Function io_popen

deps/lua/src/liolib.c:174–180

** this function has a separated environment, which defines the ** correct __close for 'popen' files */

** correct __close for 'popen' files
*/
static int io_popen (lua_State *L) {
  const char *filename = luaL_checkstring(L, 1);
  const char *mode = luaL_optstring(L, 2, "r");
  FILE **pf = newfile(L);
  *pf = lua_popen(L, filename, mode);
  return (*pf == NULL) ? pushresult(L, 0, filename) : 1;
}


static int io_tmpfile (lua_State *L) {