gettext: PO Files
3 The Format of PO Files
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The GNU ‘gettext’ toolset helps programmers and translators at
producing, updating and using translation files, mainly those PO files
which are textual, editable files. This chapter explains the format of
PO files.
A PO file is made up of many entries, each entry holding the relation
between an original untranslated string and its corresponding
translation. All entries in a given PO file usually pertain to a single
project, and all translations are expressed in a single target language.
One PO file “entry” has the following schematic structure:
WHITE-SPACE
# TRANSLATOR-COMMENTS
#. EXTRACTED-COMMENTS
#: REFERENCE...
#, FLAG...
#| msgid PREVIOUS-UNTRANSLATED-STRING
msgid UNTRANSLATED-STRING
msgstr TRANSLATED-STRING
The general structure of a PO file should be well understood by the
translator. When using PO mode, very little has to be known about the
format details, as PO mode takes care of them for her.
A simple entry can look like this:
#: lib/error.c:116
msgid "Unknown system error"
msgstr "Error desconegut del sistema"
Entries begin with some optional white space. Usually, when
generated through GNU ‘gettext’ tools, there is exactly one blank line
between entries. Then comments follow, on lines all starting with the
character ‘#’. There are two kinds of comments: those which have some
white space immediately following the ‘#’ - the TRANSLATOR COMMENTS -,
which comments are created and maintained exclusively by the translator,
and those which have some non-white character just after the ‘#’ - the
AUTOMATIC COMMENTS -, which comments are created and maintained
automatically by GNU ‘gettext’ tools. Comment lines starting with ‘#.’
contain comments given by the programmer, directed at the translator;
these comments are called EXTRACTED COMMENTS because the ‘xgettext’
program extracts them from the program’s source code. Comment lines
starting with ‘#:’ contain references to the program’s source code.
Comment lines starting with ‘#,’ contain flags; more about these below.
Comment lines starting with ‘#|’ contain the previous untranslated
string for which the translator gave a translation.
All comments, of either kind, are optional.
After white space and comments, entries show two strings, namely
first the untranslated string as it appears in the original program
sources, and then, the translation of this string. The original string
is introduced by the keyword ‘msgid’, and the translation, by ‘msgstr’.
The two strings, untranslated and translated, are quoted in various ways
in the PO file, using ‘"’ delimiters and ‘\’ escapes, but the translator
does not really have to pay attention to the precise quoting format, as
PO mode fully takes care of quoting for her.
The ‘msgid’ strings, as well as automatic comments, are produced and
managed by other GNU ‘gettext’ tools, and PO mode does not provide means
for the translator to alter these. The most she can do is merely
deleting them, and only by deleting the whole entry. On the other hand,
the ‘msgstr’ string, as well as translator comments, are really meant
for the translator, and PO mode gives her the full control she needs.
The comment lines beginning with ‘#,’ are special because they are
not completely ignored by the programs as comments generally are. The
comma separated list of FLAGs is used by the ‘msgfmt’ program to give
the user some better diagnostic messages. Currently there are two forms
of flags defined:
‘fuzzy’
This flag can be generated by the ‘msgmerge’ program or it can be
inserted by the translator herself. It shows that the ‘msgstr’
string might not be a correct translation (anymore). Only the
translator can judge if the translation requires further
modification, or is acceptable as is. Once satisfied with the
translation, she then removes this ‘fuzzy’ attribute. The
‘msgmerge’ program inserts this when it combined the ‘msgid’ and
‘msgstr’ entries after fuzzy search only. ⇒Fuzzy Entries.
‘c-format’
‘no-c-format’
These flags should not be added by a human. Instead only the
‘xgettext’ program adds them. In an automated PO file processing
system as proposed here, the user’s changes would be thrown away
again as soon as the ‘xgettext’ program generates a new template
file.
The ‘c-format’ flag indicates that the untranslated string and the
translation are supposed to be C format strings. The ‘no-c-format’
flag indicates that they are not C format strings, even though the
untranslated string happens to look like a C format string (with
‘%’ directives).
When the ‘c-format’ flag is given for a string the ‘msgfmt’ program
does some more tests to check the validity of the translation.
DONTPRINTYET ⇒msgfmt Invocation, ⇒c-format Flag and *noteDONTPRINTYET ⇒msgfmt Invocation, ⇒c-format Flag and ⇒
c-format.
‘objc-format’
‘no-objc-format’
Likewise for Objective C, see ⇒objc-format.
‘python-format’
‘no-python-format’
Likewise for Python, see ⇒python-format.
‘python-brace-format’
‘no-python-brace-format’
Likewise for Python brace, see ⇒python-format.
‘java-format’
‘no-java-format’
Likewise for Java ‘MessageFormat’ format strings, see ⇒
java-format.
‘java-printf-format’
‘no-java-printf-format’
Likewise for Java ‘printf’ format strings, see ⇒java-format.
‘csharp-format’
‘no-csharp-format’
Likewise for C#, see ⇒csharp-format.
‘javascript-format’
‘no-javascript-format’
Likewise for JavaScript, see ⇒javascript-format.
‘scheme-format’
‘no-scheme-format’
Likewise for Scheme, see ⇒scheme-format.
‘lisp-format’
‘no-lisp-format’
Likewise for Lisp, see ⇒lisp-format.
‘elisp-format’
‘no-elisp-format’
Likewise for Emacs Lisp, see ⇒elisp-format.
‘librep-format’
‘no-librep-format’
Likewise for librep, see ⇒librep-format.
‘ruby-format’
‘no-ruby-format’
Likewise for Ruby, see ⇒ruby-format.
‘sh-format’
‘no-sh-format’
Likewise for Shell, see ⇒sh-format.
‘awk-format’
‘no-awk-format’
Likewise for awk, see ⇒awk-format.
‘lua-format’
‘no-lua-format’
Likewise for Lua, see ⇒lua-format.
‘object-pascal-format’
‘no-object-pascal-format’
Likewise for Object Pascal, see ⇒object-pascal-format.
‘smalltalk-format’
‘no-smalltalk-format’
Likewise for Smalltalk, see ⇒smalltalk-format.
‘qt-format’
‘no-qt-format’
Likewise for Qt, see ⇒qt-format.
‘qt-plural-format’
‘no-qt-plural-format’
Likewise for Qt plural forms, see ⇒qt-plural-format.
‘kde-format’
‘no-kde-format’
Likewise for KDE, see ⇒kde-format.
‘boost-format’
‘no-boost-format’
Likewise for Boost, see ⇒boost-format.
‘tcl-format’
‘no-tcl-format’
Likewise for Tcl, see ⇒tcl-format.
‘perl-format’
‘no-perl-format’
Likewise for Perl, see ⇒perl-format.
‘perl-brace-format’
‘no-perl-brace-format’
Likewise for Perl brace, see ⇒perl-format.
‘php-format’
‘no-php-format’
Likewise for PHP, see ⇒php-format.
‘gcc-internal-format’
‘no-gcc-internal-format’
Likewise for the GCC sources, see ⇒gcc-internal-format.
‘gfc-internal-format’
‘no-gfc-internal-format’
Likewise for the GNU Fortran Compiler sources, see ⇒
gfc-internal-format.
‘ycp-format’
‘no-ycp-format’
Likewise for YCP, see ⇒ycp-format.
It is also possible to have entries with a context specifier. They
look like this:
WHITE-SPACE
# TRANSLATOR-COMMENTS
#. EXTRACTED-COMMENTS
#: REFERENCE...
#, FLAG...
#| msgctxt PREVIOUS-CONTEXT
#| msgid PREVIOUS-UNTRANSLATED-STRING
msgctxt CONTEXT
msgid UNTRANSLATED-STRING
msgstr TRANSLATED-STRING
The context serves to disambiguate messages with the same
UNTRANSLATED-STRING. It is possible to have several entries with the
same UNTRANSLATED-STRING in a PO file, provided that they each have a
different CONTEXT. Note that an empty CONTEXT string and an absent
‘msgctxt’ line do not mean the same thing.
A different kind of entries is used for translations which involve
plural forms.
WHITE-SPACE
# TRANSLATOR-COMMENTS
#. EXTRACTED-COMMENTS
#: REFERENCE...
#, FLAG...
#| msgid PREVIOUS-UNTRANSLATED-STRING-SINGULAR
#| msgid_plural PREVIOUS-UNTRANSLATED-STRING-PLURAL
msgid UNTRANSLATED-STRING-SINGULAR
msgid_plural UNTRANSLATED-STRING-PLURAL
msgstr[0] TRANSLATED-STRING-CASE-0
...
msgstr[N] TRANSLATED-STRING-CASE-N
Such an entry can look like this:
#: src/msgcmp.c:338 src/po-lex.c:699
#, c-format
msgid "found %d fatal error"
msgid_plural "found %d fatal errors"
msgstr[0] "s'ha trobat %d error fatal"
msgstr[1] "s'han trobat %d errors fatals"
Here also, a ‘msgctxt’ context can be specified before ‘msgid’, like
above.
Here, additional kinds of flags can be used:
‘range:’
This flag is followed by a range of non-negative numbers, using the
syntax ‘range: MINIMUM-VALUE..MAXIMUM-VALUE’. It designates the
possible values that the numeric parameter of the message can take.
In some languages, translators may produce slightly better
translations if they know that the value can only take on values
between 0 and 10, for example.
The PREVIOUS-UNTRANSLATED-STRING is optionally inserted by the
‘msgmerge’ program, at the same time when it marks a message fuzzy. It
helps the translator to see which changes were done by the developers on
the UNTRANSLATED-STRING.
It happens that some lines, usually whitespace or comments, follow
the very last entry of a PO file. Such lines are not part of any entry,
and will be dropped when the PO file is processed by the tools, or may
disturb some PO file editors.
The remainder of this section may be safely skipped by those using a
PO file editor, yet it may be interesting for everybody to have a better
idea of the precise format of a PO file. On the other hand, those
wishing to modify PO files by hand should carefully continue reading on.
An empty UNTRANSLATED-STRING is reserved to contain the header entry
with the meta information (⇒Header Entry). This header entry
should be the first entry of the file. The empty UNTRANSLATED-STRING is
reserved for this purpose and must not be used anywhere else.
Each of UNTRANSLATED-STRING and TRANSLATED-STRING respects the C
syntax for a character string, including the surrounding quotes and
embedded backslashed escape sequences. When the time comes to write
multi-line strings, one should not use escaped newlines. Instead, a
closing quote should follow the last character on the line to be
continued, and an opening quote should resume the string at the
beginning of the following PO file line. For example:
msgid ""
"Here is an example of how one might continue a very long string\n"
"for the common case the string represents multi-line output.\n"
In this example, the empty string is used on the first line, to allow
better alignment of the ‘H’ from the word ‘Here’ over the ‘f’ from the
word ‘for’. In this example, the ‘msgid’ keyword is followed by three
strings, which are meant to be concatenated. Concatenating the empty
string does not change the resulting overall string, but it is a way for
us to comply with the necessity of ‘msgid’ to be followed by a string on
the same line, while keeping the multi-line presentation left-justified,
as we find this to be a cleaner disposition. The empty string could
have been omitted, but only if the string starting with ‘Here’ was
promoted on the first line, right after ‘msgid’.(1) It was not really
necessary either to switch between the two last quoted strings
immediately after the newline ‘\n’, the switch could have occurred after
_any_ other character, we just did it this way because it is neater.
One should carefully distinguish between end of lines marked as ‘\n’
_inside_ quotes, which are part of the represented string, and end of
lines in the PO file itself, outside string quotes, which have no
incidence on the represented string.
Outside strings, white lines and comments may be used freely.
Comments start at the beginning of a line with ‘#’ and extend until the
end of the PO file line. Comments written by translators should have
the initial ‘#’ immediately followed by some white space. If the ‘#’ is
not immediately followed by white space, this comment is most likely
generated and managed by specialized GNU tools, and might disappear or
be replaced unexpectedly when the PO file is given to ‘msgmerge’.
---------- Footnotes ----------
(1) This limitation is not imposed by GNU ‘gettext’, but is for
compatibility with the ‘msgfmt’ implementation on Solaris.
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