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In this demonstration,

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we're going to walk through

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how to schedule tasks.

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We're going to perform this by

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two different methods.

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We're going to use the "at" command,

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which will execute a one-time function or command

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in the future one time.

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Then we're going to go over cron jobs,

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using the "crontab" command.

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Cron is when we want to schedule tasks

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so they occur repeatedly in the future.

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And this, we're going to schedule all of our

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mainest jobs to run automatically over and over again.

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So the first thing we want to check out is the "at" command,

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which I'm going to create a simple file.

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OK, so we're going to add this to our directory.

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Now we're going to run a test

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to execute in the future one time.

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And that's going to be: remove this touch file

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that we just created, file A.

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So let's make sure it's in there.

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OK, we see file A.

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About six down.

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Now we're going to run a command,

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and we want to execute two minutes from now.

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So we're going to do: "at now + 2 minutes".

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And the interacting prompt is going to pop up.

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And here, all we do is input the commands

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that we want to run.

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We're going to remove,

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force,

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and do Ctrl + D.

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OK

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Now we're going to look at the queue, "atq".

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Now we see a schedule

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to execute in the next two minutes.

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OK. Time has passed.

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Now let's check the queue.

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Alright, that's the first indication that

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the command went through.

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Now let's look through our list.

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I'm going to "grep" for the file A,

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just to be clear it's out there.

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Alright.

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Alright. We're going to see now that file A

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is no longer there.

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So again, we used the "at" to execute a function or command

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one time in the future.

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In this next scenario, we're going to go through

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and use the "crontab" command

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to schedule an email reminder

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at a specific time in the future.

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Now the way the cron command is broken up,

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once you're editing the actual file,

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the first five fields are just going to reference

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different time periods.

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So the first field is going to reference minutes.

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The second field is going to represent hours.

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Next is going to be the day of the month.

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Fourth is going to be the month.

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And the fifth field is going to represent a day of the week,

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if you're going to make it a repetitive task.

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For example: "1" would equal Monday,

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so that means every Monday on this time,

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or maybe even a future date.

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Typically we're just going to use the

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minutes, hours and day.

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Or if you want to do one specific day,

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you're going to use

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minutes, hours, day, and day of the month.

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In this example, we're just going to use

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a specific hour in the future.

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And if it doesn't have any day tied to it,

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it's assumed it's going to occur daily.

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So we're going to set an email to be sent to us

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every day at a certain time.

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So let's try that first.

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"sudo crontab"

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To the user.

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I'll use myself.

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And "e" means edit.

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Alright. So we're going to do this

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for five minutes in the future.

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Or, four minutes in the future.

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Let's make it 17:20, if we look at my clock.

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So we'll put "20" here for the minutes.

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"17".

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Everything has to be in a 24-hour format.

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We'll put "bin/echo".

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Let's do "Please fill in your time sheet."

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The last field is going to be

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a path to the command that you're trying to execute.

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So an example:

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we're trying to execute a simple "echo" command.

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And it's going to email this information to us.

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OK, click.

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Right click.

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Alright.

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Alright, let's check that mail really quick.

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OK, we see July 4th today.

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OK. We see that it was successfully received

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at 17:20 and one second.

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Alright, that sums that up.

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We went through how to use the "at" command

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for a future transaction.

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We also went over how to use a "crontab", edit that.

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We sent an email to ourself in the future.

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And right now it's set for a recurring task

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that happens once a day.

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Thank you for sticking with this walkthrough,

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and I'll see you in the next lesson.