Re: nohup definition should be changed

[Paul Eggert]

Nick Maclaren <address@hidden> writes:

> Implementors need no encouragement to produce damn-fool programs that
> require (say) a controlling terminal, an X display or a fancy TERM
> setting for non-interactive or line-mode use....  But enshrining
> that dementia in POSIX is even worse.

I suspect we may be straying from the original point (namely, the
question whether POSIX should be changed to allow "nohup" to close a
tty stdin) and are starting to worry about implementation details.  If
an implementation guarantees that "/" or "/dev/none" exists with
certain properties, the "nohup" implementer can take advantage of that
fact -- that's outside the scope of POSIX.  But this leaves the
question whether POSIX should allow "nohup" to close a stdin tty.

By the way, I assume that it's OK for "nohup" (or for any utility) to
open (say) /dev/null a few times.  That is, I assume there's no
prohibition by POSIX on implementations of standard utilities opening
files (and thereby consuming a few file descriptors).  Hence, if nohup
is allowed to close a stdin tty, it's also allowed to open stdin and
point it at /dev/null, or at /, or whereever it likes.  If this
assumption isn't correct, I suppose the original proposal
<http://www.opengroup.org/austin/mailarchives/ag/msg08344.html> needs
rewording.

> '/' need NOT be present, let alone accessible.

'/' must be present on all conforming POSIX systems; it is required by
XBD 10.1 "The following directories shall exist on conforming
systems".  '/dev/null' must also be present, along with a few other
files.