How to Use LLEN Command in Redis to Get List Length

Use the LLEN command in Redis to get the number of elements in a list stored at a given key. The command syntax is LLEN key, which returns an integer representing the list length.

Syntax

The LLEN command syntax is simple:

• LLEN key: Returns the length of the list stored at key.
• If the key does not exist, it returns 0.
• If the key exists but is not a list, it returns an error.

redis

LLEN mylist

Example

This example shows how to create a list, add elements, and then use LLEN to get its length.

redis

127.0.0.1:6379> LPUSH mylist "apple"
(integer) 1
127.0.0.1:6379> LPUSH mylist "banana"
(integer) 2
127.0.0.1:6379> LPUSH mylist "cherry"
(integer) 3
127.0.0.1:6379> LLEN mylist
(integer) 3

Output

(integer) 3

Common Pitfalls

Common mistakes when using LLEN include:

• Using LLEN on a key that is not a list, which causes an error.
• Expecting LLEN to return null for non-existing keys; it returns 0 instead.
• Confusing LLEN with commands that return list elements.

redis

127.0.0.1:6379> SET mykey "notalist"
OK
127.0.0.1:6379> LLEN mykey
(error) WRONGTYPE Operation against a key holding the wrong kind of value

-- Correct usage --
127.0.0.1:6379> LLEN nonexistingkey
(integer) 0

Output

(error) WRONGTYPE Operation against a key holding the wrong kind of value
(integer) 0

Quick Reference

Command	Description	Returns
LLEN key	Get length of list at key	Integer length or 0 if key missing
LPUSH key value	Add value to front of list	New list length
LRANGE key start stop	Get elements from list	List of elements

Key Takeaways

Use LLEN to get the number of elements in a Redis list by specifying its key.

LLEN returns 0 if the list key does not exist, not an error or null.

Using LLEN on a non-list key causes a type error.

LPUSH can add elements to a list before checking its length with LLEN.

LLEN only returns the count, not the list elements themselves.