Returns the remaining time to live of a key that has a timeout. This introspection capability allows a Redis client to check how many seconds a given key will continue to be part of the dataset.
Return value
Integer reply: TTL in seconds, -2 when key does not exist or -1 when key does not
have a timeout.
Examples
redis>
SET mykey "Hello"
OKredis> EXPIRE mykey 10
(integer) 1redis> TTL mykey
(integer) 10