How to Use XLEN Command in Redis for Stream Length

Use the XLEN command in Redis to get the number of entries in a stream. The syntax is XLEN key, where key is the stream name. It returns an integer representing the stream length.

Syntax

The XLEN command syntax is simple:

• XLEN key: Returns the number of entries in the stream stored at key.

If the stream does not exist, it returns 0.

redis

XLEN mystream

Example

This example shows how to add entries to a Redis stream and then use XLEN to get the number of entries.

redis

127.0.0.1:6379> XADD mystream * sensor-id 1234 temperature 19.8
"1588151234567-0"
127.0.0.1:6379> XADD mystream * sensor-id 1235 temperature 20.1
"1588151234568-0"
127.0.0.1:6379> XLEN mystream
(integer) 2

Output

(integer) 2

Common Pitfalls

Common mistakes when using XLEN include:

• Using XLEN on a key that is not a stream, which causes an error.
• Expecting XLEN to return the total size in bytes instead of the number of entries.
• Not handling the case when the stream does not exist, which returns 0.

Always ensure the key is a stream before calling XLEN.

redis

127.0.0.1:6379> XLEN notastream
(error) WRONGTYPE Operation against a key holding the wrong kind of value

# Correct usage:
127.0.0.1:6379> XLEN mystream
(integer) 2

Output

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

(integer) 2

Quick Reference

Command	Description
XLEN key	Returns the number of entries in the stream at key
XADD key * field value	Adds an entry to the stream
XRANGE key - +	Reads entries from the stream

Key Takeaways

Use XLEN to get the count of entries in a Redis stream quickly.

XLEN returns 0 if the stream does not exist.

Do not use XLEN on keys that are not streams to avoid errors.

XLEN counts entries, not the byte size of the stream.

Combine XLEN with XADD and XRANGE for full stream management.