4.3BSD - /usr/man/cat1/at.0

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 let‐
       ters 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  recog‐
       nizably 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/lib/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/lib/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/lib/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       March 20, 1986                           AT(1)