use crontab to run bash script code example

Example 1: set cron job in ubuntu

Setting Up a Website Backup through Cron :-
===========================================
Step 1: Update your server. As a best practice, we will update and upgrade
our server with the following command.
	apt-get update && apt-get upgrade

Step 2: Verify if the cron package is installed.
	dpkg -l cron
    
	a) Our example output let’s us know that the cron package is installed, along 
	with its version:

||/ Name Version Architecture Description
+++-=========================-=================-=================-========================================================
ii cron 3.0pl1-128ubuntu2 amd64 process scheduling daemon

	b) Install cron package if necessary.
		sudo apt-get install cron

	c) Ensure that the cron service is running with the following command:
		systemctl status cron
		
Example Output:
----------------
* cron.service - Regular background program processing daemon
Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset:enabled)
Active: active (running) since Sat 2018-10-27 02:53:20 EDT; 5 days ago

Step 3: Configure the cron job. When you are logged in as your user, you are
creating a cron job under that user. Creating a cron jobs owner is helpful
when to know who is in charge of the cron as well as how to alter the cron 
job in the future.
	crontab -e

Step 4: The system asks which editor you’d like to use; this tutorial is using option 2 (vim.basic).

tom@host2:~$ crontab -e
no crontab for tom - using an empty one
Select an editor. To change later, run 'select-editor'.
1. /bin/ed
2. /usr/bin/vim.basic
3. /usr/bin/vim.tiny
Choose 1-3 []: 2

Step 5: In this file, you’ll see # signs followed by the direction on how to
#use the file. Allow us a minute to explain the syntax needed to create a cron
#task.

# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed

Example 2: how to run a script in crontab every day

+---------------- minute (0 - 59)
 |  +------------- hour (0 - 23)
 |  |  +---------- day of month (1 - 31)
 |  |  |  +------- month (1 - 12)
 |  |  |  |  +---- day of week (0 - 6) (Sunday=0 or 7)
 |  |  |  |  |
 *  *  *  *  *  command to be executed