How to determine which character is used as decimal separator (radix point) or thousand separator, u-CodePudding

Comming from this answer to Format currency in Bash, I wonder for ways to determine which characters are used as numeric separators.

There are lot of issue regarding locales and number formating, for sample:

printf '%.5f\n' $(bc -l <<<'4*a(1)')
3.14159

LANG=de_DE printf '%.5f\n' $(bc -l <<<'4*a(1)')
bash: printf: 3.14159265358979323844: invalid number
3,00000

binary calculator bc seem not handling locale correctly...

Under mentioned answer, searching for decimal separator (or radix character), I've used this:

int2amount() {
    local TIMEFORMAT=%U _decsep
    read _decsep < <(eval 'time true' 2>&1)
    _decsep=${_decsep//[0-9]}
    ...
}

This work fine:

pi() { local TIMEFORMAT=%U _decsep;read _decsep < <(eval 'time true' 2>&1);_decsep=${_decsep//[0-9]};
       local pi=$(bc -l <<<'4*a(1)')
       printf '%.5f\n' ${pi/./$_decsep}
}

pi
3.14159
LANG=de_DE pi
3,14159

But as thousand separator is a lot easier to find:

printf -v ts "%'d" 1111 ; ts=${ts//1}

There is no fork, so system footprint is very light.

So I could imagine at begin of source file, something like:

numericSeparators() {
    local TIMEFORMAT=%U
    read NUM_DEC_SEP < <(eval 'time true' 2>&1)
    NUM_DEC_SEP=${NUM_DEC_SEP//[0-9]}
    printf -v NUM_THO_SEP "%'d" 1111
    NUM_THO_SEP=${NUM_THO_SEP//1}
}
numericSeparators
declare -r NUM_THO_SEP NUM_DEC_SEP
...

But I think <(eval 'time true' 2>&1) heavy for the goal. I'm searching for a lighter and/or cleaner way for determine them (even both decimal and thousand separators).

Thanks to dan's answer, my functions would become simplier and quicker!

pi() {
    local _decsep pi=$(bc -l <<<'4*a(1)')
    printf -v _decsep %.1f 1
    printf '%.5f\n' ${pi/./${_decsep:1:1}}
}

pi
3.14159
LANG=de_DE.UTF-8 pi
3,14159

numericSeparators() {
    local numtest
    printf -v numtest "%'.1f" 1111
    NUM_THO_SEP=${numtest:1:1}
    NUM_THO_SEP=${NUM_THO_SEP/1}
    NUM_DEC_SEP=${numtest: -2:1}
}
numericSeparators

for loctest in   C   en_US.UTF-8   de_DE.UTF-8   ;do
    LANG=$loctest numericSeparators
    printf '  %-12s thousand: \47%s\47 decimal: \47%s\47\n' \
            "$loctest"  "$NUM_DEC_SEP"  "$NUM_THO_SEP"
done

  C            thousand: '.' decimal: ''
  en_US.UTF-8  thousand: '.' decimal: ','
  de_DE.UTF-8  thousand: ',' decimal: '.'

CodePudding user response：

You can get the locale's radix character (decimal separator) with:

printf -v ds '%#.1f' 1
ds=${ds//[0-9]}

And the thousands grouping separator, with:

printf -v ts "%'d" 1111
ts=${ts//1}

Some locales (eg. C) have no thousands separator, in which case $ts is empty. Conversely, if the radix character is not defined by the locale, POSIX (printf(3)) says it should default to .. The # flag guarantees that it will be printed.