Arithmetic Operation In Bash

To learn about this topic, let’s start with a problem.

Snippet of code below is to be implemented:

a=13
b=12

# Please calculate their quotinent (a / b) 

As much as I have learnt about arithmetic operations, there are 4 kinds of feasible solutions for BASH.

• $(( expression )) gives the result of the calculation
• Also you can do calculation using `expr expression`
• To do calculation and assign the result directly, you can try this: ((result = $a + $b)) as well as ((result = a + b)), where result, a and b are all shell variables.
• Using bc calculator with pipe.

For that problem, and with the help of the hints, we can provide 4 structurally different solutions respectively.

# Sol.1 
result=$((a / b))

# Sol.2
result=`expr a / b`

# Sol.3
((result = a / b))

# Sol.4  
result=`echo "scale=16; $a/$b" | bc"`

If you try them all out, you will find that only the last solution gives float number as result. So one thing you should bear in mind is that built-in calculation of bash only does integers. To do float points, you must get the assistanse of external tools, in which bc is the one mostly referred to.

Built-in arithmetic operation in bash only does integers.

With this basic experience with arthmetic operation of bash and help of GOOGLE SEARCH, you can now solve more problems.

— Feb 7, 2019