.Id $Id: at.1.in,v 1.8 1997/09/28 20:00:25 ig25 Exp $
.TH AT 1 "Nov 1996" local "Linux Programmer's Manual"
.SH NAME
at, batch, atq, atrm \- queue, examine or delete jobs for later execution
.SH SYNOPSIS
.B at
.RB [ -V ]
.RB [ -q 
.IR queue ]
.RB [ -f
.IR file ]
.RB [ -mldbv ]
.B TIME
.br
.B "at -c"
.I job
.RI [ job... ]
.br
.B atq
.RB [ -V ]
.RB [ -q
.IR queue ]
.br
.B atrm
.RB [ -V ]
.I job
.RI [ job... ]
.br
.B batch
.RB [ -V ]
.RB [ -q
.IR queue ]
.RB [ -f
.IR file ]
.RB [ -mv ]
.RB [ TIME ]
.SH DESCRIPTION
.B at
and
.B batch
read commands from standard input or a specified file which are to
be executed at a later time, using
.BR /bin/sh .
.TP 8
.BR at
executes commands at a specified time.
.TP 8
.BR 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.
.TP 8
.BR atrm
deletes jobs, identified by their job number.
.TP 8
.BR batch
executes commands when system load levels permit; in other words, when the load average
drops below @LOADAVG_MX@, or the value specified in the invocation of
.BR atrun .
.PP
.B At
allows fairly complex time
specifications, extending the POSIX.2 standard.  It accepts times
of the form 
.B 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
.B midnight,
.B noon,
or
.B teatime
(4pm)
and you can have a time-of-day suffixed with
.B AM
or
.B 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
.B month-name
.B day
with an optional
.B year,
or giving a date of the form
.B MMDDYY
or
.B MM/DD/YY
or
.B DD.MM.YY.
The specification of a date
.I must
follow the specification of the time of day.
You can also give times like
.B now
.B \+
.I count
.I time-units,
where the time-units can be
.B minutes,
.B hours,
.B days,
or
.B weeks
and you can tell
.B at
to run the job today by suffixing the time with
.B today
and to run the job tomorrow by suffixing the time with
.B tomorrow.
.PP
For example, to run a job at 4pm three days from now, you would do
.B at 4pm + 3 days,
to run a job at 10:00am on July 31, you would do
.B at 10am Jul 31
and to run a job at 1am tomorrow, you would do
.B at 1am tomorrow.
.PP
The exact definition of the time specification can be found in
.IR @prefix@/doc/at/timespec .
.PP
For both
.BR at " and " batch ,
commands are read from standard input or the file specified
with the
.B -f
option and executed.
The working directory, the environment (except for the variables
.BR TERM ,
.BR DISPLAY
and
.BR _ )
and the umask are retained from the time of invocation.
An
.BR "at " \-
or
.BR "batch "\-
command invoked from a 
.B 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
.BR @MAIL_CMD@ .
If
.B at
is executed from a 
.B su(1)
shell, the owner of the login shell will receive the mail.
.PP
The superuser may use these commands in any case.
For other users, permission to use at is determined by the files
.I @ETCDIR@/at.allow
and
.IR @ETCDIR@/at.deny .
.PP
If the file
.I @ETCDIR@/at.allow
exists, only usernames mentioned in it are allowed to use
.BR at .
.PP
If
.I @ETCDIR@/at.allow
does not exist,
.I @ETCDIR@/at.deny
is checked, every username not mentioned in it is then allowed
to use
.BR at .
.PP
If neither exists, only the superuser is allowed use of at.
.PP
An empty 
.I @ETCDIR@/at.deny
means that every user is allowed use these commands, this is the
default configuration.
.SH OPTIONS
.TP 8
.B -V
prints the version number to standard error.
.TP 8
.BI \-q " queue"
uses the specified queue.
A queue designation consists of a single letter; valid queue designations
range from
.B a
to 
.BR z .
and
.B A
to
.BR Z .
The
.B @DEFATQ@
queue is the default for
.B at
and the
.B @DEFBQ@
queue for
.BR batch .
Queues with higher letters run with increased niceness.  The special
queue "=" is reserved for jobs which are currently running.
.P
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
.BR atq
is given a specific queue, it will only show jobs pending in that queue.
.TP 8
.B \-m
Send mail to the user when the job has completed even if there was no
output.
.TP 8
.BI \-f " file"
Reads the job from
.BI file
rather than standard input.
.TP 8
.B \-l
Is an alias for
.B atq.
.TP
.B \-d
Is an alias for
.B atrm.
.TP
.TP
.B \-v
Shows the time the job will be executed.
.P
Times displayed will be in the format "1997-02-20 14:50" unless the
environment variable
.B POSIXLY_CORRECT 
is set; then, it will be "Thu Feb 20 14:50:00 1996".
.TP
.B
\-c
cats the jobs listed on the command line to standard output.
.SH FILES
.I @ATJBD@
.br
.I @ATSPD@
.br
.I /proc/loadavg
.br
.I /var/run/utmp
.br
.I @ETCDIR@/at.allow
.br
.I @ETCDIR@/at.deny
.SH SEE ALSO
.BR cron (1),
.BR nice (1),
.BR sh (1),
.BR umask (2),
.BR atd (8).
.SH BUGS
The correct operation of
.B batch
for Linux depends on the presence of a
.IR proc -
type directory mounted on
.IR /proc .
.PP
If the file
.I /var/run/utmp
is not available or corrupted, or if the user is not logged on at the
time 
.B at
is invoked, the mail is sent to the userid found
in the environment variable
.BR LOGNAME .
If that is undefined or empty, the current userid is assumed.
.PP
.B At
and
.B 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
.BR nqs .
.SH AUTHOR
At was mostly written by Thomas Koenig, ig25@rz.uni-karlsruhe.de.