AT(1) — Silicon Graphics
NAME
at − execute commands at a later time
SYNOPSIS
at time [ day ] [ file ]
DESCRIPTION
At squirrels away a copy of the named file (standard input default) to be used as input to sh(1) at a specified later time. A cd(1) command to the current directory is inserted at the beginning, followed by assignments to all environment variables. When the script is run, it uses the user and group ID of the creator of the copy 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 1530 fr week
At programs are executed by periodic execution of the command /usr/lib/atrun from cron(1M). The granularity of at depends upon how often atrun is executed.
Standard output or error output is lost unless redirected. The directory /usr/spool/at/past must be present or at will not run.
EXAMPLE
at 10:25
ls -l /etc > /dev/console
will cause the directory /etc to be listed in long format on device /dev/console at approximately 10:25 pm on the same day. The exact time this is executed will depend on how often /usr/lib/atrun is scheduled to run in /usr/lib/crontab; e.g., if /usr/lib/atrun is set up to run every 15 minutes, the above command will be executed at 10:30 am. A temporary file is created in directory /usr/spool/at containing the "ls -l" command to be executed; this temporary file will be removed upon completion of the command. Note that /usr/lib/crontab must contain a schedule entry for /usr/lib/atrun in order for "at" to work.
FILES
/usr/spool/at/yy.ddd.hhhh.uu activity to be performed at hour hhhh of day ddd of year yy. uu is a unique number.
/usr/spool/at/lasttimedone contains hhhh for last hour of activity.
/usr/spool/at/past directory of activities now in progress.
/usr/lib/atrun program that executes activities that are due.
/usr/lib/crontab cron table entry for running atrun.
SEE ALSO
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.
Version 2.1 — January 02, 1985