Jerry Peek wrote:

I need to shut down my Linux system before a trip out of town.  I want
the client (boinc_4.19_i686-pc-linux-gnu) to finish computing, return
its results, and not download any more.  So I killed the running client
with Ctrl-C (signal 2), then restarted it with the -exit_when_idle
option.

Don't know, possibly it fetches one last wu to process then exits?  "Get,
process and report work, then exit."  Not quite like classic where the
command was stop_after_send.txt.  http://boinc.berkeley.edu/client_unix.php 
Maybe for s@h you could try the stop_after_send.txt in the project client
as per classic?