363 lines
7.4 KiB
Groff
363 lines
7.4 KiB
Groff
.\" $FreeBSD$
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.Dd June 1, 2018
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.Dt "AT" 1
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.Os
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.Sh NAME
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.Nm at ,
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.Nm batch ,
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.Nm atq ,
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.Nm atrm
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.Nd queue, examine or delete jobs for later execution
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.Sh SYNOPSIS
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.Nm at
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.Op Fl q Ar queue
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.Op Fl f Ar file
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.Op Fl mldbv
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.Ar time
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.Nm at
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.Op Fl q Ar queue
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.Op Fl f Ar file
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.Op Fl mldbv
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.Fl t
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.Sm off
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.Op Oo Ar CC Oc Ar YY
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.Ar MM DD hh mm Op . Ar SS
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.Sm on
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.Nm at
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.Fl c Ar job Op Ar job ...
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.Nm at
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.Fl l Op Ar job ...
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.Nm at
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.Fl l
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.Fl q Ar queue
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.Nm at
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.Fl r Ar job Op Ar job ...
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.Pp
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.Nm atq
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.Op Fl q Ar queue
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.Op Fl v
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.Pp
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.Nm atrm
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.Ar job
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.Op Ar job ...
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.Pp
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.Nm batch
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.Op Fl q Ar queue
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.Op Fl f Ar file
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.Op Fl mv
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.Op Ar time
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.Sh DESCRIPTION
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The
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.Nm at
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and
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.Nm batch
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utilities
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read commands from standard input or a specified file which are to
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be executed at a later time, using
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.Xr sh 1 .
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.Bl -tag -width indent
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.It Nm at
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executes commands at a specified time;
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.It Nm atq
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lists the user's pending jobs, unless the user is the superuser; in that
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case, everybody's jobs are listed;
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.It Nm atrm
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deletes jobs;
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.It Nm batch
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executes commands when system load levels permit; in other words, when the load average
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drops below _LOADAVG_MX, or the value specified in the invocation of
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.Nm atrun .
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.El
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.Pp
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The
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.Nm at
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utility allows some moderately complex
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.Ar time
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specifications.
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It accepts times of the form
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.Ar HHMM
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or
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.Ar HH:MM
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to run a job at a specific time of day.
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(If that time is already past, the next day is assumed.)
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As an alternative, the following keywords may be specified:
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.Em midnight ,
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.Em noon ,
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or
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.Em teatime
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(4pm)
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and time-of-day may be suffixed with
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.Em AM
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or
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.Em PM
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for running in the morning or the evening.
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The day on which the job is to be run may also be specified
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by giving a date in the form
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.Ar \%month-name day
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with an optional
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.Ar year ,
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or giving a date of the forms
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.Ar DD.MM.YYYY ,
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.Ar DD.MM.YY ,
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.Ar MM/DD/YYYY ,
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.Ar MM/DD/YY ,
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.Ar MMDDYYYY , or
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.Ar MMDDYY .
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The specification of a date must follow the specification of
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the time of day.
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Time can also be specified as:
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.Op Em now
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.Em + Ar count \%time-units ,
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where the time-units can be
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.Em minutes ,
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.Em hours ,
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.Em days ,
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.Em weeks ,
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.Em months
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or
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.Em years
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and
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.Nm
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may be told to run the job today by suffixing the time with
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.Em today
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and to run the job tomorrow by suffixing the time with
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.Em tomorrow .
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.Pp
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For example, to run a job at 4pm three days from now, use
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.Nm at Ar 4pm + 3 days ,
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to run a job at 10:00am on July 31, use
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.Nm at Ar 10am Jul 31
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and to run a job at 1am tomorrow, use
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.Nm at Ar 1am tomorrow .
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.Pp
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The
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.Nm at
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utility also supports the
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.Tn POSIX
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time format (see
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.Fl t
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option).
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.Pp
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For both
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.Nm
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and
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.Nm batch ,
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commands are read from standard input or the file specified
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with the
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.Fl f
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option and executed.
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The working directory, the environment (except for the variables
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.Ev TERM ,
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.Ev TERMCAP ,
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.Ev DISPLAY
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and
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.Em _ )
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and the
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.Ar umask
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are retained from the time of invocation.
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An
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.Nm
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or
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.Nm batch
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command invoked from a
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.Xr su 1
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shell will retain the current userid.
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The user will be mailed standard error and standard output from his
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commands, if any.
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Mail will be sent using the command
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.Xr sendmail 8 .
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If
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.Nm
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is executed from a
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.Xr su 1
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shell, the owner of the login shell will receive the mail.
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.Pp
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The superuser may use these commands in any case.
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For other users, permission to use
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.Nm
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is determined by the files
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.Pa _PERM_PATH/at.allow
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and
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.Pa _PERM_PATH/at.deny .
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.Pp
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If the file
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.Pa _PERM_PATH/at.allow
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exists, only usernames mentioned in it are allowed to use
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.Nm .
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In these two files, a user is considered to be listed only if the user
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name has no blank or other characters before it on its line and a
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newline character immediately after the name, even at the end of
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the file.
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Other lines are ignored and may be used for comments.
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.Pp
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If
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.Pa _PERM_PATH/at.allow
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does not exist,
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.Pa _PERM_PATH/at.deny
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is checked, every username not mentioned in it is then allowed
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to use
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.Nm .
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.Pp
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If neither exists, only the superuser is allowed use of
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.Nm .
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This is the default configuration.
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.Sh IMPLEMENTATION NOTES
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Note that
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.Nm
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is implemented through the
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.Xr cron 8
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daemon by calling
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.Xr atrun 8
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every five minutes.
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This implies that the granularity of
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.Nm
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might not be optimal for every deployment.
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If a finer granularity is needed, the system crontab at
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.Pa /etc/crontab
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needs to be changed.
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.Sh OPTIONS
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.Bl -tag -width indent
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.It Fl q Ar queue
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Use the specified queue.
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A queue designation consists of a single letter; valid queue designations
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range from
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.Ar a
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to
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.Ar z
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and
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.Ar A
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to
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.Ar Z .
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The
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.Ar _DEFAULT_AT_QUEUE
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queue is the default for
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.Nm
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and the
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.Ar _DEFAULT_BATCH_QUEUE
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queue for
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.Nm batch .
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Queues with higher letters run with increased niceness.
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If a job is submitted to a queue designated with an uppercase letter, it
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is treated as if it had been submitted to batch at that time.
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If
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.Nm atq
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is given a specific queue, it will only show jobs pending in that queue.
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.It Fl m
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Send mail to the user when the job has completed even if there was no
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output.
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.It Fl f Ar file
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Read the job from
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.Ar file
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rather than standard input.
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.It Fl l
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With no arguments, list all jobs for the invoking user.
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If one or more
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job numbers are given, list only those jobs.
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.It Fl d
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Is an alias for
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.Nm atrm
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(this option is deprecated; use
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.Fl r
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instead).
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.It Fl b
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Is an alias for
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.Nm batch .
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.It Fl v
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For
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.Nm atq ,
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shows completed but not yet deleted jobs in the queue; otherwise
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shows the time the job will be executed.
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.It Fl c
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Cat the jobs listed on the command line to standard output.
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.It Fl r
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Remove the specified jobs.
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.It Fl t
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Specify the job time using the \*[Px] time format.
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The argument should be in the form
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.Sm off
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.Op Oo Ar CC Oc Ar YY
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.Ar MM DD hh mm Op . Ar SS
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.Sm on
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where each pair of letters represents the following:
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.Pp
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.Bl -tag -width indent -compact -offset indent
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.It Ar CC
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The first two digits of the year (the century).
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.It Ar YY
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The second two digits of the year.
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.It Ar MM
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The month of the year, from 1 to 12.
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.It Ar DD
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the day of the month, from 1 to 31.
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.It Ar hh
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The hour of the day, from 0 to 23.
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.It Ar mm
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The minute of the hour, from 0 to 59.
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.It Ar SS
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The second of the minute, from 0 to 60.
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.El
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.Pp
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If the
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.Ar CC
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and
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.Ar YY
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letter pairs are not specified, the values default to the current
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year.
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If the
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.Ar SS
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letter pair is not specified, the value defaults to 0.
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.El
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.Sh FILES
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.Bl -tag -width _ATJOB_DIR/_LOCKFILE -compact
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.It Pa _ATJOB_DIR
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directory containing job files
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.It Pa _ATSPOOL_DIR
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directory containing output spool files
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.It Pa /var/run/utx.active
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login records
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.It Pa _PERM_PATH/at.allow
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allow permission control
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.It Pa _PERM_PATH/at.deny
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deny permission control
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.It Pa _ATJOB_DIR/_LOCKFILE
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job-creation lock file
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.El
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.Sh SEE ALSO
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.Xr nice 1 ,
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.Xr sh 1 ,
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.Xr umask 2 ,
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.Xr atrun 8 ,
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.Xr cron 8 ,
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.Xr sendmail 8
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.Sh AUTHORS
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.An -nosplit
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At was mostly written by
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.An Thomas Koenig Aq Mt ig25@rz.uni-karlsruhe.de .
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The time parsing routines are by
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.An David Parsons Aq Mt orc@pell.chi.il.us ,
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with minor enhancements by
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.An Joe Halpin Aq Mt joe.halpin@attbi.com .
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.Sh BUGS
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If the file
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.Pa /var/run/utx.active
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is not available or corrupted, or if the user is not logged on at the
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time
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.Nm
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is invoked, the mail is sent to the userid found
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in the environment variable
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.Ev LOGNAME .
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If that is undefined or empty, the current userid is assumed.
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.Pp
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The
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.Nm at
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and
|
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.Nm batch
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utilities
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as presently implemented are not suitable when users are competing for
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resources.
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If this is the case, another batch system such as
|
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.Em nqs
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may be more suitable.
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.Pp
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Specifying a date past 2038 may not work on some systems.
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