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✓ ANSWER ACCEPTED

What do you do to fix this string manipulation "match" returning nil?

Asked 463 views1 answers

Here's my script:

Players.PlayerAdded:Connect(function(plr)
	plr.Chatted:Connect(function(msg)
		-- Check for admin here.
		if(msg:sub(1,1)=="/")then
			local command, arg1, arg2 = msg:match("^%/(%S+)%s+(%a+)%s(.+)$")
			
			print(command)
			print(arg1)
			print(arg2)
		end
	end)
end)

Everything's fine, I define the service Players elsewhere but if I added it this would be a standalone script.

The area of problem is here:

local command, arg1, arg2 = msg:match("^(%S+)%s+(%a+)%s(.+)$")

And it works like I want it to. Examples:

"/displayMessage all Hey guys!"

print(command) -- displayMessage
print(arg1) -- all
print(arg2) -- Hey guys!

However some commands will only require two arguments, but then everything's nil.

"/kill me"

print(command)  -- nil
print(arg1)     -- nil
print(arg2)     -- nil

How could I fix this?

This code is mostly from one of my past questions.

I modified Blue's solution a little to fit my new situation here, but I'm still really bad with string manipulation. :c

Thanks for any help!

AnonymousEdited

1 answer

✓ Accepted answer

With string.match nil will be returned if there is no capture found / matched.

For an admin script it might be best to build a argument table as this will support a ever changing amount or args ie one function to manage them all.

I find that it can simplify an admin script to just check for the admin command prefix in your case the / then cut out the prefix.

-- we should also check the string size before
if msg:sub(1,1) == '/' then
	msg = msg:sub(2) -- remove the prefix
end

Now that we no longer have the prefix we can split the string using the white space followed by a varying number of characters ie [o or more white space characters] [as many non white space characters as possible]

We can represent this as a string pattern like so %S-(%a+).

But this will not capture any players with any numbers or commands with punctuation in so we need a set resulting in our finished pattern %S-([%a%d%p]+)

Example:-

local testData = {
	'/kill me ??',
	'/ kill me ??',
	'/kill me',
	'/   kill   me',
	'/kill',
	'/ kill ',
	'adsa',
	'/displayMessage all Hey guys!',
	'a',
	'/kill guest11',
	'/kill me!!'
}

for i=1, #testData do
	print('--------- Test ' .. tostring(i) .. ' -----------')
	local msg = testData[i]
	if msg:sub(1,1) == '/' then
		msg = msg:sub(2)
		for c in msg:gmatch('%S-([%a%d%p]+)') do
			print(c, #c)
		end
	end
end

Output:-

--[[
--------- Test 1 -----------
kill 4
me 2
?? 2
--------- Test 2 -----------
kill 4
me 2
?? 2
--------- Test 3 -----------
kill 4
me 2
--------- Test 4 -----------
kill 4
me 2
--------- Test 5 -----------
kill 4
--------- Test 6 -----------
kill 4
--------- Test 7 -----------
--------- Test 8 -----------
displayMessage 14
all 3
Hey 3
guys! 5
--------- Test 9 -----------
--------- Test 10 -----------
kill 4
guest11 7
--------- Test 11 -----------
kill 4
me!! 4
]]

I hope this helps

AnonymousEdited Permalink

2 comments

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<3

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:3

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