expr, echo and bc -l supporting arithmetic operations in shell script

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In the last blog we understood, how to install package the network way of installation.

1. The expr command

The expr command evaluates expressions and returns the result. It only supports integer arithmetic.

Syntax of expr command

expr operand1 operator operand2

Examples of using expr command

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--37-59:~$ expr 6 + 3
9
--37-59:~$ expr 6 - 3
3
--37-59:~$ expr 6 / 3
2
--37-59:~$ expr 6 \* 3  #Here * is reserver characte meaning "everything". So, to escape it we use backslash.
18

2. echo with double parathesis →

Here we don’t need to separate the operands and the operators with space. Also not required to escape the * with backslash.

Examples of using echo with operators

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$ A = 6
$ B = 3
$ echo $(( A + B ))
9
$ echo $(( A-B ))
3
$ echo $((A/B))
2
$ echo $(( A * B ))
18

3. bc -l i.e. basic calculator for floating point number

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$ A = 6
$ B = 3
$ echo $A / $B | bc -l
3.33333

Conclusion

In the this blog we understood, the use of echo with double parenthesis, expr, and use of basic calculator in shell scripting.

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