Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Christian Gollwitzer <auriocus@gmx.de>
Newsgroups: comp.lang.tcl
Subject: Re: Event loop and http::geturl
Date: Fri, 27 Jun 2025 16:35:08 +0200
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In-Reply-To: <103kcha$3ll1r$1@dont-email.me>

Am 26.06.25 um 23:02 schrieb et99:
> I wonder, if you are reading a file that is being written from another 
> process, sort of like a "tail" program, doesn't tcl's [fileevent 
> <channel> readable <script>] trigger constantly? Isn't this in effect a 
> tight polling loop?

The underlying mechanism is select() or poll(). To my knowledge, this 
only works for pipes/sockets, not for files. The "tail -f" program runs 
stat() in a loop to see if the file date or size has changed.

On Linux, you could also use inotify (there is a Tcl package) to get 
callbacks when the file is changed

      Christian