RE: File protocol host need not be limited to "localhost"
Charles C. Fu (ccwf@bacchus.com)
Wed, 15 Jul 1998 03:32:25 -0700 (PDT)
Jeff Kowalski writes:
> Was a decision reached on this proposal?
Which was a follow-up to an earlier message in which he wrote:
>> [under Windows] it's perfectly legal while on host "foo" to request
>> file://server/folder/item. On Win32, and on other systems, this
>> requests the "item" stored in "folder" on the "server" machine. On
>> Win32, it magically works.
Actually, it is illegal but happens to work with Explorer, does not
work with Netscape under Windows, and may or may not work with other
Windows clients.
In general, the exact details of file URL handling is up to the client
you're using. It's pretty uniform on UNIX systems but is NOT uniform
amongst Windows clients. In particular, Netscape and Explorer handle
file URLs differently under Windows. Here are some examples:
- Netscape correctly handles escapes (like file:///c%3A/ for the
C drive), but Explorer does not.
- Netscape allows file:/// (which is empty), but Explorer does not.
- Explorer allows file:///\\remotehost\share\
and file:////remotehost/share/, but Netscape does not.
I'm sure there are other differences.
[Windows Examples]
> file://c:/temp/test.txt => open (FH, "c:/temp/test.txt");
> file://c:\temp\test.txt => open (FH, "c:\\temp\\test.txt");
> file://localhost/c:/temp/test.txt => open (FH, "c:/temp/test.txt");
> file://remotehost/c:/temp/test.txt is not legal
Only the localhost example above is technically legal since host
portions of file URLs must be fully qualified domain names,
'localhost', or empty. The second example is also illegal because a
mandatory '/' must follow the host portion. For the details, see
RFC1738 (Uniform Resource Locators). For everyone's convenience, the
relevant section is included below.
The first two examples can be made legal by writing them as
<URL:file:///c:/temp/test.txt>. This happens to work with both
Explorer and Netscape. Again, be warned that it may or may not work
with other Windows clients.
As for UNC paths, I am not aware of a legal way to use them in file
URLs which works with both Netscape and Explorer.
-ccwf
======================================================================
3.10 FILES
The file URL scheme is used to designate files accessible on a
particular host computer. This scheme, unlike most other URL schemes,
does not designate a resource that is universally accessible over the
Internet.
A file URL takes the form:
file://<host>/<path>
where <host> is the fully qualified domain name of the system on
which the <path> is accessible, and <path> is a hierarchical
directory path of the form <directory>/<directory>/.../<name>.
For example, a VMS file
DISK$USER:[MY.NOTES]NOTE123456.TXT
might become
<URL:file://vms.host.edu/disk$user/my/notes/note12345.txt>
As a special case, <host> can be the string "localhost" or the empty
string; this is interpreted as `the machine from which the URL is
being interpreted'.
The file URL scheme is unusual in that it does not specify an
Internet protocol or access method for such files; as such, its
utility in network protocols between hosts is limited.