About X: Frequently Asked Questions
This file contains answers to frequently asked questions about X. Here is
a list of the questions that are answered:
A client is an application or program, such as a clock or a terminal
emulator. A server acts as an intermediary between the client
(application) and the display. It takes information from an
input device, such as a mouse, and sends it to the client. It also
takes information from the client and sends it to the graphics
- What is the client-server model?
- Explain the term "remote display"?
- How do I run a program on one machine and display it
- Does the DISPLAY environment variable work for
- The DISPLAY variable doesn't seem to work. Why?
- What are resources?
- How do I set resources?
- How do I know what resources I can set for an application?
- How do I run the same program twice with different
- Does the GL recognize resources now?
- How do I find out what fonts are available?
- Does Silicon Graphics provide any tools to help with the
- What is a good approach to take in looking for resources?
- What is the precedence for resource files?
- What files affect the window manager and what is their
relationship to each other?
- Do I need my own .4Dwmrc file?
- Can I run different window managers?
- How do I choose a different window manager as the default?
- Where can I learn more about the Window Manager behavior?
- How do I recover from a failed customization attempt?
- What is the difference between .xsession and .sgisession?
- After copying /usr/lib/X11/xdm/Xsession to .xsession,
I can't login.
- What are the important login and resource files for
- What is the sequence of events that occur at login time?
- What books about the X Window System and OSF/Motif do
------ ------ -------
|X |<------- |X |----->|Screen |
|client|-------> |server| |Display|
------ X ------ -------
Typically, a client and server run on the same workstation. Clients,
however, can be run from other machines via a network (including
machines with different operating systems and architecture). This
allows you to run a compute-intensive program on one machine and render
the results on your workstation screen.
The DISPLAY environment variable lets you specify the machine on
which you want the X client to be displayed. You can specify the local
machine in one of three ways :
Similarly, you can specify a remote host:
- a) setenv DISPLAY :0
- b) setenv DISPLAY localhost:0
- c) setenv DISPLAY yourhost:0 where yourhost is your machine name.
Yes. GL programs display on the machine specified by the DISPLAY
environment variable. This occurs because the GL now uses the
Distributed Graphics Library (DGL) capabilities by default.
It is important to remember that only Silicon Graphics' machines
can displayGL. For networks running NIS (formerly yellow pages),
it is important to add the compiler flag "-lsun".
Sometimes, when trying to display to a remote server, you see these
messages: "permission denied" or "can't connect to server"
message. To solve permission problems, you need to disable access
control on the remote server using the xhost command. This is the
default behavior on Silicon Graphics' machines.
If you have problems connecting to a server, check to make sure you used
the correct ethernet addresses and the server is up and running. Where
NIS is used, also make sure the client is linked with "-lsun".
Basically, resources are "attributes" that control the
look and feel of an application. Resources include color, fonts,
size, location, and more. Resources can have a complex format for
For a complete description of resources, including a description
of "loose" and "tight" bindings, consult a book listed in the
bibliography for question #25.
There are many ways to set resources. Resources may be listed
in files or contained in a data base. It is recommended that
you consult a Book on X as well as the man page for "xrdb"
for detailed descriptions. Generally speaking, if xrdb is not
used, resource files are specified through environment
variables. Question #14 addresses the precedence of these
files and variables.
- setenv DISPLAY remotehost:0
For some examples, see the file /usr/tutor/Customize/example.Xdefaults.
The most common place to find resource variables for a particular
application is in the man page for that application.
For example, take a look at the man page for `xwsh'. Look for
the section heading called `RESOURCES'. This section lists
each resource for `xwsh', and in some cases, the valid
values for that resource.
Also, many major applications are built on top of the
Xt toolkit. There are standard resources that these
applications recognize. For a more complete description,
see one of the books on Xt listed in the bibliography.
To accomplish this task, you need to take advantage of the
"instance vs class" concept. This concept is explained further
in most books on Xt.
Many applications have a resource that lets you to give it a unique name.
For example, from the xwsh man page :
Using the -name option allows you to give "names" to different
instances of xwsh and assign different resources to each one.
So if you want two different xwsh's with different resource sets,
give them two different names, say howdymom and howdydoody, for example.
Add the following to your ~/.Xdefaults file (if you use .Xdefaults) :
- -name instance-name
- Provide a unique name for an xwsh window. This name becomes
the instance name of the specific xwsh, with the class name
always being "XWsh".
- howdymom*foreground: SeaGreen
- howdydoody*foreground: SGIBeet
Yes. For complete information see the man page for GLRESOURCES.
Here is the beginning of the man page :
- Now all you have to do is start them up :
- xwsh -name howdymom&
- xwsh -name howdydoody&
GLRESOURCES(3G) Silicon Graphics GLRESOURCES(3G)
The xfontsel and xlsfonts utilities help you find appropriate fonts.
xlsfonts lists the fonts; xfontsel provides an interface for selecting
a desired font. To use xfontsel, choose "Font Names" from the
Customization rollover menu in the Toolchest. Please see the man
pages and the IRIS Utilities Guide for further information.
Yes. The Customization rollover menu in the Toolchest contains three
entries: Window Info, Color Names, and Font Names. Please refer
to the man pages on these commands for details: xfontsel, xlsfonts,
xwininfo, xdpyinfo, xprop, appres, listres, and xrdb.
- GL Resources - X resources used by GL programs
- In IRIX 4.0 and later, the GL responds to several X resources, allowing
run-time control over some aspects of GL programs.
- This man page assumes you are somewhat familiar with X resources, if you
are not, you should read some X documentation such as Volume 3 of the
O'Reilly X books.
- The GL uses resources names with the prefixes
- appname.gl. (instance prefix)
- Appname.GL. (class prefix)
- where appname and Appname are derived from the argument to the GL
program's first call to winopen(3G) upper case.
Also, see the "WorkSpace User's Guide" and the example files in
The following is a recommended list of steps
to take when searching for a resource, binding, behavior, etc.
The following list indicates the weight of set resources.
Items at the top have the greatest weight.
- Look in the 4.0 Transition Guide.
- Look in /usr/tutor/Customize.
- Look in /usr/demos.
- Look in ~4Dgifts. (Available with the development option.)
- If the client you are interested in is a GL client, see the
man page for GLRESOURCES.
- Look in /usr/lib/X11/app-defaults/ClientName.
- Look in /usr/lib/X11/system.* .
- Look through the man page for the client you are interested in.
- Look in
O'Reilly & Associates Vol. III. It has many gems
pertaining to standard X clients.
- Look in the documentation that came with your application.
- Look in the OSF Motif manuals.
- Post to comp.windows.x if you can not find
an answer using steps 1 through 11.
- Hard coded values for resources.
- Command line arguments.
- Resources pointed to by $XENVIRONMENT.
- Resource values loaded into the Resource Data Base via xrdb.
- Resources pointed to by other environment variables :
- IF $XUSERFILESEARCHPATH is set
- then it contains a list of directories to search.
- ELSE IF $XAPPLRESDIR is set
- it contains a single directory, and a short list of related
directories (e.g. adjusted for language) is where resource
files must be found.
- Look in a short list of places related to $HOME (e.g.
language adjusted). This includes files in $HOME that have
the name of the class of the application.
- Resource values set in $HOME/.Xdefaults, provided that the
RESOURCE_MANAGER property hasn't been set via the xrdb command.
(see the third paragraph in the xrdb man page)
- Values set in /usr/lib/X11/app-defaults/*.
- Values set through through the application's fall back mechanism.
- ~/.4Dwmrc, if you have one
- ~/.Xdefaults (or wherever you set resources)
When 4Dwm is started, it looks for ~/.4Dwmrc. If it does
not exist, it looks at /usr/lib/X11/system.4Dwmrc. The
definitions for button bindings, menus, etc are contained
in these files. For a better description of bindings,
look in /usr/tutor/Customize/example.4Dwmrc and
/usr/people/4Dgifts/.4Dwmrc. Also see the man pages for 4Dwm.
The resource set for the bindings will actually "choose"
which binding definition is set.
Not necessarily. As mentioned in the previous question,
actual bindings are determined by resource names. If there
is a binding definition in /usr/lib/X11/system.4Dwmrc
that you like, you may choose it by setting the appropriate
In Irix 4D1-4.0, you may choose 4Dwm, mwm, twm, or uwm. Note that GL
programs are guaranteed to work only under 4Dwm.
To use another window manager at login time, you
must use a .xsession file. Please see question #21.
The man pages for 4Dwm and mwm contain a wealth of
information on the window manager. There are
also online files. You may want to read
/usr/tutor/Customize/example.4Dwmrc as well as
/usr/people/4Dgifts/.4Dwmrc (if you have the IDO option).
The OSF/Motif manuals listed in the bibliography are
also good places to find information. (4Dwm is based
If your attempt at customization leaves you in a state
where buttons and menus are no longer recognized, you
can recover by pressing the
simultaneously. A menu appears that will let you
choose Motif, Iris, or user defaults. Choose either
Motif or Iris defaults and then push OK. This
restarts the window manager to a usable state.
From the login event sequence mentioned earlier, you will note
that /usr/lib/X11/xdm/Xsession tries to exec $HOME/.xsession
if it exists. This is how you would go about changing
programs started by default. An example is the start of the
window manager. There is a discussion on xsession files in volume
3 of the
O'Reilly series. For examples of alternate xsession files
look at /usr/people/4Dgifts/.xsession or /usr/demos/.xsession.
If you don't have a $HOME/.xsession file, /usr/lib/X11/xdm/Xsession
starts things for you and eventually looks for $HOME/.sgisession.
This is a good way to start additional programs without
changing what is started by default.
After copying this file to your home directory, you need
to remove all references to "xsession". References to xsession
cause the system to try to execute $HOME/.xsession, which will
create an infinite loop.
The following three file groupings indicate where files that
affect your login session reside.
1) /usr/lib/X11/* - This is THE starting place. Here you find
the system default bindings for Motif, 4Dwm, and the
Toolchest. The xdm directory lives here as well as the
app-defaults directory. xdm controls the session management. Many
application defaults are set in the app-defaults directory.
2) $HOME/[.Xdefaults, .4Dwmrc, .chestrc, .xsession, .sgisession] -
Here you find the files that control your system set-up.
You create these files; they don't exist when you first log in.
3) /usr/bin/X11 - This is where the binaries live. It makes
life nice to include this directory in your path.
This is a bare bones synopsis of the events that occur when
you log in to the console via xdm (xdm is the default method
of logging in).
Introductory Texts on the X Window System
- Provide a "failsafe" (nographics) login if required/requested.
- Exec $HOME/.xsession if it exists. If it exists, the remaining
steps should normally be included in the users .xsession file as
- Load $HOME/.Xresources if it exists.
- Set XUSERFILESEARCHPATH.
- Incorporate a "shell" environment
into the "session". (man userenv)
- Set the root background and cursor.
- Start 4Dwm.
- Wait for 4Dwm to come up.
- Disable display access control (xhost +). (man xhost)
- Execute $HOME/.sgisession if it exists.
- Start WorkSpace if the user wants it.
- Put a Toolchest on each screen.
- Start the console.
- Exec the "reaper". (man reaper / endsession)
Introductory Texts on the OSF/Motif Toolkit :
- - O'Reilly and Associates, Inc. "The Definitive Guides to the
X Window System", by Adrian Nye. Vol. 1, "Xlib Programming
Manual", Sebastopol, CA., 1990.
- Contains the introductory elements for programming with the
Xlib, the lowest level of the X window system. Discusses
concepts such as X color capacities, windows, events,
- O'Reilly and Associates Inc., "The Definitive Guides to
the X Window System", by Valerie Quercia and Tim O'Reilly. Vol. 3,
"X Window System User's Guide", Sebastopol, CA., 1988, 1989.
- Discusses being an end user of the X window system. Covers
topics like window manages, font specifications, standard X
clients and resources.
Reference Texts for the X Window System :
- - Young, Douglas A., "X Window Systems Programming and Applications
with Xt" (OSF/Motif Edition). Prentice Hall. Englewood
Cliffs, NJ. 1990.
- A thorough book starting with the basics of programming with
a toolkit though advanced topics. Contains source code for
several small complete applications. (Source code for this
book is also available on line in the /usr/src directory of
the Motif Development option.)
- - O'Reilly and Associates Inc., "The Definitive Guides to
the X Window System", by Adrian Nye and Tim O'Reilly. Vol. 4,
"X Toolkit Intrinsics Programming Manual", Sebastopol, CA., 1990.
- Another reference for programming with the OSF/Motif
toolkit. Covers topics including basic programming,
widgets, resources, and more advanced topics.
Reference Texts for the OSF/Motif Toolkit :
- - O'Reilly and Associates Inc., "The Definitive Guides to
the X Window System", by Adrian Nye. Vol. 2,
"Xlib Reference Manual", Sebastopol, CA., 1988.
- Complete reference for Xlib library routines.
- - Scheifler, Robert and James Gettys, X Window System, Second Edition,
Digital Press, 1990. ISBN 1-55558-050-5.
- Referred to as "the Bible" of Xlib and X Protocol reference.
- - Open Software Foundation, "OSF/Motif Programmer's Guide".
Release 1.1, Prentice Hall. Englewood Cliffs, NJ. 1990.
- Exhaustive reference of every widget in the OSF/Motif library.
- - Asente, Paul J. and Ralph R. Swick. "X Window System Toolkit".
X Version 11, Release 4. Digital Press. 1990.
- Very in-depth reference to the structure and operation of
an X window system toolkit.
Burkhard Kirste, 1993/08/26