[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#29617: `seq 1 --help' doesn't give help
From: |
Eric Blake |
Subject: |
bug#29617: `seq 1 --help' doesn't give help |
Date: |
Fri, 8 Dec 2017 12:55:04 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
On 12/08/2017 11:38 AM, address@hidden wrote:
> Hello,
>
> I am using coreutils version 8.27 on Fedora, and I don't see this fixed in
> 8.28's NEWS.
>
> $ seq 1 --help
> seq: invalid floating point argument: ‘--help’
> Try 'seq --help' for more information.
Interesting bug!
>
> We should be able to put the options anywhere and not necessarily before any
> arguments.
Yes, when possible.
> And even if not (e.g. POSIX conformance overrides,)
POSIX does say you have to write 'foo -- --help' if you want to
guarantee that --help is treated as a literal argument rather than
option, but it also says that the moment you specify '--help' (or any
other parameter starting with two dashes without the -- end-of-options
parameter), you are already in undefined territory. So we can do
whatever we want when encountering '--help' - which is part of the
reason WHY the GNU project prefers making 'foo args --help' print help
output where possible.
> --help should be handled specially to conform to the GNU coding standards. [1]
Yes.
But the reason that it fails is because we use getopt_long(...,
"+f:s:w") - where the leading '+' specifically requests that we NOT
allow option reordering. Why? Because 'seq' is MOST useful if it can
parse negative numbers easily. We deemed it more important to support
'seq 2 -1 1' without requiring the user to write 'seq -- 2 -1 1' - but
in doing so, it also means that we can't reorder options, so any obvious
non-option (like '1' in your example) makes all other parameters
non-options (including '--help' in your example).
It might be possible to do a two-pass parse over argv: one that looks
just for --help (and where treating -1 as an option is a no-op), and the
second that actually parses things in order now that it knows --help is
not present. But that's a lot of code to add for a corner case, so I
won't be writing the patch; but I also won't turn it down if someone
else wants to write the patch.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
signature.asc
Description: OpenPGP digital signature