I downloaded a large directory (with subdirectories) from http by wget but hidden files (.filename) were left out.How can I download it?EDITED for @dhagI used command: wget --mirror --no-parent https://.../directory  --user=... --password=...I don't know answer on your second question but I can download hidden file in this way wget --mirror --no-parent https://.../directory/.hidden_file_name  --user=... --password=... but the way is very inefficient.
What is a flag to download hidden files by wget?
wget
Dhag's comment is correct. wget download the page with url that is passed in its command line. Well wget may receive arguments like that:wget -r --no-parent http://host/dirand the argument -r means download recursively. But the recursive download does not mean download everything in the directory dir. It means download the page with given url, find all links in the page and download all linked pages.Well the url may lead to a directory on the server. But http server then provides a html page containing links to each file (if directory listing is allowed). The page then contains something like<a href=filename1>filename1</a><p><a href=filename2>filename2</a>The html page may contains other info like file sizes, file types, owners and so on. But all information is generated on the server side and clients like wget can just parse the information provided by server and follow links listed in the page with this 'directory listing'.So if a file is hidden and it is not listed in the directory listing it is a server decision and you cannot force server to provides more information via a wget parameter. Nevertheless you are not out of luck. Most of http server may be configured and administrator may decide what files are hidden. For example the apache server has a configuration option IndexIgnore and it contains patterns of file that should be hidden. 