list of prime numbers till 100 shell script program

This 'sieve' defines a method of identifying prime numbers. I call this particular script 'sieve' after the Sieve of Eratosthenes that it implements. Try it out and you'll see a list of numbers in order thanks to the numeric sort at the bottom of the script. This script will take some time to run if you want all primes under a billion, but it works quickly with relatively small numbers. If you need to generate a group of prime numbers, you could use a script like that shown below, provide it with the upper limit for the primes you're interested in and sit back and watch. Using the factor command, as shown above, you can easily find some prime numbers - both small and very large ones in fact. When you run the script, you will see somethig like this: Since factor's output consists of both the original number and its factors, we're going to make use of the fact that any factor command output with only two pieces of text indicates the number is prime otherwise it is not.

$list of prime numbers till 100 shell script program$

Using the factor command, you could then easily write a script to determine if a number if prime or not. Doesn't this kind of thinking make you miss middle school? In fact, every factor for any number is prime otherwise it would be factored further. I wouldn't have been able to do that in my head! Factor 6021285687865665911, on the other hand and you'll see this: $ factor 6021285687865665911 Prime numbers are easy to recognize or 'think through' if they're, say, under 50. If you use factor with a number that isn't prime, you get two or more factors.

$list of prime numbers till 100 shell script program$

If you use factor with a prime number, you get a single factor - the number itself. But how is Unix helpful?įor one thing, Unix systems generally have a command called factor that will show you the factors for a number - the numbers that multiplied result in the number. So we start out with 2, 3, 5, 7, 11 and 13 and then move through to infinity. The smallest prime number is 2, but no other numbers divisible by 2 can be prime.

A prime number is a natural (whole and non-negative, they are sometimes called 'counting numbers') number greater than 1 that can only be divided (leaving no remainders) by 1 and itself. It's probably been a while since you learned about them, but the definition is simple. Other than for their use in cryptography, prime numbers might not be on your list of favorite topics, but prime numbers have some very interesting qualities.

List of prime numbers till 100 shell script program