The documents will not be written to the appropriate files, but all will be concatenated together
and written to file. If - is used as file, documents will be printed to standard output,
disabling link conversion. (Use ./- to print to a file literally named -.)
Use of -O is not intended to mean simply "use the name file instead of the one in the URL;"
rather, it is analogous to shell redirection: wget -O file http://foo is intended to work like
wget -O - http://foo > file; file will be truncated immediately, and all downloaded content will
be written there.