FUNCTION LOAD

Load a library to Valkey.

The command receives a single mandatory parameter which is the source code that implements the library. The library payload must start with Shebang statement that provides a metadata about the library (like the engine to use and the library name). Shebang format: #!<engine name> name=<library name>. Currently engine name must be lua.

For the Lua engine, the implementation should declare one or more entry points to the library with the server.register_function() API. Once loaded, you can call the functions in the library with the FCALL (or FCALL_RO when applicable) command.

When attempting to load a library with a name that already exists, the Valkey server returns an error. The REPLACE modifier changes this behavior and overwrites the existing library with the new contents.

The command will return an error in the following circumstances:

• An invalid engine-name was provided.
• The library's name already exists without the REPLACE modifier.
• A function in the library is created with a name that already exists in another library (even when REPLACE is specified).
• The engine failed in creating the library's functions (due to a compilation error, for example).
• No functions were declared by the library.

For more information please refer to Introduction to Valkey Functions.

Examples

The following example will create a library named mylib with a single function, myfunc, that returns the first argument it gets.

127.0.0.1:6379> FUNCTION LOAD "#!lua name=mylib \n server.register_function('myfunc', function(keys, args) return args[1] end)"
mylib
127.0.0.1:6379> FCALL myfunc 0 hello
"hello"

RESP2/RESP3 Reply

Bulk string reply: the library name that was loaded.