crontab

---
tags: [ job, scheduler, periodic ]
---
# set a shell
SHELL=/bin/bash

# set a PATH
PATH=/usr/bin:/usr/sbin:/usr/local/bin

# incorrect way of seeting PATH
PATH=$PATH:/do/not/do/this

# crontab format
* * * * *  command_to_execute
- - - - -
| | | | |
| | | | +- day of week (0 - 7) (where sunday is 0 and 7)
| | | +--- month (1 - 12)
| | +----- day (1 - 31)
| +------- hour (0 - 23)
+--------- minute (0 - 59)

# example entries
# every 15 min
*/15 * * * * /home/user/command.sh

# every midnight
0 0 * * * /home/user/command.sh

# every Saturday at 8:05 AM
5 8 * * 6 /home/user/command.sh

# compute your crontab periodicity format online
https://crontab.guru/

# be careful with % sign (percent), it has special meaning, see https://crontab.guru/ for explanation
% signs must be escaped such as \%

# view log
journalctl | grep CRON