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Date: Tue, 11 Aug 2009 17:11:18 +0200
From: Ed Schouten <ed@80386.nl>
To: Bob Bishop <rb@gid.co.uk>
Message-ID: <20090811151118.GF1292@hoeg.nl>
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Cc: Ivan Radovanovic <rivanr@gmail.com>, Doug Barton <dougb@freebsd.org>,
	freebsd-current@freebsd.org
Subject: Re: Weird console bug
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* Bob Bishop <rb@gid.co.uk> wrote:
> stat(2) its standard output?

It is likely that very old versions of isatty(3) called fstat(2) and
looked at st_rdev to determine whether it was a TTY. This is indeed to
how various related functions like ptsname(3) worked.
Nowadays stuff is implemented as follows:

- isatty(3) just calls tcgetattr(3), which uses TIOCGETA.
- ttyname(3) first calls isatty(3) and then fdevname(), which uses
  FIODGNAME.
- ptsname(3) first uses TIOCPTMASTER to see whether the file descriptor
  is a pseudo-terminal master and then fdevname().

Which is nice, because everything goes by name and not by device number.
For example, ptsname(3) on Linux generates the name by looking at the
major/minor number.

--=20
 Ed Schouten <ed@80386.nl>
 WWW: http://80386.nl/

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