是否有可能linux文件描述符0 1 2不适用于stdin，stdout和stderr？

When a program begins, does it take file descriptors 0, 1 and 2 for stdin, stdout and stderr by default?. And will API calls such as open(...), socket(...) not return 0, 1 and 2 since these values are already taken?. Is there any case in which open(...) or socket(...) would return 0, 1 or 2. And 0, 1 and 2 are not related with stdin, stdout, and stderr.When a program begins, does it take file descri