Redis: ERR wrong number of arguments for '…' command

What it means

Every Redis command takes a fixed number of arguments, or at least a minimum: GET takes exactly one key, SET at least a key and a value, HSET a key and then field-value pairs. Redis checks the count before anything else, and if it’s wrong it refuses the command, naming it in lower case:

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

Nothing ran. For a subcommand the name has a | in it: CONFIG GET with nothing to get is 'config|get'.

The count is of what reached the server, not what you typed. A variable that turned out empty, a list that was empty, or a value that was split in two all change it, which is why the command often looks right in your code.

Close relatives:

The count is right but the words aren’t: an unknown option, or a value split by a space, is usually ERR syntax error instead.
Inside a Lua script, redis.call('GET') fails with ERR Wrong number of args calling Redis command from script (Valkey: Wrong number of args calling command from script).
Inside a transaction, the command is refused as you queue it and EXEC discards everything (EXECABORT).

Common causes

An empty value that disappeared. In a shell, redis-cli SET user:1 $NAME with NAME empty sends only SET user:1. The same happens in code that builds the argument list and leaves out empty strings or nulls.
An empty list spread into a variadic command. MGET, DEL, SADD, LPUSH, HSET and ZADD need at least one key or element. Called with an empty array of keys or elements, a client can send the command name alone.
An odd number of field-value pairs. MSET k1 v1 k2, HSET h f1 v1 f2, or a dictionary flattened with one value missing.
A missing key name, often from a key built out of a variable that was empty.
Text from another database: SELECT * FROM users is Redis’s SELECT (switch database), which takes one argument.

How to fix it

See what was actually sent

Check the command’s shape with COMMAND DOCS <name> (its arguments), or COMMAND INFO <name>, whose second field is the arity: a positive number is the exact count including the command name, a negative one is the minimum (set is -3: at least a key and a value).

On a server you control, MONITOR prints every command as it arrives, with each argument quoted, so a missing or split argument is visible. It slows a busy server down: run it briefly, not on a loaded production server.

Quote values in the shell

redis-cli SET user:1 "$NAME"        # an empty NAME becomes "", not nothing
redis-cli HSET user:1 name "Ada Lovelace"

Quoting keeps an empty value as an empty string (a valid value) and keeps a value with spaces in one piece.

Don’t send variadic commands with nothing in them

Check the list before the call: if there are no keys, skip the MGET or DEL; if there are no fields, skip the HSET. For pairs, build the arguments from a map or a list of pairs rather than a flat list you assemble by hand.

Use the right command

If you meant to run SQL, Redis isn’t the place: it has no tables or SELECT … FROM. SELECT <n> switches the connection to database n.

Reproduce it

Redis 8.10.2 and Valkey 8.1.10 gave the same replies, in database 15:

GET
(error) ERR wrong number of arguments for 'get' command
SET seo:err:k
(error) ERR wrong number of arguments for 'set' command
HSET seo:err:h f
(error) ERR wrong number of arguments for 'hset' command
MSET seo:err:a 1 seo:err:b
(error) ERR wrong number of arguments for 'mset' command
SELECT * FROM users
(error) ERR wrong number of arguments for 'select' command
CONFIG GET
(error) ERR wrong number of arguments for 'config|get' command
SET seo:err:k ''
OK

The last line shows an empty string is a perfectly good value: it’s a missing one that fails. DEL, LPUSH, ZADD, XADD and EVAL with too few arguments got the same error.

From a shell (sign-in options left out), with the variable empty, then set to a name with a space, then quoted:

sh -c 'redis-cli SET seo:err:user:1 $NAME'      # NAME empty
sh -c 'redis-cli SET seo:err:user:1 $NAME'      # NAME="Ada Lovelace"
sh -c 'redis-cli SET seo:err:user:1 "$NAME"'    # NAME="Ada Lovelace"

ERR wrong number of arguments for 'set' command
ERR syntax error
OK

Unquoted, Ada Lovelace became two arguments, and SET read Lovelace as an option, hence a syntax error rather than this one.

From a script, EVAL "return redis.call('GET')" 0:

(error) ERR Wrong number of args calling Redis command from script script: 72273adc3c5955bf8543f1ad6ce893355b89617d, on @user_script:1.

Valkey 8.1.10: ERR Wrong number of args calling command from script, then the same suffix.

In Inlet

Query tabs take redis-cli commands, one a line, and complete command names, namespaces and hash fields as you type. A value with spaces goes in quotes there as in redis-cli. When the server refuses a command, Inlet shows its message and links to this page.

ERR wrong number of arguments for '…' command