Bug#3276: screen upgrade trashes running sessions...

[eichin@kitten.gen.ma.us (Mark W. Eichin)]

package: screen
version: 3.7.1-4

screen.postinst has:

#this is to remove the "/tmp/screens has incorrect permissions" after
#upgrading to this (3.7.1) version of screen from 3.6 or earlier.

rm -rf /tmp/screens

This means that if screen is upgraded while someone is using it, they
lose the ability to reattach -- because the pipe gets nuked. I haven't
looked at the sources to see if there is a way to recover (ie. to tell
screen to write a new pipe in place) but in the meantime, it might be
nice to protect this with a "killall -0 screen" and only do the remove
if the exit status of killall is non-zero. (A warning about running
screens might be nice... though if the whole thing is wrapped in a
check for the correct permissions, that would help too...)