Does Posix require any devices

There is no single standard or tool to query hardware devices on Linux systems in general. Depending on your host's architecture, and which of its components you must query, and how much detail you need about it, you may need one or more tools specific to that component. However some commands/tools are in wider use and have greater mindshare than others. Following are some--that may or may not be available for your particular host--but are nonetheless Generally Regarded As Useful and widely available from major package managers (though I only link to Debian below):

all-purpose query tools:

• hwinfo. hwinfo --short - gives a useful overview of The Whole Enchilada, and info hwinfo shows many other options for querying specific subsystems in detail.
• inxi is part of a larger "collection of system administration tools" with similarly general capabilities.

tools for specific subsystems:

• dmidecode - processor, memory and motherboard details from BIOS
• lscpu - processor details from /proc/cpuinfo
• lspci - PCI devices, typically graphics cards, audio cards, network cards
• lsusb - USB devices in general
• ls -l /dev/disk/by-{id,label}/ - block devices and their block device files
• ls -l /sys/class/net/ - network devices and their network interfaces
• udevinfo - block devices, if using udev

I encourage people to expand this list if some essential tool is missing.

That was raised on the Austin group mailing list in March 2012. Here's the final message on that (by Geoff Clare of the Austin Group (the body that maintains POSIX), who is also the one who raised the issue in the first place). Here copied from the gmane NNTP interface:

Date: Fri, 16 Mar 2012 17:09:42 +0000
From: Geoff Clare <gwc-7882/jkIBncuagvECLh61g@public.gmane.org>
To: austin-group-l-7882/jkIBncuagvECLh61g@public.gmane.org
Newsgroups: gmane.comp.standards.posix.austin.general
Subject: Re: Strange addressing issue in sed

Stephane Chazelas <stephane_chazelas-Qt13gs6zZMY@public.gmane.org> wrote, on 16 Mar 2012:
>
> 2012-03-16 15:44:35 +0000, Geoff Clare:
> > I've been alerted to an odd behaviour of sed on certified UNIX
> > systems that doesn't seem to match the requirements of the
> > standard.  It concerns an interaction between the 'n' command
> > and address matching.
> > 
> > According to the standard, this command:
> > 
> > printf 'A\nB\nC\nD\n' | sed '1,3s/A/B/;1,3n;1,3s/B/C/'
> > 
> > should produce the output:
> > 
> > B
> > C
> > C
> > D
> > 
> > GNU sed does produce this, but certified UNIX systems produce this:
> > 
> > B
> > B
> > C
> > D
> > 
> > However, if I change the 1,3s/B/C/ to 2,3s/B/C/ then they produce
> > the expected output (tested on Solaris and HP-UX).
> > 
> > Is this just an obscure bug from common ancestor code, or is there
> > some legitimate reason why this address change alters the behaviour?
> [...]
> 
> I suppose the idea is that for the second 1,3cmd, line "1" has
> not been seen, so the 1,3 range is not entered.

Ah yes, now it makes sense, and it looks like the standard does
require this slightly strange behaviour, given how the processing
of the "two addresses" case is specified:

    An editing command with two addresses shall select the inclusive
    range from the first pattern space that matches the first address
    through the next pattern space that matches the second.  (If the
    second address is a number less than or equal to the line number
    first selected, only one line shall be selected.) Starting at the
    first line following the selected range, sed shall look again for
    the first address. Thereafter, the process shall be repeated.

It's specified this way because the addresses can be BREs, but if
the same matching process is applied to the line numbers (even though
they can only match at most once), then the 1,3 range on that last
command is never entered.

-- 
Geoff Clare <g.clare-7882/jkIBncuagvECLh61g@public.gmane.org>
The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England

And here's the relevant part of the rest of the message (by me) that Geoff was quoting:

I suppose the idea is that for the second 1,3cmd, line "1" has
not been seen, so the 1,3 range is not entered.

Same idea as in

printf '%s\n' A B C | sed -n '1d;1,2p'

whose behavior differ in traditional (heirloom toolchest at
least) and GNU.

It's unclear to me whether POSIX wants one behavior or the
other.

So, (according to Geoff) POSIX is clear that the GNU behaviour is non-compliant.

And it's true it's less consistent (compare seq 10 | sed -n '1d;1,2p' with seq 10 | sed -n '1d;/^1$/,2p') even if potentially less surprising to people who don't realise how ranges are processed (even Geoff initially found the conforming behaviour "strange").

Nobody bothered reporting it as a bug to the GNU folks. I'm not sure I'd qualify it as a bug. Probably the best option would be for the POSIX specification to be updated to allow both behaviours to make it clear that one cannot rely on either.

Edit. I've now had a look at the original sed implementation in Unix V7 from the late 70s, and it looks pretty much like that behaviour for numeric addresses was not intended or at least not thought through completely there.

With Geoff's reading of the spec (and my original interpretation of why it happens), conversely, in:

seq 5 | sed -n '3d;1,3p'

lines 1, 2, 4 and 5 should be output, because this time, it's the end address that is never encountered by the 1,3p ranged command, like in seq 5 | sed -n '3d;/1/,/3/p'

Yet, that doesn't happen in the original implementation, nor any other implementation I tried (busybox sed returns lines 1, 2 and 4 which looks more like a bug).

If you look at the UNIX v7 code, it does check for the case where the current line number is greater than the (numerical) end address, and gets out of the range then. The fact that it doesn't do it for the start address looks more like an oversight then than an intentional design.

What that means is that there's no implementation that is actually compliant to that interpretation of the POSIX spec in that regard at the moment.

Another confusing behaviour with the GNU implementation is:

$ seq 5 | sed -n '2d;2,/3/p'
3
4
5

Since line 2 was skipped, the 2,/3/ is entered upon line 3 (the first line whose number is >= 2). But as it's the line that made us enter the range, it's not checked for the end address. It gets worse with busybox sed in:

$ seq 10 | busybox sed -n '2,7d; 2,3p'
8

Since lines 2 to 7 were deleted, line 8 is the first one that is >= 2 so the 2,3 range is entered then!