at one's fingertips
at one's fingertips {adv. phr.}
1. Within easy reach; quickly touched; nearby.
Seated in the cockpit, the pilot of a plane has many controls at his fingertips.
2. Readily usable as knowledge or skill; familiar.
He had several languages at his fingertips.
He had the whole design of the machine at his fingertips.
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Source: A Dictionary of American Idioms