Re: printf, left-justification ignored in 5.0.8

[Stephane Chazelas <stephane.chazelas@gmail.com>]

2015-06-12 13:30:50 +0200, Vincent Lefevre:
> 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.

I beleive the real reason was to align on C printf (not wprintf
for instance) (makes little sense to me)

> > 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.

Well, that's a general problem with LC_* handling. Here however
it can be worked around by using several invocations of printf.

[...]
> > 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".
[...]

While I agree that could be useful feature, note that zsh is not
(and will never be I hope) a superset of ksh93. The emulation
mode changes some behaviour that othewise differ from ksh. It
covers mostly ksh88, and zsh has a few features from ksh93 but
that's about it.

-- 
Stephane