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 playername. This code is in something like this:

game:GetService("Players").PlayerAdded:Connect(function(Player)
    Player.Chatted:Connect(function(Message)
        if string.sub(1, #Message) == "/kill " then
            --this means the string starts with /kill and is expecting an argument. 
            --How can I parse this argument from the string
        end
    end)
end)

Edit: I want to add /setdata <Playername> <DataToChange eg. money> <Value> Example command:

/setdata MyRobloxUsername Money 10000

I am trying to use something like this to do so

local Command, Playername, DataToChange, Value = string.match(???)

I just need to get the values from the string into variables. I can figure out how to change the data using the variables myself. Just how to get the values from the string. How can I do what I am describing?

I unaccepted the answer because I need further help. Once I get this help I will re accept it. My next request is similar, but with 3 arguments instead of 1. I need help as string:Match() is very counter intuitive to me

score 2 · Answer 1 · answered Sep 05 '19 at 18:56

2

Use string.match:

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

answered Sep 05 '19 at 18:56

lhf

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2

This is not an extensible solution. @JulianTiemann I suggest you use a [string split](https://stackoverflow.com/questions/1426954/split-string-in-lua) equivalent that will put separate words in a table. – BotOfWar Sep 08 '19 at 02:41

score 0 · Accepted Answer · answered Sep 17 '19 at 21:03

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.

This solution has trouble with commands that do not have arguments. Things like '/nukeAll' will not parse properly. — Kylaaa, Sep 17 '19 at 22:38

score -1 · Answer 3 · answered Oct 04 '19 at 05:02

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)

I would upvote but I lost all my 30 reputation for "rude or abusive" — , Oct 04 '19 at 22:18

How to dissect and parse a string in lua?

3 Answers3