Ubuntu Manpage: at, batch, atq, atrm - queue, examine, or delete jobs for later execution

NAME

       at, batch, atq, atrm - queue, examine, or delete jobs for later execution

SYNOPSIS

       at [-V] [-q queue] [-f file] [-mMlv] timespec ...
       at [-V] [-q queue] [-f file] [-mMkv] [-t time]
       at -c job [...]
       atq [-V] [-q queue]
       at [-rd] job [...]
       atrm [-V] job [...]
       batch
       at -b

DESCRIPTION

at and batch read commands from standard input or a specified file which are to be executed at a later
time, using /bin/sh.

at executes commands at a specified time.

atq 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.

atrm deletes jobs, identified by their job number.

batch 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 atd.

At allows fairly complex time specifications, extending the POSIX.2 standard. It accepts times of the
form HH:MM 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 midnight, noon, or teatime (4pm) and you can have a time-of-day suffixed
with AM or PM 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 month-name day with an optional year, or giving a date of the form
MMDD[CC]YY, MM/DD/[CC]YY, DD.MM.[CC]YY or [CC]YY-MM-DD. The specification of a date must follow the
specification of the time of day. You can also give times like now + count time-units, where the time-
units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the
time with today and to run the job tomorrow by suffixing the time with tomorrow.

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.

If you specify a job to absolutely run at a specific time and date in the past, the job will run as soon
as possible. For example, if it is 8pm and you do a at 6pm today, it will run more likely at 8:05pm.

The definition of the time specification can be found in /usr/share/doc/at/timespec.

For both at and batch, commands are read from standard input or the file specified with the -f option and
executed. The working directory, the environment (except for the variables BASH_VERSINFO, DISPLAY, EUID,
GROUPS, SHELLOPTS, TERM, UID, and _) and the umask are retained from the time of invocation.

As at is currently implemented as a setuid program, other environment variables (e.g., LD_LIBRARY_PATH or
LD_PRELOAD) are also not exported. This may change in the future. As a workaround, set these variables
explicitly in your job.

An at - or batch - command invoked from a su(1) 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
/usr/sbin/sendmail. If at is executed from a su(1) 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 /etc/at.allow and /etc/at.deny. See at.allow(5) for details.

OPTIONS

-V prints the version number to standard error and exit successfully.

-q queue
uses the specified queue. A queue designation consists of a single letter; valid queue
designations range from a to z and A to Z. The a queue is the default for at and the b queue for
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 average apply. If atq is given a specific queue, it will only show jobs pending in that
queue.

-m Send mail to the user when the job has completed even if there was no output.

-M Never send mail to the user.

-f file Reads the job from file rather than standard input.

-t time run the job at time, given in the format [[CC]YY]MMDDhhmm[.ss]

-l Is an alias for atq.

-r Is an alias for atrm.

-d Is an alias for atrm.

-b is an alias for batch.

-v 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".

-c cats the jobs listed on the command line to standard output.

FILES

       /var/spool/cron/atjobs
       /var/spool/cron/atspool
       /proc/loadavg
       /var/run/utmp
       /etc/at.allow
       /etc/at.deny

BUGS

       The correct operation of batch for Linux depends on the presence of a proc-  type  directory  mounted  on
       /proc.

       If  the  file /var/run/utmp is not available or corrupted, or if the user is not logged on at the time at
       is invoked, the mail is sent to the userid found  in  the  environment  variable  LOGNAME.   If  that  is
       undefined or empty, the current userid is assumed.

       At  and  batch as presently implemented are not suitable when users are competing for resources.  If this
       is the case for your site, you might want to consider another batch system, such as nqs.

AUTHOR

       At was mostly written by Thomas Koenig.

                                                   2009-11-14                                              AT(1)