at - Unix, Linux Command
.Id $Id: at.1.in,v 1.8 1997/09/28 20:00:25 ig25 Exp $
at, batch, atq, atrm - queue, examine or delete jobs for later execution
at [-V] [-q queue] [-f file] [-mldbv] TIME
at [-V] [-q queue] [-f file] [-mldbv] -t time_arg
at -c job [job...]
atq [-V] [-q queue]
atrm [-V] job [job...]
batch [-V] [-q queue] [-f file] [-mv] [TIME]
batch read commands from standard input or a specified file which are to
be executed at a later time .
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
and you can have a time-of-day suffixed with
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
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
executes commands at a specified time.
lists the users pending jobs, unless the user is the superuser; in that
case, everybodys jobs are listed. The format of the output lines (one
for each job) is: Job number, date, hour, job class.
deletes jobs, identified by their job number.
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
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
at and batch, commands are read from standard input or the file specified
-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.
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
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
If the file
/etc/at.allow exists, only usernames mentioned in it are allowed to use
/etc/at.allow does not exist,
/etc/at.deny is checked, every username not mentioned in it is then allowed
If neither exists, only the superuser is allowed use of at.
/etc/at.deny means that every user is allowed use these commands, this is the
at daemon can be configured through the
/etc/sysconfig/atd configuration file, which contains examples of settings.
Times displayed will be in the format "1997-02-20 14:50" unless the
POSIXLY_CORRECT is set; then, it will be "Thu Feb 20 14:50:00 1997".
prints the version number to standard error.
-q queue ||
uses the specified queue.
A queue designation consists of a single letter; valid queue designations
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.
atq is given a specific queue, it will only show jobs pending in that queue.
Send mail to the user when the job has completed even if there was no
-f file ||
Reads the job from
file rather than standard input.
Is an alias for
Is an alias for
Shows the time the job will be executed.
cats the jobs listed on the command line to standard output.
-t time_arg |
Submit the job to be run at the time specified by the
time_arg option argument, which must have the same format as specified for the
-t time option argument ([[CC]YY]MMDDhhmm).
at will record the values of
environment variables present at time of
at invocation. When the commands are run at the specified time,
at will restore these variables to their recorded values .
These variables are excluded from this processing and are never
at when the commands are run :
The value of the SHELL environment variable at the time of
at invocation will determine which shell is used to execute the
at job commands. If SHELL is unset when
at is invoked, the users login shell will be used; otherwise,
if SHELL is set when
at is invoked, it must contain the path of a shell interpreter
executable that will be used to run the commands at the specified time.
TERM, DISPLAY, SHELLOPTS, _, PPID, BASH_VERSINFO, EUID, UID, GROUPS.
If the user submitting the
at job is not the super-user, variables that alter the behaviour of the
LD_LIBRARY_PATH , cannot be recorded and restored by
The correct operation of
batch for Linux depends on the presence of a
proc- type directory mounted on
If the file
/var/run/utmp is not available or corrupted, or if the user is not logged on at the
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.
batch as presently implemented are not suitable when users are competing for
If this is the case for your site, you might want to consider another
batch system, such as
At was mostly written by Thomas Koenig, email@example.com.