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Learn to schedule jobs to run automatically at the Linux command line.
Videos can also be accessed from the Linux Essentials Playlist on YouTube.
Linux crontab Command Summary with Examples (3:44)
Our forty-fourth word, or command to memorize is
crontab from our category
crontab allows you to create and
schedule automated jobs.
||List crontab for the current user|
||Edit crontab for the current user|
||Specify a different user|
Recall that we recently covered time, and now we'll automate a command.
Before we start, it helps to think of commands as mini programs and
most follow this structure:
command -option(s) argument(s).
crontab command has
5 options and the arguments point you to the user's
crontab file, located in one central
Unlike most commands, help is not available with double-dash
crontab, normally an administrator
edits a file that is read by a program called
cron, which runs in the
background after startup.
crontab syntax is tricky so I'll be
brief here. There are six entries. The first five set the timing, and
sixth is the command.
So why is
crontab an important command?
Well, you don't want a human to remember and to do everything on Linux
so scheduling is a vital task.
And now you know how to do that.
Okay, the best way to embed this in your memory is by typing in your own terminal window.
Find this on your Mac using a program called Terminal. On Linux use Terminal or Konsole, and currently Microsoft is adding this functionality to Windows.
Here we go. I'll show you the output first and then we'll review the
crontab entry. Let's
cat video44.txt, which we'll pretend
is a log file. I programmed
so that every minute, a
date command, from video 15 if you
recall, runs and is appended to this file.
All of this up here is instructional, commented out using the pound sign
#, and here asterisk
* means every. So
every minute, of every hour, of every day of the month, of every month,
and every day of the week, it will run this command:
date >> ~/linux/video44.txt.
And last, let's
cat again to see if
another log entry was appended.
Okay, very good.
Okay now you know how to use
And you know the syntax for commands, options and arguments.
One last tip about the
cron jobs suck system
crontab often requires
Okay, thanks for visiting today. I hope this was a helpful
introduction to the
For an overview of the 100 videos, the 8 quizzes, a cheat sheet, the categories and a Q&A section, visit:
To better understand this tutorial I suggest watching the video.
sleepcommand, hit Back.
pscommand, click Next.
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