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Date: Thu, 23 Apr 2015 15:16:23 +0100
From: Stephane Chazelas <>
Subject: Re: open(2) with side effects

2015-04-23 15:08:43 +0200, Florian Weimer:
> How common are file names on Linux which, when just opened and closed
> (maybe with fstat or fgetattr inbetween), trigger side effects, such as
> tape rewind?

Depends what you mean by side effect.

named pipes come to mind.

If a process is blocked on open() with O_RDONLY or O_WRONLY on a
named pipe, then when another process comes along and does the
symmetric (O_WRONLY or O_RDONLY) open(), the first process is
unblocked, and when you close() it, the other process will see
eof() on the fd or get a SIGPIPE if it writes...

Opening /dev/ptmx causes a new pts to be allocated. I'd expect
many other devices to allocate something upon an open.

Opening any file gets you closer to the limit of number of open

Opening a file prevents its disk space from being reclaimed upon
the last unlink...


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