PostgreSQL programs (server and client) can issue their messages in your favorite language — if the messages have been translated. Creating and maintaining translated message sets needs the help of people who speak their own language well and want to contribute to the PostgreSQL effort. You do not have to be a programmer at all to do this. This section explains how to help.
We won't judge your language skills — this section is about
software tools. Theoretically, you only need a text editor. But
this is only in the unlikely event that you do not want to try out
your translated messages. When you configure your source tree, be
sure to use the --enable-nls option. This will
also check for the libintl library and the
msgfmt program, which all end users will need
anyway. To try out your work, follow the applicable portions of
the installation instructions.
If you want to start a new translation effort or want to do a
message catalog merge (described later), you will need the
programs xgettext and
msgmerge, respectively, in a GNU-compatible
implementation. Later, we will try to arrange it so that if you
use a packaged source distribution, you won't need
xgettext. (If working from Git, you will still need
it.) GNU Gettext 0.10.36 or later is currently recommended.
Your local gettext implementation should come with its own documentation. Some of that is probably duplicated in what follows, but for additional details you should look there.
The pairs of original (English) messages and their (possibly) translated equivalents are kept in message catalogs, one for each program (although related programs can share a message catalog) and for each target language. There are two file formats for message catalogs: The first is the “PO” file (for Portable Object), which is a plain text file with special syntax that translators edit. The second is the “MO” file (for Machine Object), which is a binary file generated from the respective PO file and is used while the internationalized program is run. Translators do not deal with MO files; in fact hardly anyone does.
The extension of the message catalog file is to no surprise either
.po or .mo. The base
name is either the name of the program it accompanies, or the
language the file is for, depending on the situation. This is a
bit confusing. Examples are psql.po (PO file
for psql) or fr.mo (MO file in French).
The file format of the PO files is illustrated here:
# comment msgid "original string" msgstr "translated string" msgid "more original" msgstr "another translated" "string can be broken up like this" ...
The msgid's are extracted from the program source. (They need not be, but this is the most common way.) The msgstr lines are initially empty and are filled in with useful strings by the translator. The strings can contain C-style escape characters and can be continued across lines as illustrated. (The next line must start at the beginning of the line.)
The # character introduces a comment. If whitespace immediately follows the # character, then this is a comment maintained by the translator. There can also be automatic comments, which have a non-whitespace character immediately following the #. These are maintained by the various tools that operate on the PO files and are intended to aid the translator.
#. automatic comment #: filename.c:1023 #, flags, flags
The #. style comments are extracted from the source file where the
message is used. Possibly the programmer has inserted information
for the translator, such as about expected alignment. The #:
comment indicates the exact location(s) where the message is used
in the source. The translator need not look at the program
source, but can if there is doubt about the correct
translation. The #, comments contain flags that describe the
message in some way. There are currently two flags:
fuzzy is set if the message has possibly been
outdated because of changes in the program source. The translator
can then verify this and possibly remove the fuzzy flag. Note
that fuzzy messages are not made available to the end user. The
other flag is c-format, which indicates that
the message is a printf-style format
template. This means that the translation should also be a format
string with the same number and type of placeholders. There are
tools that can verify this, which key off the c-format flag.
OK, so how does one create a “blank” message
catalog? First, go into the directory that contains the program
whose messages you want to translate. If there is a file
nls.mk, then this program has been prepared
for translation.
If there are already some .po files, then
someone has already done some translation work. The files are
named language.polanguage is the
ISO 639-1 two-letter language code (in lower case), e.g.,
fr.po for French. If there is really a need
for more than one translation effort per language then the files
can also be named
language_region.poregion is the
ISO 3166-1 two-letter country code (in upper case),
e.g.,
pt_BR.po for Portuguese in Brazil. If you
find the language you wanted you can just start working on that
file.
If you need to start a new translation effort, then first run the command:
make init-po
This will create a file
progname.pot.pot to distinguish it from PO files that
are “in production”. The T stands for
“template”.)
Copy this file to
language.ponls.mk and add the
language (or language and country) code to the line that looks like:
AVAIL_LANGUAGES := de fr
(Other languages can appear, of course.)
As the underlying program or library changes, messages might be changed or added by the programmers. In this case you do not need to start from scratch. Instead, run the command:
make update-po
which will create a new blank message catalog file (the pot file
you started with) and will merge it with the existing PO files.
If the merge algorithm is not sure about a particular message it
marks it “fuzzy” as explained above. The new PO file
is saved with a .po.new extension.
The PO files can be edited with a regular text editor. The translator should only change the area between the quotes after the msgstr directive, add comments, and alter the fuzzy flag. There is (unsurprisingly) a PO mode for Emacs, which I find quite useful.
The PO files need not be completely filled in. The software will automatically fall back to the original string if no translation (or an empty translation) is available. It is no problem to submit incomplete translations for inclusions in the source tree; that gives room for other people to pick up your work. However, you are encouraged to give priority to removing fuzzy entries after doing a merge. Remember that fuzzy entries will not be installed; they only serve as reference for what might be the right translation.
Here are some things to keep in mind while editing the translations:
Make sure that if the original ends with a newline, the translation does, too. Similarly for tabs, etc.
If the original is a printf format string, the translation
also needs to be. The translation also needs to have the same
format specifiers in the same order. Sometimes the natural
rules of the language make this impossible or at least awkward.
In that case you can modify the format specifiers like this:
msgstr "Die Datei %2$s hat %1$u Zeichen."
Then the first placeholder will actually use the second
argument from the list. The
digits$printf
family of functions. You might not have heard of it before because
there is little use for it outside of message
internationalization.)
If the original string contains a linguistic mistake, report that (or fix it yourself in the program source) and translate normally. The corrected string can be merged in when the program sources have been updated. If the original string contains a factual mistake, report that (or fix it yourself) and do not translate it. Instead, you can mark the string with a comment in the PO file.
Maintain the style and tone of the original string.
Specifically, messages that are not sentences (cannot
open file %s) should probably not start with a
capital letter (if your language distinguishes letter case) or
end with a period (if your language uses punctuation marks).
It might help to read Section 53.3.
If you don't know what a message means, or if it is ambiguous, ask on the developers' mailing list. Chances are that English speaking end users might also not understand it or find it ambiguous, so it's best to improve the message.