at(1) 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 . . .
at -d job
batch
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;
date and time are recognized according to the locale specified
in the LC_TIME environment variable [see LANG on environ(5)],
as described below. Jobs queued with batch will execute when
system load level permits. at may be used with the following
options:
-f script
Reads commands to be executed from the named script
file.
-m Sends mail to the user after the job has been
completed. Mail is sent even if the job does not
produce output. Standard output and standard error
output are mailed to the user unless redirected
elsewhere. -m has no effect on jobs which already
print to standard output or standard error; the mail
message will not be duplicated. The environment
variables, current directory, umask, and ulimit are
retained when the commands are executed. Open file
descriptors, traps, and priority are lost.
-l [job] Reports all jobs scheduled for the invoking user, or
just the jobs specified. When invoked by a
privileged user, all jobs scheduled are reported.
-r job Removes specified jobs previously scheduled with at
for the invoking user. When invoked by a privileged
user, any job previously scheduled with at is
removed.
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-d job Displays the contents of the specified job.
An unprivileged user is restricted to display information only
on jobs that the user owns and that are at the user's level.
A user with the appropriate privileges is able to display
information about all jobs.
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.
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 if the user
should be denied access to at. If neither file exists, only
root 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.
If the DATEMSK environment variable is set, it points to a
template file that at will use to determine the valid time and
date values instead of the values described below. For more
information about using DATEMSK, see the last paragraph of the
DESCRIPTION section.
time may be specified as follows, where h is hours and m is
minutes: h, hh, hhmm, h: m, h: mm, hh: m, hh: mm. 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.
An optional date may be specified as either a month name
followed by a day number (and possibly a year number preceded
by a comma) or a day of the week. Month and weekday names
used for date are recognized according to the locale specified
in the LC_TIME environment variable [see LANG on environ(5)].
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. If no date is given,
today is assumed if the given hour is greater than the current
hour and tomorrow is assumed if it is less. If the given
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month is less than the current month (and no year is given),
next year is assumed.
The optional increment is simply a number suffixed by one of
the following: minutes, hours, days, weeks, months, or years.
(The singular form is also accepted.) Note that when
increment is 1 minute, at displays the warning job may not be
executed at the proper time, because the cron(1M) command's
smallest unit is the minute; that is, an at job entered at
12:01:45 and requested to run in one minute will run at
12:02:00 rather than 12:02:45. The modifier next may precede
the increment; it means ``+ 1.''
Thus valid commands include:
at 0815am Jan 24
at 8:15am Jan 24
at now + 1 day
at now next day
at 5 pm Friday
at and batch write the job number and schedule time to
standard error.
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 only remove your own jobs unless you are the
privileged user.
If the environment variable DATEMSK is set, at will use its
value as the full path name of a template file containing
format strings. The strings consist of field descriptors and
text characters and are used to provide a richer set of
allowable date formats in different languages by appropriate
settings of the environment variable LC_TIME [see LANG on
environ(5)]. [See getdate(3C) for the allowable list of field
descriptors; 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.
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at(1) at(1)
EXAMPLES
The at and batch commands read from standard input the
commands to be executed at a later time. sh(1) provides
different ways of specifying standard input. Within your
commands, it may be useful to redirect standard output.
This sequence can be used at a terminal:
batch
sort filename > outfile
CTRL-d (hold down ``control'' 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 /var/tmp.
%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 /var/tmp/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
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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
/usr/lib/locale/locale/LC_MESSAGES/uxcore
language-specific message file [See LANG on
environ(5).]
REFERENCES
atq(1), atrm(1), calendar(1), cron(1M), crontab(1), date(1),
environ(5), getdate(3C), kill(1), mail(1), nice(1), ps(1),
sh(1), sort(1)
Copyright 1994 Novell, Inc. Page 5