Random strings in Lua

string.random.lua

math.randomseed(os.time())

local charset = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890"

function string.random(length)
  if length > 0 then
    return string.random(length - 1) .. charset:sub(math.random(1, #charset), 1)
  else
    return ""
  end
end

One may prefer math.randomseed(os.clock()^5) for better entropy.

thank you very much. I shortened it a little

local charset = {}  do -- [0-9a-zA-Z]
    for c = 48, 57  do table.insert(charset, string.char(c)) end
    for c = 65, 90  do table.insert(charset, string.char(c)) end
    for c = 97, 122 do table.insert(charset, string.char(c)) end
end

local function randomString(length)
    if not length or length <= 0 then return '' end
    math.randomseed(os.clock()^5)
    return randomString(length - 1) .. charset[math.random(1, #charset)]
end

I made my own, its shorter and does the same thing:

function RandomVariable(length)
	local res = ""
	for i = 1, length do
		res = res .. string.char(math.random(97, 122))
	end
	return res
end

Oh, mysterious, you should set the random seed, it generates the same hash every time...

The calling stack would be too deep if length is great enough.
Be cautious abt the danger of stack overflow.

@mysterious4579 's solution might be better.
Thanks anyway.

math.randomseed(os.time())
local character_set = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

local string_sub = string.sub
local math_random = math.random
local table_concat = table.concat
local character_set_amount = #character_set
local number_one = 1
local default_length = 10

local function generate_key(length)
    local random_string = {}

    for int = number_one, length or default_length do
        local random_number = math_random(number_one, character_set_amount)
        local character = string_sub(character_set, random_number, random_number)

        random_string[#random_string + number_one] = character
    end

    return table_concat(random_string)
end

math.randomseed(os.time())
local character_set = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"

local string_sub = string.sub
local math_random = math.random
local table_concat = table.concat
local character_set_amount = #character_set
local number_one = 1
local default_length = 10

local function generate_key(length)
    local random_string = {}

    for int = number_one, length or default_length do
        local random_number = math_random(number_one, character_set_amount)
        local character = string_sub(character_set, random_number, random_number)

        random_string[#random_string + number_one] = character
    end

    return table_concat(random_string)
end

thank you psu man

local charset = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890"
math.randomseed(os.clock())
function randomString(length)
	local ret = {}
	local r
	for i = 1, length do
		r = math.random(1, #charset)
		table.insert(ret, charset:sub(r, r))
	end
	return table.concat(ret)
end

A small improvement over simplicity and speed

pseudo random, but super fast:

for i = 1, 10 do
	print( tostring({}):sub(10) )
end

40ae13c8
406c0640
41954060
41a91220
40ae1ac8
4195b718
41958260
41a3ea10
41a3acf0
41a3a978

local sets = {{97, 122}, {65, 90}, {48, 57}} -- a-z, A-Z, 0-9
local function string_random(chars)
	local str = ""
	for i = 1, chars do
		math.randomseed(os.clock() ^ 5)
		local charset = sets[ math.random(1, #sets) ]
		str = str .. string.char(math.random(charset[1], charset[2]))
	end
	return str
end

abc = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","r","s","t","u","v","z","y","w","q","1","2","3","4","5","6","7","8","9","0"}
local string = ""
function GeneratedString() 
    for i=1,35 do
        rdm = math.random(1,35)
        string = string..abc[rdm]
    end
    return string
end