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202 Chapter 22. Automated Tasks
22.3.4. Additional Command Line Options
Additional command line options for at and batch include:
Table 22-1. at and batch Command Line Options
Option Description
-f Read the commands or shell script from a file instead of
specifying them at the prompt.
-m Send email to the user when the job has been completed.
-v Display the time that the job will be executed.
22.3.5. Controlling Access to At and Batch
The /etc/at.allow and /etc/at.deny files can be used to restrict access to the at and
batch commands. The format of both access control files is one username on each line.
Whitespace is not permitted in either file. The at daemon (atd) does not have to be restarted
if the access control files are modified. The access control files are read each time a user tries
to execute the at or batch commands.
The root user can always execute at and batch commands, regardless of the access control
files.
If the file at.allow exists, only users listed in it are allowed to use at or batch, and the
at.deny file is ignored.
If at.allow does not exist, all users listed in at.deny are not allowed to use at or batch.
22.3.6. Starting and Stopping the Service
To start the at service, use the command /sbin/service atd start. To stop the service,
use the command /sbin/service atd stop. It is recommended that you start the service
at boot time. Refer to Chapter 8 for details on starting the cron service automatically at boot
time.
22.4. Additional Resources
To learn more about configuring automated tasks, refer to the following resources.
22.4.1. Installed Documentation
• cron man page — overview of cron.
• crontab man pages in sections 1 and 5 — The man page in section 1 contains an overview
of the crontab file. The man page in section 5 contains the format for the file and some
example entries.
• /usr/share/doc/at-
version /timespec contains more detailed information about
the times that can be specified for cron jobs.
• anacron man page — description of anacron and its command line options.