[TUHS] job control (Re: Re: FD 2

[Bakul Shah <bakul@iitbombay.org>]

On Jan 30, 2023, at 8:19 AM, Ralph Corderoy <ralph@inputplus.co.uk> wrote:
> 
> Hi Bakul,
> 
>>> There was no job control on plan9 and I can't say I ever missed it.
>> 
>> Just yesterday I realized running two “make -j 8” in parallel was
>> making them both go real slow so I stopped one of them with ^Z and
>> continued it once the other make finished.  This use case can’t be
>> handled with more windows.
> 
> If I lacked job control in that situation, I'd either SIGSTOP one of the
> two with kill(1) for a later SIGCONT or renice it to hardly get a look
> in until its peer had finished.  (The TTY's susp character for job
> control is SIGTSTP.)

Unfortunately renice command can only be used by mere users
to *increase* niceness, not decrease. Agreed that you don’t need
a tty discipline for SIGSTOP but it is quite convenient! Note that even
plan9 allows killing a process by hitting a single key but I suppose
that is done in a different way.

Steve Nickolas made a comment about how rerunning make should
simply continue from where it left off. Unfortunately many do not.
A typical silent error is an output file is created but the program is
killed before it can finish the job. The next time around this program
won’t run since the output already exists! Or you have a “make world”
situation where everything is removed before building anything!