gnuclient allows the user to request a running XEmacs process to
edit the named files or directories and/or evaluate lisp forms.
Depending on your environment, it can be an X frame or a TTY frame.
One typical use for this is with a dialup connection to a machine on
which an XEmacs process is currently running.
gnudoit is a shell script frontend to ``gnuclient -batch -eval form''.
Its use is deprecated. Try to get used to calling gnuclient directly.
gnuserv is the server program that is set running by XEmacs to
handle all incoming and outgoing requests. It is not usually invoked
directly, but is started from XEmacs by loading the gnuserv
package and evaluating the Lisp form (gnuserv-start).
gnuattach no longer exists. Its functionality has been replaced by
gnuclient -nw.
OPTIONS
gnuclient supports as much of the command line options of Emacs as
makes sense in this context. In addition it adds a few of its own.
Options with long names can also be specified using a double
hyphen instead of a single one.
-nw
This option makes gnuclient act as a frontend such that XEmacs
can attach to the current TTY. XEmacs will then open a new TTY frame.
The effect is similar to having started a new XEmacs on this TTY with
the ``-nw'' option. It currently only works if XEmacs is running on
the same machine as gnuclient. This is the default if the `DISPLAY'
environment variable is not set.
-display display, --display display
If this option is given or the `DISPLAY' environment variable is set
then gnuclient will tell XEmacs to edit files in a frame on the
specified X device.
-q
This option informs gnuclient to exit once connection has been
made with the XEmacs process. Normally gnuclient waits until
all of the files on the command line have been finished with (their
buffers killed) by the XEmacs process, and all the forms have been
evaluated.
-v
When this option is specified gnuclient will request for the
specified files to be viewed instead of edited.
-l library
Tell Emacs to load the specified library.
-batch
Tell Emacs not to open any frames. Just load libraries and evaluate
lisp code. If no files to execute, functions to call or forms to eval
are given using the
-l,
-f,
or
-eval
options, then forms to eval are read from STDIN.
-f function,
Make Emacs execute the lisp function.
-eval form
Make Emacs execute the lisp form.
-h hostname
Used only with Internet-domain sockets, this option specifies the host
machine which should be running gnuserv. If this option is not
specified then the value of the environment variable GNU_HOST is used
if set. If no hostname is specified, and the GNU_HOST variable is not
set, an internet connection will not be attempted. N.B.:
gnuserv does NOT allow internet connections unless XAUTH
authentication is used or the GNU_SECURE variable has been specified
and points at a file listing all trusted hosts. (See SECURITY below.)
Note that an internet address may be specified instead of a hostname
which can speed up connections to the server by quite a bit,
especially if the client machine is running YP.
Note also that a hostname of unix can be used to specify that
the connection to the server should use a Unix-domain socket (if
supported) rather than an Internet-domain socket.
-p port
Used only with Internet-domain sockets, this option specifies the
service port used to communicate between server and clients. If this
option is not specified, then the value of the environment variable
GNU_PORT is used, if set, otherwise a service called ``gnuserv'' is
looked up in the services database. Finally, if no other value can be
found for the port, then a default port is used which is usually 21490
+ uid.
Note that since gnuserv doesn't allow command-line options, the port for
it will have to be specified via one of the alternative methods.
-r pathname
Used only with Internet-domain sockets, the pathname argument may be
needed to inform XEmacs how to reach the root directory of a remote
machine. gnuclient prepends this string to each path argument
given. For example, if you were trying to edit a file on a client
machine called otter, whose root directory was accessible from the
server machine via the path /net/otter, then this argument should be
set to '/net/otter'. If this option is omitted, then the value is
taken from the environment variable GNU_NODE, if set, or the empty
string otherwise.
[+n] file
This is the path of the file to be edited. If the file is a directory, then
the directory browsers dired or monkey are usually invoked instead.
The cursor is put at line number 'n' if specified.
SETUP
gnuserv is packaged standardly with recent versions of XEmacs.
Therefore, you should be able to start the server simply by evaluating
the XEmacs Lisp form (gnuserv-start), or equivalently by typing
`M-x gnuserv-start'.
CONFIGURATION
The behavior of this suite of program is mostly controlled on the lisp
side in Emacs and its behavior can be customized to a large extent.
Type `M-x customize-group RET gnuserv RET' for easy access. More
documentation can be found in the file `gnuserv.el'
More examples and sample wrapper scripts are provided in the
etc/gnuserv directory of the Emacs installation.
SYSV IPC
SysV IPC is used to communicate between gnuclient and
gnuserv if the symbol SYSV_IPC is defined at the top of
gnuserv.h. This is incompatible with both Unix-domain and
Internet-domain socket communication as described below. A file called
/tmp/gsrv??? is created as a key for the message queue, and if removed
will cause the communication between server and client to fail until
the server is restarted.
UNIX-DOMAIN SOCKETS
A Unix-domain socket is used to communicate between gnuclient
and gnuserv if the symbol UNIX_DOMAIN_SOCKETS is defined at the
top of gnuserv.h. A file called /tmp/gsrvdir????/gsrv is created for
communication. If the symbol USE_TMPDIR is set at the top of gnuserv.h,
$TMPDIR, when set, is used instead of /tmp. If that file is deleted,
or TMPDIR has different values for the server and the client, communication
between server and client will fail. Only the user running gnuserv will be
able to connect to the socket.
INTERNET-DOMAIN SOCKETS
Internet-domain sockets are used to communicate between
gnuclient and gnuserv if the symbol
INTERNET_DOMAIN_SOCKETS is defined at the top of gnuserv.h. Both
Internet-domain and Unix-domain sockets can be used at the same
time. If a hostname is specified via -h or via the GNU_HOST
environment variable, gnuclient establish connections using an
internet domain socket. If not, a local connection is attempted via
either a unix-domain socket or SYSV IPC.
SECURITY
Using Internet-domain sockets, a more robust form of security is
needed that wasn't necessary with either Unix-domain sockets or SysV
IPC. Currently, two authentication protocols are supported to provide
this: MIT-MAGIC-COOKIE-1 (based on the X11 xauth(1) program) and a
simple host-based access control mechanism, hereafter called
GNUSERV-1. The GNUSERV-1 protocol is always available, whereas support
for MIT-MAGIC-COOKIE-1 may or may not have been enabled (via a #define
at the top of gnuserv.h) at compile-time.
gnuserv, using GNUSERV-1, performs a limited form of access
control at the machine level. By default no internet-domain socket is
opened. If the variable GNU_SECURE can be found in gnuserv's
environment, and it names a readable filename, then this file is
opened and assumed to be a list of hosts, one per line, from which the
server will allow requests. Connections from any other host will be
rejected. Even the machine on which gnuserv is running is not
permitted to make connections via the internet socket unless its
hostname is explicitly specified in this file. Note that a host may
be either a numeric IP address or a hostname, and that
any
user on an approved host may connect to your gnuserv and execute arbitrary
elisp (e.g., delete all your files).
If this file contains a lot of
hostnames then the server may take quite a time to start up.
When the MIT-MAGIC-COOKIE-1 protocol is enabled, an internet socket
is opened by default. gnuserv will accept a connection from
any host, and will wait for a "magic cookie" (essentially, a password)
to be presented by the client. If the client doesn't present the
cookie, or if the cookie is wrong, the authentication of the client is
considered to have failed. At this point. gnuserv falls back to
the GNUSERV-1 protocol; If the client is calling from a host listed in
the GNU_SECURE file, the connection will be accepted, otherwise it
will be rejected.
Using MIT-MAGIC-COOKIE-1 authentication
When the gnuserv server is started, it looks for a cookie
defined for display 999 on the machine where it is running. If the
cookie is found, it will be stored for use as the authentication
cookie. These cookies are defined in an authorization file (usually
~/.Xauthority) that is manipulated by the X11 xauth(1) program. For
example, a machine "kali" which runs an emacs that invokes
gnuserv should respond as follows (at the shell prompt) when set
up correctly.
kali% xauth list
GS65.SP.CS.CMU.EDU:0 MIT-MAGIC-COOKIE-1 11223344
KALI.FTM.CS.CMU.EDU:999 MIT-MAGIC-COOKIE-1 1234
In the above case, the authorization file defines two cookies. The
second one, defined for screen 999 on the server machine, is used for
gnuserv authentication.
On the client machine's side, the authorization file must contain an
identical line, specifying the
server's
cookie. In other words, on a machine "foobar" which wishes to connect
to "kali," the `xauth list' output should contain the line:
KALI.FTM.CS.CMU.EDU:999 MIT-MAGIC-COOKIE-1 1234
For more information on authorization files, take a look at the
xauth(1X11) man page, or invoke xauth interactively (without any
arguments) and type "help" at the prompt. Remember that case in the
name of the authorization protocol (i.e.`MIT-MAGIC-COOKIE-1')
is
significant!
