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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: Sun, 18 Feb 2018 13:41:25 -0500

> 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.


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.


Attachment: coreutils-seq-bug-29617.patch
Description: Binary data

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