crontab in UNIX

In UNIX:

  • Command: crontab
  • Daemon: crond
    • Start Daemon: /etc/init.d/crond start | systemctl start crond.service
    • Stop Daemon: /etc/init.d/crond stop | systemctl stop crond.service
  • Location: /var/spool/cron/etc/crontab
  • Limitation: /etc/cron.allow && /etc/cron.deny ()

    Priority: allow | deny

  • Log: /var/log/cron
  • Usage: crontab [-u username] [-l|-e|-r]
Minute (0~59) Hour (0~23) Day (1~31) Month (1~12) Week (0~7) Commands
* * * * *

These characters can be used:

Character Representation Example
* Run any time 0 15 * * 1 command
, Run at sliced time 0 12 5,10,15 * * command
- Run at scope time 30 9-18 * * * command
/n Run every other time */10 * * * * command

Example for crontab -e:

Minute (0~59) Hour (0~23) Day (1~31) Month (1~12) Week (0~7) Command
*/1 * * * * /bin/bash /the/location/of/hcismatdbcycle.sh

Example:

*/1 * * * * 

This is a standard example of the hcismatdbcycle.sh file:

#!/bin/bash
setroot
hcismatcycle -s tsmatdbCycle -p smatdb2 -t conn_4 -b out -r /work/company/cis19.1/integrator
hcismatcycle -s tsmatdbCycle -p smatdb -t conn_2 -b out
...