Bash program to check if the Number is a Prime or not

Given a number, the task is to find whether the given number is prime or not using Bash Scripting. Examples:

Input: N = 43
Output: Prime

Input: N = 35
Output: Not Prime

Prime Numbers: A prime number is a whole number greater than 1, which is only divisible by 1 and itself. First few prime numbers are : 2 3 5 7 11 13 17 19 23 …..

Approach: We run a loop from 2 to number/2 and check if there is any factor of the number. If we find any factor then the number is composite otherwise prime. Implementation:

BASH

#storing the number to be checked
number=43
i=2

#flag variable
f=0

#running a loop from 2 to number/2
while test $i -le `expr $number / 2`
do

#checking if i is factor of number
if test `expr $number % $i` -eq 0
then
f=1
fi

#increment the loop variable
i=`expr $i + 1`
done
if test $f -eq 1
then
echo "Not Prime"
else
echo "Prime"
fi

Output:

Prime

Time complexity: O(N) for input N because using a while loop

Auxiliary Space: O(1)

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