GNUSERV(1) GNUSERV(1)
NAME
gnuserv, gnuclient - Server and Clients for Emacs
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 emacs pro-
cess to edit the named files or directories and/or evalu-
ate 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 emacs
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 emacs
to handle all incoming and outgoing requests. It is not
usually invoked directly, but is started from emacs 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 Its functionality has been
replaced by gnuclient -nw.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 dou-
ble hyphen instead of a single one.
-nw This option makes gnuclient act as a frontend such
that emacs can attach to the current TTY. emacs
will then open a new TTY frame. The effect is
similar to having started a new emacs on this TTY
with the ``-nw'' option. It currently only works
if emacs is running on the same machine as gnu-
client. This is the default if the `DISPLAY' envi-
ronment variable is not set.
-display display, --display display
If this option is given or the `DISPLAY' environ-
ment variable is set then gnuclient will tell
emacs 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 emacs process. Nor-
mally gnuclient waits until all of the files on
the command line have been finished with (their
buffers killed) by the emacs 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 speci-
fied, 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 connec-
tions 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 communi-
cate between server and clients. If this option
is not specified, then the value of the environ-
ment 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 path-
name argument may be needed to inform emacs how to
reach the root directory of a remote machine.
gnuclient prepends this string to each path argu-
ment 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 with emacs on Mac OS X. Therefore,
you should be able to start the server simply by evaluat-
ing the emacs 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 cus-
tomized 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 mes-
sage 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
connect to the socket.
INTERNET-DOMAIN SOCKETS
Internet-domain sockets are used to communicate between
gnuclient and gnuserv if the symbol INTERNET_DOMAIN_SOCK-
ETS 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 connec-
tions 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 inter-
net-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 inter-
net 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 ~/.Xau-
thority) that is manipulated by the X11 xauth(1) pro-
gram. 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!
ENVIRONMENT
DISPLAY Default X device to put edit frame.
FILES
/tmp/gsrv???
(SYSV_IPC only)
/tmp/gsrvdir???/gsrv
(unix domain sockets only)
~/.emacs
emacs customization file, see emacs(1).
SEE ALSO
xauth(1X11), Xsecurity(1X11), gnuserv.el
BUGS
NULs occurring in result strings don't get passed back to
gnudoit properly.
The -nw flag does not work, due to lack of necessary func-
tionality in emacs.
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 (dkin-
dred@cmu.edu), Arup Mukherjee (arup@cmu.edu), Ben Wing
(ben@xemacs.org) and Hrvoje Niksic (hniksic@xemacs.org).
emacs server GNUSERV(1)