Re: printf, left-justification ignored in 5.0.8

[Vincent Lefevre <vincent@xxxxxxxxxx>]

On 2015-06-07 22:15:29 +0100, Stephane Chazelas wrote:
> BTW, there was a discussion lately on the Austin group mailing
> list confirming that the %20s should count bytes, not
> characters.
> 
> That is in a UTF-8 locale
> 
> printf '|%3s|\n' e é €
> 
> should print:
> 
> |  e|
> | é|
> |€|
> 
> not:
> 
> |  e|
> |  é|
> |  €|
> 
> I find the zsh behaviour more useful though,

Well, it depends on the context. As I've said in

  http://www.zsh.org/mla/workers/2012/msg00151.html

  Yes, the number is the size in bytes, not in characters. I think
  that the intent is to deal with internal structures (e.g. with
  file formats where some fields have a fixed or limited size, and
  the same syntax can be used in C to avoid buffer overflows).

I don't know if this is the real reason.

> especially considering that in zsh we can get the POSIX behaviour
> with:
> 
> $ LC_ALL=C printf '|%3s|\n' e é €
> |  e|
> | é|
> |€|

However the change of locale may affect other format specifiers,
like %f, and error messages.

> But note that to get proper alignment, rather than number of
> characters, the width of the glyphs should be considered
> instead anyway:
> 
> $ printf '|%3b|\n' e '\ue9' 'e\u301' '\uff45'
> |  e|
> |  é|
> | é|
> |  ｅ|
> 
> ksh93 has %3Ls for that:
> 
> $ printf '|%3Ls|\n' e $'\ue9' $'e\u301' $'\uff45'
> |  e|
> |  é|
> |  é|
> | ｅ|
> 
> (possibly uses wcswidth()).

This could be useful in zsh, and its support would be needed for
"emulate ksh".

-- 
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)