Ahh, I see it documented in the texinfo(5) documentation:
{
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. In the option, num is an optional decimal number optionally followed by a
size letter (‘b’, ‘c’, ‘l’) to mean count by 512-byte blocks, bytes, or lines,
optionally followed by ‘f’ which has the same meaning as -f.
}Being an obsolete feature, it might make sense to omit it in the manual page, to avoid too much noise, as long as it can't interfere with non-obsolete options.
Cheers, Alex -- <http://www.alejandro-colomar.es/>
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