On 27/06/2025 20:16, Collin Funk wrote:
Hi Jim and Pádraig,
Jim Meyering <j...@meyering.net> writes:
tail -r comes from the BSDs.
Also the BSDs don't have tac(1) which overlaps in functionality quite a bit.
I'm a bit surprised -r was added by POSIX, but fair enough.
"Surprised" is putting it lightly. I am disappointed and am tempted to
push back and to delay encumbering GNU tail with -r.
That is an option no GNU system needs, since they've all had tac since
before 1992-era textutils.
I've Cc'd Eric Blake, in case someone wants to propose adding tac to
POSIX in spite of the fact that the BSDs still lack it.
Thanks for reminding me about 'tac'. For some reason I forgot about it.
That solves my question about how to implement 'tail -r' while avoiding
arbitrary limits. But I agree that duplicating parts of 'tac' into
'tail' does not seem ideal.
Yes not ideal.
I wouldn't be rushing to implement it TBH.
Note the POSIX specified functionality is
limited to -n and a single file,
so we might be able to implement the POSIX subset
by just piping the output (of one file) to tac internally?
BSD functionality is more involved:
$ seq 10 > a; cp a b $ tail -n2 -r a b ==> a <==
10
9
==> b <==
10
9
cheers,
Pádraig
