paexec:
 - paexec: print exit status of task
 - EXIT STATUS section in man page
 - SIGUSR2 for graceful exit, i.e. complete currently running tasks
   and then exit (Thanks to Mikhailian for idea)
 - New option -gg (double -g) for reading graph of tasks in
   lower-to-upper order and running new tasks as soon as they appear
   on input.  If tasks appears on input slowly (distbb/pkgsrc) this
   may significantly improve parallelism and reduce total running time
 - pamake -- 1) shell/whatever-based script with special section that
   describes hosts, dependency graph of targets and other metainfo,
   where functions are "targets" 2) preprocessing (m4,cpp,whatever).
   Maybe it make sense to see dsh/pdsh.
 - mimic dsh and pdsh
 - PAEXEC_COMMAND as a default for -c
 - pass PAEXEC_NODEID to appropriate nodes
 - -n 'server1 server2 +5' two remote servers and five local
 - Option -n%'node_[1-20,22-30]'
 - non-blocking write(2) for sending task to the slave hosts/CPUs.
 - SIGINFO for displaying current status of tasks
 - SIGUSR1 for trying restore connection to dead client hosts
