int sqlite3_system_errno(sqlite3*);
Attempt to return the underlying operating system error code or error number that caused the most recent I/O error or failure to open a file. The return value is OS-dependent. For example, on unix systems, after sqlite3_open_v2() returns SQLITE_CANTOPEN, this interface could be called to get back the underlying "errno" that caused the problem, such as ENOSPC, EAUTH, EISDIR, and so forth.