[OpenWrt-Devel] Is printf considered to be guaranteed?

[Yousong Zhou]

On Sat, 13 Oct 2018 at 06:48, Sebastian Moeller <moeller0 at gmx.de> wrote:
>
> Dear mhei,
>
>
>
> > On Oct 12, 2018, at 20:53, Michael Heimpold <mhei at heimpold.de> wrote:
> >
> > Am Donnerstag, 11. Oktober 2018, 22:44:53 CEST schrieb Sebastian Moeller:
> >> Dear Luiz,
> >>
> >> thank you very much for this information. By now I have realized that printf
> >> evaluated locale (specifically LC_NUMERIC) at least on non-openwrt unices,
> >> which makes it unfortunately unusable for my purpose.
> >
> > forcing local, e.g.
> > LANG=C printf "%0.3f" 47.11
> > does not help?
>
>         That might actually work, I tried LC_NUMERIC which did not work on openwrt.
>
> > Maybe you could elaborate on your purpose?
>
>         Well I wanted to have a shell variable for configuring a buffer by the time in milliseconds required to empty that buffer (at a given bandwidth), but wanted to actually allow values down to microseconds.
> So I tried to use the following to effectively convert a value in (fractional) milliseconds into microseconds for use by the actual consumer like:
> TMP=1.015 ; printf %.0f\n "${TMP}e3"

Multiple a number by 1000 can be simulated with regex.  Though I would
not use this when possible

    f() {
    local v="$1"
    [ "${v%.*}" != "$v" ] || v="$v."
    v=$(echo "${v}000" | sed -re 's/([0-9]+)\.([0-9]{3}).*/\1\2/')
    echo "$1 $v"
    }

    f 1
    f 1.
    f 1.0
    f 1.12
    f 1.123
    f 1.1234

Regards,
                yousong

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