Using less in environment without controlling tty

[Cathey, Jim]

My understanding (sans looking at any particular code) is that
more/less/et al. read from stdin, write to stdout, and, if necessary,
read _commands_ from /dev/tty.  This allows them to work in a
pipeline as well as interactively.  The /dev/tty access is supposed to
be a last-ditch effort to find a channel to get interactive input from,
like password setting and the like.  So why not use isatty(stdout)
to determine whether or not to open /dev/tty?  That lets things
like:

... | less | tee outfile

work.

-- Jim