4.3BSD-UWisc/man/cat1/at.1

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
     _A_t spools away a copy of the named _f_i_l_e to be used as input
     to _s_h(1) or _c_s_h(1).  If the -c flag (for (_c_s_h(1))) or the -s
     flag (for (_s_h(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, _a_t 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
     _c_d command to the current directory and a _u_m_a_s_k command to
     set the modes on any files created by the job.  Then _a_t
     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 _t_i_m_e 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 _d_a_y 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

     _A_t programs are executed by periodic execution of the com-
     mand  /usr/lib/atrun from _c_r_o_n(8).  The granularity of _a_t
     depends upon the how often atrun is executed.





Printed 12/27/86         March 20, 1986                         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 _m_a_i_l(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 /_u_s_r/_l_i_b/_a_t_r_u_n,
     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 12/27/86         March 20, 1986                         2