Check values in txt

Question

Well, I want to save a value in a txt file, checking if there is already some value with 2 similar things. Ex:

local file = io.open("arquivo.txt", "a+")
local oi = {dia=os.date(), numero=math.random(1,10)}
if not () then -- Aqui não sei o que fazer, quero checar se no txt ja tem alguma linha com o valor numero igual a 'oi.numero', se não tiver, salva.
file:write("Data: "..oi.dia.." - Numero:"..oi.numero)
file:close()
end

Answer 1

For starters, io open. returns a Handle to the file (you are currently throwing it away)

local fil, err = io.open("arquivo.txt", "a+")
if not fil then error(err) end

After that, you can use the method Lines to traverse the lines:

for line in fil:lines() do
    -- ...
end

For each line, you will need to do a bit of string manipulation to see if the line contains the number. In your case, the most direct way would be to use the function string match., which is somewhat similar to regular expressions in other programming languages.

local n = string.match(line, "Numero:(%d+)")
if n and tonumber(n) == oi.numero then
   -- achei o número
end

---

If you need to analyze the date you can do something like

local date, n = string.match(line, "Data: (.-) Numero:(%d+)")
if date then
    -- o pattern bateu
    fazAlgoCom(date, n)
else
    -- o pattern não bateu
end

The (.-) means "0 or more any characters, as little as necessary".

However, from this point forward things start to get more complicated. I would prefer to use a more structured storage format, such as CSV, JSON or a "Luaon" of life (JSON type, but with Lua syntax). Gets more robust (for example, your current version will break if any field has a line break) and you can use some library ready to handle the work of reading and printing the strings in the right format.