redis lpushx命令

LPUSHX key value

Inserts value at the head of the list stored at key, only if key already
exists and holds a list.
In contrary to LPUSH, no operation will be performed when key does not yet
exist.

*返回值

Integer reply: the length of the list after the push operation.

*例子

redis>  LPUSH mylist “World”

(integer) 1

redis>  LPUSHX mylist “Hello”

(integer) 2

redis>  LPUSHX myotherlist “Hello”

(integer) 0

redis>  LRANGE mylist 0 -1

1) "Hello"
2) "World"

redis>  LRANGE myotherlist 0 -1

(empty list or set)
redis>