AT(1)AT(1)NAME
at, batch, atq, atrm - queue, examine or delete jobs for later execu‐
tion
SYNOPSIS
at [-V] [-q queue] [-f file] [-mldv] timespec...
at [-V] [-q queue] [-f file] [-mkdv] [-t time]
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [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 supe‐
ruser; 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 0.8, 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 spe‐
cific 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 specifica‐
tion 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.
The exact 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.
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 user‐
name 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 com‐
mands, this is the default configuration.
OPTIONS-V prints the version number to standard error and exit success‐
fully.
-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.
-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.
-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/atjobs
/var/spool/atspool
/proc/loadavg
/var/run/utmp
/etc/at.allow
/etc/at.deny
SEE ALSOcron(1), nice(1), sh(1), umask(2), atd(8).
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, ig25@rz.uni-karlsruhe.de.
2009-11-14 AT(1)
