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How can I add a command line calculator to my bash? I have found some, but all of them use the full stop as decimal mark, but I want to have it to use the comma as decimal mark as most of the world does, see picture:

map of the world showing the use of decimal marks

(source wikipedia)

  • blue: Full stop/Period (.)
  • green: Comma (,)
  • red: Momayyez (٫)
  • gray: Data unavailable

The ones that I have found (all with full stop as decimal mark) are the following, where these lines have to be put into your ~/.bashrc file:

  1. Using bc, which has the advantage, that you can calculate ridiculously large numbers:

    calc () {
      bc -l <<< "$@"
    }
    
  2. With awk, where you have mnemonic names for trigonometric and other functions and you can use fractional exponents and you can give the exponent by the two chars ** instead of the, on some keyboards difficult to type ^:

    calc () {
      awk "BEGIN { print $* ; }"
    }
    
share|improve this question
    
I doubt it's most if it includes none of India, China or the USA (those 3 account for 40% of the world population) –  Stéphane Chazelas Jan 23 at 11:58
    
Well, if you say China, India and USA (and I say Egypt) have 40% of the world’s population, and knowing that Australia and the few remaining blue countries in Africa are close to empty, the rest (60%) uses the comma as decimal mark. q.e.d. –  erik Jan 23 at 15:02
    
Pakistan, Philippines, Nigeria, Japan, Mexico are another 10%. –  Stéphane Chazelas Jan 23 at 16:01
    
Note that , also doubles as an operator in many arithmetic expressions (C, shell, perl...). ksh93, which honours the locale's decimal_point has that issue. LC_ALL=fr_FR ksh93 -c 'echo $((1,2))' outputs 1,2 and 2 in an English locale. –  Stéphane Chazelas Jan 23 at 16:12

2 Answers 2

I have found a solution.

calc () {
  awk '
    function asin(x) { return atan2(x, sqrt(1-x*x)) }
    function acos(x) { return atan2(sqrt(1-x*x), x) }
    function atan(x) { return atan2(x,1) }
    function tan(x) { return sin(x)/cos(x) }
    BEGIN { pi=atan(1)*4; print '"$(echo "$@" | tr , .)}" | tr . ,
}

This one

  • accepts numbers as 5,2 or 5.2 (i.e. both full stop and comma as decimal mark)
  • it uses comma as decimal mark for the output/solution
  • spaces and tabs are removed from input, i.e. you can enter easy readable calculations as input
  • the number pi is defined via 4*atan(1)
  • some common trigonometric functions are defined
share|improve this answer

There is no reliable way to implement that. The issue is the comma is used to separate arguments when more that one is passed to a function.

If you aren't going to use such functions, I guess the simplest way would be something like:

calc () {
  echo "scale=6;" "$@" | tr , . | bc -l | tr . ,
}

That gives:

$ calc 1 + 1
2
$ calc 1 / 3
,333333
$ calc "s(0,5)^2"   # sin(0.5)^2
,229848
$ calc "4*a(1)"     # PI
3,141592

You can of course increase the decimal precision which is here 6 digits.

share|improve this answer
    
Nice. Easier to understand than the nested awk statement. But I miss calculations like 27^(1/3) and the (for me) easier to type 27**(1/3) which awk supports. –  erik Jan 23 at 14:53

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