Exercising gethostbyname with LuaJIT FFI

gethostbyname.lua

#!/usr/bin/luajit

local ffi = require 'ffi'

ffi.cdef([[
struct hostent {
    char  *h_name;            /* official name of host */
    char **h_aliases;         /* alias list */
    int    h_addrtype;        /* host address type */
    int    h_length;          /* length of address */
    char **h_addr_list;       /* list of addresses */
};
struct hostent *gethostbyname(const char *name);

struct myaddr { uint8_t b1, b2, b3, b4; }; 
]])

if #arg == 0 then
    io.stderr:write('usage: gethost_test hostname [hostname2] [...]\n')
    os.exit(-1)
end

for _, name in ipairs(arg) do
    local hostent = ffi.C.gethostbyname(tostring(name))
    if hostent == nil then
        io.stdout:write(name, ': NONE FOUND\n')
     else
        io.stdout:write(name, ': "', ffi.string(hostent.h_name), '" : [ ')
        local i = 0
        while i < (hostent.h_length / 4) do
            local myaddr = ffi.cast('struct myaddr*', hostent.h_addr_list[i])
            io.stdout:write(string.format('%d.%d.%d.%d ',
                                          myaddr.b1, myaddr.b2, myaddr.b3, myaddr.b4))
            i = i + 1
         end
         io.stdout:write(' ]\n')
    end
end

very good