point to a tty.
Unfortunately the shell assumed that it could do all process group
handling ioctls to fd=2, but this is not correct. Jobs that redirected
fd=2 would be unable to perform the ioctls and silently fail since
the error reporting channel is fd=2... Instead open /dev/tty set
it to close on exec, and use that instead (like all other shells
do). We don't handle the case where the OS does not provide FD_CLOEXEC
or FIOCLEX, because I am lazy.
While I am there:
- Simplify the code by defining functions for tc{g,s}pgrp when OLD_TTY_DRIVER
is defined.
- make sure that 'sh &' works by stopping itself. Don't kill the shell's
process group, kill the shell itself.
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