なぜかちょっと見つけるのに時間かかったため自分用メモ。。。
2.13 Exit Status
Wget may return one of several error codes if it encounters problems.
0 No problems occurred.
1 Generic error code.
2 Parse error—for instance, when parsing command-line options, the ‘.wgetrc’ or ‘.netrc’...
3 File I/O error.
4 Network failure.
5 SSL verification failure.
6 Username/password authentication failure.
7 Protocol errors.
8 Server issued an error response.