%(extractor)s for the provider (youtube, metacafe,
etc), %(id)s for the video id and %% for a literal
percent. Use - to output to stdout.
+ --restrict-filenames Avoid some characters such as "&" and spaces in
+ filenames
-a, --batch-file FILE file containing URLs to download ('-' for stdin)
-w, --no-overwrites do not overwrite files
-c, --continue resume partially downloaded files