printf shortcomings

printf shortcomings

[Micah Elliott]

I was looking at `printf(3)` and also this lovely reference
(http://www.pixelbeat.org/programming/gcc/format_specs.html) and
noticed that the "locale thousands grouping" flag (') doesn't appear
to be supported by Zsh's builtin printf. I don't have an important
need for this today, but noticing that it could be pretty useful.

  % printf "%'i" 3210384
  print: %': invalid directive
  % /usr/bin/printf "%'i" 3210384
  3,210,384%

Is the prescription to just fall back to the system printf when
certain complex formats are needed? Or are there plans to implement
(most) everything from the system version? I see LC_NUMERIC
(zshparam(1)) hinting at the "thousands separator" but I'm not seeing
where that gets used.

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Re: printf shortcomings

[Oliver Kiddle]

Micah Elliott wrote:
> I was looking at `printf(3)` and also this lovely reference
> (http://www.pixelbeat.org/programming/gcc/format_specs.html) and
> noticed that the "locale thousands grouping" flag (') doesn't appear
> to be supported by Zsh's builtin printf. I don't have an important
> need for this today, but noticing that it could be pretty useful.

That is a reference for the GNU libc printf. The thousand grouping flag
is by no means standard. Zsh's printf largely uses the system printf
underneath, so it isn't completely trivial to support GNU specific flags
portably (keep in mind that lots of flags can be combined so it isn't
just a case of sticking a character in before every third digit). We
could pass through the ' so that it only works where supported by the
system printf but we'd need to be sure it doesn't have any nasty side
effects on some system.

If you do zmodload zsh/langinfo, you can get the thousand separator from
$langinfo[THOUSEP] so if you ever do need the feature, it may be
possible to implement it using that.

Oliver