AT(1) Linux Programmer's Manual AT(1)
NAME
at, batch, atq, atrm - queue, examine or delete jobs for later execution
SYNOPSIS
at [-V] [-q queue] [-f file] [-mldrbv] TIME
at [-V] [-q queue] [-f file] [-mldrbv] -t time_arg
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [job...]
batch [-V] [-q queue] [-f file] [-mv] [TIME]
DESCRIPTION
at and batch read commands from standard input or a specified file which are to be exe-
cuted at a later time .
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, 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 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 MMDDYY or MM/DD/YY or
DD.MM.YY. 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.
The exact definition of the time specification can be found in
/usr/share/doc/at-3.1.8/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 vari-
ables 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 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.allow and /etc/at.deny.
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 username 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 commands, this is the
default configuration.
OPTIONS
-V prints the version number to standard error.
-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 nice-
ness. The special queue "=" is reserved for jobs which are currently running.
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 Reads the job from file rather than standard input.
-l Is an alias for atq.
-d Is an alias for atrm.
-r Is an alias for atrm.
-b Is an alias for batch
-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 output.
-t time_arg
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 argument ([[CC]YY]MMDDhhmm).
ENVIRONMENT
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; otherwise, if SHELL is
set when at is invoked, it must contain 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 specified 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, GROUPS.
If the user submitting the at job is not the super-user, variables that alter the
behaviour of the loader ld.so(8), such as LD_LIBRARY_PATH , cannot be recorded and
restored by at .
FILES
/var/spool/at
/var/spool/at/spool
/proc/loadavg
/var/run/utmp
/etc/at.allow
/etc/at.deny
SEE ALSO
cron(1), nice(1), sh(1), umask(2), atd(8).
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 vari-
able 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, .
local Nov 1996 AT(1)
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