Defining a new variable from division of another two variables with bash script

Question

I have 2 variables which are up_votes and down_votes from a csv dataset. I am trying to create a new variable as percentage of up_votes / total_votes. For example, up_votes=296 down_votes=255, my output should be 53.7 but I get 25600. Here is my equations.

    x=$col3
    y=$col3+$col4
    z=($x/$y)*100
    ans=$z

Answer 1

You need to use external programs to do calculations because bash does not support float point arithmetic

#!/bin/bash


votes="topic1,0,0 topic2,296,255 topic3,3,4"

for vote_data in $votes ; do
    topic=`echo $vote_data|sed -r 's/([^,]*),([^,]*),(.*)/\1/'`
    up_votes=`echo $vote_data|sed -r 's/([^,]*),([^,]*),(.*)/\2/'`
    down_votes=`echo $vote_data|sed -r 's/([^,]*),([^,]*),(.*)/\3/'`

#    echo "$topic , up: $up_votes, down: $down_votes"

    total=`awk "BEGIN {print ($up_votes+$down_votes)}"`
    if [ $total -eq 0 ];then
    ans=divbyzero
    else
    ans=`awk "BEGIN {print 100.0*$up_votes/( $up_votes+$down_votes)}"`
    fi
    echo "$topic $ans [ $up_votes / $down_votes ]"

done

output:

topic1 divbyzero [ 0 / 0 ]
topic2 53.7205 [ 296 / 255 ]
topic3 42.8571 [ 3 / 4 ]