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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Re: Job control, minix upgrades, the universe, and everything...
Message-ID: <3724@ast.cs.vu.nl>
Date: 16 Oct 89 11:01:59 GMT
References: <1989Oct12.193113.10562@watcsc.waterloo.edu> <1166@atha.AthabascaU.CA>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 16

In article <1166@atha.AthabascaU.CA> rwa@cs.AthabascaU.CA (Ross Alexander) writes:
>
>The really useful things you get out of job control are SIGURG, SIGIO,
>SIGSTOP, and SIGCONT.  

Ah ha!  Another nice reason for not doing job control.  The signal() call
does not exist in POSIX.  Instead there is something called sigaction(),
which uses bit maps.  To conform to POSIX I need 15 signals, plus an extra
quasi-signal for detecting stack overflow in protected mode.  Thus the
bit map is naturally an unsigned short, and is full.  Job control would
mean going to longs for everything (or mediums--24 bits).

Furthermore, SIGURG and SIGIO do not exist in POSIX, not even if
_POSIX_JOB_CONTROL is defined.  SIGSTOP and SIGCONT do exist.

Andy Tanenbaum (ast@cs.vu.nl)