At allows some moderately complex TIME specifications. It accepts times of the form HHMM or HH:MM to run a job at a specific time of day. (If that time is already past, the next day is assumed.) You may also specify midnight, noon, or teatime (4pm) and you can have a time-of-day suffixed with AM or PM for running in the morning or the evening. You can also say what day the job will be run, by giving a date in the form month-name day with an optional year, or giving a date of the form MMDDYY or MM/DD/YY or DD.MM.YY. You can also give times like now + count time-units, where the time-units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the time with today and to run the job tomorrow by suffixing the time with tomorrow.
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Executing commands in the future by simply specifing the time and the program to execute:
ie, at at 6:30am Jan 30 < /usr/bin/nmap (yes, you have to specify the path) or you could do it like this;
at 1970 pm August 5 < /usr/bin/nmap . To list your job list just type in atq.