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Floating Point Math in Bash

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In this blog, quick reference notes about OpenFOAM are posted in a form of a summary to address a specific topic per post, which I think could be helpful as a reminder for my Alzheimer condition
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Floating Point Math in Bash

Posted March 6, 2013 at 14:35 by Hisham

This post is copied from: http://www.linuxjournal.com/content/...oint-math-bash
Floating Point Math in Bash, By Mitch Frazier

To use floating point arithmetic in Bash one can source this script (i.e. source floatSupport.sh). The floatSupport.sh is:

Code:
#!/bin/bash 
# 
# Floating point number functions. 

##################################################################### 
# Default scale used by float functions.

  float_scale=2 

#####################################################################
# Evaluate a floating point number expression.  

function float_eval() 
{     
     local stat=0     
     local result=0.0     
     if [[ $# -gt 0 ]]; then
         result=$(echo "scale=$float_scale; $*" | bc -q 2>/dev/null)
         stat=$?         
         if [[ $stat -eq 0  &&  -z "$result" ]]; then stat=1; fi
     fi
     echo $result
     return $stat
 }   
##################################################################### 
# Evaluate a floating point number conditional expression. 
 function float_cond()
 {
     local cond=0
     if [[ $# -gt 0 ]]; then
         cond=$(echo "$*" | bc -q 2>/dev/null)
         if [[ -z "$cond" ]]; then cond=0; fi
         if [[ "$cond" != 0  &&  "$cond" != 1 ]]; then cond=0; fi
     fi
     local stat=$((cond == 0))
     return $stat
 }
A test script:

Code:
source floatSupport.sh

# Test code if invoked directly.
 if [[ $(basename $0 .sh) == 'float' ]]; then
     # Use command line arguments if there are any.
     if [[ $# -gt 0 ]]; then
         echo $(float_eval $*)
     else
         # Turn off pathname expansion so * doesn't get expanded
         set -f
         e="12.5 / 3.2"
         echo $e is $(float_eval "$e")
         e="100.4 / 4.2 + 3.2 * 6.5"
         echo $e is $(float_eval "$e")
         if float_cond '10.0 > 9.3'; then
             echo "10.0 is greater than 9.3"
         fi
         if float_cond '10.0 < 9.3'; then
             echo "Oops"
         else
             echo "10.0 is not less than 9.3"
         fi
         a=12.0
         b=3.0
         c=$(float_eval "$a / $b")
         echo "$a / $b" is $c
         set +f
     fi
 fi
Hisham
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