|PostgreSQL 8.3.23 Documentation|
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This section describes how to implement native language support in a program or library that is part of the PostgreSQL distribution. Currently, it only applies to C programs.
Adding NLS support to a program
Insert this code into the start-up sequence of the program:
#ifdef ENABLE_NLS #include <locale.h> #endif ... #ifdef ENABLE_NLS setlocale(LC_ALL, ""); bindtextdomain("progname", LOCALEDIR); textdomain("progname"); #endif
(The progname can actually be chosen freely.)
Wherever a message that is a candidate for translation
is found, a call to
gettext() needs to be inserted.
fprintf(stderr, "panic level %d\n", lvl);
would be changed to:
fprintf(stderr, gettext("panic level %d\n"), lvl);
(gettext is defined as a no-op if no NLS is configured.)
This tends to add a lot of clutter. One common shortcut is to use:
#define _(x) gettext(x)
Another solution is feasible if the program does much
of its communication through one or a few functions, such
ereport() in the
backend. Then you make this function call
gettext internally on all input
Add a file nls.mk in the directory with the program sources. This file will be read as a makefile. The following variable assignments need to be made here:
The program name, as provided in the
List of provided translations — initially empty.
List of files that contain translatable strings,
i.e., those marked with
gettext or an alternative
solution. Eventually, this will include nearly all
source files of the program. If this list gets too
long you can make the first "file" be a + and the second word be a file that
contains one file name per line.
The tools that generate message catalogs for the
translators to work on need to know what function
calls contain translatable strings. By default,
are known. If you used
_ or other identifiers you need
to list them here. If the translatable string is
not the first argument, the item needs to be of the
form func:2 (for the
The build system will automatically take care of building and installing the message catalogs.
Here are some guidelines for writing messages that are easily translatable.
Do not construct sentences at run-time, like:
printf("Files were %s.\n", flag ? "copied" : "removed");
The word order within the sentence might be different in other languages. Also, even if you remember to call gettext() on each fragment, the fragments might not translate well separately. It's better to duplicate a little code so that each message to be translated is a coherent whole. Only numbers, file names, and such-like run-time variables should be inserted at run time into a message text.
For similar reasons, this won't work:
printf("copied %d file%s", n, n!=1 ? "s" : "");
because it assumes how the plural is formed. If you figured you could solve it like this:
if (n==1) printf("copied 1 file"); else printf("copied %d files", n):
then be disappointed. Some languages have more than two forms, with some peculiar rules. We might have a solution for this in the future, but for now the matter is best avoided altogether. You could write:
printf("number of copied files: %d", n);
If you want to communicate something to the translator, such as about how a message is intended to line up with other output, precede the occurrence of the string with a comment that starts with translator, e.g.:
/* translator: This message is not what it seems to be. */
These comments are copied to the message catalog files so that the translators can see them.