at [-V] [-q queue] [-f file] [-mldbv] TIME
The unix at command is used to schedule jobs for later execution. at either takes the commands to be executed from the standard input, stopping when it encounters end of file (entered manually by typing control-d), or from the file specified after the -f option.
at takes a time specification in the 24 hour HH:MM form, the 12 hour time folowed by AM or PM, or midnight, noon or teatime(4:00 PM); if you do not provide the date it is assumed that you mean the next occorance of the specified time (today is assumed unless the time has past in which case tomorow is assumed).
If you do not wish the next occorance of the specified time the date can be given to at. If you want the job to run today (or not run if the time specified has past) you can specify today; tomorow can also be used if you want the job to run tomorow. The date can be specified in the form 'month-name day' with an optional year, MMDDYY, MM/DD/YY, DD.MM.YY. The date specification must always follow the time specification.
You can also give a time in the form now + n[hours minutes days weeks]
The user who invokes the at command is mailed the standard output and standard error using /usr/sbin/sendmail.
Weather or not a user can invoke the at command is specified by the existance of their username in the files /etc/at.allow and /etc/at.deny. If /etc/at.allow existes than no user who is not specified in the file can invoke the at command, otherwise if the file /etc/at.deny exists then any user not specified in the /etc/at.deny file can invoke at. If neither of the files exist then only the superuser can use the at command. An empty /etc/at.deny means that every user is allowed use these commands in general, this is the default configuration.