LuaJIT checking user and group exists

example.lua

local ffi = require("ffi")
local C = ffi.C


ffi.cdef([[
struct group *getgrnam(const char *name);
struct passwd *getpwnam(const char *name);
]])


if C.getpwnam("kong") == nil then
    print("kong user does not exist")

else
    print("kong user exists")
end

if C.getpwnam("root") == nil then
    print("root user does not exist")

else
    print("root user exists")
end


if C.getgrnam("kong") == nil then
    print("kong group does not exist")

else
    print("kong group exists")
end

if C.getgrnam("root") == nil then
    print("root group does not exist")

else
    print("root group exists")
end