Exception Conditions

["Evan K. Langlois" <ekl@sdf>]

The patch for exceptional conditions is interesting, but can someone
explain what an exception condition is?  Would be something like, someone
closing a pipe your reading?  Or a media change on the drive for which
you are doing IO?   Or maybe a loss of carrier?

Or is an exceptional condition something else?   

How do read the condition?  Fread?  

Is it possible to use an exception condition with Fselect, to "wait for
carrier" or to detect the loss of such (so, could you wait for a change
in the carrier status?)

If so, then this would be very useful indeed.