Open System Services Management and Operations Guide (G06.27+, H06.04+)

Operating the OSS Environment
Open System Services Management and Operations Guide—527191-003
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Using the cron Process
For more information about the crontab command, see the crontab(1) reference
page either online or in the Open System Services Shell and Utilities Reference
Manual.
The at Command
The at command runs OSS shell commands at a time you specify. You can use the at
command to read from the standard input file or accept as arguments the names of
commands to be run and when the commands are to be run. If a file specified in an at
command is executable (that is, has the x permission for the user executing the
command), at treats the file as a command and the job consists only of this command.
If the file is not executable, at uses the file’s contents as the instructions for the job. If
at cannot find the file, the specification is passed to the date parser. If the date parser
does not recognize the specification, you receive an error message.
Variables in the shell environment, the current directory, umask, and ulimit are
retained when the commands are run; for more information about the mechanism used
to do this, see the .proto(4) reference page either online or in the Open System
Services Shell and Utilities Reference Manual. Open file descriptors, interrupts, and
priority are lost.
The at command and the cron process use these files to determine whether and
what commands to run:
You can use the at command if your login name appears in the
/usr/lib/cron/at.allow file. If that file does not exist, the at command checks
the /usr/lib/cron/at.deny file to determine whether your login name is denied
access to at. If neither file exists, only a user who has appropriate privileges can
submit a job. If the at.allow file does exist, it must include the login name of a user
who has appropriate privileges to use the at command.
The at command also allows you to:
•
Specify a file to be used as input instead of the standard input file
•
Find out information about jobs that are queued
For more information about the at command, see the at(1) reference page either
online or in the Open System Services Shell and Utilities Reference Manual.
The atq Command
The atq command prints the queue of jobs that were created using the at command
and are waiting to be run at a later time. If you have appropriate privileges and you
/var/spool/cron/atjobs/at Lists the commands to be run once.
/usr/lib/cron/at.allow Lists the user IDs that are allowed to
change the at file.
/usr/lib/cron/at.deny Lists the user IDs that are denied
access to the at file.