How to dissect and parse a string in lua?

Question

I am trying to make command arguments in Roblox. For example, /kill playername. The problem is I don\'t know how to parse the playername from the string /kill

Answer 1

If you want this to be more flexible to more commands in the future, I suggest you take both lhf's and BotOfWar's suggestions and combine them.

local function executeCommandInMessage(message)
    -- do a quick regex of the message to see if it is formatted as a command
    -- all we care about is the command, any arguments are optional.
    local command, arguments = string.match(message, "^/(%w+)[%s]?([%w%s]+)$")

    if command ~= nil then
        -- we've found a command, parse the arguments into groups of non-space characters
        -- then store each word in the parts array
        local parts = {}
        for w in arguments:gmatch("%S+") do
            table.insert(parts, w)
        end

        -- handle each command individually
        if command == "kill" then
            local player = parts[1]
            print(string.format("Killing %s", player))

        elseif command == "setdata" then
            local player = parts[1]
            local value = parts[2]
            local amount = parts[3]
            print(string.format("Setting %s on %s to %s", value, player, amount))

        -- add any further commands to the list..
        -- elseif command == "" then
        end
    end
end


-- listen for any message submitted by players
game:GetService("Players").PlayerAdded:Connect(function(Player)
    Player.Chatted:Connect(function(msg)
        -- check for any commands
        executeCommandInMessage(msg)
    end)
end)

In the future, if you need a better regex to parse the message, I suggest you take a look at how to do Lua pattern matching. They're pretty easy to read once you know what to look at.

Answer 2

I suggest splitting the string with the string.split method to get the segments, then check if the first value is what you want.

game:GetService("Players").PlayerAdded:Connect(function(Player)
    Player.Chatted:Connect(function(Message)
        local segments = Message:split(" ")
        if((#segments >= 1) and (segments[1] == "/kill")) then
            -- The rest of the arguments can be accessed like this:
            local args = {unpack(segments, 2)} -- Gets every argument after the first value,
            -- which is the command.
        end
    end)
end)

Answer 3

Use string.match:

Message=" /kill playername  "
command, arg = Message:match("%s*/(.-)%s+(.*)%s*$")