AT(1)AT(1)NAMEat - execute commands at a later time
SYNOPSISat [ -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/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 ALSOatq(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)
