I would like to do the following operation in my script:
1 - ((m - 20) / 34) I would like to assign the result of this operation to another variable. I want my script use floating point math. For example, for m = 34:
results = 1 - ((34 - 20) / 34) == 0.588 You could use the bc calculator. It will do arbitrary precision math using decimals (not binary floating point) if you set increease scale from its default of 0:
$ m=34 $ bc The -l option will load the standard math library and default the scale to 20:
$ bc -l You can then use printf to format the output, if you so choose:
printf "%.3f\n" "$(bc -l ...)" Bash does not do floating point math. You can use awk or bc to handle this. Here is an awk example:
$ m=34; awk -v m=$m 'BEGIN { print 1 - ((m - 20) / 34) }' 0.588235 To assign the output to a variable:
var=$(awk -v m=$m 'BEGIN { print 1 - ((m - 20) / 34) }') Teach bash e.g. integer division with floating point results:
#!/bin/bash div () # Arguments: dividend and divisor { if [ $2 -eq 0 ]; then echo division by 0; exit; fi local p=12 # precision local c=${c:-0} # precision counter local d=. # decimal separator local r=$(($1/$2)); echo -n $r # result of division local m=$(($r*$2)) [ $c -eq 0 ] && [ $m -ne $1 ] && echo -n $d [ $1 -eq $m ] || [ $c -eq $p ] && return local e=$(($1-$m)) let c=c+1 div $(($e*10)) $2 } result=$(div 1080 633) # write to variable echo $result result=$(div 7 34) echo $result result=$(div 8 32) echo $result result=$(div 246891510 2) echo $result result=$(div 5000000 177) echo $result Output:
1.706161137440 0.205882352941 0.25 123445755 28248.587570621468 echo $a/$b|bc -l gives the result.
Example:
read a b echo $a/$b|bc -l Enter a & b value as 10 3, you get 3.3333333333
If you want to store the value in another variable then use the code
read a b c=`echo $a/$b|bc -l` echo $c It also gives the same result as above. Try it...
Use this script open this file with favorite editor like:
$ sudo vim /usr/bin/div Then paste this code:
#!/bin/bash # Author: Danial Rikhteh Garan (danial.rikhtehgaran@gmail.com) if [[ -z "$1" ]] || [[ -z "$2" ]]; then echo "Please input two number" echo "for 100/50 use: div 10 50" exit 1; fi div=$(echo "$1/$2" | bc -l); echo 0$div | sed 's/[0]*$//g' Now chmod it to 755:
$ sudo chmod 755 /usr/bin/div Now use it:
$ div 5 100 0.05 In your script you can use this:
var=$(div 5 100); echo "$var"