AT(1) FreeBSD General Commands Manual AT(1)
NAME
at, batch - queue, examine or delete jobs for later execution
SYNOPSIS
at [-bm] [-f file] [-l [job ...]] [-q queue] -t time_arg | timespec
at -c | -r job ...
batch [-m] [-f file] [-q queue] [timespec]
DESCRIPTION
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.
-f file
Reads the job from file rather than standard input.
-l [job ...]
Displays the queue of jobs which are currently awaiting
execution. If a job argument is specified, only the specified
jobs 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.
-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 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.
-t time_arg
Specify the job time. The argument should be of the form
[[cc]yy]mmddHHMM[.SS] (matching touch(1)'s -t format), where the
parts of the argument represent the following:
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.
timespec
As well as the -t option, at alternatively 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). It is also
possible to specify midnight, noon, now, or teatime (4pm), or
have a time-of-day suffixed with AM or PM for running in the
morning or the evening. To say what day the job will be run,
give 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. A time like [now] + count time-units may be given,
where the time-units can be minutes, hours, days, weeks, months,
or years (the singular forms are also accepted). To tell at to
run the job today or tomorrow, suffix the time with today or
tomorrow. The next keyword may be used as an alias for + 1.
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. To run a job at 1am tomorrow, use at 1am tomorrow. To run a
job at midnight in one week's time, use at midnight next week.
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, PPID, SHELLOPTS, SSH_AGENT_PID, SSH_AUTH_SOCK, TERM, TERMCAP,
UID, 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. 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
run at.
An empty /var/cron/at.deny means that every user is allowed to use these
commands. This is the default configuration.
FILES
/var/cron/atjobs directory containing job files
/var/cron/at.allow allow permission control
/var/cron/at.deny deny permission control
EXIT STATUS
The at utility exits with one of the following values:
0 Jobs were successfully submitted, removed, or listed.
>0 An error occurred.
SEE ALSO
atq(1), atrm(1), nice(1), sh(1), touch(1), umask(2), cron(8)
STANDARDS
The at and batch utilities are compliant with the specification.
The at flags [-bc] and the teatime timespec are extensions to that
specification.
states that batch is equivalent to running "at -q b -m now". This
implementation permits a timespec argument, as well as the ability to
read from a file (-f) and specify a job queue (-q), and does not send
mail to the user (-m) by default.
By default, schedules at jobs in queue a and batch jobs in queue b.
The at.allow/deny mechanism is marked by as being an X/Open System
Interfaces option.
AUTHORS
at was mostly written by Thomas Koenig <
[email protected]>. The
time parsing routines are by David Parsons <
[email protected]>.
BUGS
at and batch as presently implemented are not suitable when users are
competing for resources.
FreeBSD 14.1-RELEASE-p8 November 5, 2024 FreeBSD 14.1-RELEASE-p8