#### Find the factorial of number

Before Find the factorial, We should know that the factorial function (symbol: !) means to multiply a series of descending natural numbers.

Examples:

4! = 4 × 3 × 2 × 1 = 24

5! = 5 * 4 * 3 * 2 * 1 = 120

So the rule is: n! = n × (n−1)!

Which just says “the factorial of any number is that number times the factorial of (1 smaller than that number)

But what about zero?

Zero Factorial is interesting … it is generally agreed that 0! = 1.

In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n

Let’s code to Find the factorial

```
#!/bin/bash
if [ $# -lt 1 ]; then
echo "Usage: $0 num"
exit 1
fi
let end=$1-1
num=$1
for i in `seq 1 $end`; do
let num*=$i
done
echo $num
```

** Output will be:**

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