# Primes

primes is a command-line interface for finding prime numbers, using the Sieve of Eratosthenes. It’s a simple example of a Rust program and how darned fast Rust can be. I use it often to find primes for use in cache expiries or cronjob periods, in an effort to avoid the Thundering Herd problem. When I come across arcane values like `1009`

in config files, I know I’ve been there. This is useful as quick verification that I’ve already reviewed a system, as nobody else is insane enough to set a TTL to a godforsaken value like `3593`

when `3600`

would do. Also, I’m sorry but it’s true. Prime numbers are very, very sexy. I dare you to install this utility and *not* have a grand old time.

## Primes Near

`primes near`

takes one number as input and returns the nearest prime lower than that number, and the nearest prime higher. If the number you give it is itself prime, it returns 3 numbers

`primes near 25 # returns 23,27`

`primes near 13 # returns 11,13,17`

`primes near banana # panics, because banana is not a number`

## Primes Between

Takes two numbers (unsigned integers) and returns all the primes in that range, *inclusive*:

`primes between 17 29 # returns 17,23,29`

`primes between 65000 65100 # returns 65003,65011...65089,65099`

## Getting started

To install, you must first have cargo. Then do:

`cargo install primes-cli`