at and
batch read commands from standard input or a specified file which are to be executed at a later time, using
sh(1).
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.
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
atrun(8).
at allows some moderately complex
time specifications. It accepts times of the form
HHMM or
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] or [
now] ‘+
count %time-units', where the time-units can be ‘minutes', ‘hours', ‘days', ‘weeks,' ‘months,' or ‘years' 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.
Alternatively the time may be specified in a language-neutral fashion by using the
-t options.
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,
TERMCAP,
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
sendmail(8). 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
/var/at/at.allow and
/var/at/at.deny.
If the file
/var/at/at.allow exists, only usernames mentioned in it are allowed to use
at.
If
/var/at/at.allow does not exist,
/var/at/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
/var/at/at.deny means that every user is allowed use these commands. This is the default configuration.