Re: Monitor mode handling (bug ?)

[Ganael Laplanche <ganael.laplanche@martymac.org>]

On Tuesday, January 10, 2023 10:28:42 PM CET Jilles Tjoelker wrote:

Hello Jilles,

> The loop with SIGTTIN is the right thing for an interactive job control
> shell. It ensures that two job control shells do not interfere. The idea
> is that the user can later 'fg' from the outer job control shell.
> 
> The loop also helps with suspending a job control shell, for example via
> the funcs/suspend function from the ash source (containing 'local -',
> 'set +m' and 'kill -TSTP 0'): when trying to resume the inner shell via
> 'bg' in the outer shell, it is this loop that makes the inner shell stop
> itself.

Thanks for those explanations.

> However, for a non-interactive shell, monitor mode is most useful for
> its effect of placing jobs in their own process groups. This does not
> necessarily imply any tty manipulation.
> 
> To make this possible, feature was added to FreeBSD sh in
> https://cgit.freebsd.org/src/commit/?id=cd60e2c67d52e1f957841af19128c7227880
> 743a
> 
> This commit allows using job control without a tty in non-interactive
> mode.
> [...]

This is exactly what I use fpsync for (to get a new process group). Do I 
understand that this feature is not available in Dash ?

> Manipulating the disposition of TTIN/TTOU/TSTP with job control enabled
> might be a question of "if it hurts, don't do that".

Thanks!

-- 
Ganael LAPLANCHE <ganael.laplanche@martymac.org>
http://www.martymac.org | http://contribs.martymac.org
FreeBSD: martymac <martymac@FreeBSD.org>, http://www.FreeBSD.org