at
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] [-mldbv] TIME
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, using the shell set by the
user's environment variable SHELL, the user's login shell, or ulti-
mately /bin/sh.
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 specifi-
cation 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.
/usr/share/doc/at-3.1.8/timespec contains the exact definition of the
time specification.
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, 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 com-
mands, 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.
-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 1996".
-c cats the jobs listed on the command line to standard out-
put.
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-karl-
sruhe.de.
local Nov 1996 AT(1)
