Specifications

28 Chapter 1 Executing Commands
When commands execute, output is mailed to the owner of the crontab file or to the
user named in the MAILTO environment variable in the crontab file, if one exists.
If you modify a crontab file, you must restart cron.
You use crontab to install, deinstall, or list the tables used to drive the cron daemon.
Users can have their own crontab file.
To configure your crontab file, use the crontab -e command. This displays an empty
crontab file.
An example of a configured crontab file:
SHELL=/bin/sh
PATH=/bin:/sbin:/usr/bin:/usr/sbin
HOME=/var/log
#min hour mday month wday command
30 18 * * 1-5 diskutil repairPermissions /Volumes/MacHD
50 23 * * 0 diskutil repairVolume /Volumes/MacHD
Listed below is an explanation of the crontab structure shown above.
The following crontab entry repairs disk permissions for the MacHD volume at 18:30
every day, Monday through Friday:
30 18 * * 1-5 diskutil repairPermissions /Volumes/MacHD
The following crontab entry schedules a repair volume operation to run at 23:50 every
Sunday:
50 23 * * 0 diskutil repairVolume /Volumes/MacHD
Sending Commands to a Remote Computer
You must connect to a remote computer before you can execute commands on it.
You can send commands to a remote computer using:
 Secure Shell (SSH), a tool for logging in to a remote computer and for executing
commands on a remote computer.
 Telnet, a tool for communicating with another computer using the TELNET protocol.
For information about sending commands to remote computers, see Chapter 2,
“Connecting to Remote Computers,” on page 31.