gnuserv



GNUSERV(1)                                                          GNUSERV(1)




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 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  evaluat-
       ing the Lisp form (gnuserv-start).

       gnuattach no longer exists. Its functionality has been replaced by gnu-
       client -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 vari-
               able 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 connec-
               tions  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 alterna-
               tive 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 usu-
               ally invoked instead.  The cursor is put at line number ’n’  if
               specified.



SETUP

       gnuserv  is packaged standardly with recent versions of XEmacs.  There-
       fore, 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  docu-
       mentation 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 incompati-
       ble 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 communi-
       cation.  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,  communi-
       cation  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. Cur-
       rently, 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 host-
       name, 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 pre-
       sented 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  proto-
       col;  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) program. For exam-
           ple,  a  machine  "kali"  which  runs an emacs that invokes gnuserv
           should respond as follows (at the shell prompt) when  set  up  cor-
           rectly.

               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 servers 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
               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 prop-
       erly.



AUTHOR.

       Andy   Norman  (ange@hplb.hpl.hp.com),  based  heavily  upon  etc/emac-
       sclient.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@xemacs.org).



4th Berkeley Distribution                                           GNUSERV(1)

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