thanks to sourceforge, here is a url from soruceforge net,
http://images.sourceforge.net/icons/silk/feed.png has a Last-Modified header of 'Tue, 05 Dec 2006 19:10:40 GMT' consider these two command: 1, wget -N -O dir/feed.png \ http://images.sourceforge.net/icons/silk/feed.png wget -N -O feed.png \ http://images.sourceforge.net/icons/silk/feed.png 2, wget -N \ http://images.sourceforge.net/icons/silk/feed.png 1: target file always downloaded if there is no file named 'feed.png' in current working directory. if there is a file named 'feed.png' in current working dir., then wget will check that file, and if that file is same as target, no download happens. but wget is supposed to check `dir/feed.png', not `$PWD/feed.png', could this be a bug? 2: target is downloaded only once. mtime, ctime and atime of local file remain its first download time, that is, wget dont always `open()' local file , it just `stat()' that file. if `-O' option is given, then wget always open local file, truncate it to zero length, the result is target downloaded as many times as wget run. i guess even with `-O' option, wget should check local file first, instead of truncate it for every run. the case of given muiltiple Urls and single `-O' is rare, and maybe not clearly stated in the manual.
