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Repository Details

Lua binding to libcurl

Lua binding to libcurl

Build Status Build status Coverage Status Licence


This module include three layer

  1. lcurl module provide low level pure C binding to libcurl.
    Almost ready and needs tests. I have no plans to change this API.

  2. cURL module provide compatibility for Lua-cURLv2 API.
    Almost ready and needs tests.

  3. cURL module provide new high level API.
    In fact for now it provide lcurl API directly and needed to redesign.


lcurl API
Lua-cURLv2 API
Lua-cURLv3 API

Original Lua-cURLv2 binding has several problems:

  • it can not return error codes but just raise Lua errors (Fixed. use cURL.safe module)
  • it raise Lua error from callback that may result resource leak in libcurl (Fixed.)
  • it does not provide building multipart/formdata explicitly (Fixed.)
  • it has memory leak when send multipart/formdata (Fixed.)
  • it does not save string for curl options that may result crush in libcurl (Fixed.)
  • there no way to get result for operations in multi interface (e.g. if one of easy operation fail you can not get result code/error message) (Fixed. But it does not very handy interface.)
  • you can not use your own callback function to perform operation with multi interface (Could not be fixed without changing API.)
  • you can not pass your context to callback functions (Could not be fixed without changing API.)


Using LuaRocks:

luarocks install Lua-cURL

Install current master:

luarocks install Lua-cURL --server=https://luarocks.org/dev

List of incompatibility with original Lua-cURLv2

  • objects are tables
  • multi:perform() also returns ("done",code), ("error",error) and ("response",code) records
  • writer callback does not recv string len (just string itself)
  • on Lua > 5.2 errors are objects but not strings


-- HTTP Get
    url = 'http://httpbin.org/get',
    httpheader = {
      "X-Test-Header1: Header-Data1",
      "X-Test-Header2: Header-Data2",
    writefunction = io.stderr -- use io.stderr:write()
-- HTTP Post
  :setopt_httppost(curl.form() -- Lua-cURL guarantee that form will be alive
    :add_content("test_content", "some data", {
      "MyHeader: SomeValue"
    :add_buffer("test_file", "filename", "text data", "text/plain", {
      "Description: my file description"
    :add_file("test_file2", "BuildLog.htm", "application/octet-stream", {
      "Description: my file description"
-- FTP Upload
local function get_bin_by(str,n)
  local pos = 1 - n
  return function()
    pos = pos + n
    return (str:sub(pos,pos+n-1))

  :setopt_url("ftp://moteus:[email protected]/test.dat")
    get_bin_by(("0123456789"):rep(4), 9)
-- Multi FTP Upload

-- We get error E_LOGIN_DENIED for this operation
e1 = curl.easy{url = "ftp://moteus:[email protected]/test1.dat", upload = true}
    function(t) return table.remove(t) end, {"1111", "2222"}

e2 = curl.easy{url = "ftp://moteus:[email protected]/test2.dat", upload = true}
  :setopt_readfunction(get_bin_by(("e"):rep(1000), 5))

m = curl.multi()

while m:perform() > 0 do m:wait() end

while true do
  h, ok, err = m:info_read()
  if h == 0 then break end

  if h == e1 then 
    assert(ok == nil)
    assert(err:name() == "LOGIN_DENIED")
    assert(err:no() == curl.E_LOGIN_DENIED)

  if h == e2 then 
    assert(ok == true)