Crontab Examples

Sample Uses of Cron

If you understand the Basics of Crontab and are ready to create useful tasks, you might wonder what is possible. These are simple 1 liners that you can automate. Here are a few examples of useful crontab tasks:

# basic ping check
ping -q -c1 -w3 site.com 2&>1 /dev/null || echo site.com ping failed | mail -ne -s'Server unavailable - site.com' admin@site.com

# report on current IP
ifconfig eth0 | awk '/inet / {print $2}' | mail -s "Current IP for Site.com" admin@site.com

# send info to syslog for processing
/usr/local/script.sh 2>&1 |/usr/bin/logger -t script_result

# rsync backup (requires keys setup)
rsync -rau /sourcedir X.X.X.X:/backup/destdir

# backup local file
gzip -c ~/.bash_history > ~/.backup/history-save-$(date +\%d-\%m-\%y-\%T).gz

# system backup
for file in $(find /var/backup -name "backup*" -type f |sort -r | tail -n +10); do rm -f $file; done ; tar czf /var/backup/backup-system-$(date "+\%Y\%m\%d\%H\%M-\%N").tgz --exclude /home/dummy /etc /home /opt 2>&- && echo "system backup ok"

# database backup
/usr/bin/mysqldump -uroot -p'<pass>' dbname > /backups/$(date +\%Y-\%m-\%d_\%Hh\%M).sql

# restart a process that died
ps -C thisdaemon || { thisdaemon & }

# notify of website change
HTMLTEXT=$( curl -s http://site.com > /tmp/new.html ; diff /tmp/new.html /tmp/old.html ); if [ "x$HTMLTEXT" != x ] ; then echo $HTMLTEXT | mail -s "Page has changed." admin@site.com ; fi ; mv /tmp/new.html /tmp/old.html