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how to calculate float numbers: with bash

example 

     DRIVER_MEMORY=$(( 5 * 0.6 * 0.9 ))
-bash: 5 * 0.6 * 0.9 : syntax error: invalid arithmetic operator (error token is ".6 * 0.9 ")

remark - results must be integer number - so we can round the number to down

jesse_b
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jango
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  • What is it you want though: `bash`, `awk`, or `bc`? – jesse_b Feb 12 '18 at 13:40
  • no matter but the best elegant approach – jango Feb 12 '18 at 13:41
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    http://idownvotedbecau.se/noresearch/ – Murphy Feb 12 '18 at 13:54
  • `bash` doesn't do float. The syntax error really means "error: input not an integer". `DRIVER_MEMORY=$((5*6*9/100))` or `DRIVER_MEMORY=$(((5*6*9+50)/100))` does _this_ calculation (depending on your desired rounding mode) if you want to avoid forking out another process – Fox Feb 12 '18 at 14:09
  • Write your own function for multiplication. [Here](https://stackoverflow.com/a/24431665/3776858) is an example of an integer division with floating point results. – Cyrus Feb 12 '18 at 19:17

1 Answers1

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Awk solution:

 DRIVER_MEMORY=$( awk '{ print 5*0.6*0.9 }' <<< "")

bc solution:

DRIVER MEMORY=$(echo "5*0.6*0.9" | bc)
Raman Sailopal
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    You could use a `BEGIN` statement instead of the null string redirect: `DRIVER_MEMORY=$(awk 'BEGIN{print 5*0.6*0.9}')` – jesse_b Feb 12 '18 at 14:03