Float conditional in bash

Question

Hi,

in bash I need to compare two float numbers, one which I define in the script and the other read as paramter, for that I do:

   if [[ $aff -gt 0 ]]
    then
            a=b
            echo "xxx "$aff
            #echo $CX $CY $CZ $aff
    fi

but I get the error:

[[: -309.585300: syntax error: invalid arithmetic operator (error token is ".585300")

What is wrong?

Thanks

Answer 1

Both test (which is usually linked to as [)and the bash-builtin equivalent only support integer numbers.

Answer 2

bash doesn't do floats.

Answer 3

use awk

#!/bin/bash
num1=0.3
num2=0.2
if [ -n "$num1" -a -n "$num2" ];then
  result=$(awk -vn1="$num1" -vn2="$num2" 'BEGIN{print (n1>n2)?1:0 }')
  echo $result
  if [ "$result" -eq 1 ];then
   echo "$num1 greater than $num2"
  fi
fi

Answer 4

I would use awk for that:

e=2.718281828459045
pi=3.141592653589793
if [ "yes" = "$(echo | awk "($e <= $pi) { print \"yes\"; }")" ]; then
    echo "lessthanorequal"
else
    echo "larger"
fi

Answer 5

Using bc instead of awk:

float1='0.43255'
float2='0.801222'

if [[ $(echo "if (${float1} > ${float2}) 1 else 0" | bc) -eq 1 ]]; then
   echo "${float1} > ${float2}"
else
   echo "${float1} <= ${float2}"
fi