X - a portable, network-transparent window system

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X(7) X(7)

X - a portable, network-transparent window system

The X Window System is a network transparent window system which runs
on a wide range of computing and graphics machines. It should be rela‐
tively straightforward to build the X.Org Foundation software distribu‐
tion on most ANSI C and POSIX compliant systems. Commercial implemen‐
tations are also available for a wide range of platforms.

The X.Org Foundation requests that the following names be used when
referring to this software:

X Window System
X Version 11
X Window System, Version 11

X Window System is a trademark of The Open Group.

X Window System servers run on computers with bitmap displays. The
server distributes user input to and accepts output requests from vari‐
ous client programs through a variety of different interprocess commu‐
nication channels. Although the most common case is for the client
programs to be running on the same machine as the server, clients can
be run transparently from other machines (including machines with dif‐
ferent architectures and operating systems) as well.

X supports overlapping hierarchical subwindows and text and graphics
operations, on both monochrome and color displays. For a full explana‐
tion of the functions that are available, see the Xlib - C Language X
Interface manual, the X Window System Protocol specification, the X
Toolkit Intrinsics - C Language Interface manual, and various toolkit

The number of programs that use X is quite large. Programs provided in
the core X.Org Foundation distribution include: a terminal emulator,
xterm; a window manager, twm; a display manager, xdm; a console redi‐
rect program, xconsole; a mail interface, xmh; a bitmap editor, bitmap;
resource listing/manipulation tools, appres, editres; access control
programs, xauth, xhost, and iceauth; user preference setting programs,
xrdb, xcmsdb, xset, xsetroot, xstdcmap, and xmodmap; clocks, xclock and
oclock; a font displayer, xfd; utilities for listing information about
fonts, windows, and displays, xlsfonts, xwininfo, xlsclients, xdpyinfo,
xlsatoms, and xprop; screen image manipulation utilities, xwd, xwud,
and xmag; a performance measurement utility, x11perf; a font compiler,
bdftopcf; a font server and related utilities, xfs, fsinfo, fslsfonts,
fstobdf; a display server and related utilities, Xserver, rgb, mkfont‐
dir; a clipboard manager, xclipboard; keyboard description compiler and
related utilities, xkbcomp, setxkbmap xkbprint, xkbbell, xkbevd, xkb‐
vleds, and xkbwatch; a utility to terminate clients, xkill; a firewall
security proxy, xfwp; a proxy manager to control them, proxymngr; a
utility to find proxies, xfindproxy; web browser plug-ins, libxrx.so
and libxrxnest.so; an RX MIME-type helper program, xrx; and a utility
to cause part or all of the screen to be redrawn, xrefresh.

Many other utilities, window managers, games, toolkits, etc. are
included as user-contributed software in the X.Org Foundation distribu‐
tion, or are available on the Internet. See your site administrator
for details.

There are two main ways of getting the X server and an initial set of
client applications started. The particular method used depends on
what operating system you are running and whether or not you use other
window systems in addition to X.

Display Manager
If you want to always have X running on your display, your site
administrator can set your machine up to use a Display Manager
such as xdm, gdm, or kdm. This program is typically started by
the system at boot time and takes care of keeping the server
running and getting users logged in. If you are running one of
these display managers, you will normally see a window on the
screen welcoming you to the system and asking for your login
information. Simply type them in as you would at a normal ter‐
minal. If you make a mistake, the display manager will display
an error message and ask you to try again. After you have suc‐
cessfully logged in, the display manager will start up your X
environment. The documentation for the display manager you use
can provide more details.

xinit (run manually from the shell)
Sites that support more than one window system might choose to
use the xinit program for starting X manually. If this is true
for your machine, your site administrator will probably have
provided a program named "x11", "startx", or "xstart" that will
do site-specific initialization (such as loading convenient
default resources, running a window manager, displaying a
clock, and starting several terminal emulators) in a nice way.
If not, you can build such a script using the xinit program.
This utility simply runs one user-specified program to start
the server, runs another to start up any desired clients, and
then waits for either to finish. Since either or both of the
user-specified programs may be a shell script, this gives sub‐
stantial flexibility at the expense of a nice interface. For
this reason, xinit is not intended for end users.

From the user's perspective, every X server has a display name of the


This information is used by the application to determine how it should
connect to the server and which screen it should use by default (on
displays with multiple monitors):

The hostname specifies the name of the machine to which the
display is physically connected. If the hostname is not given,
the most efficient way of communicating to a server on the same
machine will be used.

The phrase "display" is usually used to refer to a collection
of monitors that share a common set of input devices (keyboard,
mouse, tablet, etc.). Most workstations tend to only have one
display. Larger, multi-user systems, however, frequently have
several displays so that more than one person can be doing
graphics work at once. To avoid confusion, each display on a
machine is assigned a display number (beginning at 0) when the
X server for that display is started. The display number must
always be given in a display name.

Some displays share their input devices among two or more moni‐
tors. These may be configured as a single logical screen,
which allows windows to move across screens, or as individual
screens, each with their own set of windows. If configured
such that each monitor has its own set of windows, each screen
is assigned a screen number (beginning at 0) when the X server
for that display is started. If the screen number is not
given, screen 0 will be used.

On POSIX systems, the default display name is stored in your DISPLAY
environment variable. This variable is set automatically by the xterm
terminal emulator. However, when you log into another machine on a
network, you may need to set DISPLAY by hand to point to your display.
For example,

% setenv DISPLAY myws:0
$ DISPLAY=myws:0; export DISPLAY
The ssh program can be used to start an X program on a remote machine;
it automatically sets the DISPLAY variable correctly.

Finally, most X programs accept a command line option of -display dis‐
playname to temporarily override the contents of DISPLAY. This is most
commonly used to pop windows on another person's screen or as part of a
"remote shell" command to start an xterm pointing back to your display.
For example,

% xeyes -display joesws:0 -geometry 1000x1000+0+0
% rsh big xterm -display myws:0 -ls /null &

X servers listen for connections on a variety of different communica‐
tions channels (network byte streams, shared memory, etc.). Since
there can be more than one way of contacting a given server, The host‐
name part of the display name is used to determine the type of channel
(also called a transport layer) to be used. X servers generally sup‐
port the following types of connections:

The hostname part of the display name should be the empty
string. For example: :0, :1, and :0.1. The most efficient
local transport will be chosen.

The hostname part of the display name should be the server
machine's hostname or IP address. Full Internet names, abbre‐
viated names, IPv4 addresses, and IPv6 addresses are all
allowed. For example: x.org:0, expo:0, [::1]:0,, bigmachine:1, and hydra:0.1.

An X server can use several types of access control. Mechanisms pro‐
vided in Release 7 are:
Host Access Simple host-based access control.
MIT-MAGIC-COOKIE-1 Shared plain-text "cookies".
XDM-AUTHORIZATION-1 Secure DES based private-keys.
SUN-DES-1 Based on Sun's secure rpc system.
Server Interpreted Server-dependent methods of access control

Xdm initializes access control for the server and also places autho‐
rization information in a file accessible to the user. Normally, the
list of hosts from which connections are always accepted should be
empty, so that only clients with are explicitly authorized can connect
to the display. When you add entries to the host list (with xhost),
the server no longer performs any authorization on connections from
those machines. Be careful with this.

The file from which Xlib extracts authorization data can be specified
with the environment variable XAUTHORITY, and defaults to the file
.Xauthority in the home directory. Xdm uses $HOME/.Xauthority and will
create it or merge in authorization records if it already exists when a
user logs in.

If you use several machines and share a common home directory across
all of the machines by means of a network file system, you never really
have to worry about authorization files, the system should work cor‐
rectly by default. Otherwise, as the authorization files are machine-
independent, you can simply copy the files to share them. To manage
authorization files, use xauth. This program allows you to extract
records and insert them into other files. Using this, you can send
authorization to remote machines when you login, if the remote machine
does not share a common home directory with your local machine. Note
that authorization information transmitted ``in the clear'' through a
network file system or using ftp or rcp can be ``stolen'' by a network
eavesdropper, and as such may enable unauthorized access. In many
environments, this level of security is not a concern, but if it is,
you need to know the exact semantics of the particular authorization
data to know if this is actually a problem.

For more information on access control, see the Xsecurity(7) manual

One of the advantages of using window systems instead of hardwired ter‐
minals is that applications don't have to be restricted to a particular
size or location on the screen. Although the layout of windows on a
display is controlled by the window manager that the user is running
(described below), most X programs accept a command line argument of
the form -geometry WIDTHxHEIGHT+XOFF+YOFF (where WIDTH, HEIGHT, XOFF,
and YOFF are numbers) for specifying a preferred size and location for
this application's main window.

The WIDTH and HEIGHT parts of the geometry specification are usually
measured in either pixels or characters, depending on the application.
The XOFF and YOFF parts are measured in pixels and are used to specify
the distance of the window from the left or right and top and bottom
edges of the screen, respectively. Both types of offsets are measured
from the indicated edge of the screen to the corresponding edge of the
window. The X offset may be specified in the following ways:

+XOFF The left edge of the window is to be placed XOFF pixels in from
the left edge of the screen (i.e., the X coordinate of the win‐
dow's origin will be XOFF). XOFF may be negative, in which
case the window's left edge will be off the screen.

-XOFF The right edge of the window is to be placed XOFF pixels in
from the right edge of the screen. XOFF may be negative, in
which case the window's right edge will be off the screen.

The Y offset has similar meanings:

+YOFF The top edge of the window is to be YOFF pixels below the top
edge of the screen (i.e., the Y coordinate of the window's ori‐
gin will be YOFF). YOFF may be negative, in which case the
window's top edge will be off the screen.

-YOFF The bottom edge of the window is to be YOFF pixels above the
bottom edge of the screen. YOFF may be negative, in which case
the window's bottom edge will be off the screen.

Offsets must be given as pairs; in other words, in order to specify
either XOFF or YOFF both must be present. Windows can be placed in the
four corners of the screen using the following specifications:

+0+0 upper left hand corner.

-0+0 upper right hand corner.

-0-0 lower right hand corner.

+0-0 lower left hand corner.

In the following examples, a terminal emulator is placed in roughly the
center of the screen and a load average monitor, mailbox, and clock are
placed in the upper right hand corner:

xterm -fn 6x10 -geometry 80x24+30+200 &
xclock -geometry 48x48-0+0 &
xload -geometry 48x48-96+0 &
xbiff -geometry 48x48-48+0 &

The layout of windows on the screen is controlled by special programs
called window managers. Although many window managers will honor geom‐
etry specifications as given, others may choose to ignore them (requir‐
ing the user to explicitly draw the window's region on the screen with
the pointer, for example).

Since window managers are regular (albeit complex) client programs, a
variety of different user interfaces can be built. The X.Org Founda‐
tion distribution comes with a window manager named twm which supports
overlapping windows, popup menus, point-and-click or click-to-type
input models, title bars, nice icons (and an icon manager for those who
don't like separate icon windows).

See the user-contributed software in the X.Org Foundation distribution
for other popular window managers.

Collections of characters for displaying text and symbols in X are
known as fonts. A font typically contains images that share a common
appearance and look nice together (for example, a single size, bold‐
ness, slant, and character set). Similarly, collections of fonts that
are based on a common type face (the variations are usually called
roman, bold, italic, bold italic, oblique, and bold oblique) are called

Fonts come in various sizes. The X server supports scalable fonts,
meaning it is possible to create a font of arbitrary size from a single
source for the font. The server supports scaling from outline fonts
and bitmap fonts. Scaling from outline fonts usually produces signifi‐
cantly better results than scaling from bitmap fonts.

An X server can obtain fonts from individual files stored in directo‐
ries in the file system, or from one or more font servers, or from a
mixtures of directories and font servers. The list of places the
server looks when trying to find a font is controlled by its font path.
Although most installations will choose to have the server start up
with all of the commonly used font directories in the font path, the
font path can be changed at any time with the xset program. However,
it is important to remember that the directory names are on the
server's machine, not on the application's.

Bitmap font files are usually created by compiling a textual font
description into binary form, using bdftopcf. Font databases are cre‐
ated by running the mkfontdir program in the directory containing the
source or compiled versions of the fonts. Whenever fonts are added to
a directory, mkfontdir should be rerun so that the server can find the
new fonts. To make the server reread the font database, reset the font
path with the xset program. For example, to add a font to a private
directory, the following commands could be used:

% cp newfont.pcf ~/myfonts
% mkfontdir ~/myfonts
% xset fp rehash

The xfontsel and xlsfonts programs can be used to browse through the
fonts available on a server. Font names tend to be fairly long as they
contain all of the information needed to uniquely identify individual
fonts. However, the X server supports wildcarding of font names, so
the full specification


might be abbreviated as:


Because the shell also has special meanings for * and ?, wildcarded
font names should be quoted:

% xlsfonts -fn '-*-courier-medium-r-normal--*-100-*-*-*-*-*-*'

The xlsfonts program can be used to list all of the fonts that match a
given pattern. With no arguments, it lists all available fonts. This
will usually list the same font at many different sizes. To see just
the base scalable font names, try using one of the following patterns:


To convert one of the resulting names into a font at a specific size,
replace one of the first two zeros with a nonzero value. The field
containing the first zero is for the pixel size; replace it with a spe‐
cific height in pixels to name a font at that size. Alternatively, the
field containing the second zero is for the point size; replace it with
a specific size in decipoints (there are 722.7 decipoints to the inch)
to name a font at that size. The last zero is an average width field,
measured in tenths of pixels; some servers will anamorphically scale if
this value is specified.

One of the following forms can be used to name a font server that
accepts TCP connections:


The hostname specifies the name (or decimal numeric address) of the
machine on which the font server is running. The port is the decimal
TCP port on which the font server is listening for connections. The
cataloguelist specifies a list of catalogue names, with '+' as a sepa‐

Examples: tcp/x.org:7100, tcp/

One of the following forms can be used to name a font server that
accepts DECnet connections:


The nodename specifies the name (or decimal numeric address) of the
machine on which the font server is running. The objname is a normal,
case-insensitive DECnet object name. The cataloguelist specifies a
list of catalogue names, with '+' as a separator.

Examples: DECnet/SRVNOD::FONT$DEFAULT, decnet/44.70::font$special/sym‐

Most applications provide ways of tailoring (usually through resources
or command line arguments) the colors of various elements in the text
and graphics they display. A color can be specified either by an
abstract color name, or by a numerical color specification. The numer‐
ical specification can identify a color in either device-dependent
(RGB) or device-independent terms. Color strings are case-insensitive.

X supports the use of abstract color names, for example, "red", "blue".
A value for this abstract name is obtained by searching one or more
color name databases. Xlib first searches zero or more client-side
databases; the number, location, and content of these databases is
implementation dependent. If the name is not found, the color is
looked up in the X server's database. The text form of this database
is commonly stored in the file usr/share/X11/rgb.txt.

A numerical color specification consists of a color space name and a
set of values in the following syntax:


An RGB Device specification is identified by the prefix "rgb:" and has
the following syntax:


, , := h | hh | hhh | hhhh
h := single hexadecimal digits
Note that h indicates the value scaled in 4 bits, hh the value scaled
in 8 bits, hhh the value scaled in 12 bits, and hhhh the value scaled
in 16 bits, respectively. These values are passed directly to the X
server, and are assumed to be gamma corrected.

The eight primary colors can be represented as:

black rgb:0/0/0
red rgb:ffff/0/0
green rgb:0/ffff/0
blue rgb:0/0/ffff
yellow rgb:ffff/ffff/0
magenta rgb:ffff/0/ffff
cyan rgb:0/ffff/ffff
white rgb:ffff/ffff/ffff

For backward compatibility, an older syntax for RGB Device is sup‐
ported, but its continued use is not encouraged. The syntax is an ini‐
tial sharp sign character followed by a numeric specification, in one
of the following formats:

#RGB (4 bits each)
#RRGGBB (8 bits each)
#RRRGGGBBB (12 bits each)
#RRRRGGGGBBBB (16 bits each)

The R, G, and B represent single hexadecimal digits. When fewer than
16 bits each are specified, they represent the most-significant bits of
the value (unlike the "rgb:" syntax, in which values are scaled). For
example, #3a7 is the same as #3000a0007000.

An RGB intensity specification is identified by the prefix "rgbi:" and
has the following syntax:


The red, green, and blue are floating point values between 0.0 and 1.0,
inclusive. They represent linear intensity values, with 1.0 indicating
full intensity, 0.5 half intensity, and so on. These values will be
gamma corrected by Xlib before being sent to the X server. The input
format for these values is an optional sign, a string of numbers possi‐
bly containing a decimal point, and an optional exponent field contain‐
ing an E or e followed by a possibly signed integer string.

The standard device-independent string specifications have the follow‐
ing syntax:

CIEXYZ:// (none, 1, none)
CIEuvY:// (~.6, ~.6, 1)
CIExyY:// (~.75, ~.85, 1)
CIELab:// (100, none, none)
CIELuv:// (100, none, none)
TekHVC:// (360, 100, 100)

All of the values (C, H, V, X, Y, Z, a, b, u, v, y, x) are floating
point values. Some of the values are constrained to be between zero
and some upper bound; the upper bounds are given in parentheses above.
The syntax for these values is an optional '+' or '-' sign, a string of
digits possibly containing a decimal point, and an optional exponent
field consisting of an 'E' or 'e' followed by an optional '+' or '-'
followed by a string of digits.

For more information on device independent color, see the Xlib refer‐
ence manual.

The X keyboard model is broken into two layers: server-specific codes
(called keycodes) which represent the physical keys, and server-inde‐
pendent symbols (called keysyms) which represent the letters or words
that appear on the keys. Two tables are kept in the server for con‐
verting keycodes to keysyms:

modifier list
Some keys (such as Shift, Control, and Caps Lock) are known as
modifier and are used to select different symbols that are
attached to a single key (such as Shift-a generates a capital
A, and Control-l generates a control character ^L). The server
keeps a list of keycodes corresponding to the various modifier
keys. Whenever a key is pressed or released, the server gener‐
ates an event that contains the keycode of the indicated key as
well as a mask that specifies which of the modifier keys are
currently pressed. Most servers set up this list to initially
contain the various shift, control, and shift lock keys on the

keymap table
Applications translate event keycodes and modifier masks into
keysyms using a keysym table which contains one row for each
keycode and one column for various modifier states. This table
is initialized by the server to correspond to normal typewriter
conventions. The exact semantics of how the table is inter‐
preted to produce keysyms depends on the particular program,
libraries, and language input method used, but the following
conventions for the first four keysyms in each row are gener‐
ally adhered to:

The first four elements of the list are split into two groups of
keysyms. Group 1 contains the first and second keysyms; Group 2 con‐
tains the third and fourth keysyms. Within each group, if the first
element is alphabetic and the the second element is the special keysym
NoSymbol, then the group is treated as equivalent to a group in which
the first element is the lowercase letter and the second element is the
uppercase letter.

Switching between groups is controlled by the keysym named MODE SWITCH,
by attaching that keysym to some key and attaching that key to any one
of the modifiers Mod1 through Mod5. This modifier is called the
``group modifier.'' Group 1 is used when the group modifier is off,
and Group 2 is used when the group modifier is on.

Within a group, the modifier state determines which keysym to use. The
first keysym is used when the Shift and Lock modifiers are off. The
second keysym is used when the Shift modifier is on, when the Lock mod‐
ifier is on and the second keysym is uppercase alphabetic, or when the
Lock modifier is on and is interpreted as ShiftLock. Otherwise, when
the Lock modifier is on and is interpreted as CapsLock, the state of
the Shift modifier is applied first to select a keysym; but if that
keysym is lowercase alphabetic, then the corresponding uppercase keysym
is used instead.

Most X programs attempt to use the same names for command line options
and arguments. All applications written with the X Toolkit Intrinsics
automatically accept the following options:

-display display
This option specifies the name of the X server to use.

-geometry geometry
This option specifies the initial size and location of the win‐

-bg color, -background color
Either option specifies the color to use for the window back‐

-bd color, -bordercolor color
Either option specifies the color to use for the window border.

-bw number, -borderwidth number
Either option specifies the width in pixels of the window bor‐

-fg color, -foreground color
Either option specifies the color to use for text or graphics.

-fn font, -font font
Either option specifies the font to use for displaying text.

This option indicates that the user would prefer that the
application's windows initially not be visible as if the win‐
dows had be immediately iconified by the user. Window managers
may choose not to honor the application's request.

This option specifies the name under which resources for the
application should be found. This option is useful in shell
aliases to distinguish between invocations of an application,
without resorting to creating links to alter the executable
file name.

-rv, -reverse
Either option indicates that the program should simulate
reverse video if possible, often by swapping the foreground and
background colors. Not all programs honor this or implement it
correctly. It is usually only used on monochrome displays.

This option indicates that the program should not simulate
reverse video. This is used to override any defaults since
reverse video doesn't always work properly.

This option specifies the timeout in milliseconds within which
two communicating applications must respond to one another for
a selection request.

This option indicates that requests to the X server should be
sent synchronously, instead of asynchronously. Since Xlib nor‐
mally buffers requests to the server, errors do not necessarily
get reported immediately after they occur. This option turns
off the buffering so that the application can be debugged. It
should never be used with a working program.

-title string
This option specifies the title to be used for this window.
This information is sometimes used by a window manager to pro‐
vide some sort of header identifying the window.

-xnllanguage language[_territory][.codeset]
This option specifies the language, territory, and codeset for
use in resolving resource and other filenames.

-xrm resourcestring
This option specifies a resource name and value to override any
defaults. It is also very useful for setting resources that
don't have explicit command line arguments.

To make the tailoring of applications to personal preferences easier, X
provides a mechanism for storing default values for program resources
(e.g. background color, window title, etc.) that is used by programs
that use toolkits based on the X Toolkit Intrinsics library libXt.
(Programs using the common Gtk+ and Qt toolkits use other configuration
mechanisms.) Resources are specified as strings that are read in from
various places when an application is run. Program components are
named in a hierarchical fashion, with each node in the hierarchy iden‐
tified by a class and an instance name. At the top level is the class
and instance name of the application itself. By convention, the class
name of the application is the same as the program name, but with the
first letter capitalized (e.g. Bitmap or Emacs) although some programs
that begin with the letter ``x'' also capitalize the second letter for
historical reasons.

The precise syntax for resources is:

ResourceLine = Comment | IncludeFile | ResourceSpec |
Comment = "!" {}
IncludeFile = "#" WhiteSpace "include" WhiteSpace FileName WhiteSpace
FileName =
ResourceSpec = WhiteSpace ResourceName WhiteSpace ":" WhiteSpace Value
ResourceName = [Binding] {Component Binding} ComponentName
Binding = "." | "*"
WhiteSpace = { | }
Component = "?" | ComponentName
ComponentName = NameChar {NameChar}
NameChar = "a"-"z" | "A"-"Z" | "0"-"9" | "_" | "-"
Value = {}

Elements separated by vertical bar (|) are alternatives. Curly braces
({...}) indicate zero or more repetitions of the enclosed elements.
Square brackets ([...]) indicate that the enclosed element is optional.
Quotes ("...") are used around literal characters.

IncludeFile lines are interpreted by replacing the line with the con‐
tents of the specified file. The word "include" must be in lowercase.
The filename is interpreted relative to the directory of the file in
which the line occurs (for example, if the filename contains no direc‐
tory or contains a relative directory specification).

If a ResourceName contains a contiguous sequence of two or more Binding
characters, the sequence will be replaced with single "." character if
the sequence contains only "." characters, otherwise the sequence will
be replaced with a single "*" character.

A resource database never contains more than one entry for a given
ResourceName. If a resource file contains multiple lines with the same
ResourceName, the last line in the file is used.

Any whitespace character before or after the name or colon in a
ResourceSpec are ignored. To allow a Value to begin with whitespace,
the two-character sequence ``\space'' (backslash followed by space) is
recognized and replaced by a space character, and the two-character
sequence ``\tab'' (backslash followed by horizontal tab) is recognized
and replaced by a horizontal tab character. To allow a Value to con‐
tain embedded newline characters, the two-character sequence ``\n'' is
recognized and replaced by a newline character. To allow a Value to be
broken across multiple lines in a text file, the two-character sequence
``\newline'' (backslash followed by newline) is recognized and removed
from the value. To allow a Value to contain arbitrary character codes,
the four-character sequence ``\nnn'', where each n is a digit character
in the range of ``0''-``7'', is recognized and replaced with a single
byte that contains the octal value specified by the sequence. Finally,
the two-character sequence ``\\'' is recognized and replaced with a
single backslash.

When an application looks for the value of a resource, it specifies a
complete path in the hierarchy, with both class and instance names.
However, resource values are usually given with only partially speci‐
fied names and classes, using pattern matching constructs. An asterisk
(*) is a loose binding and is used to represent any number of interven‐
ing components, including none. A period (.) is a tight binding and is
used to separate immediately adjacent components. A question mark (?)
is used to match any single component name or class. A database entry
cannot end in a loose binding; the final component (which cannot be
"?") must be specified. The lookup algorithm searches the resource
database for the entry that most closely matches (is most specific for)
the full name and class being queried. When more than one database
entry matches the full name and class, precedence rules are used to
select just one.

The full name and class are scanned from left to right (from highest
level in the hierarchy to lowest), one component at a time. At each
level, the corresponding component and/or binding of each matching
entry is determined, and these matching components and bindings are
compared according to precedence rules. Each of the rules is applied
at each level, before moving to the next level, until a rule selects a
single entry over all others. The rules (in order of precedence) are:

1. An entry that contains a matching component (whether name, class,
or "?") takes precedence over entries that elide the level (that
is, entries that match the level in a loose binding).

2. An entry with a matching name takes precedence over both entries
with a matching class and entries that match using "?". An entry
with a matching class takes precedence over entries that match
using "?".

3. An entry preceded by a tight binding takes precedence over entries
preceded by a loose binding.

Programs based on the X Toolkit Intrinsics obtain resources from the
following sources (other programs usually support some subset of these

RESOURCE_MANAGER root window property
Any global resources that should be available to clients on all
machines should be stored in the RESOURCE_MANAGER property on
the root window of the first screen using the xrdb program.
This is frequently taken care of when the user starts up X
through the display manager or xinit.

SCREEN_RESOURCES root window property
Any resources specific to a given screen (e.g. colors) that
should be available to clients on all machines should be stored
in the SCREEN_RESOURCES property on the root window of that
screen. The xrdb program will sort resources automatically and
place them in RESOURCE_MANAGER or SCREEN_RESOURCES, as appro‐

application-specific files
Directories named by the environment variable XUSERFILESEARCH‐
PATH or the environment variable XAPPLRESDIR (which names a
single directory and should end with a '/' on POSIX systems),
plus directories in a standard place (usually under
/usr/share/X11/, but this can be overridden with the XFILE‐
SEARCHPATH environment variable) are searched for for applica‐
tion-specific resources. For example, application default
resources are usually kept in /usr/share/X11/app-defaults/.
See the X Toolkit Intrinsics - C Language Interface manual for

Any user- and machine-specific resources may be specified by
setting the XENVIRONMENT environment variable to the name of a
resource file to be loaded by all applications. If this vari‐
able is not defined, a file named $HOME/.Xdefaults-hostname is
looked for instead, where hostname is the name of the host
where the application is executing.

-xrm resourcestring
Resources can also be specified from the command line. The
resourcestring is a single resource name and value as shown
above. Note that if the string contains characters interpreted
by the shell (e.g., asterisk), they must be quoted. Any number
of -xrm arguments may be given on the command line.

Program resources are organized into groups called classes, so that
collections of individual resources (each of which are called
instances) can be set all at once. By convention, the instance name of
a resource begins with a lowercase letter and class name with an upper
case letter. Multiple word resources are concatenated with the first
letter of the succeeding words capitalized. Applications written with
the X Toolkit Intrinsics will have at least the following resources:

background (class Background)
This resource specifies the color to use for the window back‐

borderWidth (class BorderWidth)
This resource specifies the width in pixels of the window bor‐

borderColor (class BorderColor)
This resource specifies the color to use for the window border.

Most applications using the X Toolkit Intrinsics also have the resource
foreground (class Foreground), specifying the color to use for text and
graphics within the window.

By combining class and instance specifications, application preferences
can be set quickly and easily. Users of color displays will frequently
want to set Background and Foreground classes to particular defaults.
Specific color instances such as text cursors can then be overridden
without having to define all of the related resources. For example,

bitmap*Dashed: off
XTerm*cursorColor: gold
XTerm*multiScroll: on
XTerm*jumpScroll: on
XTerm*reverseWrap: on
XTerm*curses: on
XTerm*Font: 6x10
XTerm*scrollBar: on
XTerm*scrollbar*thickness: 5
XTerm*multiClickTime: 500
XTerm*charClass: 33:48,37:48,45-47:48,64:48
XTerm*cutNewline: off
XTerm*cutToBeginningOfLine: off
XTerm*titeInhibit: on
XTerm*ttyModes: intr ^c erase ^? kill ^u
XLoad*Background: gold
XLoad*Foreground: red
XLoad*highlight: black
XLoad*borderWidth: 0
emacs*Geometry: 80x65-0-0
emacs*Background: rgb:5b/76/86
emacs*Foreground: white
emacs*Cursor: white
emacs*BorderColor: white
emacs*Font: 6x10
xmag*geometry: -0-0
xmag*borderColor: white

If these resources were stored in a file called .Xresources in your
home directory, they could be added to any existing resources in the
server with the following command:

% xrdb -merge $HOME/.Xresources

This is frequently how user-friendly startup scripts merge user-spe‐
cific defaults into any site-wide defaults. All sites are encouraged
to set up convenient ways of automatically loading resources. See the
Xlib manual section Resource Manager Functions for more information.

This is the only mandatory environment variable. It must point
to an X server. See section "Display Names" above.

This must point to a file that contains authorization data. The
default is $HOME/.Xauthority. See Xsecurity(7), xauth(1),
xdm(1), Xau(3).

This must point to a file that contains authorization data. The
default is $HOME/.ICEauthority.

The first non-empty value among these three determines the cur‐
rent locale's facet for character handling, and in particular
the default text encoding. See locale(7), setlocale(3),

This variable can be set to contain additional information
important for the current locale setting. Typically set to
@im= to enable a particular input method. See

This must point to a directory containing the locale.alias file
and Compose and XLC_LOCALE file hierarchies for all locales. The
default value is /usr/share/X11/locale.

This must point to a file containing X resources. The default is
$HOME/.Xdefaults-. Unlike $HOME/.Xresources, it is
consulted each time an X application starts.

This must contain a colon separated list of path templates,
where libXt will search for resource files. The default value
consists of


A path template is transformed to a pathname by substituting:

%D => the implementation-specific default path
%N => name (basename) being searched for
%T => type (dirname) being searched for
%S => suffix being searched for
%C => value of the resource "customization"
(class "Customization")
%L => the locale name
%l => the locale's language (part before '_')
%t => the locale's territory (part after '_` but before '.')
%c => the locale's encoding (part after '.')

This must contain a colon separated list of path templates,
where libXt will search for user dependent resource files. The
default value is:


$XAPPLRESDIR defaults to $HOME, see below.

A path template is transformed to a pathname by substituting:

%D => the implementation-specific default path
%N => name (basename) being searched for
%T => type (dirname) being searched for
%S => suffix being searched for
%C => value of the resource "customization"
(class "Customization")
%L => the locale name
%l => the locale's language (part before '_')
%t => the locale's territory (part after '_` but before '.')
%c => the locale's encoding (part after '.')

This must point to a base directory where the user stores his
application dependent resource files. The default value is
$HOME. Only used if XUSERFILESEARCHPATH is not set.

This must point to a file containing nonstandard keysym defini‐
tions. The default value is /usr/share/X11/XKeysymDB.

XCMSDB This must point to a color name database file. The default value

This serves as main identifier for resources belonging to the
program being executed. It defaults to the basename of pathname
of the program.

Denotes the session manager to which the application should con‐
nect. See xsm(1), rstart(1).

Setting this variable to a non-empty value disables the
XFree86-Bigfont extension. This extension is a mechanism to
reduce the memory consumption of big fonts by use of shared mem‐


These variables influence the X Keyboard Extension.

The following is a collection of sample command lines for some of the
more frequently used commands. For more information on a particular
command, please refer to that command's manual page.

% xrdb $HOME/.Xresources
% xmodmap -e "keysym BackSpace = Delete"
% mkfontdir /usr/local/lib/X11/otherfonts
% xset fp+ /usr/local/lib/X11/otherfonts
% xmodmap $HOME/.keymap.km
% xsetroot -solid 'rgbi:.8/.8/.8'
% xset b 100 400 c 50 s 1800 r on
% xset q
% twm
% xmag
% xclock -geometry 48x48-0+0 -bg blue -fg white
% xeyes -geometry 48x48-48+0
% xbiff -update 20
% xlsfonts '*helvetica*'
% xwininfo -root
% xdpyinfo -display joesworkstation:0
% xhost -joesworkstation
% xrefresh
% xwd | xwud
% bitmap companylogo.bm 32x32
% xcalc -bg blue -fg magenta
% xterm -geometry 80x66-0-0 -name myxterm $*

A wide variety of error messages are generated from various programs.
The default error handler in Xlib (also used by many toolkits) uses
standard resources to construct diagnostic messages when errors occur.
The defaults for these messages are usually stored in
usr/share/X11/XErrorDB. If this file is not present, error messages
will be rather terse and cryptic.

When the X Toolkit Intrinsics encounter errors converting resource
strings to the appropriate internal format, no error messages are usu‐
ally printed. This is convenient when it is desirable to have one set
of resources across a variety of displays (e.g. color vs. monochrome,
lots of fonts vs. very few, etc.), although it can pose problems for
trying to determine why an application might be failing. This behavior
can be overridden by the setting the StringConversionWarnings resource.

To force the X Toolkit Intrinsics to always print string conversion
error messages, the following resource should be placed in the file
that gets loaded onto the RESOURCE_MANAGER property using the xrdb pro‐
gram (frequently called .Xresources or .Xres in the user's home direc‐

*StringConversionWarnings: on

To have conversion messages printed for just a particular application,
the appropriate instance name can be placed before the asterisk:

xterm*StringConversionWarnings: on

XOrgFoundation(7), XStandards(7), Xsecurity(7), appres(1), bdftopcf(1),
bitmap(1), editres(1), fsinfo(1), fslsfonts(1), fstobdf(1), iceauth(1),
imake(1), makedepend(1), mkfontdir(1), oclock(1), proxymngr(1), rgb(1),
resize(1), rstart(1), smproxy(1), twm(1), x11perf(1), x11perfcomp(1),
xauth(1), xclipboard(1), xclock(1), xcmsdb(1), xconsole(1), xdm(1),
xdpyinfo(1), xfd(1), xfindproxy(1), xfs(1), xfwp(1), xhost(1),
xinit(1), xkbbell(1), xkbcomp(1), xkbevd(1), xkbprint(1), xkbvleds(1),
xkbwatch(1), xkill(1), xlogo(1), xlsatoms(1), xlsclients(1), xls‐
fonts(1), xmag(1), xmh(1), xmodmap(1), xprop(1), xrdb(1), xrefresh(1),
xrx(1), xset(1), xsetroot(1), xsm(1), xstdcmap(1), xterm(1), xwd(1),
xwininfo(1), xwud(1). Xserver(1), Xorg(1), Xdmx(1), Xephyr(1),
Xnest(1), Xquartz(1), Xvfb(1), Xvnc(1), XWin(1). Xlib - C Language X
Interface, and X Toolkit Intrinsics - C Language Interface

X Window System is a trademark of The Open Group.

A cast of thousands, literally. Releases 6.7 and later are brought to
you by the X.Org Foundation. The names of all people who made it a
reality will be found in the individual documents and source files.

Releases 6.6 and 6.5 were done by The X.Org Group. Release 6.4 was
done by The X Project Team. The Release 6.3 distribution was from The
X Consortium, Inc. The staff members at the X Consortium responsible
for that release were: Donna Converse (emeritus), Stephen Gildea (emer‐
itus), Kaleb Keithley, Matt Landau (emeritus), Ralph Mor (emeritus),
Janet O'Halloran, Bob Scheifler, Ralph Swick, Dave Wiggins (emeritus),
and Reed Augliere.

The X Window System standard was originally developed at the Laboratory
for Computer Science at the Massachusetts Institute of Technology, and
all rights thereto were assigned to the X Consortium on January 1,
1994. X Consortium, Inc. closed its doors on December 31, 1996. All
rights to the X Window System have been assigned to The Open Group.

X Version 11 xorg-docs 1.6 X(7)