Sun Apr 04, 2010 8:51 am - Re: run a cron job only ONCE!
#3713
NAME
at, batch, atq, atrm - queue, examine or delete jobs for later execution
SYNOPSIS
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]
DESCRIPTION
at and batch read commands from standard input or a specified file which are
to be executed at a later time .
at executes commands at a specified time.
atq lists the userâs pending jobs, unless the user is the superuser; in
that case, everybodyâs 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 invo-
cation 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 spec-
ified 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 com-
mand /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.