built-in shelf
#main-output is one of the built-in program output streams.
#main-output identifies the output destination, described by the -of or
-aof directive on the OmniMark program's command line. Where there is not an
-of or -aof on the command line, then #main-output
identifies the same destination as #process-output (that is, standard output).
When #main-output and #process-output identify the same destination, the modifiers
set on #main-output are applied to the stream attachment. For example, if #main-output
is written to in text-mode and #process-output is written to in binary-mode, then the
stream attachment will be written to in text-mode. If both of these streams identify the same destination,
and one stream is buffered and the other unbuffered, OmniMark will issue a run-time warning and
the modifiers set on #main-output will be applied to the stream attachment.
#main-output is the default output (#current-output) in an OmniMark program.
The declare #main-output has declarations can be used to change some of the characteristics of
the #main-output stream.
By default, the #main-output stream in any program that uses referents is
treated as if it were opened with referents-allowed and referents-displayed.