Expr and calc command: Solve mathematical expressions in terminal

I am one of those who are always programming scripts bash to solve day-to-day situations (crack the AP / Router password, automate processes, etc.).

On certain occasions I have seen the need to assign the value of a mathematical expression to a variable, or simply work with mathematical expressions, there I find myself with the problem that bash and mathematical expressions, calculations are not very friendly. It happens that bash is not like python, what can we say variable = 1 + 5/6 (for example), in Bash we must use the command expose o tracing

Expr command

In other words, the expr command helps us to solve mathematical expressions in the terminal, with it we can calculate what we need. For example, if we want the result of 1 + 2 * 8/3 to appear, we put in the terminal:

expr 1 + 2 \* 8 / 3

And the result will appear on the screen. Here is a screenshot with some examples:

In case we want to assign to a variable the result of a mathematical expression (Ex: 10/2), it would be like this:

variable=`expr 10 / 2`

Then we check it with:

echo $variable

Calc command

This one, unlike the previous one, is exact in terms of decimals, example:

calc 15 / 4

It would show us: 3.75

Here is a screenshot with several examples:

Well, this is basically what I wanted to tell you about.

However, there are still some other interesting tips for each command (especially calc), I recommend that you read the manual:

man calc

man expr

regards