NAME
gnuserv, gnuclient - Server and Clients for XEmacs
SYNOPSIS
gnuclient [-nw] [-display display] [-q] [-v] [-l library]
[-batch] [-f function] [-eval form] [-h hostname] [-p port]
[-r remote-pathname] [[+line] file] ...
gnudoit [-q] form
gnuserv
gnuattach Removed as of gnuserv 3.x
DESCRIPTION
gnuclient allows the user to request a running XEmacs pro-
cess 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 depreciated. 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 usu-
ally 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 Its functionality has been
replaced by gnuclient -nw.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 simi-
lar 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 connec-
tion has been made with the XEmacs process. Nor-
mally 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 vari-
able 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'
EXAMPLE
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
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 gnu-
client 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 and if
deleted will cause communication between server and client
to fail. Only the user running gnuserv will be able to con-
nect to the socket.
INTERNET-DOMAIN SOCKETS
Internet-domain sockets are used to communicate between gnu-
client 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 host-
name 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 secu-
rity 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 connec-
tion 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 interac-
tively (without any arguments) and type "help" at the
prompt. Remember that case in the name of the authoriza-
tion protocol (i.e.`MIT-MAGIC-COOKIE-1') is significant!
ENVIRONMENT
DISPLAY Default X device to put edit frame.
FILES
/tmp/gsrv???
(SYSV_IPC only)
/tmp/gsrvdir???/gsrv
(unix domain sockets only)
~/.emacs
XEmacs customization file, see xemacs(1).
SEE ALSO
xauth(1X11), Xsecurity(1X11), gnuserv.el
BUGS
NULs occurring in result strings don't get passed back to
gnudoit properly.
AUTHOR.
Andy Norman (ange@hplb.hpl.hp.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 (weiner@mot.com), Darrell Kindred
(dkindred@cmu.edu), Arup Mukherjee (arup@cmu.edu), Ben Wing
(ben@xemacs.org) and Hrvoje Niksic (hniksic@srce.hr).
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