Tribblix: manual page: at.1

AT(1) User Commands AT(1)

NAME

at, batch - execute commands at a later time

SYNOPSIS

/usr/bin/at [-c | -k | -s] [-m] [-f file] [-p project]
[-q queuename] -t time

/usr/bin/at [-c | -k | -s] [-m] [-f file] [-p project]
[-q queuename] timespec...

/usr/bin/at -l [-p project] [-q queuename] [at_job_id ...]

/usr/bin/at -r at_job_id ...

/usr/bin/batch [-p project]

/usr/xpg4/bin/at [-c | -k | -s] [-m] [-f file] [-p project]
[-q queuename] -t time

/usr/xpg4/bin/at [-c | -k | -s] [-m] [-f file] [-p project]
[-q queuename] timespec...

/usr/xpg4/bin/at -l [-p project] [-q queuename]
[at_job_id ...]

/usr/xpg4/bin/at -r at_job_id ...

/usr/xpg4/bin/batch [-p project]

DESCRIPTION

at
The at utility reads commands from standard input and groups them
together as an at-job, to be executed at a later time.

The at-job is executed in a separate invocation of the shell, running
in a separate process group with no controlling terminal, except that
the environment variables, current working directory, file creation
mask (see umask(1)), and system resource limits (for sh and ksh only,
see ulimit(1)) in effect when the at utility is executed is retained
and used when the at-job is executed.

When the at-job is submitted, the at_job_id and scheduled time are
written to standard error. The at_job_id is an identifier that is a
string consisting solely of alphanumeric characters and the period
character. The at_job_id is assigned by the system when the job is
scheduled such that it uniquely identifies a particular job.

User notification and the processing of the job's standard output and
standard error are described under the -m option.

Users are permitted to use at and batch (see below) if their name
appears in the file /usr/lib/cron/at.allow. If that file does not
exist, the file /usr/lib/cron/at.deny is checked to determine if the
user should be denied access to at. If neither file exists, only a
user with the solaris.jobs.user authorization is allowed to submit a
job. If only at.deny exists and is empty, global usage is permitted.
The at.allow and at.deny files consist of one user name per line.

cron and at jobs are not be executed if the user's account is locked.
Only accounts which are not locked as defined in shadow(5) will have
their job or process executed.

batch
The batch utility reads commands to be executed at a later time.

Commands of the forms:

/usr/bin/batch [-p project]
/usr/xpg4/bin/batch [-p project]

are respectively equivalent to:

/usr/bin/at -q b [-p project] now
/usr/xpg4/bin/at -q b -m [-p project] now

where queue b is a special at queue, specifically for batch jobs.
Batch jobs are submitted to the batch queue for immediate execution.
Execution of submitted jobs can be delayed by limits on the number of
jobs allowed to run concurrently. See queuedefs(5).

OPTIONS

If the -c, -k, or -s options are not specified, the SHELL environment
variable by default determines which shell to use.

If SHELL is unset or NULL, /usr/bin/sh is used.

The following options are supported:

-c
C shell. csh(1) is used to execute the at-job.

-k
Korn shell. ksh(1) is used to execute the at-job.

-s
Bourne shell. sh(1) is used to execute the at-job.

-f file
Specifies the path of a file to be used as the
source of the at-job, instead of standard input.

-l
(The letter ell.) Reports all jobs scheduled for the
invoking user if no at_job_id operands are
specified. If at_job_ids are specified, reports only
information for these jobs.

-m
Sends mail to the invoking user after the at-job has
run, announcing its completion. Standard output and
standard error produced by the at-job are mailed to
the user as well, unless redirected elsewhere. Mail
is sent even if the job produces no output.

If -m is not used, the job's standard output and
standard error is provided to the user by means of
mail, unless they are redirected elsewhere; if there
is no such output to provide, the user is not
notified of the job's completion.

-p project
Specifies under which project the at or batch job is
run. When used with the -l option, limits the search
to that particular project. Values for project is
interpreted first as a project name, and then as a
possible project ID, if entirely numeric. By
default, the user's current project is used.

-q queuename
Specifies in which queue to schedule a job for
submission. When used with the -l option, limits the
search to that particular queue. Values for
queuename are limited to the lower case letters a
through z. By default, at-jobs are scheduled in
queue a. In contrast, queue b is reserved for batch
jobs. Since queue c is reserved for cron jobs, it
can not be used with the -q option.

-r at_job_id
Removes the jobs with the specified at_job_id
operands that were previously scheduled by the at
utility.

-t time
Submits the job to be run at the time specified by
the time option-argument, which must have the format
as specified by the touch(1) utility.

OPERANDS

The following operands are supported:

at_job_id
The name reported by a previous invocation of the at
utility at the time the job was scheduled.

timespec
Submit the job to be run at the date and time
specified. All of the timespec operands are interpreted
as if they were separated by space characters and
concatenated. The date and time are interpreted as
being in the timezone of the user (as determined by the
TZ variable), unless a timezone name appears as part of
time below.

In the "C" locale, the following describes the three
parts of the time specification string. All of the
values from the LC_TIME categories in the "C" locale
are recognized in a case-insensitive manner.

time
The time can be specified as one, two or
four digits. One- and two-digit numbers
are taken to be hours, four-digit numbers
to be hours and minutes. The time can
alternatively be specified as two numbers
separated by a colon, meaning
hour:minute. An AM/PM indication (one of
the values from the am_pm keywords in the
LC_TIME locale category) can follow the
time; otherwise, a 24-hour clock time is
understood. A timezone name of GMT, UCT,
or ZULU (case insensitive) can follow to
specify that the time is in Coordinated
Universal Time. Other timezones can be
specified using the TZ environment
variable. The time field can also be one
of the following tokens in the "C"
locale:

midnight
Indicates the time 12:00 am
(00:00).

noon
Indicates the time 12:00 pm.

now
Indicate the current day and
time. Invoking at now
submits an at-job for
potentially immediate
execution (that is, subject
only to unspecified
scheduling delays).

date
An optional date can be specified as
either a month name (one of the values
from the mon or abmon keywords in the
LC_TIME locale category) followed by a
day number (and possibly year number
preceded by a comma) or a day of the week
(one of the values from the day or abday
keywords in the LC_TIME locale category).
Two special days are recognized in the
"C" locale:

today
Indicates the current day.

tomorrow
Indicates the day following
the current day.

If no date is given, today is assumed if
the given time is greater than the
current time, and tomorrow is assumed if
it is less. If the given month is less
than the current month (and no year is
given), next year is assumed.

increment
The optional increment is a number
preceded by a plus sign (+) and suffixed
by one of the following: minutes, hours,
days, weeks, months, or years. (The
singular forms are also accepted.) The
keyword next is equivalent to an
increment number of + 1. For example, the
following are equivalent commands:

at 2pm + 1 week
at 2pm next week

USAGE

The format of the at command line shown here is guaranteed only for
the "C" locale. Other locales are not supported for midnight, noon,
now, mon, abmon, day, abday, today, tomorrow, minutes, hours, days,
weeks, months, years, and next.

Since the commands run in a separate shell invocation, running in a
separate process group with no controlling terminal, open file
descriptors, traps and priority inherited from the invoking
environment are lost.

EXAMPLES

Example 1: Typical Sequence at a Terminal

This sequence can be used at a terminal:

$ at -m 0730 tomorrow
sort < file >outfile
<EOT>

Example 2: Redirecting Output

This sequence, which demonstrates redirecting standard error to a
pipe, is useful in a command procedure (the sequence of output
redirection specifications is significant):

$ at now + 1 hour <<!
diff file1 file2 2>&1 >outfile | mailx mygroup

Example 3: Self-rescheduling a Job

To have a job reschedule itself, at can be invoked from within the
at-job. For example, this "daily-processing" script named my.daily
runs every day (although crontab is a more appropriate vehicle for
such work):

# my.daily runs every day
at now tomorrow < my.daily
daily-processing

Example 4: Various Time and Operand Presentations

The spacing of the three portions of the "C" locale timespec is quite
flexible as long as there are no ambiguities. Examples of various
times and operand presentations include:

at 0815am Jan 24
at 8 :15amjan24
at now "+ 1day"
at 5 pm FRIday
at '17
utc+
30minutes'

batch

Example 5: Typical Sequence at a Terminal

This sequence can be used at a terminal:

$ batch
sort <file >outfile
<EOT>

Example 6: Redirecting Output

This sequence, which demonstrates redirecting standard error to a
pipe, is useful in a command procedure (the sequence of output
redirection specifications is significant):

$ batch <<!
diff file1 file2 2>&1 >outfile | mailx mygroup
!

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment
variables that affect the execution of at and batch: LANG, LC_ALL,
LC_CTYPE, LC_MESSAGES, NLSPATH, and LC_TIME.

DATEMSK
If the environment variable DATEMSK is set, at uses its
value as the full path name of a template file containing
format strings. The strings consist of format specifiers
and text characters that are used to provide a richer set
of allowable date formats in different languages by
appropriate settings of the environment variable LANG or
LC_TIME. The list of allowable format specifiers is
located in the getdate(3C) manual page. The formats
described in the OPERANDS section 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.

SHELL
Determine a name of a command interpreter to be used to
invoke the at-job. If the variable is unset or NULL, sh
is used. If it is set to a value other than sh, the
implementation uses that shell; a warning diagnostic is
printed telling which shell will be used.

TZ
Determine the timezone. The job is submitted for
execution at the time specified by timespec or -t time
relative to the timezone specified by the TZ variable. If
timespec specifies a timezone, it overrides TZ. If
timespec does not specify a timezone and TZ is unset or
NULL, an unspecified default timezone is used.

EXIT STATUS

The following exit values are returned:

0
The at utility successfully submitted, removed or listed a job
or jobs.

>0
An error occurred, and the job will not be scheduled.

FILES

/usr/lib/cron/at.allow
names of users, one per line, who are
authorized access to the at and batch
utilities

/usr/lib/cron/at.deny
names of users, one per line, who are
denied access to the at and batch
utilities

ATTRIBUTES

NOTES

Regardless of queue used, cron(8) has a limit of 100 jobs in
execution at any time.

There can be delays in cron at job execution. In some cases, these
delays can compound to the point that cron job processing appears to
be hung. All jobs are executed eventually. When the delays are
excessive, the only workaround is to kill and restart cron.

April 13, 2005 AT(1)