at, batch - execute commands at a later time

---

SYNOPSIS

batch

AVAILABILITY

at

batch

DESCRIPTION

at

The at-job will be 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 will be 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 will be 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 process with the super-user privileges 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.

batch

at -q b -m now

OPTIONS

-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

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

-l

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

-m

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

If -m is not used, the job's standard output and standard error will be 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.

-q queuename

Specify in which queue to schedule a job for submission. When used with the -l option, limit the search to that particular queue. Values for queuename are limited to the lower case letters a through z. By default, at-jobs will be 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

Remove the jobs with the specified at_job_id operands that were previously scheduled by the at utility.

-t time

Submit 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

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 can follow to further qualify the time; see TZ on the environ.5 manual page. 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 will submit 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 will be 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

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

at

1.

This sequence can be used at a terminal:

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

2.
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
!

3.

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

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

4.

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

1.

This sequence can be used at a terminal:

$ batch
sort <file >outfile
<EOT>

2.

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

SHELL

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

TZ

Determine the timezone. The job will be 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 will override TZ. If timespec does not specify a timezone and TZ is unset or NULL, an unspecified default timezone will be used.

DATEMSK

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 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.

EXIT STATUS

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

SEE ALSO

NOTES

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 will be executed eventually. When the delays are excessive, the only workaround is to kill and restart cron.

Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).

Last modified 21/April/97