One feature of Clon that is beyond the ANSI standard is terminal
autodetection (it requires an ioctl call and hence a foreign
function interface). Terminal autodetection is used in several
situations, for turning on highlighting automatically and for detecting
a terminal line width.
If, for some reason, terminal autodetection is not available, Clon
will work in so-called restricted mode. This means that
--clon-highlight=auto won’t work (highlighting will not be
turned on automatically on a tty). For the same reason, unless
otherwise specified via either the COLUMNS environment variable
or the --clon-line-width option, terminal output will be formatted
for 80 columns regardless of the actual terminal width
(see Global Control in The Clon End-User Manual).