Cron is the name of program that enables unix users to execute commands or scripts (groups of commands) automatically at a specified time/date. It is normally used for sys admin commands, like makewhatis, which builds a search database for the man -k command, or for running a backup script, but can be used for anything. A common use for it today is connecting to the internet and downloading your email.
Cron is a daemon, which means that it only needs to be started once, and will lay dormant until it is required. A Web server is a daemon, it stays dormant until it gets asked for a web page. The cron daemon, or crond, stays dormant until a time specified in one of the config files, or crontabs.
||Edit your crontab file, or create one if it doesn't already exist.|
||Display your crontab file.|
||Remove your crontab file.|
minute(s) hour(s) day(s) month(s) weekday(s) command(s)
|minute||0-59||This controls what minute of the hour the command will run on.|
|hour||0-23||This controls what hour the command will run on.|
|day||1-31||This is the Day of Month, that you want the command run on.|
|month||1-12||This is the month a specified command will run on.|
|weekday||0-6||This is the Day of Week that you want a command to be run on.|
|user||root||This is the user who runs the command.|
|command||/cmd||A valid |
minute, hour, day, month, weekdaythen please include
[*]in all value field. know more
Some of most used crontab syntax mentioned below,