ATD(8) System Manager's Manual ATD(8)
atd - run jobs queued for later execution
atd [-l load_avg] [-b batch_interval] [-d] [-f] [-s]
atd runs jobs queued by at(1).
-l Specifies a limiting load factor, over which batch jobs should not be run, instead of the compile-time choice of 0.8. For an SMP
system with n CPUs, you will probably want to set this higher than n-1.
-b Specify the minimum interval in seconds between the start of two batch jobs (60 default).
-d Debug; print error messages to standard error instead of using syslog(3). This option also implies -f.
-f Run atd in the foreground.
-s Process the at/batch queue only once. This is primarily of use for compatibility with old versions of at; atd -s is equivalent to
the old atrun command.
atd won't work if its spool directory is mounted via NFS even if no_root_squash is set.
/var/spool/at The directory for storing jobs; this should be mode 700, owner root.
/var/spool/at/spool The directory for storing output; this should be mode 700, owner root.
/etc/at.allow, /etc/at.deny determine who can use the at system.
at(1), at.deny(5), at.allow(5), cron(8), crontab(1), syslog(3).
The functionality of atd should be merged into cron(8).
Check Out this Related Man Page
AT(1) General Commands Manual AT(1)
at, batch, atq, atrm - queue, examine or delete jobs for later execution
at [-V] [-q queue] [-f file] [-mMlv] timespec...
at [-V] [-q queue] [-f file] [-mMkv] [-t time]
at -c job [job...]
atq [-V] [-q queue]
at [-rd] job [job...]
atrm [-V] job [job...]
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 out-
put lines (one for each job) is: Job number, date, hour, queue, and username.
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 atd.
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 spe-
cific 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 MMDD[CC]YY, MM/DD/[CC]YY, DD.MM.[CC]YY or
[CC]YY-MM-DD. 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 definition of the time specification can be found in /usr/share/doc/at-3.1.13/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 BASH_VERSINFO, DISPLAY, EUID, GROUPS, SHELLOPTS, TERM, UID, and _) and the umask are retained
from the time of invocation.
As at is currently implemented as a setuid program, other environment variables (e.g. LD_LIBRARY_PATH or LD_PRELOAD) are also not
exported. This may change in the future. As a workaround, set these variables explicitly in your job.
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. See at.allow(5) for details.
-V prints the version number to standard error and exit successfully.
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, the job is treated as if it were submitted to batch at the
time of the job. Once the time is reached, the batch processing rules with respect to load average apply. If atq is given a spe-
cific 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.
-M Never send mail to the user.
-f file Reads the job from file rather than standard input.
-t time run the job at time, given in the format [[CC]YY]MMDDhhmm[.ss]
-l Is an alias for atq.
-r Is an alias for atrm.
-d Is an alias for atrm.
-b is an alias for batch.
-v Shows the time the job will be executed before reading the job.
Times displayed will be in the format "Thu Feb 20 14:50:00 1997".
-c cats the jobs listed on the command line to standard output.
at.allow(5), at.deny(5), atd(8), cron(1), nice(1), sh(1), umask(2).
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.
At was mostly written by Thomas Koenig, email@example.com.