value at the head of the list stored at
key, only if
exists and holds a list.
In contrary to LPUSH, no operation will be performed when
key does not yet
Integer reply: the length of the list after the push operation.
(integer) 1redis> LPUSHX mylist "Hello"
(integer) 2redis> LPUSHX myotherlist "Hello"
(integer) 0redis> LRANGE mylist 0 -1
1) "Hello" 2) "World"redis> LRANGE myotherlist 0 -1
(empty list or set)