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AT(1) |
FreeBSD General Commands Manual |
AT(1) |
at , batch ,
atq , atrm —
queue, examine or delete jobs for later execution
at |
[-q queue]
[-f file]
[-mldbv ] time |
at |
[-q queue]
[-f file]
[-mldbv ] -t
[[CC]YY]MMDDhhmm[.SS] |
batch |
[-q queue]
[-f file]
[-mv ] [time] |
The at and batch utilities read
commands from standard input or a specified file which are to be executed at a
later time, using
sh(1).
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;
atrm
- deletes jobs;
batch
- executes commands when system load levels permit; in other words, when the
load average drops below 1.5 times number of active CPUs, or the value
specified in the invocation of
atrun .
The at utility allows some moderately
complex time 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.) As an alternative, the following keywords may be specified:
midnight, noon, or
teatime (4pm) and time-of-day may be suffixed with
AM or PM for running in the morning or
the evening. The day on which the job is to be run may also be specified by
giving a date in the form month-name day with an
optional year, or giving a date of the forms
DD.MM.YYYY, DD.MM.YY,
MM/DD/YYYY, MM/DD/YY,
MMDDYYYY, or
MMDDYY. The specification of a date must follow the
specification of the time of day. Time can also be specified as:
[now] + count
time-units, where the time-units can be minutes,
hours, days, weeks,
months or years and
at may be told 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, use
at 4pm + 3 days, to run a job
at 10:00am on July 31, use at 10am
Jul 31 and to run a job at 1am tomorrow, use
at 1am tomorrow.
The at utility also supports the POSIX
time format (see -t option).
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 userid. The user will be mailed standard error and
standard output from his commands, if any. Mail will be sent using the
command
sendmail(8).
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
/var/at/at.allow and
/var/at/at.deny.
If the file /var/at/at.allow exists, only
usernames mentioned in it are allowed to use at . In
these two files, a user is considered to be listed only if the user name has
no blank or other characters before it on its line and a newline character
immediately after the name, even at the end of the file. Other lines are
ignored and may be used for comments.
If /var/at/at.allow does not exist,
/var/at/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 . This is the default configuration.
Note that at is implemented through the
cron(8)
daemon by calling
atrun(8)
every five minutes. This implies that the granularity of
at might not be optimal for every deployment. If a
finer granularity is desired, the /etc/cron.d/at file
can be edited and will be read by the system crontab, from which the
SHELL and PATH environment
variables are inherited.
-q
queue
- Use 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 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
- Read the job from file rather than standard
input.
-l
- With no arguments, list all jobs for the invoking user. If one or more job
numbers are given, list only those jobs.
-d
- Is an alias for
atrm (this option is deprecated;
use -r instead).
-b
- Is an alias for
batch .
-v
- For
atq , shows completed but not yet deleted jobs
in the queue; otherwise shows the time the job will be executed.
-c
- Cat the jobs listed on the command line to standard output.
-r
- Remove the specified jobs.
-t
- Specify the job time using the POSIX time format. The argument should be
in the form
[[CC]YY]MMDDhhmm[.SS]
where each pair of letters represents the following:
- CC
- The first two digits of the year (the century).
- YY
- The second two digits of the year.
- MM
- The month of the year, from 1 to 12.
- DD
- the day of the month, from 1 to 31.
- hh
- The hour of the day, from 0 to 23.
- mm
- The minute of the hour, from 0 to 59.
- SS
- The second of the minute, from 0 to 60.
If the CC and YY
letter pairs are not specified, the values default to the current year.
If the SS letter pair is not specified, the value
defaults to 0.
- /var/at/jobs
- directory containing job files
- /var/at/spool
- directory containing output spool files
- /var/run/utx.active
- login records
- /var/at/at.allow
- allow permission control
- /var/at/at.deny
- deny permission control
- /var/at/jobs/.lockfile
- job-creation lock file
If the file /var/run/utx.active 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.
The at and batch
utilities as presently implemented are not suitable when users are competing
for resources. If this is the case, another batch system such as
nqs may be more suitable.
Specifying a date past 2038 may not work on some systems.
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