Function io_lines

3rd/lua-5.4.3/src/liolib.c:386–410

** Return an iteration function for 'io.lines'. If file has to be ** closed, also returns the file itself as a second result (to be ** closed as the state at the exit of a generic for). */

** closed as the state at the exit of a generic for).
*/
static int io_lines (lua_State *L) {
  int toclose;
  if (lua_isnone(L, 1)) lua_pushnil(L);  /* at least one argument */
  if (lua_isnil(L, 1)) {  /* no file name? */
    lua_getfield(L, LUA_REGISTRYINDEX, IO_INPUT);  /* get default input */
    lua_replace(L, 1);  /* put it at index 1 */
    tofile(L);  /* check that it's a valid file handle */
    toclose = 0;  /* do not close it after iteration */
  }
  else {  /* open a new file */
    const char *filename = luaL_checkstring(L, 1);
    opencheck(L, filename, "r");
    lua_replace(L, 1);  /* put file at index 1 */
    toclose = 1;  /* close it after iteration */
  }
  aux_lines(L, toclose);  /* push iteration function */
  if (toclose) {
    lua_pushnil(L);  /* state */
    lua_pushnil(L);  /* control */
    lua_pushvalue(L, 1);  /* file is the to-be-closed variable (4th result) */
    return 4;
  }
  else
    return 1;
}


/*