如何根据区域设置环境变量设置浮点格式以进行显示? [英] How to format a floating point for display based on locale environment variables?

问题描述

让我们说我要在Bash脚本中打印几个浮点数. 但是我希望将浮点数显示在LC_NUMERIC区域设置环境变量中.

Lets say I have several floating point numbers to print in a Bash script. But I want the floating points numbers displayed accordingly to the LC_NUMERIC locale environment variable.

#!/usr/bin/env bash

# For consistent/reproducible error messages in this sample code
LANGUAGE=C

# The speed of light in vacum in m.s
declare -r const_C=299792458

# Declare separately when assigning command output
declare -- const_pi

# π is 4 × arc-tangent of 1, using bc calculator with math library
typeset -r const_pi="$(bc --mathlib <<<'scale=20; 4*a(1)')"

# Do it in US's English
LC_NUMERIC=en_US.utf8
printf 'LC_NUMERIC=%s\n' "${LC_NUMERIC}"
printf 'Speed of light in vacuum is:\nC=%.f m/s\n\nπ=%.10f\n' \
  "${const_C}" \
  "${const_pi}"

echo $'\n'

# Do it in France's French
# it fails because floating point format
# changes for printf parameters
LC_NUMERIC=fr_FR.utf8
printf 'LC_NUMERIC=%s\n' "${LC_NUMERIC}"
printf 'La vitesse de la lumière dans le vide est :\nC=%.f m/s\n\nπ≈%.10f\n' \
  "${const_C}" \
  "${const_pi}"

实际输出:

LC_NUMERIC=en_US.utf8
Speed of light in vacuum is:
C=299792458 m/s

π=3.1415926536


LC_NUMERIC=fr_FR.utf8
La vitesse de la lumière dans le vide est :
C=299792458 m/s

a.sh: line 29: printf: 3.14159265358979323844: invalid number
π≈3,0000000000

这是一个完美的预期结果，因为printf %f格式要求参数根据LC_NUMERIC进行格式化.

This is a perfectly expected result because printf %f format expects the argument be formatted according to LC_NUMERIC.

然后如何显示以POSIX或bc格式存储的任意浮点数，但显示时会反映LC_NUMERIC的设置?

Then how do you display arbitrary floating-point numbers that are stored in POSIX or bc's format but having display reflect the settings of LC_NUMERIC?

如果我想要代码的法文部分并显示以下输出怎么办?

What if I want the French part of the code, with the following output?

法语的预期输出:

La vitesse de la lumière dans le vide est :
C=299792458 m/s

π≈3,1415926536

推荐答案

这是Bash自己内置的printf命令的问题.独立的printf可以正常工作.

This is a problem with Bash's own built in printf command. The standalone printf works OK.

LC_NUMERIC=fr_FR.UTF8     printf 'Bad  : %f\n' 3.14
env LC_NUMERIC=fr_FR.UTF8 printf 'Good : %f\n' 3.14

输出

script.sh: line 4: printf: 3.14: invalid number
Bad  : 0,000000
Good : 3,140000

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