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bug#29617: `seq 1 --help' doesn't give help
From: |
chadweisman |
Subject: |
bug#29617: `seq 1 --help' doesn't give help |
Date: |
Mon, 19 Feb 2018 20:42:44 -0500 |
On 2/19/2018 at 8:35 PM, "Pádraig Brady" <address@hidden> wrote:
>
>On 18/02/18 10:41, address@hidden wrote:
>>
>>> On 12/08/2017 11:38 AM, Eric B 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.
>>
>> Hello,
>>
>> I've taken a stab at fixing this problem because it affects me
>fairly often.
>>
>> Instead of using a two-pass system, I check if any of the args
>we scan are --help or --version and bail if we see either. See
>attached patch.
>>
>> The bad side of this approach is that the -f, -s, and -w options
>and their associated long options aren't handled so `seq 1 -w 2
>10` still shows an error. Also, it's a kludgy sort of fix, so I
>completely understand why you wouldn't want to include it. But at
>least it's a step in the right direction to give help when we can
>instead of an error.
>>
>> Chad
>>
>
>Thanks for looking at this again.
>You attached the wrong patch.
>
Wow, did I ever! Sorry for that.
>A helper function to prescan argv to look for --help and call
>usage()
>or --version and call version_etc(), while bailing itself
>if it encounters '--', does seem useful to have in seq.
>Though note it probably shouldn't support abbreviations like --h
>etc.
>
>BTW other commands that use '+' with getopt() to exist option
>processing early are tr, basename, pathchk, printf.
>Though all those could interpret --option as a valid argument
>and so wouldn't be appropriate to treat like this.
>Likewise for all the commands the exec, like chroot, env, ...
>as --options are very often passed to the delegate commands.
>
I also tried a two-pass approach but it ended up being pretty messy. I can't
help but think using argp would make this particular problem easier to handle.
Chad
coreutils-seq.patch
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