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 .\" $FreeBSD$
 .Dd August 11, 2018
 .Dt "AT" 1
 .Os
 .Sh NAME
 .Nm at ,
 .Nm batch ,
 .Nm atq ,
 .Nm atrm
 .Nd queue, examine or delete jobs for later execution
 .Sh SYNOPSIS
 .Nm at
 .Op Fl q Ar queue
 .Op Fl f Ar file
 .Op Fl mldbv
 .Ar time
 .Nm at
 .Op Fl q Ar queue
 .Op Fl f Ar file
 .Op Fl mldbv
 .Fl t
 .Sm off
 .Op Oo Ar CC Oc Ar YY
 .Ar MM DD hh mm Op . Ar SS
 .Sm on
 .Nm at
 .Fl c Ar job Op Ar job ...
 .Nm at
 .Fl l Op Ar job ...
 .Nm at
 .Fl l
 .Fl q Ar queue
 .Nm at
 .Fl r Ar job Op Ar job ...
 .Pp
 .Nm atq
 .Op Fl q Ar queue
 .Op Fl v
 .Pp
 .Nm atrm
 .Ar job
 .Op Ar job ...
 .Pp
 .Nm batch
 .Op Fl q Ar queue
 .Op Fl f Ar file
 .Op Fl mv
 .Op Ar time
 .Sh DESCRIPTION
 The
 .Nm at
 and
 .Nm batch
 utilities
 read commands from standard input or a specified file which are to
 be executed at a later time, using
 .Xr sh 1 .
 .Bl -tag -width indent
 .It Nm at
 executes commands at a specified time;
 .It Nm atq
 lists the user's pending jobs, unless the user is the superuser; in that
 case, everybody's jobs are listed;
 .It Nm atrm
 deletes jobs;
 .It Nm batch
 executes commands when system load levels permit; in other words, when
 the load average drops below _LOADAVG_MX times number of active CPUs,
 or the value specified in the invocation of
 .Nm atrun .
 .El
 .Pp
 The
 .Nm at
 utility allows some moderately complex
 .Ar time
 specifications.
 It accepts times of the form
 .Ar HHMM
 or
 .Ar HH:MM
 to run a job at a specific time of day.
 (If that time is already past, the next day is assumed.)
 As an alternative, the following keywords may be specified:
 .Em midnight ,
 .Em noon ,
 or
 .Em teatime
 (4pm)
 and time-of-day may be suffixed with
 .Em AM
 or
 .Em PM
 for running in the morning or the evening.
 The day on which the job is to be run may also be specified
 by giving a date in the form
 .Ar \%month-name day
 with an optional
 .Ar year ,
 or giving a date of the forms
 .Ar DD.MM.YYYY ,
 .Ar DD.MM.YY ,
 .Ar MM/DD/YYYY ,
 .Ar MM/DD/YY ,
 .Ar MMDDYYYY , or
 .Ar MMDDYY .
 The specification of a date must follow the specification of
 the time of day.
 Time can also be specified as:
 .Op Em now
 .Em + Ar count \%time-units ,
 where the time-units can be
 .Em minutes ,
 .Em hours ,
 .Em days ,
 .Em weeks ,
 .Em months
 or
 .Em years
 and
 .Nm
 may be told to run the job today by suffixing the time with
 .Em today
 and to run the job tomorrow by suffixing the time with
 .Em tomorrow .
 .Pp
 For example, to run a job at 4pm three days from now, use
 .Nm at Ar 4pm + 3 days ,
 to run a job at 10:00am on July 31, use
 .Nm at Ar 10am Jul 31
 and to run a job at 1am tomorrow, use
 .Nm at Ar 1am tomorrow .
 .Pp
 The
 .Nm at
 utility also supports the
 .Tn POSIX
 time format (see
 .Fl t
 option).
 .Pp
 For both
 .Nm
 and
 .Nm batch ,
 commands are read from standard input or the file specified
 with the
 .Fl f
 option and executed.
 The working directory, the environment (except for the variables
 .Ev TERM ,
 .Ev TERMCAP ,
 .Ev DISPLAY
 and
 .Em _ )
 and the
 .Ar umask
 are retained from the time of invocation.
 An
 .Nm
 or
 .Nm batch
 command invoked from a
 .Xr 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
 .Xr sendmail 8 .
 If
 .Nm
 is executed from a
 .Xr su 1
 shell, the owner of the login shell will receive the mail.
 .Pp
 The superuser may use these commands in any case.
 For other users, permission to use
 .Nm
 is determined by the files
 .Pa _PERM_PATH/at.allow
 and
 .Pa _PERM_PATH/at.deny .
 .Pp
 If the file
 .Pa _PERM_PATH/at.allow
 exists, only usernames mentioned in it are allowed to use
 .Nm .
 In these two files, a user is considered to be listed only if the user
 name has no blank or other characters before it on its line and a
 newline character immediately after the name, even at the end of
 the file.
 Other lines are ignored and may be used for comments.
 .Pp
 If
 .Pa _PERM_PATH/at.allow
 does not exist,
 .Pa _PERM_PATH/at.deny
 is checked, every username not mentioned in it is then allowed
 to use
 .Nm .
 .Pp
 If neither exists, only the superuser is allowed use of
 .Nm .
 This is the default configuration.
 .Sh IMPLEMENTATION NOTES
 Note that
 .Nm
 is implemented through the
 .Xr cron 8
 daemon by calling
 .Xr atrun 8
 every five minutes.
 This implies that the granularity of
 .Nm
 might not be optimal for every deployment.
-If a finer granularity is needed, the system crontab at
-.Pa /etc/crontab
-needs to be changed.
+If a finer granularity is desired, the
+.Pa /etc/cron.d/at
+file can be edited and will be read by the system crontab, from which
+the SHELL and PATH environment variables are inherited. 
 .Sh OPTIONS
 .Bl -tag -width indent
 .It Fl q Ar queue
 Use the specified queue.
 A queue designation consists of a single letter; valid queue designations
 range from
 .Ar a
 to
 .Ar z
 and
 .Ar A
 to
 .Ar Z .
 The
 .Ar _DEFAULT_AT_QUEUE
 queue is the default for
 .Nm
 and the
 .Ar _DEFAULT_BATCH_QUEUE
 queue for
 .Nm batch .
 Queues with higher letters run with increased niceness.
 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.
 If
 .Nm atq
 is given a specific queue, it will only show jobs pending in that queue.
 .It Fl m
 Send mail to the user when the job has completed even if there was no
 output.
 .It Fl f Ar file
 Read the job from
 .Ar file
 rather than standard input.
 .It Fl l
 With no arguments, list all jobs for the invoking user.
 If one or more
 job numbers are given, list only those jobs.
 .It Fl d
 Is an alias for
 .Nm atrm
 (this option is deprecated; use
 .Fl r
 instead).
 .It Fl b
 Is an alias for
 .Nm batch .
 .It Fl v
 For
 .Nm atq ,
 shows completed but not yet deleted jobs in the queue; otherwise
 shows the time the job will be executed.
 .It Fl c
 Cat the jobs listed on the command line to standard output.
 .It Fl r
 Remove the specified jobs.
 .It Fl t
 Specify the job time using the \*[Px] time format.
 The argument should be in the form
 .Sm off
 .Op Oo Ar CC Oc Ar YY
 .Ar MM DD hh mm Op . Ar SS
 .Sm on
 where each pair of letters represents the following:
 .Pp
 .Bl -tag -width indent -compact -offset indent
 .It Ar CC
 The first two digits of the year (the century).
 .It Ar YY
 The second two digits of the year.
 .It Ar MM
 The month of the year, from 1 to 12.
 .It Ar DD
 the day of the month, from 1 to 31.
 .It Ar hh
 The hour of the day, from 0 to 23.
 .It Ar mm
 The minute of the hour, from 0 to 59.
 .It Ar SS
 The second of the minute, from 0 to 60.
 .El
 .Pp
 If the
 .Ar CC
 and
 .Ar YY
 letter pairs are not specified, the values default to the current
 year.
 If the
 .Ar SS
 letter pair is not specified, the value defaults to 0.
 .El
 .Sh FILES
 .Bl -tag -width _ATJOB_DIR/_LOCKFILE -compact
 .It Pa _ATJOB_DIR
 directory containing job files
 .It Pa _ATSPOOL_DIR
 directory containing output spool files
 .It Pa /var/run/utx.active
 login records
 .It Pa _PERM_PATH/at.allow
 allow permission control
 .It Pa _PERM_PATH/at.deny
 deny permission control
 .It Pa _ATJOB_DIR/_LOCKFILE
 job-creation lock file
 .El
 .Sh SEE ALSO
 .Xr nice 1 ,
 .Xr sh 1 ,
 .Xr umask 2 ,
 .Xr atrun 8 ,
 .Xr cron 8 ,
 .Xr sendmail 8
 .Sh AUTHORS
 .An -nosplit
 At was mostly written by
 .An Thomas Koenig Aq Mt ig25@rz.uni-karlsruhe.de .
 The time parsing routines are by
 .An David Parsons Aq Mt orc@pell.chi.il.us ,
 with minor enhancements by
 .An Joe Halpin Aq Mt joe.halpin@attbi.com .
 .Sh BUGS
 If the file
 .Pa /var/run/utx.active
 is not available or corrupted, or if the user is not logged on at the
 time
 .Nm
 is invoked, the mail is sent to the userid found
 in the environment variable
 .Ev LOGNAME .
 If that is undefined or empty, the current userid is assumed.
 .Pp
 The
 .Nm at
 and
 .Nm batch
 utilities
 as presently implemented are not suitable when users are competing for
 resources.
 If this is the case, another batch system such as
 .Em nqs
 may be more suitable.
 .Pp
 Specifying a date past 2038 may not work on some systems.