Loading randomly selected strings from a file

Writing a script for multiple choice questions, i have a questions.db file that holds the question. There are 10 plus in the quesitons.db file. I want to choose 5 random questions in random order. Any pointers? I'm an advid php programmer but new to lua.

thanks for the help in advance!

Split into new topic.

Please don't post questions on unrelated ancient threads.

You can use the fs api to read individual lines into an table. Then select random indexes of that table, checking for duplicates.

local file = fs.open("questions.db", "r")
local line = file:readLine()
local lines = { }
while line do
  table.insert(lines, line)
  line = file:readLine()
end
file:close()
local selectedLines = { }
while #selectedLines < 5 do
  local index = math.random(#lines)
  if lines[index] ~= "" then
    table.insert(selectedLines, lines[index])
    lines[index] = ""
  end
end

You can use this piece of code to load 5 random questions (no duplicates) into the table selectedLines from the file questions.db (assuming the functions are put into seperate lines)

That should work, but just a tip, you could shrink this:

local line = file:readLine()
local lines = { }
while line do
  table.insert(lines, line)
  line = file:readLine()
end

… down to this:

local lines = { }
for line in file.readLine do table.insert(lines, line) end

Bomb Bloke, on 19 March 2015 - 11:38 PM said:

That should work, but just a tip, you could shrink this:

local line = file:readLine()
local lines = { }
while line do
  table.insert(lines, line)
  line = file:readLine()
end

… down to this:

local lines = { }
for line in file.readLine do table.insert(lines, line) end

Wow I didn't know you could do that, thanks!

to use file:lines(), you have to use io.open instead of fs.open when opening the file. lines is a convenience added by the io wrapper, not present directly on the underlying fs file objects.

Just realised bombbloke didn't do file:lines(), he just did file.readline. Which probably works, now that I think about it. Huh. Disregard.