Cron is a scheduler that is bundled with every UNIX system. The procedure for inserting a command into the cron scheduler is just peculiar enough to merit a short example of how it works.
To enable your cron scheduler to run a job every day at 11pm, do the following
crontab -l > cron.txt
0 23 * * * /path/command
The format of each column in the cron.txt file above is as follows:
minute hour day_of_month month weekday command
These fields accept the following values:
minute 0 through 59 hour 0 through 23 day_of_month 1 through 31 month 1 through 12 weekday 0 through 6 for Sunday through Saturday
To configure cron so that script xyz.sh runs every Thursday at 3:05AM, include the following line in your crontab file.
5 3 * * 4 xyz.sh > /tmp/xyz.log 2>/tmp/xyz.log