at(1) DG/UX R4.11MU05 at(1)
NAME
at, batch - execute commands at a later time
SYNOPSIS
at [-f script] [-m] time [date] [+ increment]
at -l [job ...]
at -r job ...
batch
where:
script The name of a file containing commands
time h, hh, hhmm, h:m, h:mm, hh:m, or hh:mm, where h is hours
and m is minutes. A 24-hour clock is assumed, unless am or
pm is appended to time. If zulu is appended to time, it
means Greenwich Mean Time (GMT). time can also take on the
values: noon, midnight, and now. at now responds with the
error message too late; use now with the increment
argument, such as at now + 1 minute.
date Either a month name followed by a day number (and possibly
a year number preceded by a comma) or a day of the week.
(Both the month name and the day of the week may be spelled
out or abbreviated to three characters.) Two special
``days'', today and tomorrow are recognized. The default
is today if the given hour is greater than the current
hour, tomorrow if it is less. If the given month is less
than the current month (and no year is given), next year is
assumed.
increment A number suffixed by one of the following: minutes, hours,
days, weeks, months, or years. (The singular form is also
accepted.) If next precedes increment, it means `+ 1'.
job A job name (e.g. 123456.a)
DESCRIPTION
At and batch read commands from standard input to be executed at a
later time. at allows you to specify when the commands should be
executed, while jobs queued with batch will execute when system load
level permits.
Standard output and standard error output are mailed to the user
unless they are redirected elsewhere. The shell environment
variables, current directory, umask, and ulimit are retained when the
commands are executed. Open file descriptors, traps, and priority
are lost.
at and batch write the job number and schedule time to standard
error. Both commands read from standard input. sh(1) provides
different ways of specifying standard input. Within your commands,
it may be useful to redirect standard output.
Options
-f script Read commands to be executed from the named script file.
-l [job] Report all jobs scheduled for the invoking user, or just
the jobs specified.
-m Send mail to the user after the job has been completed,
indicating that the job is finished, even if the job
produces no output. Mail is sent only if the job has not
already generated a mail message.
-q queue Submit the job in queue queue rather than the default queue
a. The valid queues are a through z. batch submits jobs in
queue b. Queue c is reserved for cron(8) and jobs cannot be
submitted to that queue. NOTE: The user must define the
queues d through z or else the queue will function without
a specified form.
-r job Remove specified jobs previously scheduled using at.
Access Permissions
Users are permitted to use at if their name appears in the file
/etc/cron.d/at.allow. If that file does not exist, the file
/etc/cron.d/at.deny is checked to determine whether the user should
be denied access to at. If neither file exists, only a user with
appropriate privilege is allowed to submit a job. If only at.deny
exists and is empty, global usage is permitted. The allow/deny files
consist of one user name per line. These files can only be modified
by a privileged user.
Security Features
On a system with DG/UX information security, the cron daemon is a
full-fledged session initiator. This means that the submitted job
must be authorized to run at the time for which it is scheduled. This
determination is made by the cron daemon at run time. Therefore, it
is no longer safe to assume that the job will be run simply because
at or batch accepted the job when invoked by the user (per the access
restrictions described above). For a job created by at or batch,
cron will attempt to create the session via credentiald with a
service name of "at", the username of the submitting user, and the
time at which the job is scheduled to run. On systems with mandatory
access control (MAC), the label at which the job was submitted is
also requested for the new session. If the job turns out not to be
authorized, cron will send mail to the user reporting this. The
credentials of the job when it runs are determined by merging those
of the submitting user (saved by at for retrieval by cron) and those
authorized for the session by credentiald. This is done in a
restrictive way (the merge intersects features of the credentials
which grant privilege (such as capabilities) while unioning those
which limit privilege (audit mask)).
On a system with mandatory access control (MAC), the spool area,
/var/spool/cron/atjobs, is a multilevel directory. Jobs are queued at
the MAC label of the submitting process and are run at that label.
Any mail sent to the user is sent at the MAC label at which the job
was run.
Date Format
If the DATEMSK environment variable is set, at uses its value as the
pathname of a template file containing format strings. These format
strings determine the valid time and date values instead of the
values described above. The strings consist of field descriptors and
text characters and provide a richer set of allowable date formats in
different languages by appropriate settings of the environment
variable LANG or LC_TIME (see environ(5)).
For the allowable list of field descriptors, see getdate(3C). This
list is a subset of the descriptors allowed by calendar(1) that are
listed on the date(1) manual page.
The formats described above for the time and date arguments, the
special names noon, midnight, now, next, today, tomorrow, and the
increment argument are not recognized when DATEMSK is set.
Removing and Listing Jobs
at -r removes jobs previously scheduled by at or batch. The job
number is the number returned to you previously by the at or batch
command. You can also get job numbers by typing at -l. You can
remove only your own jobs unless you are a privileged user.
EXAMPLES
Valid commands include:
at 0815am Jan 24
at 8:15am Jan 24
at now + 1 day
at now next day
at 5 pm Friday
This sequence can be used at a terminal:
batch
sort filename > outfile
Ctrl-D (hold down CTRL and press `d')
This sequence, which shows redirecting standard error to a pipe, is
useful in a shell procedure (the sequence of output redirection
specifications is significant):
batch <<!
sort filename 2>&1 > outfile | mail loginid
!
To have a job reschedule itself, invoke at from within the shell
procedure, by including code similar to the following within the
shell file:
echo "sh shellfile" | at 1900 thursday next week
The following example shows the possible contents of a template file
AT.TEMPL in /etc/cron.d.
%I %p, the %est of %B of the year %Y run the following job
%I %p, the %end of %B of the year %Y run the following job
%I %p, the %erd of %B of the year %Y run the following job
%I %p, the %eth of %B of the year %Y run the following job
%d/%m/%y
%H:%M:%S
%I:%M%p
The following are examples of valid invocations if the environment
variable DATEMSK is set to /etc/cron.d/AT.TEMPL.
at 2 PM, the 3rd of July of the year 2000 run the following job
at 3/4/99
at 10:30:30
at 2:30PM
FILES
/etc/cron.d main cron directory
/etc/cron.d/at.allow list of allowed users
/etc/cron.d/at.deny list of denied users
/etc/cron.d/queuedefs scheduling information
/var/spool/cron/atjobs spool area
DIAGNOSTICS
at can detect syntax errors and times out of range.
SEE ALSO
atq(1), atrm(1), calendar(1), credentiald(1), crontab(1), date(1),
environ(5), kill(1), mail(1), nice(1), ps(1), sh(1), sort(1).
cron(1M).
getdate(3C).
Licensed material--property of copyright holder(s)