Cron
Scheduling Tasks with Cron
Scheduler Basics
minute:hour:day-of-month:month:day-of-week /command/to/execute.sh
| Field | Values | Notes |
|---|---|---|
| Minute | 0-59 | |
| Hour | 0-23 | |
| Day of Month | 1-31 | |
| Month | 1-12 | |
| Day Of Week | 0-6 | [0 is Sunday] |
Common Commands w/ Cron
crontab -l # List current Linux user's crontab entries
crontab -u <username> -l # List other Linux user's crontan entries
crontab -e # Edit crontab entries
crontab /path/to/cronjobs.txt # Load cron jobs from file
Examples of Crontab Entries
Execute job every ten minutes
*/10 * * * * /path/to/command.sh
Run job every hour, between 8am - 5pm, Monday - Friday
00 08-17 * * 1-5 /path/to/command.sh
Run job twice a day, at noon and 6pm
00 12,18 * * * /path/to/command.sh
Run job at 4:30am on Saturday, send stderr to stdout to null device
30 5 * * 6 /home/s3backup/backup_ftpdata.sh > /dev/null 2>&1
Conditional: Execute job only on 1st Tuesday of the month
0 3 1-7 * * if [ `date +\%a` = Tue ]; then /path/to/ami-genie.sh; fi
At 11:30 on Sunday, download the EZproxy RejectIP Blacklist from GitHub and write the file to /usr/local/ezmanage/includes/global_reject_ip.txt. Send an email with the download details.
30 11 * * 0 root /usr/bin/wget --output-document global_reject_ip.txt https://raw.githubusercontent.com/prbutler/EZProxy_IP_Blacklist/master/EZProxy_IP_Blacklist_RejectIP.txt -O /usr/local/ezmanage/includes/global_reject_ip.txt 2>&1 | mail -s "EZproxy: Refresh RejectIP File" -a "From: someuser \<someuser@epv1.example.org\>" anotheruser@example.org