68	868 <p>Languages with this property include:
jpayne@68	869 </p>
jpayne@68	870 <dl compact="compact">
jpayne@68	871 <dt> Celtic</dt>
jpayne@68	872 <dd><p>Gaeilge (Irish) </p></dd>
jpayne@68	873 </dl>
jpayne@68	874
jpayne@68	875 </dd>
jpayne@68	876 <dt> Three forms, special case for numbers ending in 00 or [2-9][0-9]</dt>
jpayne@68	877 <dd><p>The header entry would be:
jpayne@68	878 </p>
jpayne@68	879 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; \
jpayne@68	880 plural=n==1 ? 0 : (n==0 \|\| (n%100 > 0 && n%100 < 20)) ? 1 : 2;
jpayne@68	881 </pre></td></tr></table>
jpayne@68	882
jpayne@68	883 <p>Languages with this property include:
jpayne@68	884 </p>
jpayne@68	885 <dl compact="compact">
jpayne@68	886 <dt> Romanic family</dt>
jpayne@68	887 <dd><p>Romanian </p></dd>
jpayne@68	888 </dl>
jpayne@68	889
jpayne@68	890 </dd>
jpayne@68	891 <dt> Three forms, special case for numbers ending in 1[2-9]</dt>
jpayne@68	892 <dd><p>The header entry would look like this:
jpayne@68	893 </p>
jpayne@68	894 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; \
jpayne@68	895 plural=n%10==1 && n%100!=11 ? 0 : \
jpayne@68	896 n%10>=2 && (n%100<10 \|\| n%100>=20) ? 1 : 2;
jpayne@68	897 </pre></td></tr></table>
jpayne@68	898
jpayne@68	899 <p>Languages with this property include:
jpayne@68	900 </p>
jpayne@68	901 <dl compact="compact">
jpayne@68	902 <dt> Baltic family</dt>
jpayne@68	903 <dd><p>Lithuanian </p></dd>
jpayne@68	904 </dl>
jpayne@68	905
jpayne@68	906 </dd>
jpayne@68	907 <dt> Three forms, special cases for numbers ending in 1 and 2, 3, 4, except those ending in 1[1-4]</dt>
jpayne@68	908 <dd><p>The header entry would look like this:
jpayne@68	909 </p>
jpayne@68	910 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; \
jpayne@68	911 plural=n%10==1 && n%100!=11 ? 0 : \
jpayne@68	912 n%10>=2 && n%10<=4 && (n%100<10 \|\| n%100>=20) ? 1 : 2;
jpayne@68	913 </pre></td></tr></table>
jpayne@68	914
jpayne@68	915 <p>Languages with this property include:
jpayne@68	916 </p>
jpayne@68	917 <dl compact="compact">
jpayne@68	918 <dt> Slavic family</dt>
jpayne@68	919 <dd><p>Russian, Ukrainian, Belarusian, Serbian, Croatian </p></dd>
jpayne@68	920 </dl>
jpayne@68	921
jpayne@68	922 </dd>
jpayne@68	923 <dt> Three forms, special cases for 1 and 2, 3, 4</dt>
jpayne@68	924 <dd><p>The header entry would look like this:
jpayne@68	925 </p>
jpayne@68	926 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; \
jpayne@68	927 plural=(n==1) ? 0 : (n>=2 && n<=4) ? 1 : 2;
jpayne@68	928 </pre></td></tr></table>
jpayne@68	929
jpayne@68	930 <p>Languages with this property include:
jpayne@68	931 </p>
jpayne@68	932 <dl compact="compact">
jpayne@68	933 <dt> Slavic family</dt>
jpayne@68	934 <dd><p>Czech, Slovak </p></dd>
jpayne@68	935 </dl>
jpayne@68	936
jpayne@68	937 </dd>
jpayne@68	938 <dt> Three forms, special case for one and some numbers ending in 2, 3, or 4</dt>
jpayne@68	939 <dd><p>The header entry would look like this:
jpayne@68	940 </p>
jpayne@68	941 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=3; \
jpayne@68	942 plural=n==1 ? 0 : \
jpayne@68	943 n%10>=2 && n%10<=4 && (n%100<10 \|\| n%100>=20) ? 1 : 2;
jpayne@68	944 </pre></td></tr></table>
jpayne@68	945
jpayne@68	946 <p>Languages with this property include:
jpayne@68	947 </p>
jpayne@68	948 <dl compact="compact">
jpayne@68	949 <dt> Slavic family</dt>
jpayne@68	950 <dd><p>Polish </p></dd>
jpayne@68	951 </dl>
jpayne@68	952
jpayne@68	953 </dd>
jpayne@68	954 <dt> Four forms, special case for one and all numbers ending in 02, 03, or 04</dt>
jpayne@68	955 <dd><p>The header entry would look like this:
jpayne@68	956 </p>
jpayne@68	957 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=4; \
jpayne@68	958 plural=n%100==1 ? 0 : n%100==2 ? 1 : n%100==3 \|\| n%100==4 ? 2 : 3;
jpayne@68	959 </pre></td></tr></table>
jpayne@68	960
jpayne@68	961 <p>Languages with this property include:
jpayne@68	962 </p>
jpayne@68	963 <dl compact="compact">
jpayne@68	964 <dt> Slavic family</dt>
jpayne@68	965 <dd><p>Slovenian </p></dd>
jpayne@68	966 </dl>
jpayne@68	967
jpayne@68	968 </dd>
jpayne@68	969 <dt> Six forms, special cases for one, two, all numbers ending in 02, 03, … 10, all numbers ending in 11 … 99, and others</dt>
jpayne@68	970 <dd><p>The header entry would look like this:
jpayne@68	971 </p>
jpayne@68	972 <table><tr><td> </td><td><pre class="smallexample">Plural-Forms: nplurals=6; \
jpayne@68	973 plural=n==0 ? 0 : n==1 ? 1 : n==2 ? 2 : n%100>=3 && n%100<=10 ? 3 \
jpayne@68	974 : n%100>=11 ? 4 : 5;
jpayne@68	975 </pre></td></tr></table>
jpayne@68	976
jpayne@68	977 <p>Languages with this property include:
jpayne@68	978 </p>
jpayne@68	979 <dl compact="compact">
jpayne@68	980 <dt> Afroasiatic family</dt>
jpayne@68	981 <dd><p>Arabic </p></dd>
jpayne@68	982 </dl>
jpayne@68	983 </dd>
jpayne@68	984 </dl>
jpayne@68	985
jpayne@68	986 <p>You might now ask, <code>ngettext</code> handles only numbers <var>n</var> of type
jpayne@68	987 ‘<samp>unsigned long</samp>’. What about larger integer types? What about negative
jpayne@68	988 numbers? What about floating-point numbers?
jpayne@68	989 </p>
jpayne@68	990 <p>About larger integer types, such as ‘<samp>uintmax_t</samp>’ or
jpayne@68	991 ‘<samp>unsigned long long</samp>’: they can be handled by reducing the value to a
jpayne@68	992 range that fits in an ‘<samp>unsigned long</samp>’. Simply casting the value to
jpayne@68	993 ‘<samp>unsigned long</samp>’ would not do the right thing, since it would treat
jpayne@68	994 <code>ULONG_MAX + 1</code> like zero, <code>ULONG_MAX + 2</code> like singular, and
jpayne@68	995 the like. Here you can exploit the fact that all mentioned plural form
jpayne@68	996 formulas eventually become periodic, with a period that is a divisor of 100
jpayne@68	997 (or 1000 or 1000000). So, when you reduce a large value to another one in
jpayne@68	998 the range [1000000, 1999999] that ends in the same 6 decimal digits, you
jpayne@68	999 can assume that it will lead to the same plural form selection. This code
jpayne@68	1000 does this:
jpayne@68	1001 </p>
jpayne@68	1002 <table><tr><td> </td><td><pre class="smallexample">#include <inttypes.h>
jpayne@68	1003 uintmax_t nbytes = ...;
jpayne@68	1004 printf (ngettext ("The file has %"PRIuMAX" byte.",
jpayne@68	1005 "The file has %"PRIuMAX" bytes.",
jpayne@68	1006 (nbytes > ULONG_MAX
jpayne@68	1007 ? (nbytes % 1000000) + 1000000
jpayne@68	1008 : nbytes)),
jpayne@68	1009 nbytes);
jpayne@68	1010 </pre></td></tr></table>
jpayne@68	1011
jpayne@68	1012 <p>Negative and floating-point values usually represent physical entities for
jpayne@68	1013 which singular and plural don't clearly apply. In such cases, there is no
jpayne@68	1014 need to use <code>ngettext</code>; a simple <code>gettext</code> call with a form suitable
jpayne@68	1015 for all values will do. For example:
jpayne@68	1016 </p>
jpayne@68	1017 <table><tr><td> </td><td><pre class="smallexample">printf (gettext ("Time elapsed: %.3f seconds"),
jpayne@68	1018 num_milliseconds * 0.001);
jpayne@68	1019 </pre></td></tr></table>
jpayne@68	1020
jpayne@68	1021 <p>Even if <var>num_milliseconds</var> happens to be a multiple of 1000, the output
jpayne@68	1022 </p><table><tr><td> </td><td><pre class="smallexample">Time elapsed: 1.000 seconds
jpayne@68	1023 </pre></td></tr></table>
jpayne@68	1024 <p>is acceptable in English, and similarly for other languages.
jpayne@68	1025 </p>
jpayne@68	1026 <p>The translators' perspective regarding plural forms is explained in
jpayne@68	1027 <a href="gettext_12.html#SEC228">Translating plural forms</a>.
jpayne@68	1028 </p>
jpayne@68	1029
jpayne@68	1030 <a name="Optimized-gettext"></a>
jpayne@68	1031 <a name="SEC208"></a>
jpayne@68	1032 <h3 class="subsection"> <a href="gettext_toc.html#TOC201">11.2.7 Optimization of the *gettext functions</a> </h3>
jpayne@68	1033
jpayne@68	1034 <p>At this point of the discussion we should talk about an advantage of the
jpayne@68	1035 GNU <code>gettext</code> implementation. Some readers might have pointed out
jpayne@68	1036 that an internationalized program might have a poor performance if some
jpayne@68	1037 string has to be translated in an inner loop. While this is unavoidable
jpayne@68	1038 when the string varies from one run of the loop to the other it is
jpayne@68	1039 simply a waste of time when the string is always the same. Take the
jpayne@68	1040 following example:
jpayne@68	1041 </p>
jpayne@68	1042 <table><tr><td> </td><td><pre class="example">{
jpayne@68	1043 while (…)
jpayne@68	1044 {
jpayne@68	1045 puts (gettext ("Hello world"));
jpayne@68	1046 }
jpayne@68	1047 }
jpayne@68	1048 </pre></td></tr></table>
jpayne@68	1049
jpayne@68	1050 <p>When the locale selection does not change between two runs the resulting
jpayne@68	1051 string is always the same. One way to use this is:
jpayne@68	1052 </p>
jpayne@68	1053 <table><tr><td> </td><td><pre class="example">{
jpayne@68	1054 str = gettext ("Hello world");
jpayne@68	1055 while (…)
jpayne@68	1056 {
jpayne@68	1057 puts (str);
jpayne@68	1058 }
jpayne@68	1059 }
jpayne@68	1060 </pre></td></tr></table>
jpayne@68	1061
jpayne@68	1062 <p>But this solution is not usable in all situation (e.g. when the locale
jpayne@68	1063 selection changes) nor does it lead to legible code.
jpayne@68	1064 </p>
jpayne@68	1065 <p>For this reason, GNU <code>gettext</code> caches previous translation results.
jpayne@68	1066 When the same translation is requested twice, with no new message
jpayne@68	1067 catalogs being loaded in between, <code>gettext</code> will, the second time,
jpayne@68	1068 find the result through a single cache lookup.
jpayne@68	1069 </p>
jpayne@68	1070
jpayne@68	1071 <a name="Comparison"></a>
jpayne@68	1072 <a name="SEC209"></a>
jpayne@68	1073 <h2 class="section"> <a href="gettext_toc.html#TOC202">11.3 Comparing the Two Interfaces</a> </h2>
jpayne@68	1074
jpayne@68	1075
jpayne@68	1076 <p>The following discussion is perhaps a little bit colored. As said
jpayne@68	1077 above we implemented GNU <code>gettext</code> following the Uniforum
jpayne@68	1078 proposal and this surely has its reasons. But it should show how we
jpayne@68	1079 came to this decision.
jpayne@68	1080 </p>
jpayne@68	1081 <p>First we take a look at the developing process. When we write an
jpayne@68	1082 application using NLS provided by <code>gettext</code> we proceed as always.
jpayne@68	1083 Only when we come to a string which might be seen by the users and thus
jpayne@68	1084 has to be translated we use <code>gettext("…")</code> instead of
jpayne@68	1085 <code>"…"</code>. At the beginning of each source file (or in a central
jpayne@68	1086 header file) we define
jpayne@68	1087 </p>
jpayne@68	1088 <table><tr><td> </td><td><pre class="example">#define gettext(String) (String)
jpayne@68	1089 </pre></td></tr></table>
jpayne@68	1090
jpayne@68	1091 <p>Even this definition can be avoided when the system supports the
jpayne@68	1092 <code>gettext</code> function in its C library. When we compile this code the
jpayne@68	1093 result is the same as if no NLS code is used. When you take a look at
jpayne@68	1094 the GNU <code>gettext</code> code you will see that we use <code>_("…")</code>
jpayne@68	1095 instead of <code>gettext("…")</code>. This reduces the number of
jpayne@68	1096 additional characters per translatable string to <em>3</em> (in words:
jpayne@68	1097 three).
jpayne@68	1098 </p>
jpayne@68	1099 <p>When now a production version of the program is needed we simply replace
jpayne@68	1100 the definition
jpayne@68	1101 </p>
jpayne@68	1102 <table><tr><td> </td><td><pre class="example">#define _(String) (String)
jpayne@68	1103 </pre></td></tr></table>
jpayne@68	1104
jpayne@68	1105 <p>by
jpayne@68	1106 </p>
jpayne@68	1107 <a name="IDX1076"></a>
jpayne@68	1108 <table><tr><td> </td><td><pre class="example">#include <libintl.h>
jpayne@68	1109 #define _(String) gettext (String)
jpayne@68	1110 </pre></td></tr></table>
jpayne@68	1111
jpayne@68	1112 <p>Additionally we run the program ‘<tt>xgettext</tt>’ on all source code file
jpayne@68	1113 which contain translatable strings and that's it: we have a running
jpayne@68	1114 program which does not depend on translations to be available, but which
jpayne@68	1115 can use any that becomes available.
jpayne@68	1116 </p>
jpayne@68	1117 <a name="IDX1077"></a>
jpayne@68	1118 <p>The same procedure can be done for the <code>gettext_noop</code> invocations
jpayne@68	1119 (see section <a href="gettext_4.html#SEC31">Special Cases of Translatable Strings</a>). One usually defines <code>gettext_noop</code> as a
jpayne@68	1120 no-op macro. So you should consider the following code for your project:
jpayne@68	1121 </p>
jpayne@68	1122 <table><tr><td> </td><td><pre class="example">#define gettext_noop(String) String
jpayne@68	1123 #define N_(String) gettext_noop (String)
jpayne@68	1124 </pre></td></tr></table>
jpayne@68	1125
jpayne@68	1126 <p><code>N_</code> is a short form similar to <code>_</code>. The ‘<tt>Makefile</tt>’ in
jpayne@68	1127 the ‘<tt>po/</tt>’ directory of GNU <code>gettext</code> knows by default both of the
jpayne@68	1128 mentioned short forms so you are invited to follow this proposal for
jpayne@68	1129 your own ease.
jpayne@68	1130 </p>
jpayne@68	1131 <p>Now to <code>catgets</code>. The main problem is the work for the
jpayne@68	1132 programmer. Every time he comes to a translatable string he has to
jpayne@68	1133 define a number (or a symbolic constant) which has also be defined in
jpayne@68	1134 the message catalog file. He also has to take care for duplicate
jpayne@68	1135 entries, duplicate message IDs etc. If he wants to have the same
jpayne@68	1136 quality in the message catalog as the GNU <code>gettext</code> program
jpayne@68	1137 provides he also has to put the descriptive comments for the strings and
jpayne@68	1138 the location in all source code files in the message catalog. This is
jpayne@68	1139 nearly a Mission: Impossible.
jpayne@68	1140 </p>
jpayne@68	1141 <p>But there are also some points people might call advantages speaking for
jpayne@68	1142 <code>catgets</code>. If you have a single word in a string and this string
jpayne@68	1143 is used in different contexts it is likely that in one or the other
jpayne@68	1144 language the word has different translations. Example:
jpayne@68	1145 </p>
jpayne@68	1146 <table><tr><td> </td><td><pre class="example">printf ("%s: %d", gettext ("number"), number_of_errors)
jpayne@68	1147
jpayne@68	1148 printf ("you should see %d %s", number_count,
jpayne@68	1149 number_count == 1 ? gettext ("number") : gettext ("numbers"))
jpayne@68	1150 </pre></td></tr></table>
jpayne@68	1151
jpayne@68	1152 <p>Here we have to translate two times the string <code>"number"</code>. Even
jpayne@68	1153 if you do not speak a language beside English it might be possible to
jpayne@68	1154 recognize that the two words have a different meaning. In German the
jpayne@68	1155 first appearance has to be translated to <code>"Anzahl"</code> and the second
jpayne@68	1156 to <code>"Zahl"</code>.
jpayne@68	1157 </p>
jpayne@68	1158 <p>Now you can say that this example is really esoteric. And you are
jpayne@68	1159 right! This is exactly how we felt about this problem and decide that
jpayne@68	1160 it does not weight that much. The solution for the above problem could
jpayne@68	1161 be very easy:
jpayne@68	1162 </p>
jpayne@68	1163 <table><tr><td> </td><td><pre class="example">printf ("%s %d", gettext ("number:"), number_of_errors)
jpayne@68	1164
jpayne@68	1165 printf (number_count == 1 ? gettext ("you should see %d number")
jpayne@68	1166 : gettext ("you should see %d numbers"),
jpayne@68	1167 number_count)
jpayne@68	1168 </pre></td></tr></table>
jpayne@68	1169
jpayne@68	1170 <p>We believe that we can solve all conflicts with this method. If it is
jpayne@68	1171 difficult one can also consider changing one of the conflicting string a
jpayne@68	1172 little bit. But it is not impossible to overcome.
jpayne@68	1173 </p>
jpayne@68	1174 <p><code>catgets</code> allows same original entry to have different translations,
jpayne@68	1175 but <code>gettext</code> has another, scalable approach for solving ambiguities
jpayne@68	1176 of this kind: See section <a href="#SEC203">Solving Ambiguities</a>.
jpayne@68	1177 </p>
jpayne@68	1178
jpayne@68	1179 <a name="Using-libintl_002ea"></a>
jpayne@68	1180 <a name="SEC210"></a>
jpayne@68	1181 <h2 class="section"> <a href="gettext_toc.html#TOC203">11.4 Using libintl.a in own programs</a> </h2>
jpayne@68	1182
jpayne@68	1183 <p>Starting with version 0.9.4 the library <code>libintl.h</code> should be
jpayne@68	1184 self-contained. I.e., you can use it in your own programs without
jpayne@68	1185 providing additional functions. The ‘<tt>Makefile</tt>’ will put the header
jpayne@68	1186 and the library in directories selected using the <code>$(prefix)</code>.
jpayne@68	1187 </p>
jpayne@68	1188
jpayne@68	1189 <a name="gettext-grok"></a>
jpayne@68	1190 <a name="SEC211"></a>
jpayne@68	1191 <h2 class="section"> <a href="gettext_toc.html#TOC204">11.5 Being a <code>gettext</code> grok</a> </h2>
jpayne@68	1192
jpayne@68	1193 <p><strong> NOTE: </strong> This documentation section is outdated and needs to be
jpayne@68	1194 revised.
jpayne@68	1195 </p>
jpayne@68	1196 <p>To fully exploit the functionality of the GNU <code>gettext</code> library it
jpayne@68	1197 is surely helpful to read the source code. But for those who don't want
jpayne@68	1198 to spend that much time in reading the (sometimes complicated) code here
jpayne@68	1199 is a list comments:
jpayne@68	1200 </p>
jpayne@68	1201 <ul>
jpayne@68	1202 <li> Changing the language at runtime
jpayne@68	1203 <a name="IDX1078"></a>
jpayne@68	1204
jpayne@68	1205 <p>For interactive programs it might be useful to offer a selection of the
jpayne@68	1206 used language at runtime. To understand how to do this one need to know
jpayne@68	1207 how the used language is determined while executing the <code>gettext</code>
jpayne@68	1208 function. The method which is presented here only works correctly
jpayne@68	1209 with the GNU implementation of the <code>gettext</code> functions.
jpayne@68	1210 </p>
jpayne@68	1211 <p>In the function <code>dcgettext</code> at every call the current setting of
jpayne@68	1212 the highest priority environment variable is determined and used.
jpayne@68	1213 Highest priority means here the following list with decreasing
jpayne@68	1214 priority:
jpayne@68	1215 </p>
jpayne@68	1216 <ol>
jpayne@68	1217 <li><a name="IDX1079"></a>
jpayne@68	1218 </li><li> <code>LANGUAGE</code>
jpayne@68	1219 <a name="IDX1080"></a>
jpayne@68	1220 </li><li> <code>LC_ALL</code>
jpayne@68	1221 <a name="IDX1081"></a>
jpayne@68	1222 <a name="IDX1082"></a>
jpayne@68	1223 <a name="IDX1083"></a>
jpayne@68	1224 <a name="IDX1084"></a>
jpayne@68	1225 <a name="IDX1085"></a>
jpayne@68	1226 <a name="IDX1086"></a>
jpayne@68	1227 </li><li> <code>LC_xxx</code>, according to selected locale category
jpayne@68	1228 <a name="IDX1087"></a>
jpayne@68	1229 </li><li> <code>LANG</code>
jpayne@68	1230 </li></ol>
jpayne@68	1231
jpayne@68	1232 <p>Afterwards the path is constructed using the found value and the
jpayne@68	1233 translation file is loaded if available.
jpayne@68	1234 </p>
jpayne@68	1235 <p>What happens now when the value for, say, <code>LANGUAGE</code> changes? According
jpayne@68	1236 to the process explained above the new value of this variable is found
jpayne@68	1237 as soon as the <code>dcgettext</code> function is called. But this also means
jpayne@68	1238 the (perhaps) different message catalog file is loaded. In other
jpayne@68	1239 words: the used language is changed.
jpayne@68	1240 </p>
jpayne@68	1241 <p>But there is one little hook. The code for gcc-2.7.0 and up provides
jpayne@68	1242 some optimization. This optimization normally prevents the calling of
jpayne@68	1243 the <code>dcgettext</code> function as long as no new catalog is loaded. But
jpayne@68	1244 if <code>dcgettext</code> is not called the program also cannot find the
jpayne@68	1245 <code>LANGUAGE</code> variable be changed (see section <a href="#SEC208">Optimization of the *gettext functions</a>). A
jpayne@68	1246 solution for this is very easy. Include the following code in the
jpayne@68	1247 language switching function.
jpayne@68	1248 </p>
jpayne@68	1249 <table><tr><td> </td><td><pre class="example"> /* Change language. */
jpayne@68	1250 setenv ("LANGUAGE", "fr", 1);
jpayne@68	1251
jpayne@68	1252 /* Make change known. */
jpayne@68	1253 {
jpayne@68	1254 extern int _nl_msg_cat_cntr;
jpayne@68	1255 ++_nl_msg_cat_cntr;
jpayne@68	1256 }
jpayne@68	1257 </pre></td></tr></table>
jpayne@68	1258
jpayne@68	1259 <a name="IDX1088"></a>
jpayne@68	1260 <p>The variable <code>_nl_msg_cat_cntr</code> is defined in ‘<tt>loadmsgcat.c</tt>’.
jpayne@68	1261 You don't need to know what this is for. But it can be used to detect
jpayne@68	1262 whether a <code>gettext</code> implementation is GNU gettext and not non-GNU
jpayne@68	1263 system's native gettext implementation.
jpayne@68	1264 </p>
jpayne@68	1265 </li></ul>
jpayne@68	1266
jpayne@68	1267
jpayne@68	1268 <a name="Temp-Programmers"></a>
jpayne@68	1269 <a name="SEC212"></a>
jpayne@68	1270 <h2 class="section"> <a href="gettext_toc.html#TOC205">11.6 Temporary Notes for the Programmers Chapter</a> </h2>
jpayne@68	1271
jpayne@68	1272 <p><strong> NOTE: </strong> This documentation section is outdated and needs to be
jpayne@68	1273 revised.
jpayne@68	1274 </p>
jpayne@68	1275
jpayne@68	1276
jpayne@68	1277 <a name="Temp-Implementations"></a>
jpayne@68	1278 <a name="SEC213"></a>
jpayne@68	1279 <h3 class="subsection"> <a href="gettext_toc.html#TOC206">11.6.1 Temporary - Two Possible Implementations</a> </h3>
jpayne@68	1280
jpayne@68	1281 <p>There are two competing methods for language independent messages:
jpayne@68	1282 the X/Open <code>catgets</code> method, and the Uniforum <code>gettext</code>
jpayne@68	1283 method. The <code>catgets</code> method indexes messages by integers; the
jpayne@68	1284 <code>gettext</code> method indexes them by their English translations.
jpayne@68	1285 The <code>catgets</code> method has been around longer and is supported
jpayne@68	1286 by more vendors. The <code>gettext</code> method is supported by Sun,
jpayne@68	1287 and it has been heard that the COSE multi-vendor initiative is
jpayne@68	1288 supporting it. Neither method is a POSIX standard; the POSIX.1
jpayne@68	1289 committee had a lot of disagreement in this area.
jpayne@68	1290 </p>
jpayne@68	1291 <p>Neither one is in the POSIX standard. There was much disagreement
jpayne@68	1292 in the POSIX.1 committee about using the <code>gettext</code> routines
jpayne@68	1293 vs. <code>catgets</code> (XPG). In the end the committee couldn't
jpayne@68	1294 agree on anything, so no messaging system was included as part
jpayne@68	1295 of the standard. I believe the informative annex of the standard
jpayne@68	1296 includes the XPG3 messaging interfaces, “…as an example of
jpayne@68	1297 a messaging system that has been implemented…”
jpayne@68	1298 </p>
jpayne@68	1299 <p>They were very careful not to say anywhere that you should use one
jpayne@68	1300 set of interfaces over the other. For more on this topic please
jpayne@68	1301 see the Programming for Internationalization FAQ.
jpayne@68	1302 </p>
jpayne@68	1303
jpayne@68	1304 <a name="Temp-catgets"></a>
jpayne@68	1305 <a name="SEC214"></a>
jpayne@68	1306 <h3 class="subsection"> <a href="gettext_toc.html#TOC207">11.6.2 Temporary - About <code>catgets</code></a> </h3>
jpayne@68	1307
jpayne@68	1308 <p>There have been a few discussions of late on the use of
jpayne@68	1309 <code>catgets</code> as a base. I think it important to present both
jpayne@68	1310 sides of the argument and hence am opting to play devil's advocate
jpayne@68	1311 for a little bit.
jpayne@68	1312 </p>
jpayne@68	1313 <p>I'll not deny the fact that <code>catgets</code> could have been designed
jpayne@68	1314 a lot better. It currently has quite a number of limitations and
jpayne@68	1315 these have already been pointed out.
jpayne@68	1316 </p>
jpayne@68	1317 <p>However there is a great deal to be said for consistency and
jpayne@68	1318 standardization. A common recurring problem when writing Unix
jpayne@68	1319 software is the myriad portability problems across Unix platforms.
jpayne@68	1320 It seems as if every Unix vendor had a look at the operating system
jpayne@68	1321 and found parts they could improve upon. Undoubtedly, these
jpayne@68	1322 modifications are probably innovative and solve real problems.
jpayne@68	1323 However, software developers have a hard time keeping up with all
jpayne@68	1324 these changes across so many platforms.
jpayne@68	1325 </p>
jpayne@68	1326 <p>And this has prompted the Unix vendors to begin to standardize their
jpayne@68	1327 systems. Hence the impetus for Spec1170. Every major Unix vendor
jpayne@68	1328 has committed to supporting this standard and every Unix software
jpayne@68	1329 developer waits with glee the day they can write software to this
jpayne@68	1330 standard and simply recompile (without having to use autoconf)
jpayne@68	1331 across different platforms.
jpayne@68	1332 </p>
jpayne@68	1333 <p>As I understand it, Spec1170 is roughly based upon version 4 of the
jpayne@68	1334 X/Open Portability Guidelines (XPG4). Because <code>catgets</code> and
jpayne@68	1335 friends are defined in XPG4, I'm led to believe that <code>catgets</code>
jpayne@68	1336 is a part of Spec1170 and hence will become a standardized component
jpayne@68	1337 of all Unix systems.
jpayne@68	1338 </p>
jpayne@68	1339
jpayne@68	1340 <a name="Temp-WSI"></a>
jpayne@68	1341 <a name="SEC215"></a>
jpayne@68	1342 <h3 class="subsection"> <a href="gettext_toc.html#TOC208">11.6.3 Temporary - Why a single implementation</a> </h3>
jpayne@68	1343
jpayne@68	1344 <p>Now it seems kind of wasteful to me to have two different systems
jpayne@68	1345 installed for accessing message catalogs. If we do want to remedy
jpayne@68	1346 <code>catgets</code> deficiencies why don't we try to expand <code>catgets</code>
jpayne@68	1347 (in a compatible manner) rather than implement an entirely new system.
jpayne@68	1348 Otherwise, we'll end up with two message catalog access systems installed
jpayne@68	1349 with an operating system - one set of routines for packages using GNU
jpayne@68	1350 <code>gettext</code> for their internationalization, and another set of routines
jpayne@68	1351 (catgets) for all other software. Bloated?
jpayne@68	1352 </p>
jpayne@68	1353 <p>Supposing another catalog access system is implemented. Which do
jpayne@68	1354 we recommend? At least for Linux, we need to attract as many
jpayne@68	1355 software developers as possible. Hence we need to make it as easy
jpayne@68	1356 for them to port their software as possible. Which means supporting
jpayne@68	1357 <code>catgets</code>. We will be implementing the <code>libintl</code> code
jpayne@68	1358 within our <code>libc</code>, but does this mean we also have to incorporate
jpayne@68	1359 another message catalog access scheme within our <code>libc</code> as well?
jpayne@68	1360 And what about people who are going to be using the <code>libintl</code>
jpayne@68	1361 + non-<code>catgets</code> routines. When they port their software to
jpayne@68	1362 other platforms, they're now going to have to include the front-end
jpayne@68	1363 (<code>libintl</code>) code plus the back-end code (the non-<code>catgets</code>
jpayne@68	1364 access routines) with their software instead of just including the
jpayne@68	1365 <code>libintl</code> code with their software.
jpayne@68	1366 </p>
jpayne@68	1367 <p>Message catalog support is however only the tip of the iceberg.
jpayne@68	1368 What about the data for the other locale categories? They also have
jpayne@68	1369 a number of deficiencies. Are we going to abandon them as well and
jpayne@68	1370 develop another duplicate set of routines (should <code>libintl</code>
jpayne@68	1371 expand beyond message catalog support)?
jpayne@68	1372 </p>
jpayne@68	1373 <p>Like many parts of Unix that can be improved upon, we're stuck with balancing
jpayne@68	1374 compatibility with the past with useful improvements and innovations for
jpayne@68	1375 the future.
jpayne@68	1376 </p>
jpayne@68	1377
jpayne@68	1378 <a name="Temp-Notes"></a>
jpayne@68	1379 <a name="SEC216"></a>
jpayne@68	1380 <h3 class="subsection"> <a href="gettext_toc.html#TOC209">11.6.4 Temporary - Notes</a> </h3>
jpayne@68	1381
jpayne@68	1382 <p>X/Open agreed very late on the standard form so that many
jpayne@68	1383 implementations differ from the final form. Both of my system (old
jpayne@68	1384 Linux catgets and Ultrix-4) have a strange variation.
jpayne@68	1385 </p>
jpayne@68	1386 <p>OK. After incorporating the last changes I have to spend some time on
jpayne@68	1387 making the GNU/Linux <code>libc</code> <code>gettext</code> functions. So in future
jpayne@68	1388 Solaris is not the only system having <code>gettext</code>.
jpayne@68	1389 </p>
jpayne@68	1390
jpayne@68	1391 <table cellpadding="1" cellspacing="1" border="0">
jpayne@68	1392 <tr><td valign="middle" align="left">[<a href="#SEC197" title="Beginning of this chapter or previous chapter"> << </a>]</td>
jpayne@68	1393 <td valign="middle" align="left">[<a href="gettext_12.html#SEC217" title="Next chapter"> >> </a>]</td>
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jpayne@68	1396 <td valign="middle" align="left">   </td>
jpayne@68	1397 <td valign="middle" align="left">   </td>
jpayne@68	1398 <td valign="middle" align="left">   </td>
jpayne@68	1399 <td valign="middle" align="left">[<a href="gettext_toc.html#SEC_Top" title="Cover (top) of document">Top</a>]</td>
jpayne@68	1400 <td valign="middle" align="left">[<a href="gettext_toc.html#SEC_Contents" title="Table of contents">Contents</a>]</td>
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