AT(1) Linux Programmer’s Manual AT(1)
at, batch, atq, atrm - queue, examine or delete jobs for later execu-
at [-V] [-q queue] [-f file] [-mldbv] TIME
at [-V] [-q queue] [-f file] [-mldbv] -t time_arg
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 executed at a later time .
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, 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 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 MMDDYY or MM/DD/YY or DD.MM.YY. The specifi-
cation 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.
The exact definition of the time specification can be found in
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 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 com-
mands, 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
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.
-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 niceness.
The special queue "=" is reserved for jobs which are currently
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
-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 1997".
-c cats the jobs listed on the command line to standard out-
Submit the job to be run at the time specified by the
time_arg option argument, which must have the same format
as specified for the touch(1) utility’s -t time option
SHELL The value of the SHELL environment variable at the time
of at invocation will determine which shell is used to
execute the at job commands. If SHELL is unset when at
is invoked, the user’s login shell will be used; other-
wise, if SHELL is set when at is invoked, it must con-
tain the path of a shell interpreter executable that
will be used to run the commands at the specified time.
at will record the values of environment variables present at
time of at invocation. When the commands are run at the speci-
fied time, at will restore these variables to their recorded
values . These variables are excluded from this processing and
are never set by at when the commands are run :
TERM, DISPLAY, SHELLOPTS, _, PPID, BASH_VERSINFO, EUID, UID,
If the user submitting the at job is not the super-user, vari-
ables that alter the behaviour of the loader ld.so(8), such as
LD_LIBRARY_PATH , cannot be recorded and restored by at .
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 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
At was mostly written by Thomas Koenig, email@example.com-
local Nov 1996 AT(1)
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