Custom Cron Schedules on a Plugin

<?php

/*

Plugin Name: Mustek WooCommerce Stock Updater

Plugin URI : https://api.mustek.co.za

Description: This plugin is used to update stocks for products.

*/

register_activation_hook( __FILE__, 'call_mustek_stock_updater_init' );

function call_mustek_stock_updater_init() {

    if ( ! wp_next_scheduled( 'call_mustek_stock_updater' ) ) {

        wp_schedule_event( time(), 'minutely', 'call_mustek_stock_updater' );

    }

}

/*Filter to add custom Time in Seconds to cron scedule array*/

add_filter( 'cron_schedules', 'custom_five_minute_schedule' ); 

function custom_five_minute_schedule( $schedules ) {

  $schedules['minutely'] = array(

    'interval' =>  300, //7 days * 24 hours * 60 minutes * 60 seconds[7 * 24 * 60 * 60,]

    'display' => __( '5 Minutely', 'text-domain' )

  );

  return $schedules;

}

add_action( 'call_mustek_stock_updater', 'call_mustek_stock_updater_callback' );

function call_mustek_stock_updater_callback(){

	$url     = "https://api.mustek.co.za/Customer/ItemsStock.ashx?CustomerToken=8C6381DB-D817-A319";

	$csvData = file_get_contents($url);

	$lines   = explode(PHP_EOL, $csvData);

	$array   = array();

	foreach ($lines as $line) {

	    $array[] = str_getcsv($line);

	}

	$i = 0; 

	foreach ($array as $items) {

		if($i != 0){

		/*	print_r($items);*/

			$product = get_mustek_product_by_sku( $items[0] );

			if(is_object($product)){

				$quantity = $product->get_stock_quantity('view');

				$newstock = $items[2];

				if((int) $quantity != (int) $newstock )

				{

					wc_update_product_stock($product, $newstock);

				}

			}

		}

		$i++; 

	}

}

/*Helper Function to get Product by SKU*/

function get_mustek_product_by_sku( $sku ) {

  global $wpdb;

  $product_id = $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE meta_key='wpcf-mustek_sku' AND meta_value='%s' LIMIT 1", $sku ) );

  if ( $product_id ) return wc_get_product( $product_id );

  return null;

}