GNU Info

(librep.info)Remote Files

---

Prev: File Handlers Up: Files

---

Enter node , (file) or (file)node

Remote files
------------

   Since one of the intentions for file handlers is to allow remote
files to be accessed, a common method of providing new methods of doing
this has been implemented, in the `remote.jl' Lisp library.

   Accessing a file name matching the regular expression:

     ^/(([a-zA-Z0-9._-]+)@)?([a-zA-Z0-9._-]+):

for example `/john@host.com:file' refers to a file called `file' owned
by the user `john', on the system `host.com'.

   If no username is specified explicitly, two variables are used to
select the user:

 - Variable: remote-host-user-alist
     An alist mapping host regexps to the default user name to use for
     remote file connections to that host.

 - Variable: remote-default-user
     User name to use for remote file connections when otherwise
     unspecified. By default the current user name on the local system.

   Two variables control how individual hosts are matched to methods of
accessing files.

 - Variable: remote-auto-backend-alist
     An alist of `(HOST-REGEXP . BACKEND-TYPE)' mapping host names to
     methods of accessing remote files.

 - Variable: remote-default-backend
     A symbol defining the method to use for otherwise unselected hosts.

   A method of accessing files, or a "backend" is a symbol whose
`remote-backend' property names a function to call when files need to
be accessed. For example the `ftp' backend is initialised as:

     (put 'ftp 'remote-backend remote-ftp-handler)

   The backend function is called as `(FUNCTION SPLIT-NAME OPERATION
ARGS)'. The SPLIT-NAME is a three-element list, `(USER-OR-NIL HOST
FILE)' defining the file to be accessed. The other options are as usual.
Further details can be found in the `remote.jl', `remote-ftp.jl' and
`remote-rcp.jl' Lisp source files.

   The `ftp' backend is currently the most well-developed, several
functions and variables may be used to customise its behaviour.

 - Function: remote-ftp-add-passwd user host passwd
     Add the string PASSWD as the password for the FTP session
     connecting to USER@HOST.

 - Variable: remote-ftp-show-messages
     When true (the default), messages are displayed as FTP commands are
     executed.

 - Variable: remote-ftp-display-progress
     When true (the default) display progress of FTP transfers.

 - Variable: remote-ftp-anon-users
     A regular expression matching the user names for "anonymous" FTP
     sessions.

 - Variable: remote-ftp-anon-passwd
     The string to send as the passwd of an anonymous FTP session. By
     default the current uses email address.

   There is a problem with the `ftp' backend however; due to
limitations in the FTP protocol, not all `librep' file operations are
supported, with the most obvious exception being the `make-symlink'
function.

   When this is a problem it may be possible to use rep's custom file
transfer protocol. If it is possible to use `rsh' to connect to the
remote host in question, then the `rep' backend may be used.

   The `rep-remote' program distributed with `librep' must exist on the
remote host, this is executed via `rsh' and provides a protocol for
executing all of `librep''s file operations on that host. See the
`lisp/remote-rep.jl' file in the distribution for more details.