read commands from standard input or a specified file which are to
be executed at a later time, using
R /bin/sh .
executes commands at a specified time.
lists the user's pending jobs, unless the user is the superuser; in that
case, everybody's jobs are listed. The format of the output lines (one
for each job) is: Job number, date, hour, queue, and username.
deletes jobs, identified by their job number.
executes commands when system load levels permit; in other words, when the load average
drops below 1.5, or the value specified in the invocation of
R atd .
allows fairly complex time
specifications, extending the POSIX.2 standard. It accepts times
of the form
to run a job at a specific time of day.
(If that time is already past, the next day is assumed.)
You may also specify
and you can have a time-of-day suffixed with
for running in the morning or the evening.
You can also say what day the job will be run,
by giving a date in the form
with an optional
or giving a date of the form
The specification of a date
follow the specification of the time of day.
You can also give times like
where the time-units can be
and you can tell
to run the job today by suffixing the time with
and to run the job tomorrow by suffixing the time with
For example, to run a job at 4pm three days from now, you would do
at 4pm + 3 days,
to run a job at 10:00am on July 31, you would do
at 10am Jul 31
and to run a job at 1am tomorrow, you would do
at 1am tomorrow.
The exact definition of the time specification can be found in
R /usr/share/doc/at/timespec .
R at and batch ,
commands are read from standard input or the file specified
option and executed.
The working directory, the environment (except for the variables
R TERM ,R DISPLAY
R _ )
and the umask are retained from the time of invocation.
R at -
R batch -
command invoked from a
shell will retain the current userid.
The user will be mailed standard error and standard output from his
commands, if any.
Mail will be sent using the command
R /usr/sbin/sendmail .
is executed from a
shell, the owner of the login shell will receive the mail.
The superuser may use these commands in any case.
For other users, permission to use at is determined by the files
R /etc/at.deny .
If the file
exists, only usernames mentioned in it are allowed to use
R at .
does not exist,
is checked, every username not mentioned in it is then allowed
R at .
If neither exists, only the superuser is allowed use of at.
means that every user is allowed use these commands, this is the
prints the version number to standard error.
I -q queue
uses the specified queue.
A queue designation consists of a single letter; valid queue designations
R z .
R Z .
queue is the default for
R batch .
Queues with higher letters run with increased niceness. The special
queue "=" is reserved for jobs which are currently running.
If a job is submitted to a queue designated with an uppercase letter, the
job is treated as if it were submitted to batch at the time of the job.
Once the time is reached, the batch processing rules with respect to load
is given a specific queue, it will only show jobs pending in that queue.
Send mail to the user when the job has completed even if there was no
I -f file
Reads the job from
rather than standard input.
Is an alias for
Is an alias for
Shows the time the job will be executed before reading the job.
Times displayed will be in the format "Thu Feb 20 14:50:00 1997".
cats the jobs listed on the command line to standard output.
The correct operation of
for Linux depends on the presence of a
R proc -
type directory mounted on
R /proc .
If the file
is not available or corrupted, or if the user is not logged on at the
is invoked, the mail is sent to the userid found
in the environment variable
R LOGNAME .
If that is undefined or empty, the current userid is assumed.
as presently implemented are not suitable when users are competing for
If this is the case for your site, you might want to consider another
batch system, such as
R nqs .
At was mostly written by Thomas Koenig, email@example.com.