Arithmetic calculations in bash file

Shell Programming and Scripting
1

I have 2 numbers

xmin = 0.369000018
xmax = 0.569000006

and want to calculate

(xmax- xmin) / 5.0

I have tried using $(( )) but is always giving an error

2

Here is an approach using bc

#!/bin/bash

xmin=0.369000018
xmax=0.569000006

echo "scale=9; ( $xmax - $xmin ) / 5.0" | bc
3

The bash shell doesn't perform non-integer arithmetic.
You can do it with a recent (newer than 1988) Korn shell:

xmin=0.369000018
xmax=0.569000006
printf "%.10f\n" $(( (xmax - xmin) / 5.0))

which produces:

0.0399999976
4

Bugger. I'm stuck with bash.

---------- Post updated at 07:53 PM ---------- Previous update was at 07:49 PM ----------

I it possible to write a function to do a calculation using bc?

---------- Post updated at 08:02 PM ---------- Previous update was at 07:53 PM ----------

Seems a solution would be in awk

---------- Post updated at 08:04 PM ---------- Previous update was at 08:02 PM ----------

This did not work

compute() {

  echo "(0.569000006-0.369000018)/5.0" | awk '{ print $1 }'

}
5 
awk ' BEGIN { printf "%f\n", (0.569000006-0.369000018) / 5.0 } '
6

Aney idea what's the problem with this?

awk -v a=0.569000006 -v b=0.369000018 -v c=5.0 '{res= (a-b)/c; print res;}'
7

You need a BEGIN block which is executed once before any input is read. In this case BEGIN block runs and program exits:

awk -v a=0.569000006 -v b=0.369000018 -v c=5.0 ' BEGIN {res= (a-b)/c; print res;}'
8

This line of code will be run once for every line of input given to awk. Since there are no input lines, the code isn't run. However:

awk -v a=0.569000006 -v b=0.369000018 -v c=5.0 'BEGIN{res= (a-b)/c; print res;}'

or

awk -v a=0.569000006 -v b=0.369000018 -v c=5.0 'END{res= (a-b)/c; print res;}'

should work for you.

9

And you can do the calculation directly in the print

awk -v a=0.569000006 -v b=0.369000018 -v c=5.0 'BEGIN {print (a-b)/c}'