AT
Section: User Commands (1)
Updated: 2009-11-14
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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
[
job...]
atq
[
-V]
[
-q
queue]
at
[
-rd]
job
[
job...]
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 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 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 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/at.allow
and
/etc/at/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/at/atjobs
/var/spool/at/atspool
/proc/loadavg
/var/run/utmp
/etc/at/at.allow
/etc/at/at.deny
SEE ALSO
at.allow(5),
at.deny(5),
atd(8),
cron(1),
nice(1),
sh(1),
umask(2).
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.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- OPTIONS
-
- FILES
-
- SEE ALSO
-
- BUGS
-
- AUTHOR
-
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