rsync is a useful program of the Linux shell to perform backup copies, both local and remote
In this example, rsync is used to copy file with specific extensions (i.e., html, css, jpg, gif and png) from the folder with name www to the folder with name www_backup. The directories tree in www is copied as is in www_backup.
rsync -avm --include='*.html' --include='*.css' --include '*.jpg' --include '*.gif' --include '*.png' --filter 'hide,! */' www www_backup
the option –filter 'hide,! */' means to hide anything that is not (!) a directory (*/). The option –filter has lower precedence than the –include options, so this rule excludes all the file with the exception of the files reported in the –include options.