File: gettext.info,  Node: Combining POTs,  Prev: xgettext Invocation,  Up: Template

5.2 Combining PO Template Files
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   When a package contains sources in different programming languages
and different, incompatible ‘xgettext’ command line options are required
for these different parts of the package, the solution is to create
intermediate PO template files for each of the parts and then combine
(merge) them together.

   For example, assume you have two source files ‘a.c’ and ‘b.py’, and
want to extract their translatable strings in separate steps.

   Each of the following command sequences does this.  The output is the
same.

   • This command sequence creates intermediate POT files and then
     combines them.
          xgettext -o part-c.pot a.c
          xgettext -o part-py.pot b.py
          xgettext -o all.pot part-c.pot part-py.pot
   • This command sequence does several ‘xgettext’ invocations, with a
     single POT file that accumulates the translatable strings.
          xgettext -o all.pot a.c
          xgettext -o all.pot --join-existing b.py
   • Likewise here, but a ‘--default-domain’ option is used to denote
     the output file rather than a ‘-o’ option.
          xgettext --default-domain=all a.c
          xgettext --default-domain=all --join-existing b.py
          mv all.po all.pot

   One might be tempted to think that ‘msgcat’ can do the same thing,
through a command sequence such as:
     xgettext -o part-c.pot a.c
     xgettext -o part-py.pot b.py
     msgcat -o all.pot part-c.pot part-py.pot
But no, this does not work reliably, because sometimes ‘part-c.pot’ and
‘part-py.pot’ will contain different ‘POT-Creation-Date’ values, and
‘msgcat’ then produces an ‘all.pot’ file that has conflict markers in
the header entry.  This is because ‘msgcat’ generally is meant to
produce PO files that are to be reviewed and edited by a translator;
this is not desired here.