From: Bart Schaefer <schaefer@brasslantern.com>
To: Richard Curnow <Richard.Curnow@st.com>, zsh-users@sunsite.dk
Subject: Re: Zsh Guide chapter 5 (substitutions)
Date: Tue, 21 Aug 2001 15:34:21 +0000 [thread overview]
Message-ID: <1010821153422.ZM21739@candle.brasslantern.com> (raw)
In-Reply-To: <20010821152154.A8668@popov.bri.st.com>
On Aug 21, 3:21pm, Richard Curnow wrote:
}
} On page 74, 2nd para from the end,
}
} It seems a bit odd to signal a process to restart; why can't the
} operating system just restart it when you ask? The real answer is
} probably that signals provide an easy way for you to talk to the
} operating system without grovelling around in the dirt too much.
}
} I think it's to provide a way for a process to save and restore state
} across the suspension, by installing handlers for SIGTSTP and SIGCONT.
Saving and restoring state is one reason that there are four signals to
stop a process (STOP, TSTP, TTIN, TTOU). However, it's not the reason
that a signal is used for SIGCONT; Peter's more on target with that one.
There's no such thing as a SIGCONT handler, by the way. The process
just picks up where it left off (possibly with system calls interrupted
depending on the operating system). A typical TSTP handler looks like
save_state();
kill(getpid(), SIGSTOP); /* STOP is not catchable */
restore_state();
--
Bart Schaefer Brass Lantern Enterprises
http://www.well.com/user/barts http://www.brasslantern.com
Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net
next prev parent reply other threads:[~2001-08-21 15:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-15 23:00 Peter Stephenson
2001-08-16 2:31 ` Bart Schaefer
2001-08-17 16:55 ` Bart Schaefer
2001-08-20 18:26 ` Bart Schaefer
2001-08-20 18:35 ` Phil Pennock
2001-08-21 16:38 ` Bart Schaefer
2001-08-21 14:21 ` Richard Curnow
2001-08-21 15:34 ` Bart Schaefer [this message]
2001-08-22 17:10 martin.ebourne
2001-08-23 7:30 ` Borsenkow Andrej
2001-08-23 7:41 ` Borsenkow Andrej
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