Xsession man page on Hurd

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Xsession(5)							   Xsession(5)

NAME
       Xsession - initialize X session

SYNOPSIS
       Xsession [ session-type ]

DESCRIPTION
       /etc/X11/Xsession is a Bourne shell (sh(1)) script which is run when an
       X Window System session is begun by startx(1) or a display manager such
       as  xdm(1).   (Some display managers only invoke Xsession when specifi‐
       cally directed to so by the user; see the documentation for  your  dis‐
       play  manager  to  find	out more.)  Administrators unfamiliar with the
       Bourne shell will likely	 find  the  Xsession.options(5)	 configuration
       file easier to deal with than Xsession itself.

       Xsession	 is  not  intended  to	be invoked directly by the user; to be
       effective it needs to run in a special environment  associated  with  X
       server  initialization.	 startx, xdm, xinit(1), and other similar pro‐
       grams handle this.

       By default on a Debian system, Xsession is used by both common  methods
       of starting the X Window System, xdm (or another X display manager) and
       startx.	To change this	for  xdm,  edit	 the  ‘DisplayManager*session’
       resource	 in  the /etc/X11/xdm/xdm-config file — for other display man‐
       agers, consult their documentation.  To stop startx from using Xsession
       by default, replace the contents of the /etc/X11/xinit/xinitrc file.

       The  Xsession  script is quite flexible, and extensive customization of
       the X startup  procedure	 is  possible  without	modifying  the	script
       itself.	See “CUSTOMIZING THE STARTUP PROCEDURE” below.

   SESSION TYPES
       Xsession may optionally be passed a single argument indicating the type
       of X session to be started.  It is up to the display manager to set the
       argument.   To	pass  Xsession	an  argument  from  startx  or	xinit,
       /etc/X11/Xsession (or /etc/X11/xinit/xinitrc) must be called explicitly
       with  a	path,  as  in  startx /etc/X11/Xsession failsafe.  By default,
       three different arguments are supported:

       failsafe
	      invokes a session consisting solely of an x-terminal-emulator(1)
	      (no  window  manager  is	launched).  If the x-terminal-emulator
	      program cannot be found,	the  session  exits.   The  ‘failsafe’
	      argument	is  ignored  if	 there	is no ‘allow-failsafe’ line in
	      Xsession.options.

       default
	      produces the same behavior as if no session  type	 argument  had
	      been given at all.

       program
	      starts program if it can be found in the $PATH.  This is usually
	      a session manager or a very featureful window manager.  If  pro‐
	      gram is not found, the Xsession script proceeds with its default
	      behavior.	  This	argument   is	ignored	  if   there   is   no
	      ‘allow-user-xsession’  line in Xsession.options.	(If the admin‐
	      istrator does not want users writing their own .xsession	files,
	      it  makes	 little	 sense	to permit them to specify the names of
	      arbitrary programs to run.)  Note that the  restriction  may  be
	      easy to bypass, e.g. by using a .gnomerc file instead.

   DEFAULT STARTUP PROCEDURE
       Initially,  Xsession  performs some housekeeping.  It declares a set of
       built-in functions (see “BUILT-IN SHELL	FUNCTIONS”  below)  and	 vari‐
       ables,  then attempts to create a log file for the X session, or append
       to an existing one.  Historically this is called an ‘error’  file,  but
       it catches all sorts of diagnostic output from various X clients run in
       the user's session, not just error messages.  If it  is	impossible  to
       write  to  an  error  file, the script (and thus the X session) aborts.
       For convenience, once the error file is successfully  opened,  Xsession
       reports	the  fact that the session has started, the invoking username,
       and the date to the error file.	This makes it easier to discern	 which
       X session produced a particular line of output in the file.

       Xsession	 next  confirms that its script directory, Xsession.d, exists.
       If it does not, the script aborts.  After the script directory is  con‐
       firmed  to  be present, Xsession uses run-parts(1) to identify files in
       that directory that should be sourced (executed) in the	shell's	 envi‐
       ronment.	  Only	files  named  in  a  certain  way are sourced; see the
       run-parts manual page for a description	of  valid  characters  in  the
       filename.   (This restriction enables the administrator to move experi‐
       mental or problematic files out of the way of the script but keep  them
       in  an  obvious	place,	for  instance  by renaming them with ‘.old’ or
       ‘.broken’ appended to the filename.)

   SUPPLIED SCRIPTS
       Five shell script portions  are	supplied  by  default  to  handle  the
       details of the session startup procedure.

       /etc/X11/Xsession.d/20x11-common_process-args
	      Arguments	 are  processed as described in “SESSION TYPES” above.
	      The startup program, if one is  identified  at  this  point,  is
	      merely stored for later reference, and not immediately executed.

       /etc/X11/Xsession.d/30x11-common_xresources
	      X	 resources  are merged.	 run-parts is again used, this time to
	      identify files in the /etc/X11/Xresources directory that	should
	      be   processed   with   ‘xrdb   -merge’.	  Next,	 if  the  line
	      ‘allow-user-resources’  is  present  in  Xsession.options,   the
	      user's $HOME/.Xresources file is merged in the same way.

       /etc/X11/Xsession.d/35x11-common_xhost-local
	      Give  access to the X server to the same user on the local host.
	      If the xhost command is available, it will use it to  allow  any
	      process of the same user running on the local host to access the
	      X server.

       /etc/X11/Xsession.d/40x11-common_xsessionrc
	      Source global environment variables.  This  script  will	source
	      anything	in  $HOME/.xsessionrc  if  the	file  is present. This
	      allows the user to set global environment variables for their  X
	      session, such as locale information.

       /etc/X11/Xsession.d/50x11-common_determine-startup
	      Determine	 startup  program.  The X client to launch as the con‐
	      trolling process (the one	 that,	upon  exiting,	causes	the  X
	      server  to  exit	as  well) is determined next.  If a program or
	      failsafe argument was given and is allowed (see  above),	it  is
	      used  as	the  controlling  process.   Otherwise,	 if  the  line
	      ‘allow-user-xsession’  is	  present   in	 Xsession.options,   a
	      user-specified session program or script is used.	 In the latter
	      case, two historically popular names for user X session  scripts
	      are  searched for: $HOME/.xsession and $HOME/.Xsession (note the
	      difference in case).  The first  one  found  is  used.   If  the
	      script  is  not executable, it is marked to be executed with the
	      Bourne shell interpreter, sh.  Finally, if  none	of  the	 above
	      succeeds,	   the	  following   programs	 are   searched	  for:
	      /usr/bin/x-session-manager,    /usr/bin/x-window-manager,	   and
	      /usr/bin/x-terminal-emulator.   The first one found is used.  If
	      none are found, Xsession aborts with an error.

       /etc/X11/Xsession.d/90x11-common_ssh-agent
	      Start ssh-agent(1), if needed.  If the line  ‘use-ssh-agent’  is
	      present in Xsession.options, and no SSH agent process appears to
	      be running already, ssh-agent is marked to be  used  to  execute
	      the startup program determined previously.  Note: this function‐
	      ality may move to the ssh package in the future.

       /etc/X11/Xsession.d/99x11-common_start
	      Start the X session.  The startup program is executed, inside  a
	      Bourne shell if it is not executable, and inside an ssh-agent if
	      necessary.  The shell's exec command is used to spare a slot  in
	      the process table.

   CUSTOMIZING THE STARTUP PROCEDURE
       Of course, any of the existing files can be edited in place.

       Because	the  order in which the various scripts in /etc/X11/Xsession.d
       are executed is important, files to be added to this  directory	should
       have a well-formed name.	 The following format is recommended:

       * a two-digit number denoting sequence;

       *  the  name  of	 the  package  providing  the  script (or ‘custom’ for
       locally-created scripts);

       * an underscore;

       * a description of the script's basic function, using  only  characters
       allowed by run-parts.

       Here  is	 an  example  of  how  one  might write a script, named 40cus‐
       tom_load-xmodmap, to invoke xmodmap(1):

       SYSMODMAP="/etc/X11/Xmodmap"
       USRMODMAP="$HOME/.Xmodmap"

       if [ -x /usr/bin/X11/xmodmap ]; then
	   if [ -f "$SYSMODMAP" ]; then
	       xmodmap "$SYSMODMAP"
	   fi
       fi

       if [ -x /usr/bin/X11/xmodmap ]; then
	   if [ -f "$USRMODMAP" ]; then
	       xmodmap "$USRMODMAP"
	   fi
       fi

       Those writing scripts for Xsession to execute should  avail  themselves
       of its built-in shell functions, described below.

   BUILT-IN SHELL FUNCTIONS
       message	is  used for communicating with the user.  It is a wrapper for
       the echo(1) command and relies upon echo for its	 argument  processing.
       This function may be given an arbitrarily long message string, which is
       formatted to the user's terminal width (breaking lines  at  whitespace)
       and sent to standard error.  If the DISPLAY environment variable is set
       and the xmessage(1) program is available, xmessage is also used to dis‐
       play the message.

       message_nonl  is	 used  for communicating with the user when a trailing
       newline is undesirable; it omits a trailing newline  from  the  message
       text.  It otherwise works as message.

       errormsg	 is  used  for	indicating an error condition and aborting the
       script.	It works as message, above, except that after  displaying  the
       message, it will exit Xsession with status 1.

ENVIRONMENT
       The following environment variables affect the execution of Xsession:

       HOME   specifies	 the user's home directory; various files are searched
	      for here.

       TMPDIR names a default directory for temporary files; if the standard X
	      session  error  file  cannot be opened, this variable is used to
	      locate a place for one.

       COLUMNS
	      indicates the width of terminal device in character cells.  This
	      value is used for formatting diagnostic messages.

INPUT FILES
       /etc/X11/Xsession.d/
	      is a directory containing Bourne shell scripts to be executed by
	      Xsession.	 Files in this directory are matched  using  run-parts
	      and are sourced, not executed in a subshell.

       /etc/X11/Xresources/
	      is  a directory containing files corresponding to Debian package
	      names, each of which contains system-wide	 X  resource  settings
	      for  X clients from the corresponding package.  The settings are
	      loaded with xrdb -merge.	Files in this  directory  are  matched
	      using run-parts.

       /etc/X11/Xsession.options
	      contains configuration options for the /etc/X11/Xsession script.
	      See Xsession.options(5) for more information.

       $HOME/.Xresources
	      contains X resources specific to the  invoking  user's  environ‐
	      ment.   The  settings  are  loaded  with xrdb -merge.  Note that
	      $HOME/.Xdefaults is a relic from X Version 10 (and X11R1)	 days,
	      before  app-defaults files were implemented.  It has been depre‐
	      cated for over ten years at the time  of	this  writing.	 .Xre‐
	      sources should be used instead.

       $HOME/.xsession
	      is  a sequence of commands invoking X clients (or a session man‐
	      ager such as xsm(1)).  See the manual page for xinit for tips on
	      writing an .xsession file.

OUTPUT FILES
       $HOME/.xsession-errors
	      is  where standard output and standard error for Xsession script
	      and all X client processes are directed by default.

       $TMPDIR/filename
	      is where the X session error  file  is  placed  if  $HOME/.xses‐
	      sion-errors  cannot  be opened.  For security reasons, the exact
	      filename is randomly generated by tempfile(1).

AUTHORS
       Stephen Early, Mark Eichin, and Branden Robinson developed  Debian's  X
       session handling scripts.  Branden Robinson wrote this manual page.

SEE ALSO
       Xsession.options(5), X(7), run-parts(1), ssh-agent(1), startx(1), temp‐
       file(1), xdm(1), xmessage(1), xmodmap(1), xrdb(1), sh(1)

Debian Project			  2004-11-04			   Xsession(5)
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