AT(1)							      General Commands 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 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 scheduling 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)