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 and 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.
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:
Mac OS X crontab FAQ: How do I run a Unix job (or shell script) through the OS X crontab facility? I keep trying to edit my Mac crontab file, but my Mac won't save my crontab changes, or run my program.
Mac OS X - crontab, launchd, and launchctl
As of this writing (updated in 2014), the Mac crontab command seems to be deprecated on Mac OS X, and the Apple documentation encourages you to use their "Mac launchd" facility. Here's a blurb from the Mac OS X crontab man page:
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:
This page shows the contents of the Linux crontab man page that deals with the crontab file format (syntax), or as it says in the man page, "crontab - tables for driving cron". This crontab man page output was created on a CentOS Linux system.
You can see this same crontab man page output by entering this command on your own Linux system:
Linux crontab FAQ: How do I edit my Unix/Linux crontab file?
I was working with an experienced Linux sysadmin a few days ago, and when we needed to make a change to the root user crontab file, I was really surprised to watch him cd to the root user’s cron folder, make changes to the file, then do a
kill -HUP on the crontab process.
Thinking he knew something I didn’t know, I asked him why he did all of that work instead of just entering this: