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gnuserv, gnuclient - Server and Clients for XEmacs
[-nw] [-display display] [-q] [-v] [-l library] [-batch] [-f function] [-eval form]
[-h hostname] [-p port] [-r remote-pathname] [[+line] file] ...
gnudoit [-q] form
gnuattach Removed as of gnuserv 3.x
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.
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).
no longer exists. Its functionality has been replaced by gnuclient -nw.
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.
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’.
- 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
- -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.
- 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
- 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.
- 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
- -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
- [+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.
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
gnuclient -q -f mh-smail
gnuclient -h cuckoo -r /ange@otter: /tmp/*
gnuclient -nw ../src/listproc.c
More examples and sample wrapper scripts are provided in the etc/gnuserv
directory of the Emacs installation.
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.
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 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.
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.
- 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:
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!
- Default X device to put edit frame.
- (SYSV_IPC only)
- (unix domain sockets only)
- XEmacs customization file, see xemacs(1).
- xauth(1X11), Xsecurity(1X11),
NULs occurring in result strings don’t get passed back to
Andy Norman (email@example.com), based heavily
upon etc/emacsclient.c, etc/server.c and lisp/server.el from the GNU Emacs
18.52 distribution. Various modifications from Bob Weiner (firstname.lastname@example.org),
Darrell Kindred (email@example.com), Arup Mukherjee (firstname.lastname@example.org), Ben Wing
(email@example.com) and Hrvoje Niksic (firstname.lastname@example.org).
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