To include another file within a Texinfo file, write the
@include command at the beginning of a line and follow it on
the same line by the name of a file to be included. For example:
@include buffers.texi
@value{var} references are expanded on the @include
line. Other than that, the only @-commands allowed are @@,
@{, @} and associated @-commands such as
@atchar{}.
An included file should simply be a segment of text that you expect to
be included as is into the overall or outer Texinfo file; it
should not contain the standard beginning and end parts of a Texinfo
file. In particular, you should not start an included file with a
line saying ‘\input texinfo’; if you do, that text is inserted
into the output file literally. Likewise, you should not end an
included file with a @bye command; nothing after @bye
is formatted.
In the long-ago past, you were required to write an
@setfilename line at the beginning of an included file, but no
longer. Now, it does not matter whether you write such a line. If an
@setfilename line exists in an included file, it is ignored.
GNU Emacs Texinfo mode provides texinfo-multiple-files-update
to update node pointers and master menu with multiple include files.
See Update Outer File and Include Files.