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AT(1) Linux Programmer's Manual AT(1)
NAME
at, batch, atq, atrm - queue, examine or delete jobs for later execu-
tion
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 executed at a later time .
at executes commands at a specified time.
atq lists the user's pending jobs, unless the user is the supe-
ruser; 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 spe-
cific 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 direc-
tory, the environment (except for the variables 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 user-
name 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 com-
mands, 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
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,
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 inter-
preter 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 vari-
ables 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 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.
local Nov 1996 AT(1)
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