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1.1 root 1: .\" Copyright (c) 1980 Regents of the University of California.
2: .\" All rights reserved. The Berkeley software License Agreement
3: .\" specifies the terms and conditions for redistribution.
4: .\"
5: .\" @(#)at.1 6.2 (Berkeley) 3/20/86
6: .\"
7: .TH AT 1 "March 20, 1986"
8: .UC 4
9: .SH NAME
10: at \- execute commands at a later time
11: .SH SYNOPSIS
12: .B "at [ -c ] [ -s ] [ -m ]"
13: time
14: [ day ]
15: [ file ]
16: .SH DESCRIPTION
17: .I At
18: spools away a copy of the named
19: .I file
20: to be used as input to
21: .IR sh (1)
22: or
23: .IR csh (1).
24: If the
25: .B \-c
26: flag (for
27: .IR (csh (1)))
28: or the
29: .B \-s
30: flag (for
31: .IR (sh (1)))
32: is specified, then that shell will be used to execute the job;
33: if no shell is specified,
34: the current environment shell is used.
35: If no file name is specified,
36: .I at
37: prompts for commands from standard input until a ^D is typed.
38: .PP
39: If the
40: .B \-m
41: flag is specified, mail will be sent to the user after the job
42: has been run. If errors occur during execution of the job, then
43: a copy of the error diagnostics will be sent to the user. If
44: no errors occur, then a short message is sent informing the
45: user that no errors occurred.
46: .PP
47: The format of the spool file is as follows:
48: A four line header that includes the owner of the job, the name of the job,
49: the shell used to run the job, and whether mail will be
50: set after the job is executed. The header is followed by a
51: .I cd
52: command to the current directory and a
53: .I umask
54: command to set the modes on any files created by the job.
55: Then
56: .I at
57: copies all relevant environment variables to the spool file.
58: When the script is run, it uses the user and group ID
59: of the creator of the spool file.
60: .PP
61: The
62: .I time
63: is 1 to 4 digits, with an optional following
64: `A', `P', `N' or `M' for
65: AM, PM, noon or midnight.
66: One and two digit numbers are taken to be hours, three and four digits
67: to be hours and minutes.
68: If no letters follow the digits, a 24 hour clock time is understood.
69: .PP
70: The optional
71: .I day
72: is either
73: (1) a month name followed by a day number,
74: or
75: (2) a day of the week;
76: if the word `week' follows, invocation is moved
77: seven days further off.
78: Names of months and days may be recognizably truncated.
79: Examples of legitimate commands are
80: .IP
81: at 8am jan 24
82: .br
83: at -c -m 1530 fr week
84: .br
85: at -s -m 1200n week
86: .PP
87: .I At
88: programs are executed by periodic execution
89: of the command
90: .IR
91: /usr/lib/atrun
92: from
93: .IR cron (8).
94: The granularity of
95: .I at
96: depends upon the how often atrun is executed.
97: .PP
98: Error output is lost unless redirected or the
99: .I \-m
100: flag is requested, in which case a copy of the errors is sent to
101: the user via
102: .IR mail (1).
103: .SH FILES
104: .nf
105: /usr/spool/at spooling area
106: /usr/spool/at/yy.ddd.hhhh.* job file
107: /usr/spool/at/past directory where jobs are executed from
108: /usr/spool/at/lasttimedone last time atrun was run
109: /usr/lib/atrun executor (run by cron(8))
110: .fi
111: .SH "SEE ALSO"
112: atq(1),
113: atrm(1),
114: calendar(1),
115: sleep(1),
116: cron(8)
117: .SH DIAGNOSTICS
118: Complains about various syntax errors and times out of range.
119: .SH BUGS
120: Due to the granularity of the execution of
121: .IR /usr/lib/atrun,
122: there may be bugs in scheduling things almost
123: exactly 24 hours into the future.
124:
125: If the system crashes, mail is not sent to the user informing them that
126: the job was not completed.
127:
128: Sometimes old spool files are not removed from the directory
129: /usr/spool/at/past. This is usually due to a system crash,
130: and requires that they be removed by hand.
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