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BSD 2.11 - man page for at (bsd section 1)

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AT(1)											    AT(1)

NAME
       at - execute commands at a later time

SYNOPSIS
       at [ -c ] [ -s ] [ -m ] time [ day ] [ file ]

DESCRIPTION
       At spools away a copy of the named file to be used as input to sh(1) or csh(1).	If the -c
       flag (for (csh(1))) or the -s flag (for (sh(1))) is specified, then  that  shell  will  be
       used  to execute the job; if no shell is specified, the current environment shell is used.
       If no file name is specified, at prompts for commands from standard input until	a  ^D  is
       typed.

       If  the -m flag is specified, mail will be sent to the user after the job has been run. If
       errors occur during execution of the job, then a copy of the  error  diagnostics  will  be
       sent to the user. If no errors occur, then a short message is sent informing the user that
       no errors occurred.

       The format of the spool file is as follows: A four line header that includes the owner  of
       the  job, the name of the job, the shell used to run the job, and whether mail will be set
       after the job is executed. The header is followed by a cd command to the current directory
       and  a umask command to set the modes on any files created by the job.  Then at copies all
       relevant environment variables to the spool file.  When the script is  run,  it	uses  the
       user and group ID of the creator of the spool file.

       The  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 under-
       stood.

       The optional 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

	      at 8am jan 24
	      at -c -m 1530 fr week
	      at -s -m 1200n week

       At programs are executed by periodic execution  of  the	command  /usr/libexec/atrun  from
       cron(8).  The granularity of at depends upon the how often atrun is executed.

       Error  output  is lost unless redirected or the -m flag is requested, in which case a copy
       of the errors is sent to the user via mail(1).

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

SEE ALSO
       atq(1), atrm(1), calendar(1), sleep(1), cron(8)

DIAGNOSTICS
       Complains about various syntax errors and times out of range.

BUGS
       Due to the granularity of the execution of /usr/libexec/atrun, there may be bugs in sched-
       uling things almost exactly 24 hours into the future.

       If  the	system	crashes, mail is not sent to the user informing them that the job was not
       completed.

       Sometimes old spool files are not removed from the directory /usr/spool/at/past.  This  is
       usually due to a system crash, and requires that they be removed by hand.

4th Berkeley Distribution		 October 21, 1996				    AT(1)
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