tag 28985 notabug
close 28985
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On 24/10/17 19:21, Chris King-Parra wrote:
> Package: coreutils
> Version: 8.28
>
> Hi there,
>
> I was reading the info pages for ``expand`` this afternoon and came across the
>
> ``--tabs`` option. To my understanding, you supply it with a comma separated
>
> list of numbers. Each number specifies how many spaces to replace the next
>
> occurrence of a tab with. The ``/`` character can be used to prefix a number,
>
> which will then be used for the number of spaces to expand to for every tab in
>
> and after that occurrence.
>
> Here's an excerpt of an example from the info page, describing the ``--tabs=``
>
> option:
>
>> As a GNU extension the last tab specified can be prefixed with a ‘/’ to
>
> indicate a tab size to use for remaining positions. For example, --tabs=2,4,/8
>
> will set tab stops at position 2 and 4, and every multiple of 8 after that.
>
> The results weren’t what I expected::
>
> chris@tw-vm:~> echo 'one |two |three |' | expand --tabs=2,4,/8
> | sed 's/ /#/g' | cat -A
>
> one#|two########|three##|$
>
> For the sake of clarity, here’s the exact command output I expected::
>
> chris@tw-vm:~> echo 'one |two |three |' | expand --tabs=2,4,/8
> | sed 's/ /#/g' | cat -A
>
> one#|two####|three########|$
>
> Here is some other unexpected, but less specific, behavior::
>
> chris@tw-vm:~> echo 'one |two |three |' | expand --tabs=1,2,4
> | sed 's/ /#/g' | cat -A
>
> one#|two#|three#|$
>
> Which I expected to result in::
>
> one#|two##|three####|$
>
> Did I find a bug?
I don't think so.
The following should be instructive.
The uppercase letters are the tab stops,
and you can see the spaces aligning to those.
2,4,/8 ≡ 2,4,8,16,24, so
$ printf '%s\n' 'aBcDefgHijklmnoPqrstuvwXyz' $'one\t|two\t|three\t|' |
expand --tabs=2,4,8,16,24 | sed 's/ /#/g' | cat -A
aBcDefgHijklmnoPqrstuvwXyz$
one#|two########|three##|$
cheers,
Pádraig
