In OS X, you can run a background job on a timed schedule in two ways:
launchd
jobs and cron
jobs. (Older approaches, such as at
jobs and periodic
jobs are deprecated and should not be used.) This section explains these methods briefly and provides links to manual pages that provide additional details.Running scripts on your computer is great. Running them automatically is even greater. If you are on a Mac (or Linux), you can use our good friend crontab, which is a scheduling tool that will run jobs (scripts) at regular intervals. You add a job to crontab by editing the job list. A job is specified in the following format (first line). An easy to use editor for crontab schedules. We created Cronitor because cron itself can't alert you if your jobs fail or never start. Cronitor is easy to integrate and provides you with instant alerts when things go. I have created an /etc/crontab file on a Mac OS X that runs a few simple commands. I would like to use the crontab to echo a statement in my terminal, logout from the OS (as if I was to point my mouse to the command Logout), and I am trying to test it by running an echo statement every two minutes. Crontab file locations under Mac OSX 10.6 are now: /usr/lib/cron/tabs # Using the 'cron' scheduler Authored by: davesnothere on May 18, '11 01:15:27PM Found this old thread and while most of it seems to be helpful to me, there are some things I can't seem to make happen. I'm completely new to.nix operating systems and just now getting.
Timed Jobs Using launchd
The preferred way to add a timed job is to use
launchd
. 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.For example, the following property list runs the program
happybirthday
at midnight every time July 11 falls on a Sunday.For more information on these values, see the manual page for
launchd.plist
.Timed Jobs Using cron
Note: Although it is still supported,
cron
is not a recommended solution. It has been deprecated in favor of launchd
.Systemwide
cron
jobs can be installed by modifying /etc/crontab
. 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.Effects of Sleeping and Powering Off
If the system is turned off or asleep,
cron
jobs do not execute; they will not run until the next designated time occurs.If you schedule a
launchd
job by setting the StartCalendarInterval
key and the computer is asleep when the job should have run, your job will run when the computer wakes up. However, if the machine is off when the job should have run, the job does not execute until the next designated time occurs.All other
launchd
jobs are skipped when the computer is turned off or asleep; they will not run until the next designated time occurs.Consequently, if the computer is always off at the job’s scheduled time, both
cron
jobs and launchd
jobs never run. For example, if you always turn your computer off at night, a job scheduled to run at 1 A.M. will never be run. Copyright © 2003, 2016 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2016-09-13
Daemon to execute scheduled commands (Vixie Cron).
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 for more information.
Cron should be started from /etc/rc or /etc/rc.local. It will return immediately, so you don't need to start it with '&'.
Cron searches /var/cron/tabs for crontab files which are named after accounts in /etc/passwd; crontabs found are loaded into memory. Cron also searches for /etc/crontab which is in a different format (see crontab). Cron then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current minute. When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable in the crontab, if such exists).
Cron For Macos
Additionally, cron checks each minute to see if its spool directory's modtime (or the modtime on /etc/crontab) has changed, and if it has, cron will then examine the modtime on all crontabs and reload those which have changed. Thus cron need not be restarted whenever a crontab file is mod- ified. Note that the crontab command updates the modtime of the spool directory whenever it changes a crontab.
Directory for personal crontab files:
/usr/lib/cron/tabs
/usr/lib/cron/tabs
”Time is what prevents everything from happening at once” ~ John Archibald Wheeler
Related macOS commands:
Cron For Mac
crontab - Schedule a command to run at a later time.
Lingon GUI
Lingon GUI
Cron For Mac Download
Copyright © 1999-2020 SS64.com
Some rights reserved
Some rights reserved