From: Thierry Volpiatto <thierry.volpiatto@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: sleep-for documentation and how to pause reliably
Date: Fri, 15 Feb 2013 11:19:27 +0100 [thread overview]
Message-ID: <878v6pj2vk.fsf@gmail.com> (raw)
In-Reply-To: 83mwv6szif.fsf@gnu.org
Hi Eli,
Eli Zaretskii <eliz@gnu.org> writes:
> Am I missing something, or is our current docs of sleep-for misleading?
>
> The doc string says:
>
> (sleep-for SECONDS &optional MILLISECONDS)
>
> Pause, without updating display, for SECONDS seconds.
>
> The only way I can interpret this is that sleep-for _always_ pauses
> for that number of seconds.
>
> The ELisp manual goes even further:
>
> -- Function: sleep-for seconds &optional millisec
> This function simply pauses for SECONDS seconds without updating
> the display. It pays no attention to available input. It returns
> `nil'. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> [...]
>
> Use `sleep-for' when you wish to guarantee a delay.
> ^^^^^^^^^^^^^^^^^
>
> "Guarantee a delay". No "buts".
>
> However, in fact, sleep-for will return as soon as any input from any
> subprocess arrives. E.g., try this in *scratch*:
>
> (progn (setq proc (start-process-shell-command "ls" nil "ls"))
> (sleep-for 20)
> (message "hi"))
>
> You will see no delay at all before the message is displayed.
>
> Am I missing something? If not, apart of fixing the docs, _is_ there
> any way to wait reliably when async subprocesses are running and
> producing output?
What about using a sentinel?
(progn
(let ((proc (start-process-shell-command "ls" nil "ls")))
(set-process-sentinel proc #'(lambda (process event)
(when (string= event "finished\n"))
(sleep-for 20)
(message "hi after 20s sleeping"))))
(message "Hi now sleeping 20s"))
--
Thierry
Get my Gnupg key:
gpg --keyserver pgp.mit.edu --recv-keys 59F29997
next prev parent reply other threads:[~2013-02-15 10:19 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-15 9:22 sleep-for documentation and how to pause reliably Eli Zaretskii
2013-02-15 10:19 ` Thierry Volpiatto [this message]
2013-02-15 13:18 ` Eli Zaretskii
2013-02-15 20:36 ` Thierry Volpiatto
2013-02-16 8:40 ` Eli Zaretskii
2013-02-17 11:58 ` Xue Fuqiao
2013-02-17 16:26 ` Eli Zaretskii
2013-02-17 23:41 ` Xue Fuqiao
2013-02-15 16:11 ` Stefan Monnier
2013-02-15 18:24 ` Eli Zaretskii
2013-02-15 20:36 ` Stefan Monnier
2013-03-02 20:48 ` Johan Bockgård
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