# 2.11BSD#431 - /usr/man/cat1/at.0

    AT(1)		    UNIX Programmer's Manual		    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 understood.

         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 com-
         mand  /usr/libexec/atrun from cron(8).  The granularity of
         at depends upon the how often atrun is executed.

    Printed 11/26/99	October 21, 1996			1

    AT(1)		    UNIX Programmer's Manual		    AT(1)

         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 scheduling things
         almost exactly 24 hours into the future.

         If the system crashes, mail is not sent to the user inform-
         ing 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.

    Printed 11/26/99	October 21, 1996			2

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