Shell script to find factorial of a number using recursion

A shell script is a computer program designed to be run by the Unix shell, a command line interpreter. This blog is about a shell scripting program to find the factorial of a number using recursion.

Logic

The logic is simple. If the number 'n' is 1, return 1. Else return 'n' * 'factorial(n-1)'.

Program

#!/bin/sh

factorial()
{
if [ "$1" -gt "1" ]; then
 a=`expr $1 - 1`
 b=`factorial $a`
 c=`expr $1 \* $b`
 echo $c
else
 echo 1
fi
}

echo "Enter a number:"
 read x
 factorial $x

Things to note:
- After writing the script, change the mod of the script to enable execution. This is done by:

chmod +x factorial.sh

or

chmod 755 factorial.sh

Output of the program

Enter a number:
4
24

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