COMMAND INFO

Introduction

The COMMAND INFO command is used to retrieve detailed information about one or more specified commands in the DiceDB server. For each command, it returns an array containing the command’s name, arity (number of arguments), command flags, and key-related information.

Syntax

COMMAND INFO command-name [command-name ...]

Parameters

Parameter	Description	Type	Required
command-name	The name of the command for which information is requested.	String	No

Return Values

Condition	Return Value
Command is successful	Array containing detailed information about the specified commands.
Error	An error is returned if the command fails.

The detailed information for each command includes the following fields:

• Command Name: The name of the command.
• Arity: An integer representing the number of arguments the command expects.
  • A positive number indicates the exact number of arguments.
  • A negative number indicates that the command accepts a variable number of arguments.
• Flags (Note: Not supported currently) : An array of flags that describe the command’s properties (e.g., readonly, fast).
• First Key: The position of the first key in the argument list (0-based index).
• Last Key: The position of the last key in the argument list.
• Key Step: The step between keys in the argument list, useful for commands with multiple keys.

The structure of the returned data is as follows:

[
  [
    "command-name",
    arity,
    [
      "flag1",
      "flag2",
      ...
    ],
    first-key,
    last-key,
    key-step
  ],
  ...
]

Behavior

The COMMAND INFO command retrieves detailed information about one or more specified commands in the DiceDB server. The command operates as follows:

1. Input Arguments: The command takes a variable number of arguments, where each argument is expected to be the name of a command for which information is requested.
2. Default Behavior: If no command names are provided, the command will return default information about all available commands.
3. Command Metadata Retrieval: The command iterates over the predefined command metadata (DiceCmds) and stores the metadata in a map for quick lookup.
4. Command Name Lookup: For each provided command name, the command checks if it exists in the metadata map:
   • If the command exists, its metadata is appended to the result list.
   • If the command name is incorrect or not supported nil is appended in its place to indicate the absence of valid information.
5. Result Encoding: Finally, the result list, which contains the metadata for the valid command names and nil for any invalid ones, is encoded and returned as the output.

Errors

1. Arity Error
   • Error Message: (error) ERR wrong number of arguments for 'command|info' command
   • Occurs when an incorrect number of arguments is provided to the COMMAND INFO command.

Example Usage

Get command info for SET and MGET

127.0.0.1:7379> COMMAND INFO SET MGET
1) 1) "SET"
   2) (integer) -3
   3) (integer) 1
   4) (integer) 0
   5) (integer) 0
2) 1) "MGET"
   2) (integer) -2
   3) (integer) 1
   4) (integer) -1
   5) (integer) 1

Usage Example when mixture of valid and invalid commands

In this example, we request information for two commands: one valid (SET) and one invalid (UNKNOWNCOMMAND).

127.0.0.1:7379> COMMAND INFO SET UNKNOWNCOMMAND
1) 1) "SET"
   2) (integer) -3
   3) (integer) 1
   4) (integer) 0
   5) (integer) 0
2) (nil)

Incorrect Usage

An error is thrown when the command name passed to the COMMAND INFO command is incorrect or not supported in DiceDB.

127.0.0.1:7379> COMMAND INFO UNKNOWNCOMMAND
1) (nil)

Note:

1. If a valid command name is specified, its corresponding metadata is returned.
2. If a command name is incorrect or not supported, nil is returned in its place.