NOTE THAT THIS SECTION ONLY APPLIES IF THE
crontab PROGRAMS HAVE BEEN INSTALLED BY THE
If the program runs by the name of
it will read all the files in
should only be readable by root) and the file
then detaches itself from the terminal to live forever as a daemon
process. Additionally, it creates a UNIX socket at
/var/cron/socket, and listens for messages sent to
that socket consisting of a user name whose crontabs have been
changed. In this case, the program will re-read that user’s crontab.
This is for correct functioning with the crontab program.
Further, if the
--noetc option was not used, a job is scheduled
to run every minute to check if /etc/crontab has been modified
recently. If so, this file will also be re-read.
The options which may be used with this program are as follows.
This option causes a message to be printed on the standard output with information about the version and copyright for the current program.
This causes a short but complete usage message to be displayed on standard output.
With this option specified no commands are run. Instead, the program computes the times the commands would be run and prints the information to the screen, and then immediately exits.
The count, if supplied, indicates the number of commands to display. The default value is 8.
This tells cron not to add a job to the system which wakes up every
minute to check for modifications to
/etc/crontab. It is
recommended that this option be used (and further that the
/etc/crontab file be taken off the system altogether!)