Re: 5.93 tail -N foo bar invalid option

[Paul Eggert]

address@hidden (Karl Berry) writes:

> In coreutils 5.93, with _POSIX2_VERSION=0 (and POSIXLY_CORRECT unset), 
>   touch foo bar
>   tail -3 foo bar
> yields the error
>   tail: invalid option -- 3
> Both `tail -3 foo' and `head -3 foo bar' are ok.

Well, that's a long story.

7th Edition Unix "tail -3 foo bar" ignores "bar", and Solaris 10
"/usr/bin/tail" follows in this ancient and bogus tradition.  SUSv2
(1997) requires support for "tail -3 foo" and for "head -3 foo bar",
but it understandably does not require support for "tail -3 foo bar".

When I ran into this a while ago, I decided not to change GNU tail to
support 7th Edition Unix behavior, as that behavior is
counterintuitive and confusing and no standard requires it.  I thought
it better to reject that usage entirely.

However, if some actual programs rely on the 7th Edition Unix
behavior, I suppose that would be an argument for changing coreutils
"tail" to behave compatibly.

The coreutils documentation says this:

  For compatibility @command{tail} also supports an obsolete usage
  @samp{tail address@hidden address@hidden, which is recognized
  only if it does not conflict with the usage described
  above.

This says "tail -3 foo bar" is not supported, but it does not say so
explicitly.  Do you think an explicit statement would be helpful?