.\" $FreeBSD: src/usr.bin/at/at.man,v 1.34 2003/03/26 02:38:18 keramida Exp $
.Dd January 13, 2002
.Dt "AT" 1
.Os
.Sh NAME
.Nm at ,
.Nm batch ,
.Nm atq ,
.Nm atrm
.Nd queue, examine, or delete jobs for later execution
.Sh SYNOPSIS
.Nm at
.Op Fl q Ar queue
.Op Fl f Ar file
.Op Fl mldbv
.Ar time
.Nm at
.Op Fl q Ar queue
.Op Fl f Ar file
.Op Fl mldbv
.Fl t
.Sm off
.Op Oo Ar CC Oc Ar YY
.Ar MM DD hh mm Op . Ar SS
.Sm on
.Nm at
.Fl c Ar job Op Ar job ...
.Nm at
.Fl l Op Ar job ...
.Nm at
.Fl l
.Fl q Ar queue
.Nm at
.Fl r Ar job Op Ar job ...
.Pp
.Nm atq
.Op Fl q Ar queue
.Op Fl v
.Pp
.Nm atrm
.Ar job
.Op Ar job ...
.Pp
.Nm batch
.Op Fl q Ar queue
.Op Fl f Ar file
.Op Fl mv
.Op Ar time
.Sh DESCRIPTION
The
.Nm at
and
.Nm batch
utilities
read commands from standard input or a specified file.
The commands are executed at a later time, using
.Xr sh 1 .
.Bl -tag -width indent
.It Nm at
executes commands at a specified time;
.It Nm atq
lists the user's pending jobs, unless the user is the superuser; in that
case, everybody's jobs are listed;
.It Nm atrm
deletes jobs;
.It Nm 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
.Nm atrun .
.El
.Pp
The
.Nm at
utility allows some moderately complex
.Ar time
specifications.
It accepts times of the form
.Ar HHMM
or
.Ar HH:MM
to run a job at a specific time of day.
(If that time is already past, the next day is assumed.)
As an alternative, the following keywords may be specified:
.Em midnight ,
.Em noon ,
or
.Em teatime
(4pm)
and time-of-day may be suffixed with
.Em AM
or
.Em PM
for running in the morning or the evening.
The day on which the job is to be run may also be specified
by giving a date in the form
.Ar \%month-name day
with an optional
.Ar year ,
or giving a date of the forms
.Ar DD.MM.YYYY ,
.Ar DD.MM.YY ,
.Ar MM/DD/YYYY ,
.Ar MM/DD/YY ,
.Ar MMDDYYYY , or
.Ar MMDDYY .
The specification of a date must follow the specification of
the time of day.
Time can also be specified as:
.Op Em now
.Em + Ar count \%time-units ,
where the time-units can be
.Em minutes ,
.Em hours ,
.Em days ,
.Em weeks ,
.Em months
or
.Em years
and
.Nm at
may be told to run the job today by suffixing the time with
.Em today
and to run the job tomorrow by suffixing the time with
.Em tomorrow .
.Pp
For example, to run a job at 4pm three days from now, use
.Nm at Ar 4pm + 3 days ,
to run a job at 10:00am on July 31, use
.Nm at Ar 10am Jul 31
and to run a job at 1am tomorrow, use
.Nm at Ar 1am tomorrow .
.Pp
The
.Nm at
utility also supports the
.Tn POSIX
time format (see
.Fl t
option).
.Pp
For both
.Nm at
and
.Nm batch ,
commands are read from standard input or the file specified
with the
.Fl f
option.
The working directory, the environment (except for the variables
.Ev TERM ,
.Ev TERMCAP ,
.Ev DISPLAY
and
.Em _ ) ,
and the
.Ar umask
are retained from the time of invocation.
An
.Nm at
or
.Nm batch
command invoked from a
.Xr 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
.Xr sendmail 8 .
If
.Nm at
is executed from a
.Xr 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
.Nm at
is determined by the files
.Pa _PERM_PATH/at.allow
and
.Pa _PERM_PATH/at.deny .
.Pp
If the file
.Pa _PERM_PATH/at.allow
exists, only usernames mentioned in it are allowed to use
.Nm at .
In these two files,
a user is considered to be listed
only if the user name has no blank or other characters
before it on its line and a newline character immediately after the name,
even at the end of the file.
Other lines are ignored and may be used for comments.
.Pp
If
.Pa _PERM_PATH/at.allow
does not exist,
.Pa _PERM_PATH/at.deny
is checked, every username not mentioned in it is then allowed
to use
.Nm at .
.Pp
If neither exists, only the superuser is allowed use of
.Nm at .
.Sh IMPLEMENTATION NOTES
Note that
.Nm at
is implemented through the
.Xr launchd 8
daemon periodically invoking
.Xr atrun 8 ,
which is disabled by default.
See 
.Xr atrun 8
for information about enabling
.Nm atrun .
.Sh OPTIONS
.Bl -tag -width indent
.It Fl b
Is an alias for
.Nm batch .
.It Fl c
Cat the jobs listed on the command line to standard output.
.It Fl d
Is an alias for
.Nm atrm
(this option is deprecated; use
.Fl r
instead).
.It Fl f Ar file
Read the job from
.Ar file
rather than standard input.
.It Fl l
With no arguments, list all jobs for the invoking user.
If one or more
job numbers are given, list only those jobs.
.It Fl m
Send mail to the user when the job has completed even if there was no
output.
.It Fl q Ar queue
Use the specified queue.
A queue designation consists of a single letter; valid queue designations
range from
.Ar a
to
.Ar z
and
.Ar A
to
.Ar Z .
The
.Ar _DEFAULT_AT_QUEUE
queue (a) is the default for
.Nm at
and the
.Ar _DEFAULT_BATCH_QUEUE
queue (b) is the default for
.Nm 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
.Nm atq
is given a specific queue, it will only show jobs pending in that queue.
.It Fl r
Remove the specified jobs.
.It Fl t
Specify the job time using the \*[Px] time format.
The argument should be in the form
.Sm off
.Op Oo Ar CC Oc Ar YY
.Ar MM DD hh mm Op . Ar SS
.Sm on
where each pair of letters represents the following:
.Pp
.Bl -tag -width indent -compact -offset indent
.It Ar CC
The first two digits of the year (the century).
.It Ar YY
The second two digits of the year.
.It Ar MM
The month of the year, from 1 to 12.
.It Ar DD
the day of the month, from 1 to 31.
.It Ar hh
The hour of the day, from 0 to 23.
.It Ar mm
The minute of the hour, from 0 to 59.
.It Ar SS
The second of the minute, from 0 to 61.
.El
.Pp
If the
.Ar CC
and
.Ar YY
letter pairs are not specified, the values default to the current
year.
If the
.Ar SS
letter pair is not specified, the value defaults to 0.
.It Fl v
For
.Nm atq ,
shows completed but not yet deleted jobs in the queue; otherwise
shows the time the job will be executed.
.El
.Sh FILES
.Bl -tag -width _ATJOB_DIR/_LOCKFILE -compact
.It Pa _ATJOB_DIR
directory containing job files
(/usr/lib/cron/jobs/)
.It Pa _ATJOB_DIR/_LOCKFILE
job-creation lock file
(/usr/lib/cron/jobs/...)
.It Pa _ATSPOOL_DIR
directory containing output spool files
(/usr/lib/cron/spool/)
.It Pa _PERM_PATH/at.allow
allow permission control
(/usr/lib/cron/at.allow)
.It Pa _PERM_PATH/at.deny
deny permission control
(/usr/lib/cron/at.deny)
.It Pa /var/run/utmpx
login records
.El
.Sh SEE ALSO
.Xr nice 1 ,
.Xr sh 1 ,
.Xr umask 2 ,
.Xr compat 5 ,
.Xr atrun 8 ,
.Xr cron 8 ,
.Xr sendmail 8
.Sh BUGS
If the file
.Pa /var/run/utmpx
is not available or corrupted,
or if the user is not logged on at the time
.Nm at
is invoked, the mail is sent to the userid found
in the environment variable
.Ev LOGNAME .
If that is undefined or empty, the current userid is assumed.
.Pp
The
.Nm at
and
.Nm batch
utilities
as presently implemented are not suitable when users are competing for
resources.
If this is the case, another batch system such as
.Em nqs
may be more suitable.
.Pp
Specifying a date past 2038 may not work on some systems.
.Sh AUTHORS
At was mostly written by
.An Thomas Koenig Aq ig25@rz.uni-karlsruhe.de .
The time parsing routines are by
.An David Parsons Aq orc@pell.chi.il.us ,
with minor enhancements by
.An Joe Halpin Aq joe.halpin@attbi.com .