View Source: at(1) - Waikato Linux Users Group

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!!NAME
at, batch, atq, atrm - queue, examine or delete jobs for later execution

!!SYNOPSIS
__at__ [[ __-V__ ] [[ __-q__ ''queue'' ] [[ __-f__ ''file'' ] [[ __-mldbv__ ] __TIME__ %%%
__at -c__ ''job'' [[ ''job...'' ] %%%
__atq__ [[ __-V__ ] [[ __-q__ ''queue'' ] %%%
__atrm__ [[ __-V__ ] ''job'' [[ ''job...'' ] %%%
__batch__ [[ __-V__ ] [[ __-q__ ''queue'' ] [[ __-f__ ''file'' ] [[ __-mv__ ] [[ __TIME__ ]

!!DESCRIPTION
__at__ and __batch__ read commands from standard input or a specified file which are to be executed at a later time, using __/bin/sh__ .
;__at__ : executes commands at a specified time.
;__atq__ : lists the user's pending jobs, unless the user is the superuser; in that case, everybody's jobs are listed.  The format of the output lines (one for each job) is: Job number, date, hour, job class.
;__atrm__ : deletes jobs, identified by their job number.
;__batch__ : executes commands when system load levels permit; in other words, when the load average drops below 0.8, or the value specified in the invocation of __atrun__ .

__At__ allows fairly complex time specifications, extending the POSIX.2 standard.  It accepts times of the form  __HH:MM__ to run a job at a specific time of day. (If that time is already past, the next day is assumed.) You may also specify __midnight,__ __noon,__ or teatime(4pm) and you can have a time-of-day suffixed with __AM__ or __PM__ for running in the morning or the evening. You can also say what day the job will be run, by giving a date in the form __month-name__ __day__ with an optional __year,__ or giving a date of the form __MMDDYY__ or __MM/DD/YY__ or __DD.MM.YY.__ The specification of a date ''must'' follow the specification of the time of day. You can also give times like __now__ __+__ ''count'' ''time-units,'' where the time-units can be __minutes,__ __hours,__ __days,__ or __weeks__ and you can tell __at__ to run the job today by suffixing the time with __today__ and to run the job tomorrow by suffixing the time with __tomorrow.__

For example, to run a job at 4pm three days from now, you would do __at 4pm + 3 days,__ to run a job at 10:00am on July 31, you would do __at 10am Jul 31__ and to run a job at 1am tomorrow, you would do __at 1am tomorrow.__

The exact definition of the time specification can be found in ''/usr/share/doc/at-3.1.8/timespec'' .

For both __at__  and  __batch__ , commands are read from standard input or the file specified with the __-f__ option and executed. The working directory, the environment (except for the variables __TERM__ , __DISPLAY__ and _____ ) and the umask are retained from the time of invocation. An __at __ - or __batch __ - command invoked from a  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 __/usr/sbin/sendmail__ . If __at__ is executed from a  su(1) shell, the owner of the login shell will receive the mail.

The superuser may use these commands in any case. For other users, permission to use at is determined by the files ''/etc/at.allow'' and ''/etc/at.deny'' .

If the file ''/etc/at.allow'' exists, only usernames mentioned in it are allowed to use __at__ .

If ''/etc/at.allow'' does not exist, ''/etc/at.deny'' is checked, every username not mentioned in it is then allowed to use __at__ .

If neither exists, only the superuser is allowed use of at.

An empty  ''/etc/at.deny'' means that every user is allowed use these commands, this is the default configuration.

!!OPTIONS

;__-V__ : prints the version number to standard error.
;__-q__ '' queue'' : uses the specified queue. A queue designation consists of a single letter; valid queue designations range from __a__ to  __z__ . and __A__ to __Z__ . The __a__ queue is the default for __at__ and the __b__ queue for __batch__ . Queues with higher letters run with increased niceness.  The special queue "=" is reserved for jobs which are currently running.

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 __atq__ is given a specific queue, it will only show jobs pending in that queue.
;__-m__ : Send mail to the user when the job has completed even if there was no output.
;__-f__ '' file'' : Reads the job from __file__ rather than standard input.
;__-l__ : Is an alias for __atq.__
;__-d__ : Is an alias for __atrm.__

;__-v__ : Shows the time the job will be executed.

Times displayed will be in the format "1997-02-20 14:50" unless the environment variable __POSIXLY_CORRECT __ is set; then, it will be "Thu Feb 20 14:50:00 1996".
;.B : -c cats the jobs listed on the command line to standard output.

!!FILES
''/var/spool/at''
''/var/spool/at/spool''
''/proc/loadavg''
''/var/run/utmp''
''/etc/at.allow''
''/etc/at.deny''

!!SEE ALSO
cron(1), nice(1), sh(1), umask(2), atd(8).

!!BUGS
The correct operation of __batch__ for Linux depends on the presence of a ''proc'' - type directory mounted on ''/proc'' .

If the file ''/var/run/utmp'' is not available or corrupted, or if the user is not logged on at the time  __at__ is invoked, the mail is sent to the userid found in the environment variable __LOGNAME__ . If that is undefined or empty, the current userid is assumed.

__At__ and __batch__ as presently implemented are not suitable when users are competing for resources. If this is the case for your site, you might want to consider another batch system, such as __nqs__ .

!!AUTHOR
At was mostly written by Thomas Koenig, ig25@rz.uni-karlsruhe.de.

!!HOW TO SIMPLY USE THE BLOODY THING

 $ echo foo | at 2am
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Last edited on Monday, August 2, 2004 9:22:40 pm by CraigBox
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