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How do programs designed for scheduling (e.g. Task Scheduler in Windows, cron in Unix systems) know that it "is time" for them to run a certain scheduled command or script?
I imagine it's not something like a timed function checking the system clock every second or minute. Is there some kind of trigger being activated when a time stamp corresponding to a certain planned task is reached?
http://en.wikipedia.org/wiki/Cron#Multi-user_capability – Tamara Wijsman – 2013-01-22T11:37:13.567