'How to compare floating numbers in bash linux? [duplicate]

I'd like to use if-elif-elif-else-fi to determine a based on the range of t:

a=1000            # t=2-9.5
a=2000            # t=10-14.5
a=4000            # t=15-16.5
a=6000            # t=17-20

My bash file looks like:

t=(2 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5 18 19 20)

len=${#t[*]}

for i in `seq 0 $((len-1))`
do
    if [ $(echo "${t[i]} < 10" | bc -l) -eq 1 ];then
       a=1000
    elif [[ "${t[i]}" -ge '10' && "${t[i]}" -lt '15' ]];then
       a=2000
    elif [[ "${t[i]}" -ge '15' && "${t[i]}" -lt '17' ]];then
       a=4000
    else
       a=6000
    fi
done

And I receive error "syntax error: invalid arithmetic operator (error token is ".5")".

It seems that I don't correctly compare the floating number with integer number. Can anyone help me to solve this problem? Thanks!

linuxbash


Solution 1:[1]

When dealing with floating point numbers we mostly use bc or/and awk.

Suggesting an awk solution:

#!/bin/bash
arr=(2 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15 15.5 16 16.5 17 17.5 18 19 20)
for elm in ${arr[@]}; do
  a=$(echo ""| awk -v inp="$elm" '
  inp >=  2 && inp <=  9.5 {print 1000}
  inp >= 10 && inp <= 14.5 {print 2000}
  inp >= 15 && inp <= 16.5 {print 4000}
  inp >= 17 && inp <= 20   {print 6000}
  ')
  printf "elm=%f\ta=%d\n" $elm $a # debug trace
done

Output:

elm=2.000000    a=1000
elm=3.000000    a=1000
elm=3.500000    a=1000
elm=4.000000    a=1000
elm=4.500000    a=1000
elm=5.000000    a=1000
elm=5.500000    a=1000
elm=6.000000    a=1000
elm=6.500000    a=1000
elm=7.000000    a=1000
elm=7.500000    a=1000
elm=8.000000    a=1000
elm=8.500000    a=1000
elm=9.000000    a=1000
elm=9.500000    a=1000
elm=10.000000   a=2000
elm=10.500000   a=2000
elm=11.000000   a=2000
elm=11.500000   a=2000
elm=12.000000   a=2000
elm=12.500000   a=2000
elm=13.000000   a=2000
elm=13.500000   a=2000
elm=14.000000   a=2000
elm=14.500000   a=2000
elm=15.000000   a=4000
elm=15.500000   a=4000
elm=16.000000   a=4000
elm=16.500000   a=4000
elm=17.000000   a=6000
elm=17.500000   a=6000
elm=18.000000   a=6000
elm=19.000000   a=6000
elm=20.000000   a=6000

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Dudi Boy

Related Questions