blocking on `exit'

[gwyn%brl-vld at sri-unix.UUCP]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

A "ps" status `Z' is short for "Zombie", which is a process that has
terminated but has not been wait()ed on by its parent.  If the
original parent terminates without waiting on children, they are
"inherited" by process #1, the "init" process.  "init" normally
lays this type of zombie to rest.  However, if the parent neither
waits on the child nor terminates, the zombies remain in existence
(and they occupy slots in the kernel's process table!).  One way to
spawn a bunch of zombies is to type a bunch of &-terminated commands
to the shell with no non-& commands in between.  The first "regular"
program execution will cause the shell to wait on the terminated &
processes and free their process slots.