4.2BSD/usr/man/man1/at.1

.TH AT 1 "18 January 1983"
.UC 4
.SH NAME
at \- execute commands at a later time
.SH SYNOPSIS
.B at
time
[
day
]
[
file
]
.SH DESCRIPTION
.I At
squirrels away a copy of the named
.I file
(standard input default)
to be used as input to
.IR sh (1)
(or
.IR csh (1)
if you normally use it)
at a specified later time.
A
.I cd
command to the current directory is inserted
at the beginning,
followed by assignments to all environment variables (excepting the
variable TERM, which is useless in this context.)
When the script is run, it uses the user and group ID
of the creator of the copy file.
.PP
The
.I time
is 1 to 4 digits, with an optional following
`A', `P', `N' or `M' for
AM, PM, noon or midnight.
One and two digit numbers are taken to be hours, three and four digits
to be hours and minutes.
If no letters follow the digits, a 24 hour clock time is understood.
.PP
The optional
.I day
is either
(1) a month name followed by a day number,
or
(2) a day of the week; if the word `week' follows
invocation is moved seven days further off.
Names of months and days may be recognizably truncated.
Examples of legitimate commands are
.IP
at 8am jan 24
.br
at 1530 fr week
.PP
.I At
programs are executed by periodic execution
of the command
.I /usr/lib/atrun
from
.IR cron (8).
The granularity of
.I at
depends upon how often
.I atrun
is executed.
.PP
Standard output or error output is lost unless redirected.
.SH FILES
.ta 2i
/usr/lib/atrun	executor (run by 
.IR cron (8)).
.sp
in /usr/spool/at:
.ta .5i 2i
.br
\&	yy.ddd.hhhh.*	activity for year yy, day dd, hour hhhh.
.br
\&	lasttimedone	last \fIhhhh\fR
.br
\&	past	activities in progress
.SH "SEE ALSO"
calendar(1),
pwd(1),
sleep(1),
cron(8)
.SH DIAGNOSTICS
Complains about various syntax errors and times out of range.
.SH BUGS
Due to the granularity of the execution of
.I /usr/lib/atrun,
there may be bugs in scheduling things almost
exactly 24 hours into the future.