1AT(1)                       General Commands Manual                      AT(1)
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NAME

6       at - execute commands at a later time
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SYNOPSIS

9       at [ -c ] [ -s ] [ -m ] time [ day ] [ file ]
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DESCRIPTION

12       At spools away a copy of the named file to be used as input to sh(1) or
13       csh(1).  If the -c flag (for (csh(1))) or the -s flag (for (sh(1)))  is
14       specified, then that shell will be used to execute the job; if no shell
15       is specified, the current environment shell is used.  If no  file  name
16       is specified, at prompts for commands from standard input until a ^D is
17       typed.
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19       If the -m flag is specified, mail will be sent to the  user  after  the
20       job  has  been run. If errors occur during execution of the job, then a
21       copy of the error diagnostics will be sent to the user.  If  no  errors
22       occur,  then  a short message is sent informing the user that no errors
23       occurred.
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25       The format of the spool file is as follows: A  four  line  header  that
26       includes  the  owner of the job, the name of the job, the shell used to
27       run the job, and whether mail will be set after the  job  is  executed.
28       The  header  is followed by a cd command to the current directory and a
29       umask command to set the modes on any files created by the  job.   Then
30       at  copies  all relevant environment variables to the spool file.  When
31       the script is run, it uses the user and group ID of the creator of  the
32       spool file.
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34       The  time is 1 to 4 digits, with an optional following `A', `P', `N' or
35       `M' for AM, PM, noon or midnight.  One and two digit numbers are  taken
36       to be hours, three and four digits to be hours and minutes.  If no let‐
37       ters follow the digits, a 24 hour clock time is understood.
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39       The optional day is either (1) a month name followed by a  day  number,
40       or  (2)  a  day  of the week; if the word `week' follows, invocation is
41       moved seven days further off.  Names of months and days may  be  recog‐
42       nizably truncated.  Examples of legitimate commands are
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44              at 8am jan 24
45              at -c -m 1530 fr week
46              at -s -m 1200n week
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48       At   programs  are  executed  by  periodic  execution  of  the  command
49       /usr/libexec/atrun from cron(8).  The granularity of  at  depends  upon
50       the how often atrun is executed.
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52       Error  output is lost unless redirected or the -m flag is requested, in
53       which case a copy of the errors is sent to the user via mail(1).
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FILES

56       /usr/spool/at                spooling area
57       /usr/spool/at/yy.ddd.hhhh.*  job file
58       /usr/spool/at/past           directory where jobs are executed from
59       /usr/spool/at/lasttimedone   last time atrun was run
60       /usr/libexec/atrun               executor (run by cron(8))
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SEE ALSO

63       atq(1), atrm(1), calendar(1), sleep(1), cron(8)
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DIAGNOSTICS

66       Complains about various syntax errors and times out of range.
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BUGS

69       Due to the granularity of the execution  of  /usr/libexec/atrun,  there
70       may  be  bugs  in  scheduling  things  almost exactly 24 hours into the
71       future.
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73       If the system crashes, mail is not sent to the user informing them that
74       the job was not completed.
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76       Sometimes   old   spool  files  are  not  removed  from  the  directory
77       /usr/spool/at/past. This is usually due to a system crash, and requires
78       that they be removed by hand.
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824th Berkeley Distribution      October 21, 1996                          AT(1)
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