1
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- All right.

2
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Let's talk about at.

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At means the at daemon.

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So sudo systemctl status of atd

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is showing that atd is active and running.

6
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That's good.

7
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So as an ordinary user, I
am going to open at teatime

8
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and there we are opening the at shell

9
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and in there I'm going
to use logger TEATIME,

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and then I'm done.

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Now, this is also particular about at.

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You need to use control D.

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Control D is the end of file sign.

14
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That is what you can use
to close editor-like things

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or secondary cells, Control D.

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We haven't seen control
D very often, so far.

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And there, you can see that at
TEATIME stands for 16:00:00.

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Of course you can also use real time,

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at 10:20 for instance.

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wall COFFEETIME,

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wall is Linux commanded
to writes to all users

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that are currently logged in,

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and oops this is not doing what I wanted.

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So I need to repeat it at 20:21.

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Let me do this real fast

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because otherwise I
will be too slow again.

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Okay.

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Typo in coffee, who cares
about typo in coffee?

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What I care about is that I want to see

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that this is working.

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Wall by the way is for write all,

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and write all will write to all the users

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that currently have a
terminal session open.

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It might not work because
of security restrictions.

35
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In the old days, wall was
a nice way to pass messages

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to all users currently
connected to a system.

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Nowadays, security might
be preventing this.

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Atq, atq is showing us what exactly

39
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is scheduled for execution

40
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and the interesting thing here

41
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is that we don't see the 10:20 anymore,

42
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but we do see the 10:21.

43
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And yeah, as I mentioned the
wall is not so very successful

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but that's a wall problem,

45
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that's not an f problem.

46
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Atq is showing that the 10:21
job has been executed anyway.

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You wanna see a convincing example, okay.

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Then, at 10:22 touch /tmp/1022,

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control D,

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and there we will see
in a couple of seconds

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that this is running.

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Atq for at query is showing

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that the job is waiting for execution.

54
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Let me use at rm.

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Atrm is what you can use to remove a job

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if you don't want it anymore.

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So atrm 1 makes that the
job should now be gone.

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Is it?

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Yes, it is.

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So the only thing we
need to do now is to wait

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until it is 10:22.

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There we go.

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It is 10:22 and ls -l on tmp.

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We can see file with the name 10:22.

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It has been created at 10:22.

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So that is how you can use at.

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At is useful but it is
connected to a current,

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a current terminal session

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and that might limit it a little bit

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in what you want to do

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but it can be useful in particular
for individual user jobs.