LPUSHX

Prepends one or more elements to a list only when the list exists.

Usage: LPUSHX key element ...
Complexity: O(1) for each element added, so O(N) to add N elements when the command is called with multiple arguments.
Since: 2.2.0
ACL Categories: @fast, @list, @write
Command flags: WRITE, DENYOOM, FAST

Inserts specified values 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.

Examples

127.0.0.1:6379> LPUSH mylist "World"
(integer) 1
127.0.0.1:6379> LPUSHX mylist "Hello"
(integer) 2
127.0.0.1:6379> LPUSHX myotherlist "Hello"
(integer) 0
127.0.0.1:6379> LRANGE mylist 0 -1
1) "Hello"
2) "World"
127.0.0.1:6379> LRANGE myotherlist 0 -1
(empty array)

Replies

RESP2

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

RESP3