The ftp and file schemes are defined in RFC 1808. The
url library treats ‘ftp:’ and ‘file:’ as synonymous.
Such URLs have the form
ftp://user:password@host:port/file file://user:password@host:port/file
If the URL specifies a local file, it is retrieved by reading the file contents in the usual way. If it specifies a remote file, it is retrieved using either the Tramp or the Ange-FTP package. See Remote Files in The GNU Emacs Manual.
When retrieving a compressed file, it is automatically uncompressed
if it has the file suffix .z, .gz, .Z,
.bz2, or .xz. (The list of supported suffixes is
hard-coded, and cannot be altered by customizing
jka-compr-compression-info-list.)