bug#52077: tail: a case where -n is not taken as implicit

[Pádraig Brady]

tag 52077 notabug
close 52077
stop

On 24/11/2021 07:38, Shehu Dikko wrote:
> Package: coreutils
> Version: 9.0
>
> Do please take a look at this example:
>
> % printf '%s\n' just three lines | tee >f1 f2
> % tail -n1 f1
> lines
> % tail -n1 f*
> ==> f1 <==
> lines
>
> ==> f2 <==
> lines
> % tail -1 f1
> lines
> % tail -1 f*
> tail: option used in invalid context -- 1
> % tail --version | head -1
> tail (GNU coreutils) 9.0
>
> Note that with head and busybox tail, the outputs are unsurprising:
>
> % head -1 f*
> ==> f1 <==
> just
>
> ==> f2 <==
> just
> % head --version | head -1
> head (GNU coreutils) 9.0
> % busybox tail -1 f*
> ==> f1 <==
> lines
>
> ==> f2 <==
> lines
> %
> % uname -v
> #1 SMP Debian 4.19.194-3 (2021-07-18)

The compat for that older syntax is not extended to multiple files.
From the info docs:

  For compatibility ‘tail’ also supports an obsolete usage ‘tail
  -[NUM][bcl][f] [FILE]’, which is recognized only if it does not conflict
  with the usage described above.  This obsolete form uses exactly one
  option and at most one file.

cheers,
Pádraig