| Code Sample |
| ----------------------------------------------------------------------------- -- Little program to download files from URLs -- LuaSocket sample files -- Author: Diego Nehab -- Extended to add resume by ^thehatsrule^ -- RCS ID: $Id: get.lua,v 1.25 2007/03/12 04:08:40 diego Exp $ ----------------------------------------------------------------------------- local socket = require("socket") local http = require("socket.http") local ftp = require("socket.ftp") local url = require("socket.url") local ltn12 = require("ltn12") local lfs = require("lfs") -- formats a number of seconds into human readable form function nicetime(s) local l = "s" if s > 60 then s = s / 60 l = "m" if s > 60 then s = s / 60 l = "h" if s > 24 then s = s / 24 l = "d" -- hmmm end end end if l == "s" then return string.format("%5.0f%s", s, l) else return string.format("%5.2f%s", s, l) end end -- formats a number of bytes into human readable form function nicesize(b) local l = "B" if b > 1024 then b = b / 1024 l = "KB" if b > 1024 then b = b / 1024 l = "MB" if b > 1024 then b = b / 1024 l = "GB" -- hmmm end end end return string.format("%7.2f%2s", b, l) end -- returns a string with the current state of the download local remaining_s = "%s received, %s/s throughput, %2.0f%% done, %s remaining" local elapsed_s = "%s received, %s/s throughput, %s elapsed " function gauge(got, delta, size) local rate = got / delta if size and size >= 1 then return string.format(remaining_s, nicesize(got), nicesize(rate), 100*got/size, nicetime((size-got)/rate)) else return string.format(elapsed_s, nicesize(got), nicesize(rate), nicetime(delta)) end end -- creates a new instance of a receive_cb that saves to disk -- kind of copied from luasocket's manual callback examples function stats(size) local start = socket.gettime() local last = start local got = 0 return function(chunk) -- elapsed time since start local current = socket.gettime() if chunk then -- total bytes received got = got + string.len(chunk) -- not enough time for estimate if current - last > 1 then io.stderr:write("\r", gauge(got, current - start, size)) io.stderr:flush() last = current end else -- close up io.stderr:write("\r", gauge(got, current - start), "\n") end return chunk end end -- determines the size of a http file function gethttpsize(u) local r, c, h = http.request {method = "HEAD", url = u} if c == 200 then return tonumber(h["content-length"]) end end -- downloads a file using the http protocol function getbyhttp(u, file, sz) local save = ltn12.sink.file(file or io.stdout) local size2get = gethttpsize(u) if not size2get then io.stderr:write("Error contacting remote host.") --if not sz then do_something() end os.exit(0) end if size2get == sz then print("File already completed.") os.exit(0) end -- only print feedback if output is not stdout if file then save = ltn12.sink.chain(stats(size2get), save) end local hdrs if sz then -- resume header hdrs = { ["Range"] = "bytes=" .. sz .."-" } end local r, c, h, s = http.request {url = u, sink = save, headers = hdrs } -- todo: check for 206; fallback? if c ~= 200 then io.stderr:write(s or c, "\n") end end -- downloads a file using the ftp protocol function getbyftp(u, file, sz) local save = ltn12.sink.file(file or io.stdout) -- only print feedback if output is not stdout -- and we don't know how big the file is -- todo: can use SIZE file to get file size, but is not RFC -- would probably be easier to do 2 ftp sessions if file then save = ltn12.sink.chain(stats(), save) end local gett = url.parse(u) gett.sink = save gett.type = "i" if sz then -- try to resume; fallback? -- filler command (see below) + restart offset + retrieve file -- bug? having REST first will return 350, ftp.get returns early gett.command = 'SYST' .. '\n' .. 'REST ' .. sz .. '\nRETR' end local ret, err = ftp.get(gett) if err then print(err) end end -- determines the scheme function getscheme(u) -- this is an heuristic to solve a common invalid url poblem if not string.find(u, "//") then u = "//" .. u end local parsed = url.parse(u, {scheme = "http"}) return parsed.scheme end -- gets a file either by http or ftp, saving as <name> -- todo: check filesize etc before opening file function get(u, name) if not name then -- use the basename from the url, assuming no spaces -- better to exec `basename` instead? name = string.gsub(u, '.*/', "") -- todo: change this if not name then name = os.tmpname() print ("Using " .. name .. " to store data") end end local sz = lfs.attributes(name, "size") local mode if sz then print ("File " .. name .. " found with a size of " .. sz) print ("Trying to resume ...") mode = "a+b" else mode = "wb" end local fout = name and io.open(name, mode) local scheme = getscheme(u) if scheme == "ftp" then getbyftp(u, fout, sz) elseif scheme == "http" then getbyhttp(u, fout, sz) else print("unknown scheme" .. scheme) end end -- main program arg = arg or {} if table.getn(arg) < 1 then io.write("Usage:\n lua get.lua <remote-url> [<local-file>]\n") os.exit(1) else get(arg[1], arg[2]) end |