lftp 2.0 and later support loading modules (shared objects) at runtime. Use command `module' to load a module. It also supports loading certain modules (some of protocols and commands) automatically on demand. To compile modular lftp use: configure --with-modules You will need GCC and ELF platform (linux, freebsd-3.x, solaris, irix etc). Below are the technical details. Module is a shared object, after loading it with dlopen(3) lftp does dlsym("module_init") and calls this function with parameters argc, argv: extern "C" void module_init(int argc, const char * const *argv); The argv vector contains the arguments passed to `module' command after module name. In case of loading module on demand it is empty. Note: function _init of a module is called automatically by dlopen. It can execute constructors if the module is properly compiled with `gcc -shared'. To load modules on demand lftp uses protocol or command name to find module file. For protocols it looks for proto-<PROTOCOL>.so and for commands -- cmd-<COMMAND>.so. The modules register the protocols and commands they provide with functions FileAccess::Register and CmdExec::RegisterCommand. lftp searches module for any protocol specified in URL in open command, and only for certain compile time defined set of commands -- the commands that have NULL instead of function pointer in command table in commands.cc.