This tutorial explains about arthematic expersssions and expansion.

## Bash Athematic expressions

Arthematic expressions are used to perform mathematical operations

expressions is a term used in math to denote an operation. It contains operands and operatorto perform mathematical operatoions. `a<b`

is an expression. It may contains binary or unary operators

In bash, Experssions are created using `(())`

brackets with the operands and operators as arguments. ((a**)) is an bash expression.**

Syntax is

```
((expression))
```

expression are mathematical operations, It can contains sub expressions separated by comma.

```
result=$((12 + 11))
echo "$result"
```

Arthematic expressions are constructed using below operators

- Arthmatic Operators
- Comparision Operator

Comparision operators used to check one with another by comparing values The operators (`<, <=, >, >=, ==, !=`

)

```
a=10
b=2
if ((a > b)); then
echo "a is greater than b"
fi
```

- Logical Operators
- Conditional Statements

## Bash Athematic Expansion

`Expansion`

are same as expressions, It calculates the value of an expression and result is replaced with an value. It always prefixed by dollar sign.

```
$((expression))
```

For example, calculate the average of two numbers, print the result. Here used expansion syntax, It evaluates expression and result is replaced with an output of expression.

```
first=12
second=2
echo "The average is $(((first+second)/2))".
```

## When to Use arthematic expressions and expansions

[[]] is used to test an expression, returns boolean value(1 or 0). This will be used in the following cases

Use artheatic expression

- To perform mathematicl operations and comparision

Use artheatic expression [[]

- Comparision of strings and numbers
- Check file or directory exists