Linux man pages : soelim (1)
soelim - interpret .so requests in groff input
soelim [ -Cv ] [ -Idir ] [ files... ]
It is possible to have whitespace between the -I command line option
and its parameter.
soelim reads files and replaces lines of the form
by the contents of file. It is useful if files included with so need
to be preprocessed. Normally, soelim should be invoked with the -s
option of groff.
Note that there must be no whitespace between the leading dot and the
two characters `s' and `o'. Otherwise, only groff interprets the .so
request (and soelim ignores it).
-C Recognize .so even when followed by a character other than space
-Idir This option may be used to specify a directory to search for
files (both those on the command line and those named in .so
lines). The current directory is always searched first. This
option may be specified more than once, the directories will be
searched in the order specified. No directory search is per-
formed for files specified using an absolute path.
-v Print the version number.
Groff Version 1.18.1 27 June 2001 SOELIM(1)