Lua fork parallel processes

Question

I want to execute background processes at the same time from lua script

like:

a = io.popen("deploy.exp" .. ip1):read("*a") b = io.popen("deploy.exp" .. ip2):read("*a") 

where a, b are constantly running processes. When I do this as above, b will only start after completion. And deploy.exp script is a wait script that was used for several ssh servers and executed some commands. Then I need to get some text from a and b. Any ideas on this? I tried ExtensionProposal API. When I tried, I got one error message: " * detected glibc free (): invalid next size (fast): 0x08aa2300 ** abort".

Part Code

 for k,v in pairs(single) do command = k .. " 1 " .. table.concat(v, " ") local out = io.pipe() local pro = assert(os.spawn("./spaw.exp " .. command,{ stdout = out, })) if not proc then error("Failed to aprogrinate! "..tostring(err)) end print(string.rep("#", 50)) local exitcode = proc:wait() end 

Does anyone have any experience (or advice / where we should look) with this? or give me a sample? Thanks

BTW: I tried luaposix, but I can not find any posix.fork () sample. Can anyone share this? Tks

Answer 1

posix.fork () is part of the luaposix library , which can be installed via luarocks . It works in much the same way as fork (3) ; it creates a copy of the parent process, and both of them will do everything after calling fork (). The return value of fork () is 0 in the child process, otherwise it is the PID of the child that was just spawned. Here's a far-fetched example:

 local posix = require "posix" local pid = posix.fork() if pid == 0 then -- this is the child process print(posix.getpid('pid') .. ": child process") else -- this is the parent process print(posix.getpid('pid') .. ": parent process") -- wait for the child process to finish posix.wait(pid) end -- both processes get here print(posix.getpid('pid') .. ": quitting") 

This should print something like the following:

 $ lua fork.lua 27219: parent process 27220: child process 27220: quitting 27219: quitting 

Answer 2

You might want to try Lua Lanes (or here ), which is a portable thread library for Lua.