at, batch, atq, atrm - queue, examine, or delete jobs for later execution
at [
-V] [
-q queue] [
-f file]
[
-u username] [
-mMlv]
timespec ...
at [
-V] [
-q queue] [
-f file]
[
-u username] [
-mMkv] [
-t time]
at -c job [...]
at [
-V] -l [
-o timeformat]
[job ...]
atq [
-V] [
-q queue] [
-o timeformat]
[job ...]
at [
-rd]
job [...]
atrm [
-V]
job [...]
batch
at -b
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, 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 1.5, 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 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
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.
If you specify a job to absolutely run at a specific time and date in the past,
the job will run as soon as possible. For example, if it is 8pm and you do a
at 6pm today, it will run more likely at 8:05pm.
The definition of the time specification can be found in
/usr/share/doc/at/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.
-
-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, 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 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.
- -M
- Never send mail to the user.
-
-u username
- Sends mail to username rather than the current
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.
-
-o fmt
- strftime-like time format used for the job list
/var/spool/cron/atjobs
/var/spool/cron/atspool
/proc/loadavg
/var/run/utmp
/etc/at.allow
/etc/at.deny
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.