Setup cron job on mac os x

I keep trying to edit my Mac crontab file, but my Mac won't save my crontab changes, or run my program. Although cron 8 and crontab 5 are officially supported under Darwin, their functionality has been absorbed into launchd 8 , which provides a more flexible way of automatically executing commands. See launchctl 1 for more information. It looked like you could still use the Mac crontab facility, as implied by this note in the MacOS cron man page:.

There should be no need to start it manually.

For my purposes, I want to run a shell script every minute to ping my websites. If the sites don't respond, I want to be able to notify myself of the problem, perhaps by displaying a dialog from the MacOS Unix shell. When I dug around in the Apple documentation, I found there are three main directories you can use with launchd , and that's how I learned about this directory. Here are your three options:.

Note that when you use the first two directories shown here, you must use the sudo command to edit your files. Next, create a Mac plist file in this directory to describe the job you want to run. In my case I fired up vi to edit my file:.

The problem

Following Apple's documentation and after many errors , I ended up with these contents in my plist file:. A note about the naming convention: Apple strongly encourages you to use the naming convention I've shown here for a your filename and b your label value.

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When using the commands that I'm about to show you, you'll refer to the filename and this "label", and they encourage you to follow this naming convention to avoid namespace collisions. Having programmed in Java, this is just like the Java package naming convention, and I have no problems following it. You'll see other Mac launchd jobs running when you use the launchctl list command below, and I think after that, you'll agree that naming convention is a good idea.

Difference between cron and launchd

Next, it's important to know that your MacOS system won't pick up on this change immediately. You have to tell the Mac launchd daemon to load it, using the launchctl command, like this:. After issuing the launchctl load command I started getting output from my date command. I let it run for several minutes while I checked that everything was working, and then turned it off using this unload command:.

To test this properly, I issued the Mac launchctl unload command, like this:. This section explains these methods briefly and provides links to manual pages that provide additional details. The preferred way to add a timed job is to use launchd.

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Each launchd job is described by a separate file. This means that you can manage launchd timed jobs by simply adding or removing a file. To create a launchd timed job, you should create a configuration property list file similar to those described in Creating a launchd Property List File except that you specify a StartCalendarInterval key containing a dictionary of time values.



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For example, the following property list runs the program happybirthday at midnight every time July 11 falls on a Sunday. Per-user cron jobs can be installed using the crontab tool. The format of these crontab files is described in the man page for the crontab file format. Because installing cron jobs requires modifying a shared resource the crontab file , you should not programmatically add a cron job. All you need is a keyboard to type 'em out! There are many times when you need to run a shell script or command at regular intervals. This can be to clean up your system or run maintenance tasks on your computer.

For these jobs, you'll want to use something called "Crons.

Schedule jobs with crontab on Mac OS X | Ole Michelsen

We'll show you how to create these jobs, and how to remove them once they become unnecessary. When specifying the time at which a cron runs, there is a specialized syntax that is used to tell the operating system exactly when to run the task. The timing sequence of a cron job looks like this:. So, let's take a look at some examples: If you wanted to run the job every day at 1: And, lastly, if you wanted the job to run once a week on Wednesday, you could type the following sequence:. If you have more intricate requirements for run times of cron jobs, then you can take a look at this guide for more detail on how to format the sequence.

Note that between the asterisks, there are tabs used, and not spaces so, don't copy anything from here and paste , but type with tabs. Once you've got the sequence down, then actually creating the job is the easy part. We'll use nano to create a crontab entry that contains the timing sequence that you've figured out, as well as the command or script location that you wish to run.