AT(1) Linux Programmer's Manual AT(1)
at, batch, atq, atrm - queue, examine or delete jobs for later execution
at [-V] [-q queue] [-f file] [-mldbv] TIME
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [job...]
batch [-V] [-q queue] [-f file] [-mv] [TIME]
at and batch read commands from standard input or a specified file which are to be exe-
cuted at a later time, using the shell set by the user's environment variable SHELL, the
user's login shell, or ultimately /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, job class.
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 0.8, or the value specified in the invocation of atrun.
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 MMDDYY or MM/DD/YY or
DD.MM.YY. 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.
/usr/share/doc/at-3.1.8/timespec contains the exact definition of the time specification.
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 vari-
ables TERM, DISPLAY and _) and the umask are retained from the time of invocation. 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.
If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at.
If /etc/at.allow does not exist, /etc/at.deny is checked, every username not mentioned in
it is then allowed to use at.
If neither exists, only the superuser is allowed use of at.
An empty /etc/at.deny means that every user is allowed use these commands, this is the
-V prints the version number to standard error.
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 nice-
ness. The special queue "=" is reserved for jobs which are currently running.
If a job is submitted to a queue designated with an uppercase letter, it is treated as if
it had been submitted to batch at that time. 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.
-f file Reads the job from file rather than standard input.
-l Is an alias for atq.
-d Is an alias for atrm.
-v Shows the time the job will be executed.
Times displayed will be in the format "1997-02-20 14:50" unless the environment
variable POSIXLY_CORRECT is set; then, it will be "Thu Feb 20 14:50:00 1996".
-c cats the jobs listed on the command line to standard output.
cron(1), nice(1), sh(1), umask(2), atd(8).
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
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.
At was mostly written by Thomas Koenig, email@example.com.
local Nov 1996 AT(1)