Redis HLEN Command

The Redis HLEN command returns the number of fields in the hash stored at the specified key.

Syntax

The syntax goes like this:

HLEN key

So all we do is pass the name of the key to the command.

Suppose we set the following hash:

HSET customer firstname "Rob" lastname "Banks" age 37

Result:

(integer) 3

We just set a hash with three fields.

We can use HLEN to get the number fields in that hash:

HLEN customer

Result:

(integer) 3

The result is an integer reply of the number fields in the hash. In this case, there are three fields in the hash and so 3 is returned.

Let’s add another field to our hash:

HSET customer height 176

Result:

(integer) 1

One field was added.

Now let’s run HLEN again:

HLEN customer

Result:

(integer) 4

Now it returns 4 as expected.

Running the command against a key that doesn’t exist results in 0 being returned:

HLEN nonexistentkey

Result:

(integer) 0

Passing the wrong number of arguments results in an error:

HLEN customer lastname

Result:

(error) ERR wrong number of arguments for 'hlen' command