Linux crontab FAQ: How do I schedule Unix or Linux crontab jobs to run at intervals, like “Every five minutes,” “Every ten minutes,” “Every half hour,” and so on?
Solution: I’ve posted other Unix/Linux crontab tutorials here before (How to edit your Linux crontab file, Example Linux crontab file format), but I’ve never included a tutorial that covers the “every” options, so here are some examples to demonstrate this crontab syntax.
Table of Contents
- macOS: crontab, launchd, and launchctl
- Running a simple command every minute with Mac launchd
- 1) Move to the $HOME/Library/LaunchAgents directory
- 2) Create a Mac plist file to describe your job
- 3) Tell MacOS about your Mac plist launchd file
- 4) How Mac launchd works with system reboots
- An important note about root and sudo access
- MacOS launchd, launchctl, and plist resources
- MacOS startup jobs: cron and crontab, launchd and launchctl
MacOS crontab FAQ: How do I run a Unix job (or shell script) through the MacOS crontab facility? I keep trying to edit my Mac crontab file, but my Mac won't save my crontab changes, or run my program.Back to top
macOS: crontab, launchd, and launchctl
Many years ago (~2012-2014) I found that the Mac
crontab command was deprecated on MacOS, and the Apple documentation encouraged you to use their launchd facility. Here’s a blurb from Apple's
crontab man page:
“Darwin note: 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.”
I’ve written several things about the Linux
cron command and crontab file format before, and as a quick note, here’s some information on the format of the crontab date and time fields.
Crontab date/time fields
First, from the crontab man page documentation:
I made a mistake in configuring
logrotate on a new Linux system, and almost ran into a problem because of that. Fortunately I saw the problem before it became a BIG problem, but as a result, I decided to add a script to my Linux system to check for large files, typically log files that have grown out of control for one reason or another.
Here then is a simple Linux shell script I named LargeFileCheck.sh, which searches the filesystem for files that are larger than 1GB in size:
MySQL database backup FAQ: Can you share a Linux shell script that I can use to make a MySQL backup (i.e., a shell script that wraps the mysqldump command)?
I currently have a collection of websites on several different servers (including GoDaddy and A2 Hosting web servers), so I was just spending some time trying to automate my MySQL database backups. To that end, I just created a MySQL shell script that I use on each Linux server to make my database backups, and I thought I'd share that script here.
It looks like the Mac launchd launchctl StartInterval is broken in Mac OS X 10.6.x, at least the current version (10.6.7). When I run a Mac launchctl script like this, which used to work just fine:
I've been having a problem with a GoDaddy website lately (see my GoDaddy 4GH performance problems page, and in an effort to get a better handle on both (a) GoDaddy website downtime and (b) GoDaddy 4GH performance, I wrote a Unix shell script to download a sample web page from my website.
To that end, I created the following shell script, and then ran it from my Mac every two minutes:
Mac OS X launchd FAQ: Can you share some Mac launchd examples (also written as launchd plist examples, or launchctl examples)?
In an earlier tutorial (Mac OS X startup jobs with crontab, launchctl, and launchd) I demonstrated how to use the Mac OS X launchd facility instead of cron to run what would normally be a cron (crontab) job. As I started working with launchd and launchctl, I realized it would probably be helpful to see several different launchd examples, specifically launchd plist file examples.
Mac Unix shell + AppleScript FAQ: How can I display a dialog with AppleScript from the Unix command line shell? (Either from a command line shell like bash through the Mac OS X Terminal, or from a shell crontab job.)
Linux crontab mail FAQ: Can you share an example of a Linux crontab entry you use to send email on a regular basis?
Here's the source code for a really simple Linux mail script that I used to send an email message to one of my co-workers every month. This script used the Unix or Linux mail command to email a file to her that showed a list of all the websites on our server that she needed to bill our customers for.
Here's the source code for the email shell script: