AT(1) OpenBSD Reference Manual AT(1)
at, batch - queue, examine or delete jobs for later execution
at [-bm] [-f file] [-l [user ...]] [-q queue] -t time_arg | timespec
at -c | -r job ...
batch [-m] [-f file] [-q queue] [timespec]
at and batch read commands from standard input or a specified file which
are to be executed at a later time, via the user's shell as specified by
the SHELL environment variable. If SHELL is not set, the shell in the
user's password database entry is used instead. If all else fails, sh(1)
will be used.
The related programs are as follows:
at Executes commands at a specified time.
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 cron(8).
The options are as follows:
-b An alias for batch.
-c job ...
Prints the jobs listed on the command line to standard output.
Reads the job from file rather than standard input.
-l [user ...]
Displays the queue of jobs which are currently awaiting
execution. If a user argument is specified, only jobs belonging
to that user will be displayed. Unless the user is the
superuser, only the user's own jobs will be displayed.
-m Send mail to the user when the job has completed, even if there
was no output.
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 c queue is the default for at and the E queue for
batch. Queues with higher letters run with increased niceness.
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 the user specified the -l option and at is given a
specific queue, only jobs pending in that queue will be shown.
-r job ...
Remove the specified job(s) from the at queue.
Specify the job time. The argument should be of the form
[[cc]yy]mmddHHMM[.SS], where the parts of the argument represent
ccyy Year. If yy is specified, but cc is not, a value
for yy between 69 and 99 results in a cc value of
19. Otherwise, a cc value of 20 is used.
mm Month: a number from 1 to 12.
dd Day: a number from 1 to 31.
HH Hour: a number from 0 to 23.
MM Minute: a number from 0 to 59.
SS Second: a number from 0 to 60 (permitting a leap
second), preceded by a period. The default is 0.
at allows some moderately complex timespec specifications. It accepts
times of the form HHMM or 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
dd.mm.ccyy, dd.mm.yy, mm/dd/ccyy, mm/dd/yy, mmddccyy, or mmddyy.
The year may be given as two or four digits. If the year is given as two
digits, it is taken to occur as soon as possible in the future, which may
be in the next century -- unless it's last year, in which case it's
considered to be a typo.
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. To run a job at 1am tomorrow, you would do at 1am tomorrow.
The at utility also supports the time format used by touch(1) (see the -t
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, TERMCAP, 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 user ID. The
user will be mailed standard error and standard output from his commands,
if any. Mail will be sent using sendmail(8). If at is executed from a
su(1) shell, the owner of the login shell will receive the mail.
For non-root users, permission to run at is determined by the files
/var/cron/at.allow and /var/cron/at.deny. Note: these files must be
readable by group crontab (if they exist).
If the file /var/cron/at.allow exists, only usernames mentioned in it are
allowed to use at. If /var/cron/at.allow does not exist,
/var/cron/at.deny is checked. Every username not mentioned in it is then
allowed to use at. If neither exists, only the superuser is allowed to
An empty /var/cron/at.deny means that every user is allowed to use these
commands. This is the default configuration.
/var/cron/atjobs directory containing job files
/var/cron/at.allow allow permission control
/var/cron/at.deny deny permission control
The at utility exits with one of the following values:
0 Jobs were successfully submitted, removed, or listed.
>0 An error occurred.
atq(1), atrm(1), nice(1), sh(1), touch(1), umask(2), cron(8), sendmail(8)
The at and batch utilities are compliant with the IEEE Std 1003.1-2008
The at flags [-bc] and the batch flags [-fmq] are extensions to that
Behaviour for the -l flag differs between this implementation and IEEE
Std 1003.1-2008 (``POSIX.1'').
at was mostly written by Thomas Koenig <email@example.com>. The
time parsing routines are by David Parsons <firstname.lastname@example.org>.
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.
OpenBSD 5.1 September 4, 2011 OpenBSD 5.1
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